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Yusuf Erşahin

Abstract

Object. The authors report their experience in six patients with pineal tumors and associated hydrocephalus who underwent an endoscopic biopsy procedure and third ventriculocisternostomy (ETVC) in a single sitting.

Methods. The ETVC was successfully performed without complication in all patients; however, a ventriculoperitoneal shunt was eventually required in four. Histological diagnosis was successfully established in four patients. The authors also reviewed the literature to assess reports involving ETVC and tumor biopsy sampling in patients with pineal tumors and hydrocephalus. A total of 54 cases, including those in this study, have been reported. Fifteen percent of the patients eventually required placement of a ventricular shunt. The transient complication rate was 15% with no death. A positive tissue diagnosis was established in 89% of the cases overall.

Conclusions. The authors conclude that the endoscopic management of patients with pineal region masses and hydrocephalus may be a preferred initial strategy.

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Sherise D. Ferguson, Nancy Michael and David M. Frim

✓Despite advances in cerebrospinal fluid (CSF) diversionary techniques, shunt failure due to infection or malfunction remains a persistent problem in hydrocephalus care. The aim of this study was to evaluate the independent predictors of early shunt survival after implantation in a large cohort of patients. The authors retrospectively reviewed the records of all patients who had undergone shunt implantation procedures at their institution during an 8-year period. They analyzed the independent predictors of shunt survival in 116 failed shunt placement procedures (infection or malfunction) by performing univariate and multivariate factorial analyses. Analysis of the 116 failed shunts in the 396 new shunt placement procedures performed revealed that age was a significant independent predictor of shunt survival time in failures due to malfunction (p < 0.05) as well as infection (p < 0.05). In addition, a significant relationship between patient race and shunt survival was also found. As suggested by data in other studies focused on this outcome, early shunt failure occurs sooner in younger patients. Interestingly, this study is one of few whose data have revealed that race may affect shunt failure after implantation. Specifically, shunt failure due to infection resulted in significantly shorter shunt survival time in non-white patients compared with that in white patients. Among the shunts that failed due to malfunction, however, white patients had shorter shunt survival times.

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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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Paul H. Chapman and David M. Frim

✓ The authors report the cases of three children in whom symptomatic syringomyelia occurredde novo following an operation to relieve retethering of a previously treated lipomyelomeningocele. No patient had a Chiari malformation. In two cases, magnetic resonance imaging performed before the first operation did not show a syrinx. At the time of surgery to relieve retethering, it was discovered that one of these patients had a minor degree of terminal hydromyelia and the other had a prominent central canal within the conus medullaris. The third patient was initially studied by means of myelography, which gave no indication of a syrinx, and one was not found at the time of the surgery to release the retethering. Neurological deficits appeared abruptly within several months of operation in two children, and insidiously after 12 to 18 months in the other symptomatic individual. In all three cases, the syrinx involved the distal spinal cord adjacent to the site of the lipoma. Treatment consisted of syringosubarachnoid shunting, which arrested the progression of deficits but only partially reversed them. The details of each case are presented and the possible mechanism of syrinx formation discussed. Early recognition and treatment of this unusual but important problem are emphasized.

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Medina C. Kushen and David Frim

✓Subdural electrode arrays are placed to localize seizure foci for possible resection. The procedure is usually straightforward when an electrode grid array is placed on the brain convexity but can become complicated if the surface on which the grids are applied is not convex. Arachnoid cysts can be associated with seizures, but their topography presents a challenge to standard techniques for the placement of subdural grids. The authors report on a technique for electrode grid placement that successfully localized seizure foci in the depths of arachnoid cysts in two patients.

Subdural grids were placed to conform to the concave cyst cavity. They were held in place with rolled gelatin foam padding, which filled the arachnoid cyst. The padding was removed before removing the electrode grids and resecting the seizure focus.

Although arachnoid cysts present a technical challenge when seizure foci are located within the cyst cavity, the technique of packing the cyst cavity with gelatin foam provides good electrode contact on the concave cyst wall, allowing adequate seizure focus localization.

