Brain Tumors Flashcards

Question

Hemangioblastoma What is it? Location? Association? Classic Appearance? When in the spinal cord, it is associated with what?

Answer 1

* Hemangioblastoma is a highly vascular WHo grade I tumor associated with von Hippel-Lindau (VHL) syndrome that occurs most commonly in the cerebellum, medulla, or spinal cord. It only rarely occurs supratentorially. * Although associated with VHL, only 30% of patients with hemangioblastoma have VHL. Hemangioblastoma in a patient with VHL has a worse prognosis. * The classic appearance of hemangioblastoma is a cystic mass with an enhancing mural nodule. Prominent vessels are often seen as tubular areas of flow void. Less commonly, a hemangioblastoma may be solid or hemorrhagic. * When in the spinal cord, hemangioblastoma is often associated with a syrinx.

Answer 2

* Pleomorphic xanthoastrocytoma (PXA) is a low-grade WHo grade II astrocytoma variant. * PXA is a rare tumor of childhood and adolescents, typically with a history of chronic epilepsy. * The most common location of PXA is the temporal lobe, where it typically presents as a supratentorial cortical cystic mass with an enhancing mural nodule. The overlying dura may be thickened and enhancing. * The main differential consideration, both by imaging and clinical presentation, is ganglioglioma; however, ganglioglioma does not usually cause dural thickening.

Answer 3

* Ganglioglioma is a rare, slow-growing neuroglial tumor that typically presents in an adolescent or young adult with medically refractory temporal lobe epilepsy. * Ganglioglioma characteristically appears as a temporal lobe cyst and enhancing mural nodule, often with calcification. ganglioglioma may cause calvarial remodeling and scalloping.

Answer 4

* Juvenile Pilocytic Astrocytoma * Pleomorphic Xanthoastrocytoma * Gangliogloma * Hemangioblastoma (remember JPA and remember PXA has "astrocyoma" in it and then remember ganglioglioma is similar to PXA. . . then you just gotta remember hemangioblastoma)

Answer 5

* **S**ubependymoma * Intraventricular **M**eningioma * **C**horoid plexus papilloma/carcinoma * Central **N**eurocytoma * **S**ubependymal Giant Cell Astrocytoma MNEMONIC: "SMCkNS (smackens!) in the ventricles"

Answer 6

* Central neurocytoma is a low-grade tumor likely of neuronal origin that occurs in young adults, from teenagers to young middle aged-patients. Prognosis is excellent. * Typical imaging appearance is a **lobulated mass attached to the septum pellucidum, with numerous intratumoral cystic areas. Calcification is common**.

Answer 7

* Choroid plexus papilloma is a rare intraventricular tumor. Choroid plexus papilloma is a low-grade (WHO I) neoplasm arising from choroid plexus epithelial cells. It is the most common brain tumor in babies \<1 year old, but it may also occur in adults. * T2-weighted images show a lobulated, heterogeneous or hyperintense mass that avidly enhances on T1-weighted MRI. * In children, the atrium of the lateral ventricle is the most common location. * In adults, the fourth ventricle is the most common location. * Less commonly, choroid plexus papilloma may arise from the third ventricle or cerebellomedullary angle (shown). * Choroid plexus papilloma and carcinoma (WHO III) are not reliably distinguishable.

Answer 8

* Intraventricular meningioma appears as a solid mass, typically in the trigone of the lateral ventricle. It tends to occur in older patients, similar to other meningiomas. * Intraventricular meningiomas are typically hypercellular and homogeneously enhance, distinguishing them from other intraventricular neoplasms.

Answer 9

* Subependymal giant cell astrocytoma (SEGA) is a low-grade (WHO I) astrocytoma variant that is associated with tuberous sclerosis. Other findings in **tuberous sclerosis** include subependymal nodules and hamartomas (cortical and subcortical). * SEGA classically is an **enhancing mass in the lateral ventricle near the foramen of Monro.**

Answer 10

* Subependymoma is a non-enhancing low-grade tumor of unclear origin thought to arise from subependymal astrocytes, ependymal cells lining the ventricles, or common precursor cells. * Subependymoma is a tumor of middle-aged and older adults. It is often found incidentally. * The most common locations are the obex of the 4th ventricle (inferior 4th ventricle) or at the foramen of Monro in the lateral ventricle. The tumor usually doesn’t enhance. * Despite their similar names, subependymoma is not related to subependymal giant cell astrocytoma or with ependymoma.

