CSF Dynamics in a Patient with a Programmable Shunt
The Codman®-Medos® programmable shunt system was designed by Drs. Hakim to relieve under and over drainage problems. The system allows for non-invasive post-implantation adjustment of the opening pressure of the valve through a range of 30 to 200 mm H2O i
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CSF Dynamics in a Patient with a Programmable Shunt O. Tsuji l and K. Sato2 I Department of Neurosurgery, HITACHI General Hospital, Ibaraki, and 1Department of Neurosurgery, Juntendo University, Tokyo, Japan
Summary The Codman®-Medos® programmable shunt system was designed by Drs. Hakim to relieve under and over drainage problems. The system allows for non-invasive post-implantation adjustment of the opening pressure of the valve through a range of 30 to 200 mmH10 in 10 mm differentials. However, its wide adjustability does not simplify determination of the optimal pressure setting. The bolus injection method was used to study the intracranial pressure environment of nine adult hydrocephalic patients treated with the Codman®-Medos® programmable shunt. Changes in CSF hydrodynamics with manipulation of the pressure valve setting, and the effectiveness of the bolus injection method to determine the optimum valve pressure setting were investigated. Initial valve pressure setting at shunt implantation was determined on the basis of preoperative CSF dynamics test. Another CSF dynamics test was carried out after surgery, and the pressure setting was revised if necessary. The new setting was the maximum obtained within normal CSF hydrodynamics. If shunt overflow was suspected, pressure was set at a higher level. After resetting of the shunt, no patient encountered serious shunt-related problems in the follow-up period. This method was considerably useful for understanding of the intracranial pressure environment of patients with a programmable shunt, and determination of a better shunt setting. Keywords: CSF dynamics; hydrodynamics; programmable shunt.
Introduction The essential and sole role of a ventriculo-peritoneal shunt (V-P shunt) in a hydrocephalic patient is to obtain appropriate diversion of cerebrospinal fluid. However, under and over drainage problems remain still unsolved. In particular, over-drainage leads patients into such difficult situation as subdural hygroma/hematoma and slit ventricle syndrome. Various types of shunt systems have been designed to counter this. A large number of such reports pointed out the effectiveness of programmable shunt system in preventing and treating under/over drain-
age syndrome [2,7]. Codman®-Medos® programmable shunt system is in wide use now, and its reliability and accuracy have been well demonstrated in both laboratory and clinical settings [1]. However, its wide and fine adjustability does not simplify determination of the optimal pressure setting. The purpose of this study was to clarify changes in intracranial pressure (ICP) environments by pressure setting manipulations, and to determine the optimal setting with a CSF dynamics test utilizing the bolus injection method (CSF dynamics test) described by Marmarou et al. [6].
Materials and Methods There were a total of nine (4 women, 5 men; mean age 58.2, range 34-76) adult patients with hydrocephalus. Eight of the 9 were secondary hydrocephalus patients (seven with subarachnoid hemorrhage, one intracerebral hemorrhage)
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