Invagination of a shunt valve: an unusual complication--case report.

The authors present an unusual case of ventriculoperitoneal shunt failure due to invagination of a valve in the proximal portion of the silicone casing of the shunt system. The shunt had been in place for 5 years and the 57-year-old male patient had incurred no head injury during that period. The valve failure was discovered during evaluation of his gradual deterioration, which culminated in his functional incapacitation. Nine such cases have been reported in the literature. This complication is specifically associated with the Holter and Hakim valves and seems to a primary mechanical failure attributable to the structure of these two valves.