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Atsushi Watanabe, Tatsuya Seguchi and Kazuhiro Hongo

The authors report a rare case of overdrainage of the CSF caused by the malfunction of a Codman-Hakim programmable valve (CHPV) following a 3-T MR imaging procedure. Nine years ago this 72-year-old woman underwent ventriculoperitoneal shunt placement with a CHPV system for hydrocephalus due to subarachnoid hemorrhage. The postoperative course was uneventful and the system functioned well. A radiograph obtained immediately after 3-T MR imaging revealed that the pressure control cam in the valve system was detached from the base plate. Intracranial hypotension syndrome occurred several hours after the MR imaging study, and a CT scan revealed a decrease in ventricle size. A revision of the system promptly resolved the symptoms, and a postoperative CT scan revealed that the ventricle size was restored to normal. Examination of the extracted valve showed a Y-shaped crack in the plastic housing as well as detachment of the white marker and cam from the base plate. A reduction in the power of the flat spring to press the valve ball led to CSF overdrainage because of a loss of support by the cam. Because the patient had incurred no head injury during the day and radiographic studies of the system 5 years previously had shown detachment of the white marker, damage to the system might have been caused by a past impact. These facts may indicate that the antimagnetic performance of the system could have decreased due to a previous impact and that the strong magnetic force in a 3-T MR imaging environment might have caused detachment of the cam.

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Monitoring retraction pressure on the brain

An experimental and clinical study

Kazuhiro Hongo, Shigeaki Kobayashi, Akira Yokoh and Kenichiro Sugita

✓ The problem of minimizing tissue damage during brain retraction was studied both experimentally in dogs and clinically with the aid of newly designed strain-gauge retractor. The pressure required to obtain a specific exposure decreased gradually with time. The average time for a 50% reduction in retraction pressure was 6.6 minutes in the earlier trials of repeated retraction. The attenuation rate of retraction pressure gradually decreased when retraction of the same area was repeated. The lower the head position of the dog, the larger was the amplitude of brain retraction pressure. Clinical studies demonstrated that: 1) cerebrospinal fluid drainage was effective in decreasing the retraction pressure required; 2) use of multiple retractors reduced the pressure applied by each retractor; and 3) retraction pressure could be monitored when the strain-gauge retractors were applied to arteries and cranial nerves.

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Kazuhiro Hongo, Shigeaki Kobayashi, Masanobu Hokama and Kenichiro Sugita

✓ A case of a 30-year-old man who showed progressive pyramidal tract signs caused by compression of the left vertebral artery is presented. Initial decompression of the vertebral artery by placing a piece of sponge between the artery and medulla had no long-term effect. The left vertebral artery distal to the origin of the posterior inferior cerebellar artery was then sectioned, decompressing the medulla oblongata. The patient's symptoms improved postoperatively. This is the first reported case of brain-stem compression by an elongated vertebral artery treated by sectioning of the artery.

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Tetsuyoshi Horiuchi, Yuichiro Tanaka, Kazuhiro Hongo and Shigeaki Kobayashi

Object. Aneurysmal subarachnoid hemorrhage rarely occurs in young adults. The aim of this work was to clarify the clinical characteristics of ruptured aneurysms in young adults in the third and fourth decades of life and to compare these two age groups.

Methods. The authors retrospectively investigated 2493 patients who underwent surgical repair for ruptured cerebral aneurysms during a 14-year period (1988–2001). There were 25 patients (1%) in the third decade of life and 106 patients (4.3%) in the fourth decade. In general, favorable outcome was achieved in both groups. There were significant differences in the sizes and locations of aneurysms between the two age groups. Among patients in the fourth decade of life, the aneurysm was large and was located more often on the anterior cerebral artery.

Conclusions. In this study the authors summarize the clinical characteristics of a large series of 131 young adult patients with ruptured cerebral aneurysms. Congenital factors as well as hemodynamic stress may contribute to differences in aneurysm size and location between the two age groups.

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Kiyoshi Ito, Tatsuro Aoyama, Tetsuyoshi Horiuchi and Kazuhiro Hongo

OBJECT

The nonpenetrating titanium clip has been successfully used in peripheral arterial bypass surgery. The purpose of this study was to evaluate the leakage pressures and patterns of nonpenetrating titanium clips using a simple model that mimicked spinal surgery. In addition, the authors describe their surgical experience with these clips and the follow-up results in 31 consecutive patients.

