Tumours Flashcards

Question

57) A 46-year-old man presents with headaches and visual disturbance and is found to have bitemporal hemianopia on visual field testing. CT of the brain demonstrates a multilobulated, heterogeneous, suprasellar mass containing cystic areas and rim-like calcification. Enhancement of the solid component is observed following intravenous contrast. What is the most likely diagnosis? a. epidermoid b. craniopharyngioma c. pituitary macroadenoma d. meningioma e. Rathke’s cleft cyst

Answer 1

b. craniopharyngioma Craniopharyngiomas are the most common suprasellar mass, predominantly occurring in the first and second decades, but with a second peak in the fifth decade. Presenting symptoms include headache secondary to hydrocephalus, bitemporal hemianopia (compression of the optic chiasm) and diabetes insipidus (compression of the pituitary gland). Typical imaging features are calcification, cyst formation and enhancement that may be solid or nodular. Meningiomas may arise in the suprasellar region and commonly demonstrate calcification but are generally not cystic. Epidermoids may occasionally demonstrate rim calcification but rarely enhance following intravenous contrast. Pituitary macroadenomas may undergo haemorrhage, resulting in heterogeneity that can cause confusion with craniopharyngioma, but this typically occurs in adolescence. Calcification in macroadenomas is infrequent. Rathke’s cleft cysts are thin-walled, benign cysts arising in the anterior sellar or suprasellar region. They show no contrast enhancement and rarely calcify.

Answer 2

b. colloid cyst Colloid cysts arise from the inferior aspect of the septum pellucidum and protrude into the anterior aspect of the third ventricle, where they may cause positional headaches and hydrocephalus due to transient obstruction at the foramen of Monro. They usually contain mucinous fluid, desquamated cells and proteinaceous debris, making them hyperdense on CT. On MR scan, the high protein content, as well as the paramagnetic effect of magnesium, copper and iron in the cyst, results in high signal intensity on T1W and T2W sequences in 60% of cases. Meningiomas and ependymomas may also appear hyperdense, but location within the third ventricle is uncommon for both. Subependymal giant cell astrocytoma is a benign tumour occurring in the region of the foramen of Monro, which may cause obstruction, but it is usually hypodense and is nearly always seen in association with tuberous sclerosis. Choroid plexus papilloma predominantly occurs in children under 5 years of age, and location in the third ventricle is unusual.

Answer 3

e. meningioma Meningioma is the most common radiation-induced CNS tumour, and has been particularly associated with low-dose radiation treatment for tinea capitis. For the diagnosis of radiation-induced meningioma to be made, the meningioma must arise in the radiation field, appear after a latency period of years and should not have been the primary tumour irradiated. Radiation-induced meningiomas are more frequently multiple and have higher recurrence rates than non-radiation-induced tumours.

Answer 4

d. Sheehan’s syndrome Many of the acute neurological conditions of pregnancy occur with rising blood pressure. Sheehan’s syndrome results from haemorrhage-induced hypotension causing pituitary infarction. Early on, this appears as an enlarged homogeneous pituitary with low T1 signal, high T2 signal and post-contrast ring enhancement. Later, there is an empty sella. Clinical manifestations include visual field loss, headache, ophthalmoplegia and pituitary dysfunction (diabetes insipidus). Reversible posterior leukoencephalopathy produces cortical blindness, headaches, confusion and seizures. Those affected are often taking immunosuppressant treatment. Imaging features can be identical to eclampsia, peripartum cerebral angiopathy and hypertensive encephalopathy, but with a posterior predominance. On CT, there is low attenuation change. On MRI, there is high signal on T2W/FLAIR images. ADC maps can differentiate between likely reversible vasogenic oedema (high signal on ADC map showing unrestricted diffusion) and cytotoxic oedema (low signal due to restricted diffusion), which is more likely to progress to infarct. Microangiopathic haemolytic anaemias, such as thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome, give widespread ischaemia/infarction and haemorrhagic transformation. There is no increased risk in pregnancy of vasculitis such as systemic lupus erythematosus, Takayasu’s syndrome or Moyamoya syndrome. Arteriovenous malformation is no more likely to bleed in pregnancy, but there is an increased risk with arterial aneurysms. Haemorrhage, sepsis and pulmonary embolism cause hypotension that can cause watershed infarction as well as Sheehan’s syndrome.

Answer 5

c. dermoid Epidermoids and dermoids are congenital lesions resulting from inclusion of ectodermal elements during closure of the neural tube. Both have a squamous epithelial lining and produce keratin, but dermoids contain both ectodermal and mesodermal elements (hair follicles, sweat and sebaceous glands), while epidermoids contain only ectodermal elements. Epidermoids are lobulated masses, usually located off the midline, which compress adjacent structures such as cranial nerves, and tend to have appearances on CTand MR scan following that of CSF. Dermoids are usually midline in location and cause symptoms by obstruction of CSF pathways or by rupture and leakage of fat contents, causing chemical meningitis. They have appearances on CT and MR scan following that of fat, and are often heterogeneous with areas of calcification and other soft-tissue components. This heterogeneity helps to distinguish a dermoid from a lipoma. Arachnoid cysts are of CSF density, but may be distinguished fromepidermoids on DWI, where they do not show evidence of water restriction. Teratomas are composed of ectodermal, mesodermal and endodermal elements, and also appear heterogeneous with areas of fat, calcification and cystic components, but these lesions occur most commonly in the pineal and suprasellarregions.

Answer 6

b. lipoma Intracranial lipomas appear as well-circumscribed masses of fat density on CTwith occasional rim calcification. On MR scan, characteristic appearances are of hyperintensity on T1W images, with chemical shift artefact or signal suppression on fat-saturated sequences. Approximately 30% of intracranial lipomas occur in the pericallosal region, and there is a high incidence of associated congenital anomalies, most commonly agenesis of the corpus callosum, but also encephalocele and cutaneous frontal lipomas. Interhemispheric arachnoid cysts may occur in association with agenesis of the corpus callosum, but they are of CSF density and, like epidermoids, appear hypointense on T1W images. Dermoids have signal characteristics following those of fat, but are usually more heterogeneous and not associated with callosal anomalies. Lymphoma may involve the corpus callosum but appears isoorhypointense on T1W images.

Answer 7

d. focal low attenuation on CT Dermoid and epidermoid cysts are ectoderm-lined congenital inclusion cysts. They may not present until early adulthood due to slow growth (particularly epidermoids). Epidermoids contain only squamous epithelium whereas dermoids contain hair, sebaceous and sweat glands, and squamous epithelium. Unlike teratomas, neither is a true neoplasm. Clinical presentation is often with chemical meningitis from rupture of fatty contents. Epidermoids usually have imaging characteristics similar to water and can be differentiated from arachnoid cysts by restricted diffusion on DWI. Attenuation varies according to the keratin:cholesterol ratio and therefore can be similar to fat but is usually homogeneous. The cyst wall is very thin and is often not visible in epidermoids, and areas of calcification can infrequently be seen. Dermoids may appear more complex but are still unilocular. The wall may be thicker and calcification is more frequent. The sebaceous lipid material in a dermoid has attenuation and signal intensity characteristics of fat on CT (low attenuation) and MR (high signal on T1). ‘White epidermoids’ with high signal on T1 may be seen rarely; they are due to haemorrhage or a high fat content. However, the latter usually produces a homogeneous fat signal as opposed to dermoids, where the appearances are more heterogeneous due to the increased complexity of contents.

Answer 8

d. central neurocytoma Central neurocytomas (also known as intraventricular neurocytomas)are benign tumours of the lateral and third ventricles usually presenting in **adults aged 20–40 years.** They frequently calcify (69%) and contain cystic spaces. **Attachment to the septum pellucidum is a characteristic feature.** Lesions appear isointense to grey matter on all MR sequences and show mild-to-moderate contrast enhancement. Central neurocytomas were previously frequently mistaken for intraventricular oligodendrogliomas, which have very similar imaging features but are actually quite rare. In addition, neurocytomas undergo haemorrhage into the tumour or ventricle more frequently, helping to distinguish the two. Colloid cysts arise within the third ventricle, and rarely calcify. Subependymomas may arise in the lateral ventricles with an attachment to the septum pellucidum, and cyst formation and calcification may be seen in large tumours. However, most occur in patients **over 40 years of age.** Choroid plexus papillomas generally occur in children **under 5 years of age.**

Answer 9

a. normal appearances Opsoclonus–myoclonus syndrome is characterized by opsoclonus incombination with myoclonus of the trunk, limbs or head. It may be idiopathic or occur as a paraneoplastic syndrome, when it may follow are lapsing–remitting course. In adults, it is most commonly associated with breast and squamous cell lung carcinoma, while in children it is associated with neuroblastoma. The syndrome usually precedes diagnosis of the underlying malignancy, and in children should prompt investigation to identify an underlying neuroblastoma. MIBG whole-body scintigraphy may be helpful in identifying occult disease if conventional imaging is negative. MR scan of the brain is usually normal.

