Paediatrics

Question 1

What are the causes of an anterior mediastinal mass?

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Answer 1

• Nodal masses: lymphoma, Castleman’s disease [rare], metastatic nodal disease
• Thymic mass: thymic infiltration (e.g. lymphoma, leukaemia, thymic hyperplasia, thymoma [rare])
• Germ cell tumours: teratoma, dermoid
• Vascular malformations
• Retrosternal goitre [rare]
• Anterior diaphragmatic hernia (Morgagni hernia)
• Pericardial cysts [rare]

Lymphoma is the most common cause of a mediastinal mass in the paediatric age group accounting for over 25% of all mediastinal tumours in children.

Question 2

What are the causes of a middle mediastinal mass?

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Answer 2

• Lymph nodes: lymphoma, tuberculosis (TB), Castleman’s disease [rare], metastatic nodal disease
• Oesophageal pathology: duplication cyst, hiatus hernia, achalasia, gastric pull-up or interposition graft
• Other foregut duplication cysts: bronchogenic cyst or neurenteric cyst
• Vascular pathology: mediastinal haematoma or aneurysm (post-trauma)
• Vascular malformations

Question 3

What are the causes of a posterior mediastinal mass?

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Answer 3

• Neurogenic: neuroblastoma, ganglioneuroma, neurofibroma, schwannoma
• Phaeochromocytoma, paraganglioma, peripheral neuroectodermic tumour (PNET)
• Posterior diaphragmatic hernia (Bochdalek hernia)
• Extra-medullary haematopoiesis [rare]
• Vascular malformations
• Nodal metastatic disease

Question 4

What is the incidence of Hodgkin’s disease (HD) in children less than 5 years of age?

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Answer 4

HD is rare in children less than 5 years of age, but the incidence increases in later childhood and teenage years.

Systemic symptoms are more common with HD.

Question 5

Which type of lymphoma is more common in childhood?

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Answer 5

Overall, NHL is more common than HD in childhood.

The incidence of NHL increases greatly over the first 5 years of life and then continues to rise steadily throughout life.

Question 6

How can acute lymphoblastic leukaemia present?

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Answer 6

It can present with thymic infiltration and a large anterior mediastinal mass.

It can be difficult to differentiate the disease from lymphoblastic lymphoma (sub-type of paediatric NHL) as the malignant cells are phenotypically identical.

Question 7

How would a malignant lymphoma appear on a CXR?

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Answer 7

CXR is frequently diagnostic in malignant lymphoma and usually shows a bulky anterior mediastinal mass that may extend into the middle or posterior mediastinum.

Calcification can be seen at presentation but is usually associated with previous radiotherapy or chemotherapy.

Question 8

What are important complications to identify on CT for large mediastinal mass?

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Answer 8

• Superior vena caval obstruction (SVCO)
• Airway compromisation (tracheal compression)

Computed tomography is used to monitor treatment and detect disease progression following the diagnosis of lymphoma.

Question 9

Magnetic resonance imaging is complementary, but is not routinely used at diagnosis. Why is this?

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Answer 9

Magnetic resonance imaging is not routinely used at diagnosis due to problems with breathing and cardiac motion artefact. Moreover, MRI is not able to assess the pulmonary parenchyma.

Question 10

What is the 2nd most common cause of an anterior mediastinal mass in childhood, after lymphoma?

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Answer 10

Germ cell tumours (10%)

Germ cell tumours encompass teratomas, and malignant tumours such as seminoma, embryonal carcinoma, teratocarcinoma, and endodermal sinus (yolk sac) tumour.

Question 11

In which mediastinal compartment are mediastinal germ cell tumours most likely to be found?

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Answer 11

Anterior and superior mediastinum and often contain calcification

Mature teratomas are benign lesions, whereas immature teratomas are potentially malignant but have clinical and biological behaviour similar to mature teratomas in children less than five years of age. Most anterior mediastinal germ cell tumours are benign.

Question 12

What are the internal characteristics of a mediastinal germ cell tumour on CT?

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Answer 12

Complex mass with cystic and solid areas containing fat and irregular calcifications

Question 13

Malignant mediastinal tumours are confirmed histologically. What serum tumour markers are raised?

