Cerebral arachnoid cysts constitute about 1% of intracranial expansions, primary ones (congenital, true) are rare, their incidence ranges about 5:1000. From the view of etiopathology, these are mostly consequences of disturbed fluid circulation in embryogenesis. With current availability of CT and MR examinations, a lot of arachnoid cysts are diagnosed as clinically mute, the others are manifested with a number of symptoms, often dependent on their locations. The therapeutical methods in clinically manifested subarachnoid cysts have been discussed. Out of surgical methods, the cyst fenestration, various types of shunts and, more recently, some endoscopic interventions are used most frequently. The authors have published results of surgery for both supra- and infratentorial arachnoid cysts in 9 patients. A set involved 5 men and 4 women aged 29 – 64, mean age 43 years. The most frequent clinical symptoms were cephalgia of various type (8 patients), epileptic seizures (1 patient), trigeminal neuralgia (1 patient), and associated inborn neuropsychic disorders (2 patients). Four cases underwent the fenestration of a cyst into convexitary subarachnoid spaces (marsupialization), the cyst fenestration into basal cisterns was carried out in 2 patients, and in 3 subjects the fenestration was supported with a cystosubarachnoid drainage (shunt). A check-up performed 6 months after the intervention revealed complete disappearance of problems in 4 patients, complaints were relieved or some clinical manifestations disappeared in 3 patients, and a clinical finding was unchanged in 2 subjects. Clinical impairment was seen in no patient, no association between the change of clinical conditions and a graphic finding (enlargement/reduction of the cyst volume) was confirmed in any case. Hydrocephalus was not demonstrated in any patient before or after the surgery. The authors have discussed clinical results and argued with the opinion that volumetric regression of a cyst in a graphic finding must correspond with clinical improvement. The importance of individual approach to patients with a revealed cerebral arachnoid cyst has been stressed.

        Key words: cerebral arachnoid cyst, hydrocephalus, surgical treatment