Answer 10

(d) Elevated choline on magnetic resonance spectroscopy MR spectroscopy interrogates the chemical environment of intracerebral lesions: elevated choline is associated with high cellular turnover as found in neoplasms. Tumours are often centred upon white matter with relative sparing of the overlying cortex. Gyriform enhancement is unusual in neoplasms unless there is meningeal disease. In the acute stage, an infarct will demonstrate restricted diffusion: high signal on the DWI image and low signal on the ADC image. Cytotoxic oedema is typical of infarcts, whilst vasogenic oedema is typical of neoplasms.

Answer 11

(e) Decreased amplitude of the N-acetyl-aspartate peak (NAA) on MR spectroscopy

Answer 12

(b) Haemangiopericytoma Haemangiopericytoma is the only intra-axial mass listed.

Answer 13

(a) Surrounding vasogenic oedema is common A pilocytic astrocytoma is the most likely diagnosis. This is the most common paediatric glioma, and the characteristic appearance is of acyst with an intensely enhancing mural nodule. **Surrounding oedema is rare.** 40% of patients with both NF-1 and an optic pathway gllioma also suffer from precious puberty.

Answer 14

(e) Bony remodeling Scalloping of the adjacent bone, possibly through transmitted pulsations, is often seen in arachnoid cysts. This is never seen in subdural hygromas, but can be seen with epidermoid cysts or porencephaly.?

Answer 15

(c) Iso-intense to CSF on DWI The content of an arachnoid cyst has the same characteristics as CSF on all MR imaging sequences.

Answer 16

(e) Glioblastoma multiforme A ring-enhancing lesion that crosses the midline may represent, amongst other conditions, a glioblastoma multiforme ('a butterfly glioma'), astrocytoma or lymphoma. Abscesses rarely cross the midline. An infarct is less likely as the above distribution does not correspond to a single arterial territory.

Answer 17

(b) Pinealoma The pattern of dilatation is consistent with obstruction at the level of the aqueduct - of the options listed, a pinealoma is most likely to cause obstruction at this level.

Answer 18

(a) High signal intensity relative to grey matter on T2W imaging Schwannomas are the most common CPA mass. The epicentre of the lesion is typically in the epicenter of the internal auditory canal, typically causing a >2 mm difference in canal diameter on the affected side. Extension into the CPA causes an 'ice cream cone' appearance. On MR imaging, the lesion is iso-intense on T1W, hyper-intense on T2W and has dense enhancement (however, meningiomas also typically enhance). Ca is not typical.

Answer 19

(e) lntralesional haemorrhage. Only 1 % of meningiomas are associated with internal haemorrhage. Regarding the other characteristics: the inward bulging of the grey white junction is suggestive of an extra-axial lesion, such as a meningioma; 60% of meningiomas are associated with oedema; meningiomas are typically hyperdense on unenhanced CT imaging and are seen to enhance with i. v. contrast medium.

Answer 20

(b) Low signal on DWI Epidermoid tumours are typically iso-intense to CSF on T1 and T2W imaging, with high signal on diffusion weighted sequences and heterogeneous signal on FLAIR imaging. They do not typically enhance.

Answer 21

(e) High signal in the anterior pituitary on T2W On T1W imaging, the anterior pituitary is typically iso-intense and the posterior pituitary hyperintense; on T2W imaging, both the anterior and posterior pituitary are typically iso-intense. The gland is normally flat or concave superiorly, but may be convex in pregnancy.

Answer 22

(e) Rathke's cleft cyst - T1W hypointensity and lack of enhancement with i. v. gadolinium A Rathke's cleft cyst is typically hyperintense on T1W, and has smooth peripheral enhancement with intravenous contrast medium.

Answer 23

(e) Nodular enhancement A craniopharyngioma would typically be seen as a cyst with a mural nodule. Calcification is present in 90% of cases in the younger age group. Both craniopharyngiomas and Rathke cleft cysts have variable signal intensities on MR imaging, but most commonly craniopharyngiomas have a low signal on T1W imaging. The enhancement pattern is typically 'solid' or 'nodular', as opposed to the'rim-like' pattern seen in Rathke cleft cysts.

Answer 24

(e) Hyperdense on unenhanced imaging Oligodendrogliomas are slowly growing gliomas, most commonly located in the frontal lobes. Large nodular calcification is present in approximately 90% of cases. Cystic degeneration, ill-defined enhancement and a lack of oedema are all common. Over 80% are either hypo- or iso- dense on unenhanced CT imaging.

Answer 25

(b) Enhancement within the pre-operative tumour bed, 1 day after surgery Within the first 2 days, enhancement within the pre-operative tumourbed should be regarded as suspicious of incomplete resection. After this time, it is common for enhancing granulation tissue to develop. Dural enhancement is a normal post-operative finding.

Answer 26

(e) Dysembroplastic neuroepithelial tumour DNETs are benign tumours arising from cortical gray matter, most commonly found in the temporal lobes. They are characterised by the presence of multiple cysts and a lack of surrounding oedema. Desmoplastic infantile gangliogliomas typically occur before the 2ndbirthday; Oligodendrogliomas typically occur in 30-60 year olds.

Answer 27

(a) Incomplete haemosiderin ring Haemorrhagic metastases typically have an incomplete or absent haemosiderin ring. Calcification is rare. Most commonly, there is either nodular, eccentric or ring enhancement. This contrasts with haemorrhagic cerebrovascular malformations, which typically show minimal or central enhancement. Surrounding oedema is present in both the acute/ subacute phase.

Answer 28

(b) The mass tends to be hyperintense on T1 W The mass is most likely a medulloblastoma. These tend to be iso-to hypointense on T1W. Leptomeningeal metastases, seen as enhancing nodules, can cause seizures. Hydrocephalus is present in 90% of cases.

Answer 29

(d) Lack of enhancement with i.v.gadolinium Chordomas originate from the remnants of the embryonic notochord, and may occur at any point along the neural axis. The clivus is the second most frequently affected site. The tumour is locally aggressive,calcified in approximately 50% (giving rise to areas of low T1W) and enhances. They are typically isointense to brain parenchyma onT1W.

Answer 30

(b) The area of thickening does not enhance The 3 main criteria for the definition of a dural tail are: presence on at least two contiguous 5 mm sections through the tumour (although now sections tend to be less than 5 mm thick); the greatest thickness being adjacent to the tumour; and enhancement being greater than the tumour itself. Dural tails have classically been described in associationwith meningiomas, but can occur with other extra-axial and even intraaxial tumours.

Answer 31

(c) Chorid plexus papilloma The imaging characteristics are those of a choroid plexus papilloma. Meningiomas are rarely intraventricular and most frequently occurin middle aged women. Colloid cysts occur within the third ventricle. Ependymomas typically arise from the floor of the fourth ventricle.

Answer 32

1.a. Germinoma Germinomas are germ-cell tumours arising from primordial germ cells. They frequently occur in the midline, mostly in the pineal region but also in the suprasellar region. In men, 80% of pineal masses are germ-cell tumours, in contrast to 50% in women. They tend to occur in children or young adults (10–25 years old). Symptoms depend on the location but the case describes Parinaud syndrome – paralysis of upward gaze due to compression of the mesencephalic tectum. Germinomas may also cause hydrocephalus by compression of the aqueduct of Sylvius, thus patients may present with signs and symptoms of raised intracranial pressure. Germinomas are a known cause of precocious puberty in children under the age of ten years. They are malignant tumours and may show CSF seeding, making cytological diagnosis possible with lumbar puncture. They are, however, very radiosensitive and show excellent survival rates. Pineal teratomas tend to be heterogeneous masses containing fat and calcifications. Pineoblastoma is a highly malignant tumour which is more common in children and usually has poor tumour margins.

