Thermosensitive determination of obstructed sites in ventriculoperitoneal shunts.

A simple method is described for checking the patency of ventriculoperitoneal shunts by using a pair of small disc thermistors. With this technique, shunt patency is shown by a downward deflection of the recording trace, blockage of the ventricular catheter is indicated by a flat-line recording, and obstruction of the distal end of the abdominal catheter is demonstrated by an upward deflection. These observations were confirmed in a study of 32 hydrocephalic patients with obstructed shunts who subsequently underwent shuntography and operation. An experimental model was also devised to study the mechanism of the recording changes.