Answer 11

* Primary CNS lymphoma is lymphoma isolated to the CNS, most commonly diffuse large B-cell lymphoma. Immature blast cells form lymphoid aggregates around small cerebral blood vessels in a periventricular location. Note that the brain does not contain native lymphoid tissue. * PCNSL is known to “melt away” with chemoradiation but tends to recur aggressively. * The appearance of PCNSL depends on the immune status of the patient. Regardless of immune status, however, key imaging findings are a **periventricular location and high cellularity (hyperattenuating on CT, relatively hypointense on T2-weighted images, and reduced diffusivity).**

Answer 12

* In an immunocompetent patient, PCNSL typically presents as an enhancing periventricular mass, often crossing the corpus callosum to involve both hemispheres. Involvement of the frontal lobes and basal ganglia is most common. * The differential diagnosis for a mass involving the corpus callosum includes lymphoma, glioblastoma multiforme, and demyelinating lesion. * PCNSL in an immunocompetent individual usually enhances homogeneously, without central necrosis. This is in contrast to PCNSL in an immunocompromised patient, where central necrosis is typical.

Answer 13

* In an immunocompromised patient, PCNSL typically presents as a **periventricular ring-enhancing lesion in the basal ganglia. The ring enhancement is caused by central necrosis.** The two primary differential considerations for a ring-enhancing basal ganglial mass in an immunocompromised patient are **lymphoma and toxoplasmosis.** * Several clinical and imaging options are available to differentiate between lymphoma and toxoplasmosis: * Empirical anti-toxoplasmosis therapy and short-interval follow-up. * Thallium scanning: CNS lymphoma is thallium avid and toxoplasmosis does not take up thallium. * PET: CNS lymphoma tends to be high-grade and metabolically active. Toxoplasmosis usually does not have avid FDG uptake. * Perfusion scanning: CNS lymphoma has increased relative cerebral blood volume while toxoplasmosis is hypovascular. Note that lymphoma and toxoplasmosis cannot be reliably differentiated by enhancement. Intra-axial enhancement is a measure of capillary leakage, not perfusion. Both will enhance.

Answer 14

* Secondary CNS lymphoma represents the involvement of the CNS in a patient with known extra-cerebral lymphoma. Secondary CNS lymphoma **tends to involve the meninges and may cause leptomeningeal carcinomatosis or epidural cord compression.** * Less commonly, secondary CNS involvement of lymphoma may present as a parenchymal mass.

Answer 15

* The most common primary tumors to cause parenchymal metastases are **lung, breast, and melanoma.** * Most metastases are hematogenous and arise at the **gray-white junction**, where there is a caliber change in the small arterioles. * **Enhancement is universal**, as capillaries produced by an extra-CNS primary tumor do not have a functioning blood-brain barrier. * Larger metastases often feature marked edema, while small metastases may present as tiny enhancing foci that are apparent only on the post-contrast images.

Answer 16

* Meningioma is by far the most common extra-axial tumor. It arises from meningoepithelial cells called arachnoid “cap” cells. meningiomas typically occur in elderly adults with a female predominance and are most often asymptomatic. * The vast majority are benign, but 1-2% are anaplastic or malignant. Both benign and malignant meningiomas can metastasize, although this is uncommon. * Multiple meningiomas are seen in neurofibromatosis type 2 or following radiation therapy. * Meningiomas can occur anywhere in the neuraxis but are most commonly supratentorial and parasagittal. * Meningiomas may also be intraventricular (in the trigone/atrium of the lateral ventricle) or intra-osseous. Intra-osseous meningioma may mimic fibrous dysplasia. * On noncon CT, meningiomas are usually hyperattenuating relative to brain and approximately 25% calcify. * On MRI, appearance can be variable with iso- or slightly hypointense signal on T1-weighted images and variable signal intensity on T2-weighted images. There is typically a broad-based attachment to the dura. * Meningiomas avidly enhance. An enhancing dural tail is thought to be due to vasoactive substances released by the meningioma rather than tumor spread to the dura. * Despite the extra-axial location of most meningiomas, there may be extensive white matter edema, thought to be due to vasoactive factors and a pial vascular supply. * There is often a discordance between the size of meningioma and degree of white matter edema, with severe edema possible even with a very small tumor.