Answer 33

2d. Meningioma It is rare for meningiomas to occur intraventricularly (2–5% of all meningiomas) but they are **the most common trigonal intraventricular mass in adulthood.** They tend to occur in 40 year old females.

Answer 34

3. e. Pituitary adenoma Pituitary adenomas are divided into microadenomas (<1 cm) and macroadenomas (>1 cm). Macroadenomas may present with endocrine dysfunction but are generally less active than microadenomas. Thus, macroadenomas often present with symptoms of mass effect on the optic chiasm, or if there is lateral extension into the cavernous sinuses patients may present with other local cranial nerve palsies (III, IV, VI). The differential diagnosis of a suprasellar mass includes (‘SATCHMO’): Suprasellar extension of pituitary adenoma/sarcoid; Aneurysm/arachnoid cyst; TB/teratoma (other germ-cell tumours); Craniopharyngioma; Hypothalamic glioma or hamartoma; Meningioma/ metastases (especially breast); and Optic/chiasmatic glioma. In this case, the sellar is widened and the floor is eroded suggesting the mass arises from the pituitary itself. Low-density/low-intensity regions on CT/T1 MRI correspond to necrotic areas and high-signal foci on T1 MRI (found relatively frequently) represent areas of recent haemorrhage.

Answer 35

5. c. Haemangioblastoma Haemangioblastoma is the most common primary intra-axial, infratentorial tumour in adults. They are benign autosomal dominant tumours of vascular origin. Approximately 20% occur with von Hippel–Lindau disease. Other associations include phaeochromocytomas, syringomyelia and spinal cord haemangioblastomas. **About 20% of tumours cause polycythaemia.** Typical CT and MRI appearances are of a largely cystic mass with an enhancing mural nodule. Oedema may be absent or extensive but calcification is rare. Prognosis is 85% post-surgical five-year survival rate. Infratentorial pilocytic astrocytomas may have very similar appearances to haemangioblastomas but some differences exist that can help differentiate the two. Pilocytic astrocytomas predominantly occur in children and young adults, are generally larger (>5 cm) than haemangioblastomas, may contain calcifications and are not associated with polycythaemia.

Answer 36

6. d. Pilocytic astrocytoma Pilocytic astrocytoma is the most common paediatric glioma and accounts for approximately 85% of all cerebellar astrocytomas in children. Peak age is between birth and nine years old. (Over 80% of haemangioblastomas occur in adulthood.) They are associated with neurofibromatosis type 1 (café-au-lait spots and skeletal abnormalities). The most common appearance is of a cyst with an intensely enhancing mural nodule (arachnoid cyst should be devoid of an enhancing nodule). They occasionally calcify (calcification is rare in haemangioblastomas). They run a relatively benign clinical course and almost never recur following surgical excision. There is no malignant transformation to anaplastic form.

Answer 37

17. a. Choroid plexus papilloma Eighty-six per cent of choroid plexus papillomas occur below the age of five years and they represent approximately 65% of choroid tumours. Large aggregation of choroid produces CSF at an abnormal rate. This CSF overproduction contributes to hydrocephalus. The most common location in children is the trigone of the lateral ventricle, the third ventricle is unusual and the fourth ventricle and cerebellopontine angle are more common in adults. The tumour shows a smooth lobulated border and small calcifications are common. There is intense homogeneous enhancement. Approximately 5% undergo malignant transformation to choroid plexus carcinoma. Meningiomas are the most common trigonal intraventricular mass in adulthood. They rarely occur under the age of 20. Cavernous haemangiomas tend to occur in the third to sixth decades and are located in the subcortical cerebrum.

Answer 38

20. e. Oligodendroglioma This is an uncommon glioma which usually presents as a large mass at the time of diagnosis. Mean age is 30–50 years and they are more common in men than women. The majority are located in the frontal lobe (_60%), although they can occur anywhere within the central nervous system, including the cerebellum, brainstem, spinal cord, ventricles and optic nerve. Large nodular clumps of calcifications are present in up to approximately 90% of tumours. Cystic degeneration and haemorrhage are uncommon. Prognosis depends on the grade of the tumour. High-grade tumours show 20% ten-year survival whereas lowgradetumours show 46% ten-year survival. Although astrocytomas can calcify, the calcifications are rarely large and nodular. Glioblastomas rarely calcify. Gangliogliomas are more common in the temporal lobes and deep cerebral tissues and the majority of them (80%) occur below the age of 30 years. Ependymomas often demonstrate fluid levels due to internal haemorrhage.

Answer 39

21. d. Renal cell metastasis with subsequent CT staging Brain metastases account for approximately a third of all intracranial tumours and are the most common intracranial neoplasm. They characteristically occur at the corticomedullary junction of the brain and have surrounding oedema that typically exceeds the tumour volume. Multiple lesions are present in approximately two-thirds of cases and should be searched for with administration of intravenous contrast. Most are hypodense on CT unless haemorrhagic or hypercellular, hence the lesion in this case is haemorrhagic. This lends itself to a differential of primary neoplasms which includes melanoma, renal cell carcinoma, thyroid carcinoma, bronchogenic carcinoma and breast carcinoma. The history of back pain also suggests bone metastases. Glioblastoma multiforme usually appears as an irregular, heterogeneous, low-density mass. Abscesses typically demonstrate ring enhancement post-contrast and may show loculation and specules of gas. The patient’s history describes collapse rather than headache or confusion following a fall, which moves the differential away from traumatic contusion. Although prostate cancer typically metastasises to the vertebrae, it is an uncommon primary site for brain metastases, especially as the lesion described is haemorrhagic.

Answer 40

23. c. Central neurocytoma Central neurocytoma is an intraventricular WHO grade II neuroepithelial tumour with neuronal differentiation. This rare neoplasm tends to occur between the ages of 20–40 years. Patients typically present with symptoms and signs of hydrocephalus. Imaging typically demonstrates **a globular lesion attached to the septum pellucidum.** Calcification is considered characteristic, however it may be absent in approximately half the cases. On MRI, the lesions are usually isointense to grey matter and show dense contrast enhancement. It is extremely uncommon to see peritumoural oedema. Heterotopic grey matter should not enhance, contain calcium, nor be attached to the septum pellucidum. Intraventricular meningiomas are typically located at the trigone. Subependymomas are hyperintense to grey matter on T2 while ependymomas tend to be heterogeneous, childhood lesions that occur in and around the fourth ventricle.

Answer 41

26. a. Diffusion-weighted MR imaging Epidermoid and arachnoid cysts can look very similar on CT and standard MRI T1- and T2-weighted imaging. Both demonstrate signal intensity similar to CSF. Arachnoid cysts and the majority of epidermoid cysts do not calcify nor enhance. Arachnoid cysts are typically found in the floor of the middle cranial fossa near the tip of the temporal lobe (50%). Although intracranial epidermoid cysts are more commonly found at the cerebellar pontine angle, they may be found in the middle cranial fossa. Both arachnoid and epidermoid cysts may have associated bone erosion indicating their chronicity. Diffusion-weighted imaging is useful at distinguishing between the two as epidermoids appear bright indicating the marked restriction of water diffusion. Arachnoid cysts appear dark in keeping with signal from CSF.

Answer 42

30. c. Hypothalamic hamartoma Hypothalamic hamartoma is not a true tumour by definition. It presents either with precocious puberty or with **gelastic seizures (paroxysms of inappropriate emotional outbursts, usually laughing).** The lesion is well defined, arising from the floor of the third ventricle/around the tuber cinereum of the thalamus and extending inferiorly into the suprasellar cistern or interpeduncular cistern. The imaging characteristics described are typical. **They do not enhance.**

Answer 43

32. b. Lipoma This is a congenital tumour that results from abnormal differentiation of the meninx primitiva – that which eventually differentiates into pia, arachnoid and internal dura mater. They account for less than 1% of brain tumours but are associated with congenital abnormalities, **most commonly dysgenesis of the corpus callosum** to some degree. This is particularly likely when the lipoma is located anteriorly rather than posteriorly. On CT they are well-circumscribed masses with negative Hounsfield units and occasional calcification, and they do not enhance. Characteristically, they are T1 hyperintense and slightly less hyperintense on T2. Dermoids and teratomas can show similar characteristics, with fat and calcium content. Teratomas may enhance, although dermoids do not. However, the lesion is much more likely to be a lipoma given its position (dermoids tend to be extra-axial (spinal canal); teratomas are much more commonly found around the pineal region, floor of the third ventricle, posterior fossa and spine) and given the association with corpus callosum abnormalities.