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Answer 13

• Alpha-fetoprotein (AFP)
• β-HCG

Question 14

True or false?

Thymic hyperplasia almost always occurs with an autoimmune disease.

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Answer 14

False

Thymic hyperplasia can occur with myasthaenia gravis, Grave’s disease and other autoimmune diseases but is frequently idiopathic.

Question 15

True or false?

In cases of thymic hyperplasia, the gland increases in size and weight but remains architecturally normal.

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Answer 15

True

The gland increases in size and weight but remains architecturally normal. Heterogeneity, nodularity, calcification or cystic changes in the thymus are always abnormal in children and raise the possibility of infection, infiltration or tumour within the gland.

Question 16

True or false?

Thymic cysts are rare and usually asymptomatic

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Answer 16

True

They can, however, be complicated by haemorrhage causing sudden enlargement, which may compress the airway leading to acute respiratory distress.

Question 17

True or false?

On imaging, thymic cysts are always multilocular.

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Answer 17

False

On imaging studies, thymic cysts are unilocular or multilocular and contain fluid.

Question 18

What are indicators of a thymomas malignancy?

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Answer 18

• Increasing size
• Invasion of adjacent mediastinal structures
• Associated pleural effusion

Differentiation between benign and malignant lesion cannot be made with certainty on imaging.

Question 19

What is Castleman’s disease?

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Answer 19

Castleman’s disease probably represents a diverse group of rare lymphoproliferative disorders rather than a single disease entity. It is otherwise known as angiofollicular lymphoid hyperplasia or giant lymph node hyperplasia.

The disorder can be localised or multicentric but, in children, it is usually a localised, benign condition and many patients are asymptomatic.

Question 20

Which chromosomal abnormalities are mediastinal lymphatic malformations associated with?

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Answer 20

Turner’s syndrome and trisomies

The mediastinum is an uncommon site for vascular malformations to occur, but the majority are lymphatic in origin.

Appear as smooth soft tissue masses often in the first two years of life. Spontaneous shrinkage can occur and sudden enlargement is an indication of bleeding or inflammation.

**MRI **is the imaging modality of choice!

Question 21

CT and MRI imaging features of haemangiomas?

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Answer 21

• CT: Homogenous masses with intense, persistent enhancement, usually organised in lobular pattern.
• MRI: Typically intermediate signal intensity on T1W and high signal intensity T2W with vascular flow voids in and around the lesion.

Haemangiomas are benign tumours of endothelial cells common in infancy.

Question 22

What primary tumours commonly metastasise to mediastinal lymph nodes?

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Answer 22

• Osteogenic sarcoma
• Wilm’s tumour
• Ewing’s sarcoma
• Neuroblastoma

Inflammatory causes of middle mediastinal lymph node enlargement are even less common, mostly due to granulomatous disease, including tuberculosis (TB).

Question 23

Chest radiograph shows a discrete, soft tissue attenuation, rounded sub-carinal mass. What middle mediastinal mass is this likely to be?

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Answer 23

Bronchogenic cyst

Bronchogenic cysts are the most common type of congenital malformations of the embryonic foregut.

They are thin-walled cysts filled with mucoid material that rarely communicate with the tracheobronchial tree.

They can migrate during development and may be found in the neck, pericardium or at vertebral or subpleural sites.

Question 24

Neurenteric cysts are frequently right-sided and often associated with vertebral body anomalies. Can you think of any such vertebral anomalies?

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Answer 24

• Hemivertebra
• Butterfly verterbra
• Anterior spina bifida

Neurenteric cysts occur when there is failure of separation of the foregut and notochord.

More than 50% of children with a neurenteric cyst have abnormal neurology.

Question 25

What are the MRI appearances of a foregut duplication cyst? ## Footnote 5_030

Answer 25

* Hypointense on T1W * Hyperintense on T2W ## Footnote Proteinaceous fluid within the cysts can increase the signal intensity on T1W sequences and blood products give variable signal intensities on T1W and T2W sequences.