Answer 17

* Breast (most common) * Lymphoma * Melanoma * Small cell lung cancer MNEMONIC: BLaMS (kinda goes with interventricular tumors mnemonic lol)

Answer 18

MNEMONIC: Posterior fossa tumors really puts a "HaMpER" on a child's life. . . and partly in intramedullar spinal tumors! * **H**emangioblastoma (3rd most common intramedullary spinal tumor) * j**PA** (note that astrocytoma is most common intramedullary tumor in children) * **M**edulloblastoma * **E**pendymoma (note that ependymoma is most common intramedullary tumor in adults) * AT**R**T

Answer 19

MNEMONIC: I found some "HAMM" in the posterior fossa of this adult. * Hemangioblastoma * Astrocytoma * Medulloblastoma * Metastasis

Answer 20

* The cerebellopontine angle (CPA) is the region between the pons and cerebellum and the posterior aspect of the petrous temporal bone. * Important structures of the CPA include the 5th, 7th, and 8th cranial nerves, and AICA. * most lesions of the CPA are extra-axial and located in the CPA cistern itself, although some may arise in the internal auditory canal (IAC), temporal bone, or rarely intra-axially from the pons or cerebellum. * CPA masses are more common in adults. * Schwannoma, Meningioma, Arachnoid Cyst, Aneurysm, Epidermoid Cyst, Intra-axial Neoplasm.

Answer 21

* **A**rachnoid Cyst * **M**eningioma * (intra-axial **N**eoplasm) * **E**pidermoid Cyst * **S**chwannoma * **I**ntra-axial Neoplasm. * **A**neurysm MNEMONIN: "CPA angle masses can cause AMnESIA"

Answer 22

* Although meningioma is overall the most common extra-axial mass in adults, it is only the second most common mass of the CPA, representing approximately 10-15% of all CPA masses. * Meningiomas often feature a short segment of dural enhancement and may induce adjacent bony hyperostosis. Approximately 20% calcify, in contrast to schwannomas where calcification is rare. * In contrast to schwannoma, a CPA meningioma does not enlarge the porus acousticus.

Answer 23

* Schwannoma of the vestibulocochlear nerve, also known as a vestibular schwannoma, is by far the most common cerebellopontine angle mass, representing greater than 75% of all CPA masses. * Vestibular schwannoma is hyperintense on T2-weighted images and avidly enhances. * The characteristic ice cream cone appearance describes the “cone” protruding through (and widening) the porus acousticus and the “ice cream” exerting mass effect on the cerebellar-pontine junction. Schwannoma may become cystic, especially when larger. * Schwannomas of other cranial nerves in the CPA, including the facial or trigeminal nerves, are less common. Trigeminal schwannoma may extend into Meckel's cave.

Answer 24

* An arachnoid cyst is a benign CSF-filled lesion that is usually congenital. Although most arachnoid cysts are supratentorial, the cerebellopontine angle is the most common infratentorial location. * An arachnoid cyst will follow CSF signal on all sequences, including complete suppression on FLAIR. Unlike an epidermoid cyst, an arachnoid cyst does not have restricted diffusion.

Answer 25

* Vertebrobasilar aneurysm arising from PICA, AICA, vertebral or basilar, may appear as a well-defined, avidly enhancing CPA lesion and may be initially mistaken for a schwannoma or meningioma on contrast-enhanced CT. * On MRI, clues to a vascular etiology would flow void and pulsation artifacts. * MRA or CTA is diagnostic.

Answer 26

* An epidermoid cyst is a congenital lesion arising from ectopic ectodermal epithelial tissue. * Epidermoids progressively enlarge from desquamation of keratinized epithelium lining the cyst. The mass characteristically insinuates in between structures, encasing cranial nerves and vessels. Gross pathology features a characteristic “cauliflower-like” surface. * On CT, epidermoid cysts may mimic arachnoid cysts and appear as a water-attenuation cystic structure. On MRI, an epidermoid cyst has similar signal characteristics to CSF on T1- and T2-weighted images. Unlike arachnoid cysts, an epidermoid does not usually suppress on FLAIR. * Diffusion sequences show very bright signal on diffusion-weighted images. * Postsurgical DWI follow-up is critical to detect any residual focus, which will be DWI bright. * Rarely, epidermoids may exhibit signal hyperintensity on unenhanced T1-weighted imaging, also known as “white epidermoids.”