Answer 44

36. c. Chordoma Chordomas originate from malignant transformation of notochordal cells. They are typically located in the sacrum (50%), clivus (35%) and vertebrae (15%). They may rarely be found in the mandible, maxilla and scapula. Spheno-occipital chordomas typically affect males and females in equal incidence and the average age ranges from 20 to 40 years. The majority of them demonstrate bone destruction and amorphous calcification. The solid components show variable but often marked contrast enhancement and MRI may show **a ‘soap-bubble’ appearance.** Bone sclerosis is rare. The description given is that of a malignant process. Meningiomas typically affect older females and only rarely (<1%) arise from the clivus. Plasmacytomas tend to occur in an older age group, are more common in the thoracic/lumbar spine and are often osteolytic and grossly expansile lesions. Metastasis is a possibility, although from the description given – particularly the calcification and amount of tumour extension – chordoma remains the most likely diagnosis.

Answer 45

44. c. Primary CNS lymphoma (PCNSL) PCNSL is the second most common cause of a CNS mass in patients with AIDS (behind toxoplasmosis). Typical features include periventricular location with subependymal spread and crossing of the corpus callosum. Non-contrast CT may show a hyperdense lesion due to dense cellularity (for this reason it may also be hypointense on T2/FLAIR). There is often a paucity of oedema and frequent ring enhancement due to central necrosis (note this is in contrast with the solid homogeneous enhancement seen with lymphoma in the immunocompetent patient). Cryptococcosis is the most common cause of fungal infection in AIDS patients. CT is frequently normal and MRI shows low T1 and high T2 signal intensities without enhancement in the lenticulostriate region. Progressive multifocal leukoencephalopathy typically shows bilateral white matter lesions in the periventricular region, centrum semiovale or subcortical white matter, which are hypointense on T1 and hyperintense on T2/FLAIR. There is typically no oedema nor mass effect and no contrast enhancement.

Answer 46

45. b. Dysembryoblastic neuroepithelial tumour (DNET) DNETs are benign tumours of neuroepithelial origin which arise from the cortical/deep grey matter. They are preferentially located supratentorially (temporal 62%, frontal 31%). CT demonstrates a hypoattenuating mass and there may be thinning and remodelling of the underlying inner table reflecting the slow growth of the tumour. On MRI they are hypointense on T1, hyperintense on T2 and small intratumoural cysts may be present to cause a characteristic ‘bubbly’ appearance. There is minimal mass effect and no associated vasogenic oedema. A third of lesions show calcification and most tumours do not enhance. If present, the enhancement is faint and patchy. Gangliogliomas and cavernous haemangiomas are other tumours which may cause epilepsy in children. Cavernous haemangiomas are typically dense on CT and commonly calcify. PNETs have a tendency for necrosis, cyst formation and calcification. They also tend to be hyperdense on CT due to high nuclear to cytoplasmic ratio.

Answer 47

50. b. Gliomatosis cerebri (GC) GC is a diffusely infiltrative glioma that may be present with or without a dominant mass. It must, however, involve two or more lobes and usually involves contiguous areas. It affects all age groups and can be of varying histological grade. Presentation may be enigmatic as the normal cerebral architecture is usually preserved. Alternatively, patients present with seizures, headache and personality disorders. Prognosis is poor. MRI findings include diffuse T2 (and proton density) hyperintensity throughout the white matter that usually extends to involve the deep grey nuclei with enlargement of cerebral structures. It is often bilateral and symmetric with minor mass effect and absence of necrosis. The differential diagnosis of symmetric white matter lesions includes microvascular change, encephalitis, demyelinating disease, vasculitis and leukoencephalopathy. GC is the most likely diagnosis in this scenario as there is **involvement of the corpus callosum and the pattern is infiltrative with enlargement of the thalami (cerebral structures).**

Answer 48

54. d. Craniopharyngioma Craniopharyngiomas (CPs) are the most common sellar/suprasellar region mass in children. They are benign lesions that originate from epithelial remnants (Rathke pouch) of the adenohypophysis and show a bimodal age distribution with peaks at the first and second decades (75%) and in the fifth decade (25%). They are more common in males. If the tumour presses on the pituitary gland, the patient may present with features of diabetes insipidus. Similarly, compression on the hypothalamus may lead to growth disturbance, compression on the optic chiasm may cause bitemporal hemianopia, and compression of ventricular outflow may cause raised intracranial pressure from resulting hydrocephalus. Classically, CPs appear as calcified, mixed cystic and solid tumours with enhancement of the solid component. They may be T1-bright due to proteinaceous components. Long-term survival in children is good (>90%). Germinomas are typically non-cystic and non-calcified. PNETs frequently show haemorrhage, necrosis and calcification and may resemble the appearance described for CPs. However, they are rarely found in the suprasellar region and are much more common in the posterior fossa. Chiasmatic gliomas are usually iso/hypointense on T1 and imaging usually defines optic nerve involvement.

Answer 49

55. a. Medulloblastoma Medulloblastomas are highly malignant lesions that account for 30–40% of all posterior fossa tumours. They typically arise from the roof of the fourth ventricle and 75% of cases occur in the first decade of life. On imaging, they are typically seen as hyperdense midline vermian masses which abut the roof of the fourth ventricle and cause hydrocephalus. There is usually mild to moderate perilesional oedema. Cystic change (high signal on T2), haemorrhage and calcification (low signal on T2) are frequently seen. They are fast-growing tumours and approximately 20% of cases demonstrate CSF dissemination at the time of diagnosis. For this reason it is important to actively search for evidence of further cranial or spinal disease. Treatment is usually a combination of surgery and radiotherapy. Subependymomas typically occur in middle-aged or elderly patients. Pilocytic astrocytomas are typically cystic with an enhancing nodule. Metastases are generally multiple and occur in older patients. Ependymomas are usually hypo/isodense on CT.

Answer 50

A High signal on diffusion-weighted MRI Epidermoid cysts appear bright on diffusion-weighted imaging due to markedly restricted water diffusion. There is free diffusion of water within arachnoid cysts; therefore, diffusion weighted imaging is very useful to distinguish between the two.

Answer 51

C Ependymoma Ependymomas are usually intraventricular. The myxopapillary type tends to occur in the region of the filum terminale in young adults.

Answer 52

A Choroid plexus tumour The age of the child and the description of the tumour fit best with a choroid plexus tumour. Another diagnosis that should be considered is medulloblastoma, but this tends to occur in an older age group with peak presentation at 7 years.

Answer 53

B Germinoma ''Pineal and suprasellar germ cell tumours may be synchronous and if so are pathognomonic. Teratomas tend to be more heterogeneous.

Answer 54

D Medulloblastoma Medulloblastoma is the most common posterior fossa tumour in children, accounting for 30-^10%.

Answer 55

A Arachnoid cyst Arachnoid cysts are commonly an incidental finding. They do not calcify or enhance and they show identical imaging characteristics to CSF.

Answer 56

C Haemangioblastoma Haemangioblastoma is the commonest primary intra-axial tumour below the tentorium cerebelli in adults. Pilocytic astrocytomas have a similar appearance but are rare in adults.

Answer 57

A Craniopharyngioma The main differential diagnosis would be a Rathke's cleft cyst but this would not show enhancement or calcification (calcification is more common inchildhood craniophaiyngiomas).

Answer 58

E Vestibular schwannoma

Answer 59

B A 6-mm poorly enhancing mass in the anterior pituitary Prolactinomas are the most common functioning pituitary microadenoma. They typically arise laterally in the anterior lobe of the pituitary gland.?

Answer 60

D Meningioma

Answer 61

A Chordoma The commonest site for chordomas is the spheno-occipital synchondrosis ofthe clivus

Answer 62

A Hyperdense cerebellar mass in the midline with heterogeneous enhancement Medulloblastoma is typically a hyperdense midline vermian mass with perilesional oedema, patchy enhancement and hydrocephalus.