Question 26

What are the causes of pneumomediastinum in children? ## Footnote 5_030

Answer 26

* **Trauma** * Asthma * Foreign body aspiration * Complication of positive pressure ventilation ## Footnote Mediastinal air is seen as a thin, lucent stripe of air outlining the contours of the mediastinal structures, particularly the large vessels. When mediastinal air elevates and outlines the lobes of the thymus in younger children this appearance is often likened to **'angel wings'**.

Question 27

Name two benign variants of neurogenic tumours originating in the nerve sheath. ## Footnote 5_030

Answer 27

* Schwannoma * Neurofibroma ## Footnote Both have similar radiographic appearances, being **sharply marginated spherical or lobulated paraspinous masses** and schwannomas may contain **calcification**. The tumours can erode or destroy ribs and widen nerve root foramina. * CT: Homogenous or heterogenous appearances * MRI: Low-intermediate signal intensity on T1W and high signal intensity on T2W

Question 28

Name four malignant variants of neurogenic tumours originating in the nerve sheath. ## Footnote 5_030

Answer 28

* Malignant schwannoma * Malignant neurofibroma * Spine cell sarcoma * Neurogenic fibrosarcoma ## Footnote Malignant tumours of nerve sheath origin are very rare in children but can occur in **adolescents**. These are often high-grade malignancies, many occurring in patients with NF1.

Question 29

Name a benign variant of neurogenic tumours originating in the autonomic ganglia. ## Footnote 5_030

Answer 29

Ganglioneuroma ## Footnote These are benign, sympathetic neural tumours, representing 40-60% of this group.

Question 30

Name two malignant variants of neurogenic tumours originating in the autonomic ganglia. ## Footnote 5_030

Answer 30

* Ganglioneuroblastoma * Neuroblastoma ## Footnote Ganglioneuroblastomas are **uncommon** and have histological features of both neuroblastoma and ganglioneuroma. Their malignant potential is variable and this is also reflected in their prognosis. Neuroblastoma is the **most malignant** of the ganglion tumours. They are fast-growing tumours with malignant behaviour exhibited in over 50%. The tumour may manifest due to neural compression, thoracic scoliosis or symptoms related to the production of **catecholamine**.

Question 31

Name two benign variants of neurogenic tumours originating in the paraganglionic system. ## Footnote 5_030

Answer 31

* Phaeochromocytoma * Paraganglioma Malignant variants are: * Malignant phaeochromocytomas * Malignant paraganglioma ## Footnote Approximately 10% of phaeochromocytomas are found in **extra-adrenal locations** and these are known as paraganglionic tumours. If the tumours secrete catecholamine, symptoms such as the following may be present: * Hypertension * Flushing * Watery diarrhoea **Iodine-123 MIBG **scanning is also useful in the detection of paragangliomas.

Question 32

Name a variant of neurogenic tumours originating in the peripheral neuroectodermic tumour (PNET). ## Footnote 5_030

Answer 32

Askin tumour ## Footnote PNET is a generic term for small, round tumours that are likely neural in origin.

Question 33

What the imaging modality of choice for evaluating **posterior** mediastinal masses detected on a CXR? ## Footnote 5_030

Answer 33

MRI

Question 34

What are the MRI appearances of sympathetic ganglion tumours? ## Footnote 5_030

Answer 34

* Intermediate signal intensity on T1W * High signal intensity on T2W ## Footnote Although CT can better detect calcification and bony involvement, including metastatic disease, MRI is superior in determining chest wall invasion and intraspinal extent.

Question 35

What is the role of radioisotope scintigraphy in a patient with suspected ganglion cell tumour? ## Footnote 5_030

Answer 35

It is an essential component of the imaging of the patient. **Iodine-123 metaiodobenzylguanidine (MIBG)** is taken up in **autonomic ganglion cell tumours** and **paragangliomas**, and is particularly valuable in: * Detection of metastatic disease * Monitoring response to treatment

Question 36

What are the MRI appearances of paraganglionic tumours? ## Footnote 5_030

Answer 36

* Lower signal intensity than liver on T1W * Very high signal on T2W

Question 37

What are the types of congenital diaphragmatic hernias? Which is the most common type? ## Footnote 5_030

