15 Primary intracranial anomalies

Question 1

Commonest location for arachnoid cysts?

Answer 1

Middle cranial fossa (related to sylvian fissure in 49% of cases)

Question 2

How do arachnoid cysts occur?

Answer 2

Congenital lesions that occur during development from splitting of the arachnoid membranes.

Therefore contain fluid that is identical to CSF, is intra-arachnoid and does not communicate with ventricle.

Question 3

What cells line the wall of an arachnoid cyst?

Answer 3

Meningothelial cells - +ve for EMA (Epithelial membrane antigen) and -ve for CEA (carcinoembryonic antigen)

May also be ‘complex’ and contain neuroglia, ependymal and other tissue types

Question 4

What is the incidence of arachnoid cysts?

Answer 4

On autopsy series found to be 5 per 1000

1% of intracranial masses.

Question 5

In which condition might you see bilateral arachnoid cysts?

Answer 5

Hurler’s syndrome

Question 6

How do you classify middle fossa cysts?

Answer 6

Galassi classification (1983)

Type 1. binconvex anterior middle-fossa. No/minimal mass effect. Communicates with subarachnoid spaces on CT with water soluble contrast.

Type 2. Rectangular shaped, in connection with anterior and intermediate sylvian fissure. Partially communicates with subarachnoid spaces on CT + WSC

Type 3. Involves whole sylvian fissure, mass effect and midline shift with bony remodelling. Minimal communication with subarachnoid space.

Question 7

What are the surgical treatment options for arachnoid cyst?

Answer 7

needle aspiration/burr hole drainage
craniotomy and excising/fenestrating cyst walls into cisterns
endoscopic fenestration
shunting of cyst

Question 8

Which type of arachnoid cyst should not be shunted?

Answer 8

suprasellar cysts - (promotes cyst enlargement)
Can be managed surgically with transcallosal approach or transventricular endoscopic approach. (Pierre-Khan et al)
Endocrinopathies tend to persist.

Question 9

What proportion of single suture craniosynostosis have elevated ICP?

Answer 9

approx 11% (no ref)

Question 10

What head shape does saggital synostosis cause?

Answer 10

scaphocephaly / dolichocephaly

Question 11

What causes trigonocephaly?

Answer 11

metopic suture synostosis

Question 12

How do you tell the difference between lambdoid suture synostosis causing posterior plagiocephaly and positional plagiocephaly?

Answer 12

Head shape (trapezius shape in lambdoid and parallelogram in positional)
Ear position (pulled back in lambdoid and pushed forward/neutral in positional)

Question 13

What is the incidence of craniosynostosis?

Answer 13

0.6/1000 live births

Question 14

What percentage of non-syndromic saggital suture synostosis have raised ICP?

Answer 14

44%

Ref: Wall et al. 2014

Question 15

What is the commonest single suture craniosynostosis?

Answer 15

Saggital suture

Question 16

What is ‘Harlequin eye’?

Answer 16

Seen in coronal synostosis on Xray on the abnormal side because of the higher orbital bar. Can cause amblyopia as well.

Question 17

What is the incidence of craniosynostosis?

Answer 17

0.6 per 1000 live births

Question 18

Single suture craniosynostosis that can cause ambylopia?

Answer 18

Coronal suture

Question 19

What causes trigonocephaly?

Answer 19

Metopic suture synostosis

Question 20

What deformity does saggital suture synostosis cause?

Answer 20

scaphocephaly/dolichocephaly

Question 21

How can you differentiate between postural plagiocephaly and posterior plagiocephaly due to do lambdoid synostosis?

Answer 21

Ear position

head shape

Question 22

What proportion of patients with saggital suture synostosis have raised ICP?

Answer 22

44%

ref Wall et al 2014

Question 23

What is the difference in phenotype between Aperts and Crouzons?

Answer 23

Aperts have syndactyly

Question 24

What is Harlequin’s eye sign?

Answer 24

X-ray finding in unilateral coronal synostosis. Seen on the normal side as eye gets pulled up.