Answer 63

1. D. Germinoma. The lesion is described in the pineal region, so the differential of pineal tumours should beconsidered. These are differentiated between germ cell tumours and pineal cell tumours. Germinomas account for 40% of all pineal region masses and are much more frequent in males than females. They are also the most common germ cell tumour, with teratomas and choriocarcinoma having different imaging characteristics. The main differential in this case is between pineoblastoma and germinoma, as both occur in patients of this age group and both are hyperdense on CT. Imaging features described to help differentiate are the avid enhancement, which is more characteristic of germinomas, but can occur in either. Central calcification is seen commonly in germinomas, but is uncommon in pineoblastomas, and when it occurs is often peripheral, giving the impression of an ‘exploded’ pineal gland. Subarachnoid seeding is seen in both tumours and if present CSF sampling can yield a tissue diagnosis. Pineocytomas occur in an older age group and in frequently cause subarachnoid seeding.

Answer 64

10. C. Haemangiopericytoma. The imaging findings clearly describe an extra-axial tumour. These are classed as either lesions of meningeal origin or tumours of neurogenic origin. The broad dural base and dural tail indicates that this is a tumour of meningeal origin. Meningioma is the most common of these tumours, but the imaging characteristics are not typical. World Health Organization (WHO) 1 and 2 meningiomas demonstrate uniform enhancement, although haemorrhage into meningiomas is recognized. WHO 3 meningiomas (malignant meningiomas) are indicated on imaging when there is invasion of the adjacent parenchyma, which is not described. Otherwise the diagnosis of malignant meningioma is made by an aggressive pattern of growth on serial imaging and biopsy. The dual arterial supply is also atypical. While meningiomas can have dual supply, they more typically derive their arterial supply from the external carotid (via the meningeal artery). Melanocytomas are suggested on imaging by increased signal on T1WI and are more commonly infratentorial. Without this the diagnosis is again reached most commonly following biopsy. All the features described are typical of haemangiopericytoma.

Answer 65

3. B. Metastasis. The answer options give some of the classical radiological differentials for a ring-enhancing lesion in the brain: MAGIC DR (metastasis, abscess, glioblastoma multiforme, infarct, contusion, demyelinating conditions and post-radiotherapy change). The clinical history should steer the reader toward the first two. DWI is reasonably useful at differentiating between these two (exceptions being in some fungal infections and toxoplasmosis), with necrotic metastasis having unrestricted diffusion and abscess having restricted diffusion. The appearances in this case are slightly confused by the DWI b1000 imaging showing increased signal. However, the presence of increased signal on the ADC map correctly identifies this as being T2 shine through, showing the importance of checking both sequences.

Answer 66

5. E. Oligodendroglioma. Prior to evaluating the imaging characteristics, the patient’s demographics should be consideredin this case, as in all cases of intracranial masses, as it will help limit the differential diagnosis significantly. The patient is an adult, thus making DIG and DNET unlikely. Secondly, considerthe temporal lobe location. Haemangioblastomas are usually infratentorial in location, especially in the absence of a history of von Hippel–Lindau syndrome. All the other lesions are classical temporal lobe tumours. Finally, considering the imaging characteristics, both PXA and oligodendrogliomas may be entirely solid, but cysts are commonly seen in PXAs. Calcification is seen in 60–80% of oligodendrogliomas, but is rarely seen in PXAs. Similarly haemorrhage, while not typical of oligodendrogliomas, is rare in PXAs.

Answer 67

12. E. Medulloblastoma. This is the most common malignant posterior fossa tumour in children, generally occurring before 10 years of age. The vast majority (85%) arise in the cerebellar vermis. They are hyperdense due to their high cellular content. Calcification is uncommon, occurring in up to 20% of cases. Pilocytic astrocytoma typically present as a cystic mass with an enhancing nodule. The most common location is the cerebellum, but they usually occur in other sites when associated with neurofibromatosis type 1. Haemangioblastomas are rare in children and even in the setting of von Hippel-Lindau syndrome typically manifest in early adulthood. Ependymomas are usually more heterogenous owing to calcification, cystic change, and haemorrhage. The tumour arises from ependymal cells that line the ventricular system and central canal of the spinal cord. Brainstem gliomas are hypodense on CT and may show exophytic growth into the adjacent cisternal spaces.

Answer 68

14. A. Pilocytic astrocytoma. This question deals with the classical neurological differential diagnosis of a posterior fossa mass in a child. While there are many causes, pilocytic astrocytoma and medulloblastoma account for over 60% of all childhood posterior fossa masses. Pilocytic astrocytomas have a classical appearance of being cystic lesions with an avidly enhancing mural nodule. However, 30% of pilocytic astrocytomas are solid tumours. In differentiating them from medulloblastomas, pilocytic astrocytomas often arise more peripherally and displace the fourth ventricle, where as medulloblastomas usually arise centrally from the vermis. Subarachnoid seeding is seen in up to 50% of cases of medulloblastoma. Ependymomas are also included in the differential. As these arise from the ependyma lining the ventricle, they tend to be centred on the fourth ventricle in children. Metastases are the most common cause of a posterior fossa mass in adults, but are less common in children.

Answer 69

15. C. Vestibular nerve schwannoma. Even in the absence of the imaging findings this would be a reasonable bet as it accountsfor 75% of CPA tumours. However, assessment of the imaging characteristics increases thelikelihood of this diagnosis. The second most common cause of CPA tumour is meningioma(10%). Differentiating features are lack of a dural tail, acute angle with the petrous bone (seenin schwannomas, less commonly with meningiomas, which make an obtuse angle), and, mostimportantly, expansion of the internal auditory canal (IAC). Facial nerve schwannomas can appear in the same site and appear identical, but they only constitute 4% of lesions in this site and assuch would not be the most likely cause. The facial nerve lies in the antero-superior portion ofthe IAC, although it cannot usually be separated from the mass in the IAC on imaging.

Answer 70

17. B. Elevated choline, reduced NAA, Cho/Cr ratio of 2. NAA is thought to be a marker of neuronal integrity, choline indicates cell turnover, and creatine indicates cell metabolism. Lactate is not detectable in normal brain spectra but is elevated in inflammation, infarction, and some neoplasms. Most brain conditions, whether neoplastic, vascular,or demyelinating, are associated with a reduction in NAA. A notable exception is Canavan’sdisease, which causes a rise in NAA. Choline is elevated in many disorders, but is markedly increased in high-grade neoplasms. It has been reported that the ratio of choline to creatinecan be used to help grade tumours, with a ratio over 1.5 indicating high grade in the majority ofcases. A reduced choline and NAA in an area of tumour can indicate necrosis.

Answer 71

25. D. FLAIR. On a FLAIR sequence, epidermoid cysts can be differentiated from arachnoid cysts because the former show mixed iso- to hyperintense signal, but with poor demarcation, while the signal of the latter is suppressed, like the signal of CSF. DWI offers a finding specific for extra-axial epidermoid cysts by showing very high signal.Restricted ADC compared to CSF, almost comparable to that of the brain and T2 shine-througheffect, both play an important role in the high signal intensity of epidermoid cyst at DWI. This can therefore be useful in helping to distinguish them from arachnoid cyst.

Answer 72

53. A. Rathke cleft cyst. These are benign cystic lesions of the pituitary fossa derived from the Rathke pouch. They are usually asymptomatic. Rathke cleft cysts are located in the midline between the anterior and posterior pituitary lobes and have a characteristic kidney shape on axial images. They arehomogenously hyperintense on T1WI, due to high protein concentration, and hypointenseon T2WI, due to low intracystic water content. They do not enhance following contrast administration. Absence of a fluid–fluid level is helpful in differentiating Rathke cleft cyst from hemorrhagic adenoma. Acute haemorrhage has heterogenous signal on T2WI and may demonstrate thin peripheral enhancement on T1WI. Craniopharyngiomas have variable solid, cystic, and calcified components. They demonstrate heterogenous enhancement following contrast. They may be intrasellar or suprasellar. A pseudo-fluid–fluid level may occasionally be seen in craniopharyngioma. Lipoma and cholesterol granuloma are hyperintense on both T1WI and T2WI.

Answer 73

41. A. No change in size, shape, or signal intensity on follow-up MRI. Hypothalamic hamartomas are developmental malformations located in the tuber cinereum ofthe hypothalamus. The typical patient is male, in the first or second decade of life, presenting withprecocious puberty or gelastic seizures. On MRI, they appear as well-defined pedunculated or sessile lesions that are iso/mildlyhypointense on T1WI and iso/hyperintense on T2WI, with no contrast enhancement orcalcification. Lack of interval change strongly supports the diagnosis.

