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  • Author or Editor: Lilliana Goumnerova x
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David M. Frim and Lilliana C. Goumnerova

Object. With the commercial availability of a variety of shunt systems, there is considerable controversy over the choice of the most appropriate shunt valve for each individual with hydrocephalus. Although the performance characteristics of all shunt systems are well documented in the laboratory setting, there is little description of the in vivo dynamics of intracranial pressure (ICP) after implantation of commonly used shunt systems in humans. The authors coupled telemonitoring devices to several different shunt systems to measure the performance characteristics of these valve systems with respect to intraventricular pressure (IVP) at increments of head elevation.

Methods. Twenty-five patients with different shunt systems and three control patients without shunts were studied for IVP at 0°, 15°, 30°, 45°, 60°, 75°, and 90° of head elevation, and the resultant curves were analyzed for the best-fit regression coefficient. For purposes of analysis the authors grouped shunt valve systems by design characteristics into three groups: differential-pressure valves (r = −0.321 ± 0.061; 11 patients), nonsiphoning systems (r = −0.158 ± 0.027; 10 patients), and flow-regulated valves (r = −0.16 ± 0.056; four patients); there were three control patients without shunts (r = −0.112 ± 0.037).

Conclusions. The authors found that differential-pressure valves always caused ICP to drop to 0 by 30° of head elevation, whereas all other valve systems caused a more gradual drop in ICP, more consistent with pressures observed in the control patients without shunts. Not surprisingly, the differential-pressure valve group was found to have a significant difference in mean regression coefficient when compared with those in whom nonsiphoning shunts (p < 0.023) or no shunts were placed (p < 0.049). These data provide a basis for evaluating shunt valve performance and for predicting valve appropriateness in patients in whom characteristics such as pressure and flow dynamics are weighed in the choice of a specific valve for implantation.

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Cormac O. Maher, Lilliana Goumnerova, Joseph R. Madsen, Mark Proctor and R. Michael Scott


Patients who have undergone prior myelomeningocele or lipomyelomeningocele repair may present with symptomatic retethering of the spinal cord. In some cases, symptomatic tethering may recur after previous untethering operations. The expected outcome following repeated untethering in a patient after two or more prior untethering operations is not well described.


The authors examined surgical indications, techniques, and outcomes for 30 repeated untethering operations in 22 patients who had undergone a previous repair of the primary spinal disorder and at least two subsequent untethering operations.

The mean age at repeated untethering was 12.3 years. Presenting symptoms were pain (70%), weakness (70%), urinary symptoms (57%), and sensory changes (27%). The mean duration of symptoms was 7.5 months, and a longer symptomatic interval correlated with an increased number of prior operations. Total circumferential untethering was accomplished in 11 cases (37%). Postoperative symptomatic improvement was noted most often for pain (81%), and less often for urinary symptoms (53%) and weakness (48%). Complications included postoperative cerebrospinal fluid leakage or pseudomeningocele and new postoperative lower-extremity dysesthesia in five cases (17%). An increasing number of prior untethering operations was associated with a worse result for pain relief and a greater chance of significant morbidity.


Multiple repeated untethering operations offer symptomatic relief to well-selected patients with this condition.