Clinical experience with a new pressure-adjustable shunt valve.

The pressure-adjustable valve system Codman Medos allows valve pressure adjustment in 18 steps between 30 and 200 mm H2O. A series of 90 patients, 15 children and 75 adults, who were shunted with this new programmable valve, is reported. Indication for shunt insertion were various types of hydrocephalus in 79 cases, malfunction of a medium pressure membrane valve shunt system in 9 cases and an arachnoid cyst and pseudotumour each in one case. The valve pressure was programmed prior to insertion to 200 mm H2O in the adults and according to age in children and was modified postoperatively according to the clinical course. Underdrainage with subdural fluid collections appearing in 5 patients could be managed by valve pressure adjustment alone in 2 cases. One malfunctioning of the valve mechanism was due to mechanical obstruction. At the time of follow-up, 7 to 29 months after operation, outcome was excellent in 64 patients, good with marked improvement but residual symptoms in 19 patients and unchanged in 7 patients. The possibility of adjusting the valve pressure to the patient's demands was frequently used in children and adult normal pressure hydrocephalus patients with satisfying clinical results.