[Diagnosis and treatment of central nervous system arachnoid cyst]

Arachnoid cysts of the CNS are uncommon lesions of considerable interest and importance, the origins and exact nature of which remain uncertain (congenital, posttraumatic, infectious or other). They form a well defined pathological entity and account for less than 1% of all CNS space-occupying lesions. Their membranous walls resemble slightly thickened arachnoid with CSF-like fluid. They are loosely attached to the dura mater and cerebral cortex, and are often adherent along the base of the skull or falx or located next to midline of the posterior fossa. A variety of clinical problems may be produced by such lesions depending on the location. The authors report five cases of arachnoid cysts diagnosed by CT and MRI. Four cysts were treated surgically (2 within posterior fossa, 2 spinal) and one intracellar cyst was treated conservatively. The value of CT and MRI in preoperative diagnosis and postoperative follow-up is emphasized and the symptomatology and choice of treatment are discussed.