Arachnoid cyst is a congenital lesion deriving from the splitting of the arachnoid membrane. It is an intra-arachnoid sac filled with cerebro-spinal fluid and non- communicating with the ventricular system. It represents 1% of all intracranial masses. Incidence is 5 per 1000 in autopsy series. 75% of cases are seen in children. F:M = 1: 3-5. Its most common location is in middle cranial fossa (MCF) (50-60%), cerebellopontine angle (10%), suprasellar arachnoid cyst (10%), miscellaneous (10%).
Classification: type 1 - small, spindle shaped, limited to anterior MCF; type 2 - superior extent along sylvian fissure; type 3 - fills entire MCF. The presentation varies with its location: elevated intracranial pressure; seizures; acute symptoms (for hemorrhage or rupture of the cyst); focal signs of a space occupying lesion; in retrocerebellar location it may mimic Dandy-Walker malformation.
Treatment: often none. The cyst may be fenestrated, drained or shunted to the peritoneum by a low-pressure valve.
Classification: type 1 - small, spindle shaped, limited to anterior MCF; type 2 - superior extent along sylvian fissure; type 3 - fills entire MCF. The presentation varies with its location: elevated intracranial pressure; seizures; acute symptoms (for hemorrhage or rupture of the cyst); focal signs of a space occupying lesion; in retrocerebellar location it may mimic Dandy-Walker malformation.
Treatment: often none. The cyst may be fenestrated, drained or shunted to the peritoneum by a low-pressure valve.
References
- Handbook of Neurosurgery - fifth edition - Mark S. Greenberg - ed. Thieme.
- Diagnostic Imaging - Brain - Osborn - First edition;second printing- Amirsys - Elsevier Saunders - 2004.