Answer 27

* A posterior fossa intra-axial neoplasm may invade laterally into the CPA. * An exophytic brainstem glioma or metastasis may invade into the CPA. * Medulloblastoma tends to occur in the midline in children, though lateral involvement of the cerebellar hemispheres can be seen in older children or young adults. * Ependymoma may extend into the CPA by squeezing through the lateral 4th ventricular foramina of Lushka * Hemangioblastoma, associated with VHL disease, typically presents in the cerebellar hemisphere as a fluid-secreting tumor with a cyst and enhancing nodule. There are often prominent flow voids feeding the tumor. * The other intracranial manifestation of VHL seen on imaging is an endolymphatic sac tumor, which occurs along the posterior petrous ridge.

Answer 28

* The pituitary gland is formed from Rathke’s pouch, which is a superior invagination from the primitive oral cavity. The pituitary gland sits in the sella turcica, a cup-shaped depression of the basisphenoid bone. The pituitary is composed of an anterior and a posterior lobe. * Rathke’s pouch closes off to form a vesicle that involutes. Sometimes, the involution is incomplete and a cleft can be left behind, which may give rise to craniopharyngioma or Rathke’s cleft cyst. * The anterior lobe of the pituitary produces and secretes endocrine hormones, including growth hormone, ACTH, prolactin, TSH, FSH, and LH (FLAT PiG). * The posterior lobe of the pituitary is derived from neuroectoderm and is composed of axons from the hypothalamus, through which vasopressin and oxytocin are transported. * The pituitary gland has a wide range of normal morphology, depending on patient age, sex, and hormonal/pregnancy status. The gland may be convex superiorly in adolescent or pregnant females. The normal posterior pituitary is hyperintense on T1-weighted MRI and is called the “posterior pituitary bright spot,” best seen on sagittal images.

Answer 29

* The empty sella is a normal variant when seen in isolation. An empty sella is partially filled with CSF, with the gland flattened against the floor of the sella. * Empty sella is also a component of the constellation of findings in pseudotumor cerebri. Pseudotumor cerebri, also known as idiopathic intracranial hypertension.

Answer 30

* Pseudotumor cerebri, also known as idiopathic intracranial hypertension, is a syndrome associated with elevated CSF pressure, visual changes, and headaches that is typically seen in obese black females. Imaging findings include empty sella, enlargement of Meckel's cave, and optic disc protrusion into the posterior globes. The ventricles are normal in size or slightly reduced in caliber. The sigmoid or transverse sinus may be stenotic.

Answer 31

* The first step in the evaluation of a sellar region mass is to determine if the mass is intrinsic to the pituitary or if the mass represents an adjacent extra-pituitary lesion. * The differential for an intrinsic pituitary mass is rather limited and includes pituitary adenoma (most common), Rathke’s cleft cyst, and hypophysitis. Craniopharyngioma may rarely occur in the sella, but essentially never occurs within the pituitary gland itself. Remember DDx for primary pituitary neoplasm: **A**denoma (mico/macro), **R**athke's cleft cyst, and **H**ypophysitis (lymphocytic/granulomatous) -MNEMONIC: "RAH in the pituitary"

Answer 32

* A pituitary microadenoma is a pituitary adenoma \<10 mm in size. Patients seek medical attention due to symptoms of hormone excess, not mass effect. * Most microadenomas are hypoenhancing relative to the pituitary, although ACTH secreting adenomas may be hyperenhancing.

Answer 33

* A macroadenoma is defined as an adenoma \>10 mm in size. Patients usually present with mass effect (e.g., compression of the optic chiasm) rather than endocrine dysfunction. * The bony sella is often enlarged. Macroadenomas may encase the carotid but tend not to narrow it. In contrast, meningiomas or metastases can narrow the carotid. Pituitary macroadenoma may bleed after medical treatment, producing a complex MRI appearance. * Intra-tumoral hemorrhage is distinct from pituitary apoplexy. Pituitary apoplexy is a clinical syndrome of a severe headache and endocrine dysfunction caused by hemorrhage into an otherwise normal pituitary.

