Ch15 Intracranial anomalies Flashcards
What are the most common locations for arachnoid cysts?
Middle fossa (50% in the sylvian fissure), CPA (10%), suprasellar (10%) and posterior fossa (10%).
What are the imaging features of an arachnoid cyst?
Follows CSF on call sequences and associated with remodelling of the bone.
How do you manage an incidental arachnoid cyst?
MRI+C and single further f/u study in 6 months to rule out increase in size.
What is the aetiology of an arachnoid cyst?
Developmental splitting of the arachnoid membrane. Histologically are lined by meningothelial cells and are positive for EMA.
What is the incidence of arachnoid cysts?
5 per 1000 at autopsy
What condition are bilateral arachnoid cysts associated with?
Hurler’s syndrome (mucopolysaccaridosis)
What is the main differential diagnosis of an arachnoid cyst?
Epidermoid (shows restricted diffusion) Porencephalic cyst (lined by WM) Schizencephaly (lined by heterotopic GM)
How do suprasellar arachnoid cysts present?
Endocrinopathy Developmental delay Hydrocephalus Visual loss Precocious puberty Bobble-head doll syndrome
What is the classification for arachnoid cysts?
Galassi classification 1 - temporal pole and communicates with subarachnoid space during cisternography. 2 - anterior 1/2 of sylvian fissure with partial communication with subarachnoid space. 3 - Involves entire sylvian fissure and shows no communication with subarachnoid space.
What are the treatment options for arachnoid cysts?
- needle aspiration / burr hole drainage (high recurrence rate) 2. Craniotomy, excision of cyst wall and fenestration into basal cisterns (higher morbidity and may need a VP shunt) 3. Endoscopic fenestration 4. Cyst shunting into the peritoneum (become shunt dependent)
What valve should be used if shunting an arachnoid cyst?
Low pressure
What are the surgical approaches for drainage of a suprasellar arachnoid cyst?
Transcallosal transventricular and transcortical transventricular
When do the fontanelles close?
Anterior fontanelle 2-3 years Mastoid fontanelle - 1 year Posterior fontanelle 2-3 months Sphenoid fontanelle 6 months
When is 90% of adult head size achieved?
1 year. Full size by age 7.
When do mastoid air cells form?
6 years
What is primary craniosynostosis?
Prenatal deformity caused by suture fusion
What is secondary craniosynostosis?
Metabolic (Rickets), Drugs (AEDs), Haemotological (Sickle cell / thalassemia) and structural (microcephaly)
What are the surgical indications for multi-suture craniosynostosis?
Impedes brain growth and for raised ICP. Note 10% of single suture craniosynostosis also develop raised ICP.
Which craniosynostosis may result in amblyopia?
Coronal
What do you feel when palpating a craniosynostosis?
Ridge (except lambdoid which may be a trough)
What does metopic synostosis cause?
Trigonocephaly
What does single coronal suture synostosis cause?
Anterior plagiocephaly
What does bilateral coronal suture synostosis cause?
Brachycephaly
What does sagittal suture synostosis cause?
Scaphocephaly