15 Primary intracranial anomalies Flashcards
Commonest location for arachnoid cysts?
Middle cranial fossa (related to sylvian fissure in 49% of cases)
How do arachnoid cysts occur?
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.
What cells line the wall of an arachnoid cyst?
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
What is the incidence of arachnoid cysts?
On autopsy series found to be 5 per 1000
1% of intracranial masses.
In which condition might you see bilateral arachnoid cysts?
Hurler’s syndrome
How do you classify middle fossa cysts?
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.
What are the surgical treatment options for arachnoid cyst?
needle aspiration/burr hole drainage
craniotomy and excising/fenestrating cyst walls into cisterns
endoscopic fenestration
shunting of cyst
Which type of arachnoid cyst should not be shunted?
suprasellar cysts - (promotes cyst enlargement)
Can be managed surgically with transcallosal approach or transventricular endoscopic approach. (Pierre-Khan et al)
Endocrinopathies tend to persist.
What proportion of single suture craniosynostosis have elevated ICP?
approx 11% (no ref)
What head shape does saggital synostosis cause?
scaphocephaly / dolichocephaly
What causes trigonocephaly?
metopic suture synostosis
How do you tell the difference between lambdoid suture synostosis causing posterior plagiocephaly and positional plagiocephaly?
Head shape (trapezius shape in lambdoid and parallelogram in positional) Ear position (pulled back in lambdoid and pushed forward/neutral in positional)
What is the incidence of craniosynostosis?
0.6/1000 live births
What percentage of non-syndromic saggital suture synostosis have raised ICP?
44%
Ref: Wall et al. 2014
What is the commonest single suture craniosynostosis?
Saggital suture
What is ‘Harlequin eye’?
Seen in coronal synostosis on Xray on the abnormal side because of the higher orbital bar. Can cause amblyopia as well.
What is the incidence of craniosynostosis?
0.6 per 1000 live births
Single suture craniosynostosis that can cause ambylopia?
Coronal suture
What causes trigonocephaly?
Metopic suture synostosis
What deformity does saggital suture synostosis cause?
scaphocephaly/dolichocephaly
How can you differentiate between postural plagiocephaly and posterior plagiocephaly due to do lambdoid synostosis?
Ear position
head shape
What proportion of patients with saggital suture synostosis have raised ICP?
44%
ref Wall et al 2014
What is the difference in phenotype between Aperts and Crouzons?
Aperts have syndactyly
What is Harlequin’s eye sign?
X-ray finding in unilateral coronal synostosis. Seen on the normal side as eye gets pulled up.
Craniosynostosis associated with 19p chromosome abnormality
Metopic synostosis
Which suture synostosis can be felt as an indentation rather than ridge?
Lambdoid
What is the pattern of inheritance (and which gene) is implicated in Crouzon and Aperts?
FGFR (fibroblast growth factor receptor) gene
Autosomal dominant
Can be sporadic (more likely in Aperts)
Nasal polypoid mass in newborn - what is the diagnosis?
Encephalocoele until proven otherwise
How are encephalocoeles classified?
On location, based on system by Suwanwela and Suwanwela.
- Occipital (often involves vascular structures)
- Cranial Vault
- fronto-ethmoidal - through the face
- basal
- post fossa
What is the eitiology of encephalocoeles?
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
How do basal encephalocoeles present?
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.
Define Dandy Walker Malformation
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
How do you differentiate between Dandy Walker malformation/variant and Blakes Pouch Cyst
in BPC there is no vermian agenesis or hypoplasia
What is Joubert’s syndrome?
Absence or underdevelopment of cerebellar vermis
What is PHACES syndrome?
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
What is the treatment of Dandy Walker?
Shunting the posterior fossa cyst and management of the hydrocephalus. If no hydrocephalus can be managed conservatively
What causes aqueductal stenosis?
congenital - associated with chiari or NF
Acquired
Inflammation (following haemorrhage or infection)
Tumours/cysts
Treatment options for aqueductal stenosis?
VP shunt
a Torkildsen shunt (shunting a lateral ventricle to the cisterna magna) may work in adult cases
Endoscopic third ventriculostomy
What is Aicardi syndrome?
agenesis of CC, seizures, retardation, patches of retinal pigmentation. likely X-linked
What is the incidence of intracranial lipomas?
8 in 10 000 on autopsy series
What conditions are associated with intracranial lipomas?
other midline abnormalities - agenesis of CC, spina bifida, encephalocoele, Myelomeningocoele.
How do hypothalamic hamartomas present?
gelastic seizures - present in 92%
epileptic encephalopathy
precocious puberty
developmental delay - worse if epileptic encephalopthy prolonged
behavioural disturbance
What are the subtypes of hypothalamic hamartoma?
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
What is the first line treatment of hypothalamic hamartomas?
Symptomatic. Precocious puberty treated with GnRH analogues and antiseizure medication for gelastic seizures.
Surgical/stereotactic intervention indicated for those refractory to medical treatment