Answer 34

* Part of RAH (intrinsic pituitary masses) * Lymphocytic hypophysitis is an autoimmune inflammatory disorder usually seen in peripartum women that may affect the pituitary and infundibulum. It presents with diabetes insipidus, headache, visual impairment, and endocrine dysfunction. * MRI shows thickening and intense enhancement of the pituitary stalk, usually with enlargement of the pituitary gland that may appear similar to a macroadenoma. * Lymphocytic hypophysitis responds to steroid therapy.

Answer 35

* Part of RAH (intrinsic pituitary masses) * Granulomatous inflammation of the pituitary and infundibulum can be secondary to sarcoidosis, Wegener granulomatosis, tuberculosis, and Langerhans cell histiocytosis (LCH) * LCH hypophysitis is a disease of children. In all cases, imaging is identical to lymphocytic hypophysitis.

Answer 36

* The most common suprasellar lesion in a child is **craniopharyngioma**, while the most common suprasellar lesion in an adult is a **pituitary macroadenoma** that has extended superiorly.

Answer 37

* **S**arcoidosis/ **S**uprasellar extension of an adenoma. * **A**neurysm. * **T**eratoma (dermoid cyst)/**T**olosa hunt. * **C**raniopharyngioma/**C**left cyst (Rathke’s). * **H**ypothalamic glioma (adults)/**H**ypothalamic hamartoma (children). * **M**eningioma/**M**etastasis. * **O**ptic nerve glioma. MNEMONIC: SATCHMO

Answer 38

* Craniopharyngioma is the most common suprasellar lesion of childhood, arising from squamous epithelial remnants of Rathke’s pouch that produce keratin. * Craniopharyngioma occurs in a bimodal age distribution. The majority of cases are lesions of childhood, but craniopharyngioma may occur uncommonly in late middle age. * Most involve both the sella and suprasellar regions. Although, craniopharyngioma may rarely involve only the sella, it is almost always separate from the pituitary gland. * Craniopharyngioma has potential for enamel production and almost always calcifies. * The characteristic intracystic machine-oil seen on gross examination is composed of desquamated squamous epithelium, keratin, and cholesterol. * MRI shows a complex cystic mass containing protein or blood products (hyperintense on T1-weighted images). * There is avid enhancement of the solid elements and cyst walls. * In contrast to Rathke’s cleft cyst, craniopharyngioma almost always enhances, is almost always calcified, and is almost always separate from the pituitary.

Answer 39

* Similar to craniopharyngioma, Rathke’s cleft cyst is also a remnant of the embryologic Rathke’s pouch, the precursor of the anterior lobe of the pituitary gland. In contrast to craniopharyngioma, Rathke’s cleft cyst is made of simple columnar or cuboidal epithelium. * While craniopharyngioma is the most common suprasellar lesion of childhood, Rathke’s cleft cyst is typically seen in middle-aged adults, twice as commonly in females. * Rathke’s cleft cyst is reportedly very common in autopsy studies (up to 22% incidence), but clinically is usually asymptomatic or discovered incidentally. * Imaging appearance is dependent on the protein content of the cyst. The intra-cystic fluid may be isointense to CSF if low protein and hyperintense on T1-weighted images if high protein. High protein content may cause incomplete nulling of the intracystic fluid on FLAIR. * The claw sign represents enhancing pituitary tissue completely wrapped around the cyst. * It is usually possible to distinguish craniopharyngioma from Rathke’s cleft cyst. * Unlike craniopharyngioma, Rathke’s cleft cyst does not enhance (although rim enhancement is often seen) and does not calcify. Rathke’s cleft cyst may occasionally be inseparable from the pituitary, but craniopharyngioma is nearly always distinct.

Answer 40

* Meningioma is the second most common suprasellar tumor in adults. Most common in middle-aged females, it typically presents with visual loss due to optic pathway involvement. * There are several dural reflections in the region of the sella from which a meningioma may arise, including the tuberculum sella, clinoid process, planum sphenoidale, and sphenoid wing. * Imaging shows isointense signal on T1-weighted images, variable signal on T2-weighted images, and uniform, intense contrast enhancement. * There is often an enhancing dural tail. meningioma may cause adjacent hyperostosis due to vasoactive factors. * An important imaging finding of a parasellar meningioma is the tendency to encase and narrow the cavernous or supraclinoid internal carotid artery. * In contrast to a pituitary adenoma, the sella is usually normal and the pituitary can be identified separately.