Answer 74

73. B. Lactate peak on MR spectroscopy. Neuroepithelial tumours are either low grade (WHO I and II) or high grade (WHO III and IV). The classification relies on pathology, but as this requires brain biopsy it is not without significant risk. Advanced MRI techniques play an increasing role in helping to differentiate these lesions, as low-grade lesions may be managed via a ‘watch and wait’ approach. Conventional MRI is poorly sensitive for glioma grading, as low-grade gliomas can enhance (in up to 20%) and up to 30% of non-enhancing gliomas are malignant. MR perfusion can help differentaiate, as rCBV tends to increase with tumour grade. A threshold of 1.75 is commonly utilized to separate low- from high grade gliomas, but low-grade oligodendrogliomas can give misleadingly elevated rCBV values. The classic MR spectroscopy features of high-grade lesions are elevated choline and reduced NAA.In addition an elevated lactate signal is typical of high-grade lesions secondary to the anaerobic environment. ADC is usually lower in high-grade lesions, but there is considerable overlap and so ADC maps are insufficient on their own for predicting tumour grade.

Answer 75

74. B. Erosion of the adjacent porus acousticus. A large meningioma at the cerebellopontine angle can easily grow into the adjacent internal auditory meatus (IAM), but typically does so without causing any enlargement or erosion of this structure. Most vestibular schwannomas arise from the inferior vestibular nerve within the IAM and as they grow they smoothly erode the posterior edge of the porus acousticus. Although dural enhancement has been described adjacent to vestibular schwannomas, anenhancing ‘dural tail’ would be a finding more commonly associated with a lesion arising from the dura, typically a meningioma. Bony hyperostosis is a finding that is associated with meningioma. Both meningiomas andvestibular schwannomas typically show avid enhancement with intravenous gadolinium.

Answer 76

75. C. Loss of the posterior pituitary bright spot. Autoimmune hypophysitis (AH) and non-secreting pituitary adenomas can only be differentiated with certainty on histology. As a result, approximately 40% of patients with AH are misdiagnosedas having pituitary macroadenoma and undergo unnecessary surgery. Hormone production is compromised in both conditions, although a history of infertility is common with adenomas, whereas patients with AH typically achieve spontaneous pregnancy. In an attempt to develop ascoring system to differentiate the two conditions, a recent study found that features significantly associated with AH over adenoma were age <30, relation to pregnancy, homogenous gadolinium enhancement, loss of the posterior pituitary bright spot, and enlarged stalk. Features consistent with adenoma were asymmetrically enlarged pituitary, size >6 cm3, and associated sinus mucosal thickening. The normal posterior pituitary gland is bright on T1WI due to the rich content of vasopressin neurosecretory granules. This is frequently lost in AH due to direct autoimmuneinvolvement of the neurohypophysis, whereas it is conserved in the majority of adenomas, evenwhen displaced by large tumour size.

Answer 77

12 Answer B. Enhancement following gadolinium Acoustic neuromas are also known as vestibular schwannomas and are the most common tumours of the cerebellopontine angle. They arise from the perineural Schwann cells of the vestibular division of the VIII cranial nerve and are usually unilateral. In Type II neurofibromatosis they are, by definition, bilateral. A vestibular schwannoma displays the characteristic imaging appearances that are common to all schwannomas; on CT imaging they are isointense with brain parenchyma, exhibiting enhancement post contrast and containing cystic components. On MRI the lesion is isointense with brain parenchyma on T1 W images, hyperintense on T2 and displays enhancement post gadolinium.

Answer 78

21 Answer A: En plaque spread along the skull base It is assumed she has a meningioma. Erosion of the jugular foramen is suggestive of a glomus jugulare tumour while smooth expansion would be expected in a vagal schwannoma. Enhancement occurs in both neuromas and meningiomas, and therefore is not a distinguishing feature. Thickening of the dura is seen in meningitis or dural metastasis and is an unlikely finding in a jugular foramen meningioma.

Answer 79

47 Answer A: Pilocytic astrocytoma Pilocytic astrocytoma is the most likely diagnosis as it is low density on CT with calcification and nodular enhancement. They are commonly located in the vermis (50%) and are complicated by hydrocephalus. They commonly occur before the age of nine and are characteristically a cyst with an enhancing nodule. Haemangioblastoma is a serious consideration, but more commonly occurs in the paravermian position; the nodule is hyperdense on non-contrast CT and they virtually never calcify. Both lesions can be cystic with a solid enhancing nodule. Haemangioblastomas occur more commonly in adults and as part of VHL syndrome.

Answer 80

48 Answer B: Renal cell carcinoma Malignant melanoma, choriocarcinoma, oat cell, thyroid and renal cell carcinoma all cause hyperdense cerebral metastases. They all enhance brightly with contrast.

Answer 81

49 Answer D: Arising from the vermis

Answer 82

50 Answer A: Dural tail This woman has a parasagittal meningioma. Evidence of a dural tail is very typical of meningiomas but it can also occur in dura metastasis.

Answer 83

51 Answer B: Gliomatosis cerebri Gliomatosis cerebri is a grade 3 WHO classification cerebral tumour, which affects at least two or more lobes and is principally centred in the cortex and has little mass affect or architectural distortion. It typically affects patient aged 40-50 years of age. On CT imaging it can be easily missed but features are loss of the grey-white matter differentiation with minor enlargement of the cortex. On MRI imaging bright signal is seen within the affected area and contrast is minimal. Prognosis is poor with 50% one-year survival.

Answer 84

52 Answer B: Pleomorphic xanthoastrocytoma Pleomorphic xanthoastrocytoma is a superficial grade 2 tumour and accounts for 1 % of all intracranial tumours. It occurs in a younger group of patients with a mean age of 26 years. It preferentially affects the superficial temporal lobe and is cystic with an enhancing nodule and with peritumoral vasogenic oedema

Answer 85

53 Answer A: Low signal This patient has an arachnoid cyst, which typically has similar signal characteristics to CSF (bright on T2W, low on T1W and FLAIR). On DWI the signal characteristic is similar to CSF and hence is low

Answer 86

14 Answer E: Isointense to grey matter on T1-weighted images A trigeminal nerve schwannoma displays the characteristic imaging appearances that are common to all schwannomas. On CT imaging they are isointense with brain parenchyma, exhibiting enhancement post contrast and containing cystic components. On MRI imaging the lesion is likely to be isointense with brain parenchyma on T1, hyperintense on T2-weighted images and shows enhancement post gadolinium.

Answer 87

45 Answer B: Primary CNS lymphoma 1ry lymphoma is the most likely answer because of the position, the hyperdensity on CT and the necrotic centre. Cerebral lymphoma is often hyperdense due to the dense cellularity, although this may not be the case in patients who are immunocompromised. Toxoplasmosis is also a consideration but these are more often multiple. Herpes encephalitis is an unlikely diagnosis as patient is relatively well and typical imaging features are asymmetric high signal in the frontal and temporal lobes on T2W imaging.

Answer 88

46 Answer A: Arachnoid cyst Arachnoid cysts are common incidental findings, which are CSF-filled cystic lesions within the arachnoid space. They are found within the middle fossa, perisellar cisterns, retrocerebellar cisterns and cerebellopontine angle. They are thin-walled cystic lesions which are CSF density (0-20 HU) and do not enhance with contrast. There is often bone remodelling and compression of the underlying parenchyma. On MR imaging it has the same signal characteristics as CSF on Ti, T2, FLAIR and DWI. They can be complicated by haemorrhage. Epidermoids appear very similar to arachnoid cysts on CT but on FLAIR and DWI they are bright and will be brighter than CSF on T1-weighted images.

Answer 89

47 Answer A: Lipoma Intracranial lipoma is an uncommon mass accounting for I% of all intracranial tumours. They commonly present in the callosal cistern but can occur in any cistern. On CT they are well defined, of similar density to fat (-100 HU) with peripheral calcification and no enhancement. On MRI the signal characteristics are similar to fat but inhomogeneous on PD. Craniopharyngiomas are usually sellar or suprasellar. Arachnoid cysts have the same signal as CSE Epidermoids are usually lobulated and off midline. Dermoids are usually more heterogeneous.

Answer 90

48 Answer B: Craniopharyngioma Craniopharyngiomas are intrasellar or suprasellar lesions and most commonly occur in the first two decades of life. They are high signal on T2 and can be either high or low signal on T1-weighted imaging, the low signal areas being due to calcification. Bony destruction occurs in 75% of cases and also in 75% of cases the mass is principally cystic.