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Bakhtiar Yamini, Daniel Refai, Charles M. Rubin and David M. Frim

Object. The authors report their experience in six patients with pineal tumors and associated hydrocephalus who underwent an endoscopic biopsy procedure and third ventriculocisternostomy (ETVC) in a single sitting.

Methods. The ETVC was successfully performed without complication in all patients; however, a ventriculoperitoneal shunt was eventually required in four. Histological diagnosis was successfully established in four patients. The authors also reviewed the literature to assess reports involving ETVC and tumor biopsy sampling in patients with pineal tumors and hydrocephalus. A total of 54 cases, including those in this study, have been reported. Fifteen percent of the patients eventually required placement of a ventricular shunt. The transient complication rate was 15% with no death. A positive tissue diagnosis was established in 89% of the cases overall.

Conclusions. The authors conclude that the endoscopic management of patients with pineal region masses and hydrocephalus may be a preferred initial strategy.

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Nathan R. Selden

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Ashley Ralston, Patti Ogden, Michael H. Kohrman and David M. Frim

Vagus nerve stimulators (VNSs) are currently an accepted treatment for intractable epilepsy not amenable to ablative surgery. Battery death and lead damage are the main reasons for reoperation in patients with VNSs. In general, any damage to the lead requires revision surgery to remove the helical electrodes from the vagus nerve and replace the electrode array and wire. The electrodes are typically scarred and difficult to remove from the vagus nerve without injury. The authors describe 6 patients with VNSs who presented with low lead impedance on diagnostic testing, leading to the intraoperative finding of lead insulation disruption, or who were found incidentally at the time of implantable pulse generator battery replacement to have a tear in the outer insulation of the electrode wire. Instead of replacement, the wire insulation was repaired and reinforced in situ, leading to normal impedance testing. All 6 devices remained functional over a follow-up period of up to 87 months, with 2 of the 6 patients having a relatively shorter follow-up of only 12 months. This technique, applicable in a subset of patients with VNSs requiring lead exploration, obviates the need for lead replacement with its attendant risks.

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David M. Frim, Bonnie Padwa, Deidre Buckley, Robert M. Crowell and Christopher S. Ogilvy

✓ The location of the carotid artery bifurcation and the distance atherosclerotic disease extends distally in the internal carotid artery (ICA) are two factors that contribute to the technical difficulty of carotid endarterectomy. When the bifurcation is high (above C-3) or the disease extends distally, standard approaches may not provide adequate exposure for dissection of plaque or for arteriotomy repair. A simple method of mandibular subluxation is described for added exposure of the distal carotid artery. The criteria for use of this method include: a carotid bifurcation at or above C-2; disease extending to within 2 cm of the skull base; and a small-caliber distal ICA lumen with the expectation of a patch graft extending close to the skull base. In dentulous patients, the mandible is subluxed by attaching an intradental wire from the ipsilateral mandibular bicuspid to an intradental wire around the contralateral maxillary bicuspid. In edentulous patients, a wire is placed around the ipsilateral mandible and secured to a wire placed through the anterior nasal spine. The entire preoperative subluxation requires 10 to 15 minutes under anesthesia and an additional 1 to 2 minutes postoperatively to remove the wires. A single skin suture and an absorbable intraoral suture were placed in some edentulous patients.

This technique has been evaluated over a 15-month reference period during which 115 carotid endarterectomies were performed. The criteria stated above were met in seven cases (six patients, 6%) and jaw subluxation was performed preoperatively. An additional 1 to 2 cm of distal exposure was obtained by using this technique and endarterectomy proceeded without complication. A slight “shift” of the standard anatomical landmarks occurred due to the movement of the mandible, which was easily recognized. There were no significant postoperative complaints related to the subluxation; specifically, no temporomandibular joint pain, no other postoperative pain, and no tooth damage were encountered. It is concluded that this relatively simple approach to mandibular subluxation provided significant added exposure to the distal ICA without notably increasing operative time. In addition, there was no morbidity and little additional care was needed when compared with other more radical approaches to high carotid artery exposure.