Answer 37

1. **Posterior** hernia (foramen of **Bochdalek**) - Most common type and more frequent on the **LEFT** side (75%) 2. **Anterior** hernia (foramen of **Morgagni**) - Less common and more frequent on **RIGHT** side ## Footnote *PBL and AMR

Question 38

What does a pleuropulmonary pseudotumour mimic? ## Footnote 5_030

Answer 38

Paraspinal mass ## Footnote Pleuropulmonary pseudotumour is the name given to atypical left lower lobe pneumonia with collapse or consolidation. This is thought to occur because of a lax or absent attachment of the pulmonary ligament, which allows the affected segment to collapse towards the mediastinum. Clinical signs and symptoms of infection in this situation is reassuring and **an irregular border** to the 'mass' on CXR and CT is helpful in the differentiation between pseudotumour and actual posterior mediastinal tumours.

Question 39

What are the most common mediastinal masses in children? ## Footnote 5_030

Answer 39

* Malignant lymphoma * Benign thymic enlargement * Teratomas * Duplication cysts * Neurogenic tumours

Question 40

Developmental dysplasia of the hip (DDH) is the most common disorder of the MSK system in infancy. Is it known to affect the femoral head or acetabulum? ## Footnote 5_126

Answer 40

Acetabulum ## Footnote The hallmark of DDH is acetabular dysplasia resulting in a **shallow or dysmorphic socket** for the femoral head. Shearing forces from instability and displacement of the femoral head damage the growth plate of the acetabular roof preventing normal ossification. When DDH is diagnosed late **(>4 months)** in a child starting to walk with abnormal gait, **surgical intervention** is often needed to reposition the femoral head into the joint socket.

Question 41

What are the names of the neonatal clinical examination to assess for DDH? ## Footnote 5_126

Answer 41

* Barlow manoeuvre - Tests hip dislocatability * Ortolani test - Aims to reduce a dislocated hip ## Footnote These are performed at **birth and 6 weeks of ages**, but have a low positive predictive value. The role of imaging is to: * Make a diagnosis * Monitor treatment * Decide when treatment can end

Question 42

When does the femoral head ossific nucleus become visible on x-ray? ## Footnote 5_126

Answer 42

Within the first 9 months after birth ## Footnote Infants **over the age of 1 year** requires plain radiographs for diagnosis as the ossific nucleus if the limiting factor for the use of ultrasound.

Question 43

What is the Hilgrenreiner's line? ## Footnote 5_126

Answer 43

A line connecting the superolateral margin of the triradiate cartilage of the two hips. ## Footnote The baseline for the acetabular index and Perkins’ line

Question 44

What is the acetabular index line? ## Footnote 5_126

Answer 44

A line drawn from the most superolateral ossified edge of the acetabulum to the superolateral margin of the triradiate cartilage to form an angle with the baseline (Hilgenreiner's). ## Footnote It averages **27.5°** in the new born with an upper limit of 30°.

Question 45

What is the Perkins' line? ## Footnote 5_126

Answer 45

A line drawn from the most superolateral ossified edge of the acetabulum perpendicular to the baseline

Question 46

Name the labelled anatomy (1-9) ## Footnote 5_126

Answer 46

1. Bony femoral shaft 2. Cartilaginous femoral head 3. Capsular fold (3) 4. Joint capsule (4), 5. Labrum 6. Cartilaginous acetabular roof 7. Bony acetabular roof 8. Lower limb of ilium adjacent to triradiate cartilage 9. Bony rim

Question 47

# Graf types 1-4 What are the angle measurements that would indicate a normal hip joint? ## Footnote 5_126

Answer 47

Type 1: hips (α 60° or more) are normal 'mature' hip joints and should be developed by 3 months Type 2: immature hip joints * Type 2a (α 43-59°) is appropriate for a child <3 months of age * Type 2b (α 50-59°) is called dysplastic if the child is >3 months of age * Type 2c (α 43-49°) is critical and may dislocate without treatment Type 3: (α <43°) the cartilage roof is displaced upwards Type 4: (α <43° or usually not measurable) the cartilage roof displaced downwards towards the original acetabulum ## Footnote * Graf types 1 and 2 (centred hips) * Graf types 3 and 4 (decentred hips)

