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