A New Ventriculoperitoneal Shunt with a Telemetric Intracranial Pressure Sensor: Clinical Experience in 94 Patients with Hydrocephalus

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Abstract
We have developed a telemetric intracranial pressure sensor (OSAKA telesensor; Nagano Keiki Seisakusyo Co. Ltd., Tokyo, Japan) and investigated the clinical usefulness of new ventriculoperitoneal shunting with an OSAKA telesensor, an on-off valve, and a programmable valve.The OSAKA telesensor was applied in 94 patients at Osaka Medical College between March 1986 and December 1995. Postoperative management, postoperative course, postural change of intracranial pressure (ICP), and zero drift of the OSAKA telesensor were investigated.ICP was measured easily in all patients with no inconvenience. The setting of the programmable valve was adjusted postoperatively 38 times in 25 patients. Postoperative ICP in the upright position was -14.9 +/- 4.5 mm Hg, and the difference in ICP between the supine and the upright position was about 20 mm Hg. The slope of the decrease in ICP with continuous postural changes from the supine to the upright position was steep until about 30 to 45 degrees but became incrementally less or even rose slightly about this angle. The initial slope was steeper when the shunt was open than when the shunt was closed; it was also steeper postoperatively than preoperatively. This initial slope, therefore, may indicate the intracranial compliance. Seven cases of shunt malfunction were diagnosed correctly by ICP measurements. Zero drift of the OSAKA telesensor was easily corrected by comparing the ICP reading from the telesensor with the puncture pressure in the on-off valve.The OSAKA telesensor is very useful in the postoperative care and pathophysiological evaluation of patients with hydrocephalus.