Answer 41

* An astrocytoma involving the visual pathway (optic nerve, optic chiasm, and optic tract) is the second most common suprasellar mass in children (craniopharyngioma is most common). A substantial minority of patients with optic pathway glioma have neurofibromatosis type 1. * In contrast to the low-grade tumor of childhood, optic glioma is an aggressive tumor when it occurs in adults. * Tumors are isointense on T1-weighted images, hyperintense on T2-weighted images, and usually enhance.

Answer 42

* The most common intracranial germ cell tumor is a germinoma, of which 80% arise in the pineal region and 20% arise in the parasellar region. * Germinomas are primarily seen in children and adolescents. * Imaging shows a homogeneous, intensely enhancing midline mass. The mass is hypointense on T2-weighted images and dark on ADC map due to hypercellularity.

Answer 43

* Epidermoid and dermoid cysts are congenital benign inclusion cysts. * Epidermoids occur most commonly in middle-aged adults in the cerebellopontine angle, but can be seen less commonly in the parasellar region. * Epidermoids follow CSF signal on T1- and T2-weighted images. In contrast to a simple arachnoid cyst, epidermoid is hyperintense on FLAIR and diffusion sequences show restricted diffusion. * Dermoids are most common in young adult males in the posterior fossa, but may occasionally occur in the parasellar region. They may contain intracystic fat which can cause chemical meningitis or ventriculitis with rupture.

Answer 44

* A saccular supraclinoid internal carotid artery aneurysm may mimic a suprasellar tumor. * Although parasellar aneurysms are relatively uncommon, it is essential never to biopsy a mass that may represent an aneurysm. * Pulsation artifact may be present on conventional MRI sequences. CTA or MRA would be diagnostic.

Answer 45

* Hypothalamic hamartoma is not a true neoplasm, but represents ectopic hypothalamic neural tissue. * It is a rare lesion of childhood that classically presents with precocious puberty and gelastic seizures (laughing spells). * Hypothalamic hamartoma characteristically appears as a sessile mass between the pituitary stalk and the mammillary bodies. * Hypothalamic hamartoma does not enhance and is isointense to gray matter.

Answer 46

* **Breast** cancer is by far the most common lesion to metastasize to the parasellar region. * Parasellar lymphoma is rare but may occur in **older adults**.

Answer 47

* Craniopharyngioma * Hypothalamic Hamartoma * Langerhans Cell Histiocytosis Hypophysitis * Optic pathway glioma * Germ Cell Tumor MNEMONIC: "CHLOG in the child's suprasella"

Answer 48

* Craniopharyngioma * Rathke's cleft cyst * Aneurysm * Meningioma * Pituatary macroadenoma extension * Lymphocytis or granulomatous hypophysitis MNEMONIC: "CRAMPL in the suprasellar region of an adult"

Answer 49

* The pineal gland is located in the midline at the level of the midbrain. It is situated between the thalami at the posterior aspect of the third ventricle. The internal cerebral veins and vein of Galen are located superior and posterior to the pineal gland, respectively. * The principal neuronal cell of the pineal gland is the pinealocyte, which is a modified retinal neuronal cell that is innervated by the sympathetic plexus originating in the retina. The pineal gland releases melatonin, which modulates the sleep/wake cycle. * The pineal gland does not have a blood-brain barrier. * A mass lesion in the pineal region may cause compression of the midbrain, compression of the cerebral aqueduct of Sylvius, or compression of the tectal plate. * Compression of the tectal plate produces Parinaud syndrome, which is the inability to look up (upward gaze paralysis), pupillary light dissociation, and nystagmus. * The first step in evaluating a pineal region mass is to determine if the lesion is arising from the pineal gland itself or from an adjacent structure. * A mass of the pineal gland is extra-axial. * Tumors of pineal cell origin tend to lift the internal cerebral veins, while tentorial meningiomas tend to depress the internal cerebral veins. The relationship of any pineal region mass to the internal cerebral veins is key for surgical planning and approach.