Question 25

Craniosynostosis associated with 19p chromosome abnormality

Answer 25

Metopic synostosis

Question 26

Which suture synostosis can be felt as an indentation rather than ridge?

Answer 26

Lambdoid

Question 27

What is the pattern of inheritance (and which gene) is implicated in Crouzon and Aperts?

Answer 27

FGFR (fibroblast growth factor receptor) gene Autosomal dominant Can be sporadic (more likely in Aperts)

Question 28

Nasal polypoid mass in newborn - what is the diagnosis?

Answer 28

Encephalocoele until proven otherwise

Question 29

How are encephalocoeles classified?

Answer 29

On location, based on system by Suwanwela and Suwanwela. 1. Occipital (often involves vascular structures) 2. Cranial Vault 3. fronto-ethmoidal - through the face 4. basal 5. post fossa

Question 30

What is the eitiology of encephalocoeles?

Answer 30

two main theories: arrested closure of normal confining tissue allows herniation through persistent defect early outgrowth of neural tissue prevents normal closure of cranial coverings

Question 31

How do basal encephalocoeles present?

Answer 31

Persistent CSF leak or recurrent meningitis May be associated with other craniofacial deformities, including: cleft lip, bifid nose, optic-nerve dysplasia, coloboma and microphthalmia, hypothalamic-pituitary dysfunction.

Question 32

Define Dandy Walker Malformation

Answer 32

enlarged posterior fossa with partial (hypoplasia) or complete agenesis of the cerebellar vermis and cystic dilatation of the fourth ventricle which is distorted and encased in a neuroglial vascular membrane. Hydrocephalus is also present

Question 33

How do you differentiate between Dandy Walker malformation/variant and Blakes Pouch Cyst

Answer 33

in BPC there is no vermian agenesis or hypoplasia

Question 34

What is Joubert's syndrome?

Answer 34

Absence or underdevelopment of cerebellar vermis

Question 35

What is PHACES syndrome?

Answer 35

acronym for a group of findings including Posterior fossa malformations, cervicofacial Hemangioma, Arterial anomalies of the head and neck, Coarctation of the aorta and cardiac defects, Eye anomalies and Sternal cleft. Ratio girls:boys = 9:1. Thought to begin during gestation weeks 8–10

Question 36

What is the treatment of Dandy Walker?

Answer 36

Shunting the posterior fossa cyst and management of the hydrocephalus. If no hydrocephalus can be managed conservatively

Question 37

What causes aqueductal stenosis?

Answer 37

congenital - associated with chiari or NF Acquired Inflammation (following haemorrhage or infection) Tumours/cysts

Question 38

Treatment options for aqueductal stenosis?

Answer 38

VP shunt a Torkildsen shunt (shunting a lateral ventricle to the cisterna magna) may work in adult cases Endoscopic third ventriculostomy

Question 39

What is Aicardi syndrome?

Answer 39

agenesis of CC, seizures, retardation, patches of retinal pigmentation. likely X-linked

Question 40

What is the incidence of intracranial lipomas?

Answer 40

8 in 10 000 on autopsy series

Question 41

What conditions are associated with intracranial lipomas?

Answer 41

other midline abnormalities - agenesis of CC, spina bifida, encephalocoele, Myelomeningocoele.

Question 42

How do hypothalamic hamartomas present?

Answer 42

gelastic seizures - present in 92% epileptic encephalopathy precocious puberty developmental delay - worse if epileptic encephalopthy prolonged behavioural disturbance

Question 43

What are the subtypes of hypothalamic hamartoma?

Answer 43

pedunculated or parahypothalamic: narrower base attached to the floor of the hypothalamus (not arising within hypothalamus). No distortion of 3rd ventricle. Generally associated with precocious puberty more than seizures intrathalamic or sessile: within hypothalamus (distorting the 3rd ventricle) or broad attachment to hypothalamus. More often associated with seizures. 66% have developmental delay, 50% have precocious puberty

Question 44

What is the first line treatment of hypothalamic hamartomas?

Answer 44

Symptomatic. Precocious puberty treated with GnRH analogues and antiseizure medication for gelastic seizures. Surgical/stereotactic intervention indicated for those refractory to medical treatment