Ventriculo peritoneal Shunt Malfunction with Anti-siphon Device in Normal pressure Hydrocephalus Report of -Three Cases- Mitsuru SEIDA, Umeo ITO, Shuichi TOMIDA, Shingo YAMAZAKI and Yutaka INABA* Department of Neurosurgery, Musashino Red Cross Hospital, Musashino, Tokyo; *Department of Neurosurgery, Tokyo Medical and Dental University, Tokyo - Abstract Three patients with normal-pressure hydrocephalus, treated by installation of a low-pressure ven triculo-peritoneal shunt system equipped with an anti-siphon device, did not improve in clinical signs and ventricular size on computed tomography (CT). However, the lumbar infusion mano metric test in the horizontal position showed that the shunt systems were functioning and cerebro spinal fluid absorption was good in all patients. The clinical signs and ventricular dilatation on CT were remarkably improved by replacing the shunt system to one without an anti-siphon device. The shunt malfunction seemed to be caused by the anti-siphon function itself, especially when the pa tients were in sitting and/or standing position. Key words: normal-pressure hydrocephalus, ventriculo-peritoneal shunt, anti-siphon device, lumbar infusion test
Fig. I Serial computed tomography (CT) scans of Case 1. up per: Prior to the initial operation. Ventricular dilatation is obvious. middle: After the initial operation (ven triculo-peritoneal (V-P) shunt with anti-siphon device). There was no improvement in the ventricular size or periventricular lucency (PVL). lower: Following the se cond operation (shunt revision using a shunt system without anti-siphon device). Ventricular dilatation and PVL disappeared. Fig. 2 Lumbar infusion test in Case 1 after the initial operation is functioning and the cerebrospinal fluid (CSF) ab sorption is good. *Infusion at the rate of 1 ml/min of saline, with shunt system closed. **Infusion at the rate of 2 ml/min of saline, with shunt system opened. ***In fusion at the rate of I ml/min of saline, with shunt system opened.
Fig. 3 Serial CT scans of Case 2. upper: Prior to the initial operation. Ventricular dilatation and PVL are obvious. middle: After the initial operation (V-P shunt with anti siphon device). There was no improvement in the ven tricular dilatation or PVL. lower: Following the second operation (shunt revision using a shunt system without anti-siphon device). Ventricular size improved. Fig. 4 Lumbar infusion test in Case 2 after the initial operation is functioning and the CSF absorption is good. *Infu sion at the rate of 1 ml/min of saline, with shunt system closed. **Infusion at the rate of 1 ml/min of saline, with shunt system opened. ***Infusion at the rate of 2 ml/ min of saline, with shunt system opened.
Fig. 6 Lumbar infusion test in Case 3 after the initial operation is functioning and the CSF absorption is good. *Infu sion at the rate of I ml/min of saline, with shunt system closed. **Infusion at the rate of 2 ml/min of saline, with shunt system opened. ***Infusion at the rate of 1 ml/ min of saline, with shunt system opened. Fig. 5 Serial CT scans of Case 3. upper: Prior to the initial operation. Ventricular dilatation and PVL are obvious. middle: After the initial operation (V-P shunt with anti siphon device). There was no improvement in ventricu lar dilatation, and a thin subdural hematoma was seen in the right fronto-parietal region. lower: Following the second operation (shunt revision using a shunt system without anti-siphon device). Ventricular size improved.
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