Answer 50

* Extragonadal germ cell tumors can be found in the pineal gland as well as other intracranial and extracranial midline locations including the suprasellar region, mediastinum, and sacrococcygeal region. Extragonadal germ cell tumors are thought to be due to aberrant migration of totipotent germ cells during early embryogenesis. * Germinoma and teratoma are germ cell tumors, which are the most common and second most common pineal region tumors, respectively. * Germinoma (extra-gonadal seminoma) is the most common pineal region tumor and has a peak incidence in the second decade of life (age 10-19). Pineal germinoma is seen much more commonly in males, but suprasellar germinoma does not show a gender predilection. * Germinoma is a highly cellular, avidly enhancing tumor that is slightly hyperdense on CT, isointense on T1- and T2-weighted images, and is dark on ADC map. Germinoma characteristically “engulfs” the pineal gland and promotes its calcification, resulting in a central area of calcification. Imaging of the entire neuraxis is recommended as leptomeningeal deposits can occur. Treatment is radiotherapy, with an excellent prognosis. Pineal germinoma may present with a synchronous suprasellar germ cell tumor.

Answer 51

* Teratoma is the second most common pineal region tumor and confers a worse prognosis than germinoma. * Teratoma has a heterogeneous imaging appearance. * Intralesional fat is suggestive of teratoma. Teratoma is prone to hemorrhage and coarse calcification.

Answer 52

* Pineal cysts are seen commonly on MRI and have a prevalence as high as 40% on autopsy series. They are more common in women. Most pineal cysts are less than 1 cm and asymptomatic, but may cause symptoms due to mass effect. * Very few pineal cysts grow and follow-up of small pineal cysts is not routinely recommended. * Pineal cysts are usually not entirely simple. Most cysts do not fully suppress on FLAIR. most cysts do display some peripheral enhancement, and rim calcification can be seen about 25% of the time. * A differential consideration is a pineocytoma, which would demonstrate internal enhancement and may have cystic components. However, a truly cystic pineocytoma is considered very rare. * A potential pitfall is that if imaging is delayed after contrast administration (by greater than 60 minutes), gadolinium may diffuse into the cyst, causing it to appear solid. In rare cases, it may not be possible to differentiate a hemorrhagic pineal cyst from pineocytoma.

Answer 53

* A pineocytoma is a low-grade (WHO grade I or II), slow-growing pinealocyte tumor. * Any solid component should enhance. Pineocytoma may feature cystic change, however, which can make differentiation from a pineal cyst difficult.

Answer 54

* Pineoblastoma is a highly malignant WHo grade IV tumor of young children, of the same primitive neuroectodermal tumor (PNET) type as medulloblastoma. * The term trilateral retinoblastoma is used when bilateral retinoblastomas are also present (both the retina and pineal gland are light-sensing organs). The sella is additionally involved in quadrilateral retinoblastoma. * Pineoblastoma often presents with obstructive hydrocephalus. * Pineoblastoma characteristically appears as a poorly defined pineal mass that may invade into adjacent structures. High cellularity causes restricted diffusion. * In contrast to germinoma, which “engulfs” and induces calcification of the pineal gland, pineoblastoma peripherally calcifies in a pattern that has been likened to “exploded” calcification. * Pineoblastoma has a propensity for leptomeningeal metastasis and CSF seeding.

Answer 55

* Due to the lack of a blood-brain barrier, metastases to the pineal gland occur relatively commonly, but rarely in the absence of a known malignancy. * Leptomeningeal disease is present in two-thirds of patients with pineal metastasis.

Answer 56

* **Gliomas**: Gliomas (most commonly astrocytomas) of varying grade may occur in adjacent intraaxial structures such as the tectum, midbrain, or splenium of the corpus callosum. * **Vein of Galen Aneurysm:** Despite the name, a Vein of Galen “aneurysm” is not a true aneurysm. Instead, it represents dilation of the Vein of Galen due to an arteriovenous fistula between the anterior or posterior circulation and the venous plexus leading to the Vein of Galen. * **Quadrigeminal Plate Lipoma**: A lipoma of the quadrigeminal plate is a rare lesion that be seen in isolation or associated with agenesis or hypoplasia of the corpus callosum. The quadrigeminal plate is another name for the tectum. * **Meningioma**: The tentorial apex, adjacent to the pineal gland, is a characteristic location for meningioma. As previously discussed, a tentorial meningioma tends to depress the internal cerebral veins, in contrast to a pineal-based mass, which typically elevates the internal cerebral veins.

Brain Tumors Flashcards

(80 cards)