METHODS

The authors compared nonpenetrating titanium clips and expanded polytetrafluoroethylene (ePTFE) sutures in relation to the water pressure that could be tolerated by sutured ePTFE sheets, and the leakage pressure patterns were determined. The changes in leakage pressures at 5 minutes, 30 minutes, and 12 hours were examined when the clips and sutures were used in combination with the mesh-and-glue technique in an in vitro study. Thirty-one patients underwent spinal intradural procedures using nonpenetrating titanium clips to suture the dura maters using the meshand-glue technique, involving fibrin glue and polyglycolic acid-fibrin sheets.

RESULTS

A significant difference was apparent between the ePTFE suture group and the nonpenetrating titanium clip group, with the latter showing a leakage pressure that could be sustained and was 1508% higher than that of the former (p = 0.001). In relation to leakage patterns, the nonpenetrating titanium clips did not make any suture holes in the ePTFE sheet and fluid leakage occurred between the clips, whereas fluid leakage was associated with the pressure elevation that occurred at the suture holes made by the ePTFE sutures. Of the 31 patients who underwent spinal intradural procedures using nonpenetrating titanium clips, 1 (3.2%) experienced cerebrospinal fluid (CSF) leakage postoperatively. No other complications—for example, allergic reactions, adhesions, or infections—were encountered.

CONCLUSIONS

The interrupted placement of nonpenetrating titanium clips enables dural closure without creating any holes. These clips facilitate improvements in the initial leakage pressure and reduce postoperative CSF leakage following spinal surgery. The authors conclude that it is very beneficial to suture the spinal dura mater using nonpenetrating titanium clips given the anatomical characteristics of the spinal dura mater and the fact that the clips do not create suture holes.

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Toru Koyama, Kazuhiro Hongo, Yuichiro Tanaka and Shigeaki Kobayashi

✓ Despite recent advances in three-dimensional imaging based on a voxel-rendering method, these techniques do not simulate the morphological changes that occur during surgery. The authors' goal was to develop a computer-graphics model to simulate the manipulation that occurs during surgery when clipping a cerebral aneurysm.

The authors developed an application program to interpolate the contours of models of an artery and an aneurysm clip. The center of displacement was determined inside the arterial model. The directions of displacement were changed to simulate saccular and broad-neck aneurysms, and the intensity of displacement was calculated by using a cosine-based formula. The morphological changes in a saccular aneurysm that may occur during clipping were calculated in x, y, and z coordinates by using sine- and cosine-based formulas. Clip movement was integrated with the aneurysm model, thus simulating the manipulation used during clipping of a cerebral aneurysm. Surgery performed to clip a basilar artery (BA) aneurysm via the transsylvian approach was simulated, in which displacement of the internal carotid artery and clipping of the BA aneurysm were necessary. The movements of an aneurysm clip and clip applicator were designed to represent those occurring when a surgeon actually manipulates a BA aneurysm.

The authors have named this methodological tool “virtual clipping.” Use of this tool would assist the preoperative choice of clipping style and selection of the best clip.

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Han Soo Chang, Kazuhiro Hongo and Hiroshi Nakagawa

Object. This study was aimed at clarifying the effect of intraoperative hypotensive anesthesia on the outcome of early surgery in patients with subarachnoid hemorrhage (SAH) caused by saccular cerebral aneurysms. Other factors were also screened for possible effects on the outcome.

Methods. Hospital charts in 84 consecutive patients with SAH who underwent aneurysm clipping by Day 4 were examined. Possible factors affecting the outcome were analyzed using multiple logistic regression with the dichotomous Glasgow Outcome Scale score as the outcome variable. The relationship between the intraoperative hypotension and the occurrence and severity of vasospasm was studied using both single- and multivariate analyses.

Conclusions. Intraoperative hypotension had a significantly adverse effect on the outcome of SAH. Hypotension was also related to more frequent and severe manifestations of vasospasm. A long-lasting effect of brain retraction is possibly the cause of this phenomenon. The data contained in this study preclude the use of intraoperative hypo- tension even in a limited form.