Question 48

Which hips are unstable? ## Footnote 5_126

Answer 48

* All decentred hips (types 3 and 4) * Some 2c (critical) hips * Someone entirely normal neonatal hips

Question 49

What is the abnormality? ## Footnote 5_127

Answer 49

There is marked irregularity, fragmentation and sclerosis of the **right proximal femoral epiphysis**. Appearances are in keeping with **Perthes disease**. ## Footnote * Legg-Calve-Perthes disease is idiopathic **avascular necrosis** of the proximal femoral epiphysis * Typically occurs in the younger child and is more common in boys * It can be bilateral, asymmetrical and the contralateral hip may present at a later stage * Absence of the normal femoral epiphysis can cause abnormal acetabular remodelling

Question 50

MRI is useful in confirming a diagnosis of Perthes disease. What are the MRI features? ## Footnote 5_127

Answer 50

* **Hypointense **irregularity of the ossification nucleus on T1W and T2W * Marked synovial hypertrophy and joint effusion

Question 51

What is the abnormality? ## Footnote 5_127

Answer 51

Avulsion fracture at the right anterior/inferior iliac spine.

Question 52

What muscle originates from the anterior superior iliac spine? ## Footnote 5_127

Answer 52

Sartorius

Question 53

What muscle originates from the inferior superior iliac spine? ## Footnote 5_127

Answer 53

Rectus femoris

Question 54

Can ultrasound alone diagnose septic arthritis? ## Footnote 5_127

Answer 54

No. The presence of an effusion is **non-specific**! In small children, the absence of an ultrasound detectable effusion **does not** exclude a septic arthritis. ## Footnote Only Perthes disease can be confidently diagnosed by ultrasound. Differentiating between septic arthritis and transient synovitis can be difficult! Septic arthritis should be treated properly with **joint lavage and antibiotic cover**.

Question 55

What is the abnormality? ## Footnote 5_127

Answer 55

Small lucency on the medial aspect of the proximal right femoral metaphysis. There is surrounding sclerosis with a small dense calcific focus and features are suggestive of **osteoid osteoma**. ## Footnote Bone scan of osteoid osteoma shows an area of increased activity in the proximal right femoral metaphysis. Note this is a posterior image and therefore the discrepancy in side orientation.

Question 56

Describe the CT appearances of an osteoid osteoma. ## Footnote 5_127

Answer 56

Sclerosis around the lucent area with a central dense centre.

Question 57

Which MRI sequence is the **most sensitive** in detecting oedema in the muscles, bones or fluid in the joint? ## Footnote 5_127

Answer 57

Short tau inversion recovery (STIR)

Question 58

What is the abnormality? ## Footnote 5_127

Answer 58

Alteration of the fat plane around the right superior pubic ramus. Soft tissue swelling is seen as a convexity over the pubic ramus. ## Footnote MRI shows oedema and soft tissue swelling in the superior pubic ramus and surrounding soft tissues.

Question 59

What conditions can cause avascular necrosis? ## Footnote 5_127

Answer 59

* Gaucher's disease * Sickle cell disease * Steroids * Juvenile dermatomyositis * Juvenile idiopathic arthritis

Question 60

What is SUFE? ## Footnote 5_127

Answer 60

**Slipped upper femoral epiphysis** - Posterior medial movement of the proximal femoral epiphysis * More common in **adolescent boys** than girls * Associated with **obesity**, endocrine dysfunction, rickets and previous DDH * Acute or gradual onset * Greater risk of SUFE on the contralateral side if positive previous history

Question 61

What x-ray views are used to assess for SUFE? ## Footnote 5_127

Answer 61

AP and frog lateral views

Question 62

What is the most common vascular tumour in paediatric patients? ## Footnote 5_031

Answer 62

Haemangiomas ## Footnote Vascular malformations, which are less common than haemangiomas, but are very important and easy to understand if you recognise the four basic types of vascular malformation.

