Arachnoid cysts in adults: long-term follow-up of patients treated with internal shunts to the subdural compartment.

BACKGROUND: We have previously presented an alternative method for surgical decompression of intracranial arachnoid cysts. This minimally invasive method, with insertion of an internal shunt from the cyst to the subdural compartment, seemed to be an efficient and simple, and hence promising technique. The aim of the present study was to investigate the long-term results of this procedure.
METHODS: This study is a questionnaire-based retrospective study that includes 31 adult patients (>18 years) who were operated on in our department for an arachnoid cyst in the temporal fossa or overlying the frontal convexity with the internal shunt technique between April 1990 and October 2003. Follow-up ranged from 15 months to 14.8 years (mean = 8.2 years).
RESULTS: Of the patients, 83% were asymptomatic or had insignificant complaints at follow-up. A total of 17% reported no reduction of the preoperative complaints. No patient experienced worsening of the symptoms. The cyst was no longer visible on postoperative radiologic examinations in 37% of the patients. In 37%, the postoperative fluid volume was less than 50% of the original volume. In 13%, the cyst volume was reduced but the postoperative volume was greater than 50% of the original cyst volume. Thus, the cyst was unchanged in only 13% of the patients. There was no correlation between volume reduction and clinical improvement. A complication (subdural hygroma or hematoma) occurred in 7 patients, all with temporal cysts, leading to reoperation in 4. None of the complications caused permanent neurologic deficits or invalidity. Seven patients were reoperated on because of suspected or established treatment failure.
CONCLUSIONS: The internal shunt technique is a relatively simple, safe, and efficient alternative method for treatment of arachnoid cysts. It should be considered a valuable alternative in the treatment of arachnoid cysts.