Answer 91

49 Answer D: Hypothalamic hamartoma Hypothalamic hamartoma is a tumour of the tuber cinereum. Patients are typically less than two years of age and present with **precocious puberty and gelastic seizures (spasmodic laughter).** They are most commonly seen in the tuber cin- ereum or mammillary bodies. On CT they present as a round well defined homogeneous mass with no enhancement. On MRI they tend to be isointense on both Ti- and T2-weighted imaging.

Answer 92

50 Answer C: Suprasellar cistern This patient has a germinoma and the second most common site is in the suprasellar region (2 0%). Germinomas account for 2 % of all paediatric brain tumours and are commonly seen in males aged between 10 and 25 years of age. Patients commonly have Parinaud's syndrome (paralysis of upward gaze). On CT there is a well-defined hyperdense mass within the pineal gland and on MRI it is isointense on Ti and low signal on T2-weighted imaging. On both CT and MRI there is bright enhancement with contrast.

Answer 93

51 Answer C: Choroid plexus papilloma Choroid plexus papillomas account for 2-5% of intracranial tumours in childhood. There is a male sex predominance and up to 80% present before the age of one year old. They are a large collection of choroid plexus fronds, which produce excess CSF leading to hydrocephalus. Five per cent transform into malignant choroid plexus carcinomas, which show signs of invasion. This is an uncommon site for astrocytomas.

Answer 94

52 Answer A: Rathke's cleft cysts Rathke's cleft cysts are embryological remnants of the Rathke's pouch. The cysts are lined by columnar and cuboidal cells and occur in the intrasellar region. They are high signal on T2 and can be high or low signal on T1-weighted imaging. Rathke's cleft cysts can compress the pituitary gland. They are usually asymptomatic but may cause hypopituitarism. Treatment is either with cyst aspiration or cystectomy.

Answer 95

56 Answer A: Ruptured dermoid cyst Dermoid cysts are usually midline and are well-defined masses with fat, skin, sebaceous glands and sweat glands. They are fat density on CT and high signal on both Ti- and T2-weighted imaging. These are prone to rupture and as the fat molecules are less dense than CSF they tend to lie in the most superior areas of the ventricles (temporal and frontal horn of the lateral ventricles).

Answer 96

58 Answer A: Hypothalamic glioma These are the most common hypothalamic masses accounting for 10-15% of supratentorial tumours in children and present between the ages of two and four years old. This child is showing visual deficits and diencephalic syndrome, which is present in up to 20% of cases. The inhomogeneous enhancement is caused by tumour necrosis. Craniopharyngioma and astrocytomas are uncommon in these sites. Hypothalamic hamartomas are rare and usually present before the age of two years old. They are round isodense lesions that do not enhance on CT.

Answer 97

64 Answer D. Hypointense on T1-weighted images, variable on T2-weighted images, homogeneous enhancement with a hypointense rim post gadolinium Medulloblastoma is the most malignant infratentorial neoplasm. The duration of symptoms is usually less than one month prior to presentation. The most common site of tumour in this age group is the vermis cerebelli and the roof of the fourth ventricle

Answer 98

23 Answer A: Epidermoid The most important differential for an epidermoid here is an arachnoid cyst. On FLAIR (fluid attenuated inversion recovery, i.e. a `water-suppressed' pulse technique) sequences, an arachnoid cyst will be low signal similar to that of stationary water while epidermoids are high signal. These could also be differentiated by diffusion-weighted MR. Both an acoustic neuroma and a cystic meningioma would have areas of enhancement on T1-weighted images.

Answer 99

39 Answer B: Pilocytic astrocytoma Pilocytic astrocytoma is one of the most common childhood cancers of the posterior fossa. It is also the most benign astrocytoma and is associated with neurofibromatosis type I. The symptoms are dependent on the position of the tumour. T2-weighted images are the differentiating sequences, as PNETs and ependymomas are isointense. Medulloblastomas are isointense on T1-weighted images and usually have a ring of vessels between the tumour and the brain

Answer 100

47 Answer D: Craniopharyngioma Craniopharyngiomas have a bimodal distribution with three-quarters occurring in the first two generations and one-quarter within the fifth decade. Patient's symptoms depend on the site of the tumour; for example, with diabetes insipidus when compression of the thalamus occurs or bitemporal hemianopia when compression of the optic chiasm. Tumours occur in the tuber cinereum, suprasellar and infrasellar regions. On CT tumours appear as a cystic solid midline mass with peripheral calcification and the solid portion enhances with contrast. On MRI the mass is typically high signal on T1- and T2 -weighted imaging with enhancement of the solid components with contrast.

Answer 101

48 Answer B: Oligodendroglioma Oligodendrocytoma is a slow-growing grade 2 cerebral tumour that is more common in men aged 30- 60 years. It has a propensity for the frontal lobes and involves both the cortex and white matter. On CT there is heavy calcification within the tumour and surrounding vasogenic oedema. Erosion of the inner table of the skull occurs, thus aiding the differential from meningiomas. There is variable enhancement with contrast. On MRI the tumour is hypointense on T1W and hyperintense on T2 and FLAIR except in the areas of calcification.

Answer 102

49 Answer A: Overproduction of CSF This child has a choroid plexus papilloma. They commonly occur in the lateral ventricles in children and the fourth ventricle and CPA in adults. They are commonly smooth lobulated masses which brightly enhance with contrast. Hydrocephalus is usually due to overproduction of CSE

Answer 103

50 Answer A: Meningioma All the listed tumours occur within the cerebellopontine angle (CPA). Both meningiomas and acoustic neuromas can cause expansion of the internal auditory canal and enhance brightly with contrast. Meningioma is the most likely because there is calcification within the lesion described.

Answer 104

51 Answer C: Low signal on T1 and high signal on T2 This patient most likely has an epidermoid as it is heterogeneous, lobulated and off midline. Epidermoids are most commonly homogeneously low signal on Ti and high signal on T2-weighted imaging.

Answer 105

55 Answer A: Low signal This patient has an arachnoid cyst, which typically has similar signal characteristics to CSF (bright on T2W, low on T1W and FLAIR). On DWI the signal characteristic is similar to CSF and so is low.

Answer 106

64 Answer E: Craniopharyngioma Craniopharyngioma can also present with diabetes insipidus from compression of the pituitary gland. Epidermoids of the CNS usually present at a later age (10-60 years old) with different symptoms but can have bony destruction and calcification. Rathke's cleft cysts and pituitary adenomas do not cause bony destruction and are unlikely to contain calcification.

Answer 107

69 Answer C: Uniformly thick enhancing wall Differentiating ring enhancing metastasis and ring enhancing abscesses can be difficult. Metastases typically appear as thick irregular ring enhancing lesions within the corticomedullary region. Abscesses tend to demonstrate a thinner, more uniform enhancing wall. Abscesses point towards ventricles and demonstrates restricted diffusion.

Answer 108

3. (b) Meningioma These are all typical features of a meningioma. Medulloblastoma is a childhood infratentorial tumour which is usually hyperdense and enhances with contrast. Lymphoma can be isodense with homogenous enhancement but usually is associated with significant peritumoral oedema and no calcifications. Glioblastoma multiforme is seen as an irregular lesion with mass effect, oedema and a heterogenous enhancement pattern. Sarcoma metastases are rare and would induce peritumoral oedema.

Answer 109

4. (a) Hypothalamic hamartoma Also called hamartoma of the tuber cinereum, this is seen in children less than 2 years of age. Precocious puberty is due to luteinising releasing hormone secretion. Craniopharyngioma presents with growth failure and visual field defects. Kallmann syndrome presents with hypogonadism in later age. Pituitary adenomas are seen in girls (9–13 years of age) and are usually prolactin or adrenocorticotropic hormonesecreting lesions.

Answer 110

20. (a) Schwannoma Vestibular schwannomas are the most common cerebellopontine angle tumours with typical imaging features as given above. These are typically benign, slow growing tumours from Schwann cells which envelop and myelinate cranial, spinal and peripheral nerves. In the skull, they most commonly arise in the cerebellopontine angle, from the vestibular portion of the 8th cranial nerve. The main differential diagnosis is meningioma, which can also grow from the 8th cranial nerve. A schwannoma is hyperintense on T2 while a meningioma is isohypointense. Also, a meningioma forms an obtuse angle with the petrous bone while a schwannoma forms an acute angle. Finally, a meningioma may have a dural tail, which is absent in a schwannoma.