Question 63

What are the MRI appearances of an haemangioma? ## Footnote 5_031

Answer 63

* Well-defined and homogenous * Isointense on T1W * Bright on T2W * Signal voids within the lesion (high vascularity)

Question 64

What complication is associated with venous malformations? ## Footnote 5_031

Answer 64

Recurrent venous thomboses ## Footnote Ultrasound is vital in confirming that the lesion: * Is venous not lymphatic * Contains slow-flowing or stagnant blood and is not a fast-flowing arteriovenous connection or fistula

Question 65

What are the MRI appearances of a venous malformation? ## Footnote 5_031

Answer 65

* Isointense to muscle on T1W * Bright on T2W ## Footnote Interventional radiologists may offer injection sclerotherapy to induce fibrosis and shrinkage of the lesion.

Question 66

What are the associated complications for lymphatic malformations? ## Footnote 5_031

Answer 66

* Mass effect * Prone to **spontaneous haemorrhage** * Very prone to **infection** ## Footnote * Typical lesions contain large, thin-walled cysts * Also known as cystic hygroma (H&N)

Question 67

What are the MRI appearances of a lymphatic malformation? ## Footnote 5_031

Answer 67

* Isointense to muscle on T1W * Bright on T2W ## Footnote Lymphatic malformations look very similar to venous malformations, except they do not enhance.

Question 68

Is ultrasound sensitive at detecting an AVM? ## Footnote 5_031

Answer 68

Useful to confirm presence of extremely high flow within the lesion (only real value) ## Footnote Magnetic resonance imaging protocols need to be well designed to fully delineate the anatomy of a high-flow lesion.

Question 69

What imaging modality is the best initial scan to perform to assess a vascular anomaly? ## Footnote 5_031

Answer 69

Ultrasound: * High flow vs low flow * Solid vs cystic ## Footnote Cross-sectional imaging should be conducted in the form of **MRI** wherever possible. Computed tomography provides less useful information and carries a **high radiation burden**.

Question 70

What are the most common type of tumour to arise from the cerebral hemispheres in children? ## Footnote 5_112

Answer 70

Astrocytomas (30%) ## Footnote * Cortical lesions are often small presenting with seizures * Deep lesions are often large presenting with signs and symptoms of raised ICP * The histology of paediatric supratentorial astrocytoma varies from low grade (WHO Grade 1) **pilocytic astrocytoma** through to high-grade (WHO Grade 4) **glioblastoma multiforme**

Question 71

How are low and high-grade astrocytomas differentiated? ## Footnote 5_112

Answer 71

This difference is demonstrated by comparing the histology and MR signal of the solid components of the tumours, with their corresponding histopathological slides. ## Footnote **The higher the grade of the astrocytoma, the more cellular the solid component of the tumour.** This affects the CT density and MR intensity of these tumours and may help suggest the presence of a low-grade astrocytoma vs a more malignant tumour.

Question 72

Where are pilocytic astrocytomas most commonly centred? ## Footnote 5_112

Answer 72

Basal ganglia and thalami ## Footnote Patients with **neurofibromatosis type 1 (NF1)** have an increased risk of all types of astrocytoma. Primary treatment is **surgical excision**, although this may be incomplete in deep lesions, where risk of damage to important central structures limits excision.

Question 73

What are the CT appearances of a pilocytic astrocytoma? ## Footnote 5_112

Answer 73

* Low density solid components * Heterogenous enhancement (95%) * Rare calcification (20%) * Very rarely haemorrhage * No peri-tumoural oedema

Question 74

What are the MRI appearances of a pilocytic astrocytoma? ## Footnote 5_112

Answer 74

* Solid components: T1 iso-/hypointense and very T2 hyperintense to grey matter * Cystic components: T1 and T2 hyperintense to CSF

Question 75

What is the most common primary intra-cerebral tumour in adults? ## Footnote 5_112

Answer 75

Glioblastoma multiforme (GBM) - WHO grade 4 astrocytoma ## Footnote * Rare in children * May cross over to the contralateral hemisphere via the corpus callosum - **'butterfly glioma'** * May also spread into the **subpial space** via the CSF * Distant metastases are rare * **Poor prognosis** (better in children)

Question 76

What are the CT appearances of a glioblastoma multiforme? ## Footnote 5_112

Answer 76

* Heterogenous mass * Central necrosis * Intra-tumoural haemorrhage * Marked peri-tumoural vasogenic oedema * Iso-/mildly hypodense solid components * Rare calcification