Answer 111

5. (b) Craniopharyngioma This has a bimodal age distribution (5-10 years and 50-60 years) presenting with fits and visual symptoms. High signal on T1 and T2 are due to cholesterol crystals in the cyst and solid portions enhance. Germinomas are solid tumours with homogenous enhancement. They may present with visual impairment. The lesion is hypointense on T1 and slightly hyperintense on T2. Hypothalamic hamartoma is rare and arises from the tuber cinereum. Pituitary microadenoma is low signal on T1. Arachnoid cysts show cerebrospinal fluid features on MRI and do not enhance.

Answer 112

8. (c) Colloid cyst Colloid cysts are seen in the region of the interventricular foramen and cause positional and intermittent obstruction, leading to hydrocephalus and headaches. The lesion is dense on CT and high signal on T1 and T2 sequences as they commonly contain large protein molecules and the paramagnetic effect of iron and copper in the cyst. Dermoid contains fat whereas arachnoid cysts show CSF features on imaging. Meningioma is usually low signal on T1 and high signal on T2.

Answer 113

10. (a) Cerebellar haemangioblastoma These CT features are typical of this lesion. Metastases usually have ring-like enhancement or homogenous enhancement rather than having a mural nodule. Cystic astrocytomas are usually > 5 cm, show calcifications, thick walled and have no enhancing mural nodule. An arachnoid cyst is a possibility if no enhancing nodule seen. Medulloblastoma is uncommon in adults and is usually a solid tumour with homogenous enhancement.

Answer 114

11. (c) Epidermoid cyst This resembles CSF on non-enhanced CT. On MRI, the lesion is isointense, or slightly hyperintense to CSF. Incomplete attenuation on FLAIR and high signal on diffusion (suggesting restricted diffusion) concludes the diagnosis. Non enhancement is the rule.

Answer 115

20. (b) Diffuse brainstem glioma Brainstem gliomas form up to 15% of all paediatric CNS tumours. There is an association with neurofibromatosis type 1. They commonly present with symptoms of diplopia, weakness, unsteady gait, headache, dysarthria, nausea and vomiting. These are poorly marginated and involve more than 50% of the brainstem at the level of maximum involvement. Minimal or no contrast enhancement is seen.

Answer 116

21. (a) Pineal germinoma (also called pinealoma) This is the most common pineal tumour and is associated with precocious puberty in children less than 10 years old. The finding of pineal calcification before 10 years with a pineal mass enhancing with contrast is usually diagnostic. Hydrocephalus is secondary to compression of the cerebral aqueduct. Medulloblastoma is a tumour usually in the posterior fossa, and presenting in childhood. Suprasellar meningioma does not arise from the pituitary fossa

Answer 117

22. (d) Craniopharyngioma Craniopharyngioma is the most common suprasellar tumour in paediatrics and usually cystic. Calcification is seen in 90% of the cases. These lesions contain highly proteinaceous fluid, cholesterol and blood products resulting in high signal on T1, T2 and FLAIR images.

Answer 118

24. (b) Astrocytoma These MRI appearances are typical of a grade II astrocytoma. Grade III are more infiltrative and show more surrounding oedema. Oligodendrogliomas show calcifications. Arachnoid cysts show CSF density on all sequences. Metastatic lesions and lymphoma enhance with gadolinium.

Answer 119

25. (c) Haemangioblastoma This is the most common posterior fossa tumour in adults after metastases. They are usually seen in the cerebellum and there is an association with von Hippel–Lindau disease. CT appearances are typically with a large hypodense cyst and an enhancing mural nodule. The cyst wall does not usually enhance. On MRI, flow voids may be seen representing draining vessels adjacent to the nodule. Juvenile pilocytic astrocytoma is seen in young age and is not associated with feeding vessels. Metastases are usually multiple in older people.

Answer 120

31. (a) Arachnoid cyst An arachnoid cyst returns signal characteristics of cerebrospinal fluid. High on T2, intermediate on T1 and no restriction on diffusion-weighted images.

Answer 121

32. (c) Oligodendroglioma These tumours are seen in young adults and are usually located in the peripheral cerebrum. They typically begin in the hemispheric white matter and grow towards the cortex. They are well circumscribed but non-encapsulated. Calcification is a common feature.

Answer 122

33. (d) Chiasmal glioma Chiasmal glioma is associated with NF1 in 15-25% cases. Craniopharyngioma tends to displace the chiasm rather than enlarge it. It is often cystic and may show calcification. Lymphoma is more likely to involve peripheral nerves. Tuberculosis may involve the chiasm but in the setting of basal meningitis, leptomeningeal enhancement and multiple cranial neuropathies.

Answer 123

37. (b) Cerebellopontine angle lipoma Lesion has characteristics of fat on all sequences (high signal on T1 and T2 with loss of signal on fat-suppression imaging).

Answer 124

41. (c) Glioblastoma multiforme These tumours are typically inhomogeneous on CT and MRI, showing irregular areas of peripheral enhancement. Tumour necrosis is a hallmark of glioblastoma multiforme.

Answer 125

42. (c) Lymphoma This is seen not only in immunocompromised but also immunocompetent patients. On CT, the lesion is usually hyperdense showing homogenous enhancement. Resolution with steroids and/or RTx is a characteristic finding of cerebral lymphoma.

Answer 126

43. (c) Melanoma metastases The T2 shortening effect is attributed to the paramagnetic effects of iron and copper bound to melanin.

Answer 127

44. (a) Meningioma These tumours arise from the arachnoid ‘cap’ cells of the arachnoid villi.

Answer 128

Answers: (a) Not correct (b) Correct (c) Correct (d) Not correct (e) Not correct Explanation: HB is a vascular tumour of the CNS. It occurs most often in the cerebellum, where it is the most common primary neoplasm in adults. HBs are less commonly seen in the spinal cord and rarely occur elsewhere in the CNS. Cerebellar hemangioblastomas are traditionally classified into 4 types. Type one is a simple cyst without macroscopic nodule. Type II (most common) is a cyst with a mural nodule. Type III: solid tumours & type IV: solid tumours with small internal cysts.

Answer 129

Answers: (a) Correct (b) Not correct (c) Correct (d) Correct (e) Not correct Explanation: Pineoblastomas show avid enhancement on post contrast images. The isodense to hyperdense on CT. They are similar to medulloblastoma as the both are part of neuroectodermal tumour group.

Answer 130

Answers: (a) Correct (b) Correct (c) Correct (d) Not correct (e) Correct Explanation: Dermoids and epidermoids are benign lesions and slow-growing and never become malignant.

Answer 131

Answers: (a) Correct (b) Not correct (c) Not correct (d) Correct (e) Not correct Explanation: Meningiomas do not cause expansion of internal auditory canal. They are usually less bright on T2-weighted MRI. Acoustic neuromas usually enhance avidly on postcontrast images.

Answer 132

Answers: (a) Not correct (b) Not correct (c) Correct (d) Not correct (e) Correct Explanation: Medulloblastoma is the second commonest paediatric tumour, second only to astrocytoma however it is the commonest paediatric posterior fossa tumour. It occurs more commonly in males. Calcifications are seen in up to 20% of patients. Cystic changes or necrosis are seen in up to 50%. They are usually hyperdense on CT. On MRI, they are usually hypointense to grey matter on T1 images and variable appearance on T2-weighted images. Oedema is almost always seen.

Answer 133

Answers: (a) Not correct (b) Correct (c) Not correct (d) Not correct (e) Correct Explanation: CNS lymphoma are usually B-cell non-Hodgkin’s lymphoma. They are usually hyperdense on unenhanced CT. There show intermediate to low signal on T2-weighted MR images.

Answer 134

Answers: (a) Correct (b) Correct (c) Not correct (d) Not correct (e) Correct Explanation: Juvenile pilocytic astrocytomas are at the second commonest posterior fossa tumours after medulloblastoma. Only 20% of these calcify. Brainstem gliomas mostly affect the pons.

Answer 135

Answers: (a) Correct (b) Not correct (c) Not correct (d) Correct (e) Correct Explanation: Dermoid cysts are usually hyperintense on T1-weighted MR images but this signal characteristic can be seen in other lesions example lipoma. Hence their differentiation is not recommended on T1-weighted MR images. Dermoid cysts are usually seen in orbit, oral and nasal cavities however orbit is the most common site.

Tumours Flashcards

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