Question 77

What are the MRI appearances of a glioblastoma multiforme? ## Footnote 5_112

Answer 77

* Heterogenous mass * Large areas of necrosis * Intra-tumoural cysts * Sub-acute haemorrhage * Marked peri-tumoural vasogenic oedema * Vivid heterogenous enhancement of solid components

Question 78

What type of astrocytic tumour is almost exclusively in tuberous sclerosis? ## Footnote 5_112

Answer 78

Subependymal giant cell astrocytoma (SEGA) - WHO grade 1 astrocytoma ## Footnote *** 5-15% of TS patients develop a SEGA** * Usually along the wall of the lateral ventricle adjacent to the foramina of Munro * Occur at any age (peak age: 5-10 years old) * Good prognosis (tumour occurence is unusual) * May occasionally haemorrhage

Question 79

What are the CT appearances of a SEGA? ## Footnote 5_112

Answer 79

On CT: * Hypo-/isodense mass * May contain calcification * Heterogeneous marked enhancement ## Footnote General image findings: * Lobulated mass adjacent to the foramen of Munro * Presence of intracerebral features of TS: subependymal hamartomas and subcortical tubers * Hydrocephalus

Question 80

What are the MRI appearances of a SEGA? ## Footnote 5_112

Answer 80

* Heterogenous * T1 hypo-/isointense to grey matter * T2 hyperintense to grey matter ## Footnote The most reliable way to distinguish a giant cell astrocytoma is **interval growth**.

Question 81

What tumour develops from the ependymal lining of the ventricles? ## Footnote 5_112

Answer 81

Ependymoma - WHO grade 2 (low-grade well-differentiated) or 3 (high-grade anaplastic tumour) ## Footnote * Presentation is variable depending on site of origin * Prognosis is highly dependent on extent of resection * CSF metastases may occur (poor prognostic finding) * **One third of ependymomas arise supratentorially in the periventricular white matter**

Question 82

What are the CT appearances of an ependymoma? ## Footnote 5_112

Answer 82

* Large variably enhancing heterogenous mass * Calcification (50%) ## Footnote Supratentorial ependymoma typically arise in the **periventricular white matter**, are usually spherical, lobulated and well-demarcated, with **little peritumoural oedema**.

Question 83

What are the MRI appearances of an ependymoma? ## Footnote 5_112

Answer 83

* **Variable T1 and T2 signa**l due to small cysts, blood products and calcification * None to mild enhancement

Question 84

What supratentorial tumour is histologically similar to infratentorial medulloblastoma? ## Footnote 5_112

Answer 84

Supratentorial primitive neuroectodermal tumour (PNET) ## Footnote * Rare tumour (1% of paediatric primary brain tumour) * May arise from cerebral hemispheres, pineal gland or suprasellar region * **CSF metastases are common** * Treatment is aggressive surgery + chemotherapy + craniospinal radiotherapy * Supratentorial PNET have a worse prognosis than medulloblastoma

Question 85

What are the CT appearances of a supratentorial PNET? ## Footnote 5_112

Answer 85

* Heterogenous mass with iso-/hyperdense solid components * Calcification (50-70%) * Heterogenous enhancement * Mild peri-tumoural oedema * Necrosis and haemorrhage (common)

Question 86

What are the MRI appearances of a supratentorial PNET? ## Footnote 5_112

Answer 86

* Heterogenous mass with areas of necrosis * Blood products of varying ages * Heterogenous enhancement * Mild peri-tumoural oedema * Solid component:T1 hypo-/isodense to grey matter and T2 iso-/hyperintense to grey matter ## Footnote It may not be possible to reliably distinguish supratentorial PNET from supratentorial ependymoma, but it is worth noting that **PNET are more common and are likely to enhance more**.

Question 87

What tumour arises from dysplastic germinal matrix cell and migrate out to cortex? ## Footnote 5_112

Answer 87

Dysembryoplastic neuroepithelial tumour (DNET) ## Footnote * Accounts for 1-2% of primary intracranial tumours in the under 20-year-olds * It is solid and may have microcystic components * No or minimal growth over a long time interval

Question 88

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Question 89

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Question 90

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