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Ryuzo Shiobara, Shigeo Toya, Shigemaru Mikouchi and Ziro Izumi

✓ Two patients are reported who were originally treated by ligation of the common carotid artery for ruptured aneurysms of the posterior communicating artery. Long-term follow-up studies showed that the aneurysms had enlarged, and direct surgery of the aneurysms was undertaken.

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Shigeo Toya, Takeshi Kawase, Youichi Iisaka, Takanobu Iwata, Toshio Aki and Tsuneo Nakamura

✓ The effect of laser radiation on the central nervous system has been studied in cases of clinical and experimental tumors. However, no report yet exists on the effects of laser radiation on the cerebral microcirculation in vivo. Cerebral fluorescein angiography permits observations of small vessels that are not possible by conventional angiography. In this study, disturbance in the epicerebral microcirculation after carbon dioxide laser radiation was localized. On fluorescein angiograms, a circular zone of nonfilling of fluorescein dye around the site of impact, 1 to 1.5 mm in diameter, was seen throughout from the arterial to late venous phase. Around the nonfilling area, thrombus formation in small vessels and extravasation of the dye were demonstrated. Such extravasation of the fluorescein remained after the dye had faded from the venules and veins. Microscopically, coagulation necrosis was observed to coincide with the area of nonfilling of fluorescein dye in the fluorescein angiograms. In areas surrounding this, edema, dilatation or rupture of the capillaries, and thrombus formation in the arterioles were observed. Such areas coincided with those of extravasation of the fluorescein dye.

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Shigeo Toya, Ryuzoh Shiobara, Jiroh Izumi, Youichi Shinomiya, Hayao Shiga and Chojiro Kimura

✓ The authors report two cases of spontaneous carotid-cavernous fistula that occurred during pregnancy. One patient was a 21-year-old woman whose symptoms improved and in whom disappearance of the carotid-cavernous fistula was confirmed by cerebral angiography after she aborted in the 12th week of pregnancy. The other patient was a 25-year-old woman in whom a carotid-cavernous fistula occurred at about the 28th week of pregnancy. The symptoms became aggravated 3 weeks after a normal delivery. Carotid-cavernous fistula was confirmed by cerebral angiography, and the clinical symptoms then improved. On the basis of cerebral angiographic findings, both patients were considered to have dural arteriovenous fistulas in the region of the cavernous sinus and both demonstrated spontaneous improvement.

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Kazunari Yoshida, Shigeo Toya, Mitsuhiro Ohtani, Shunichi Okui, Nobuo Takenaka and Kenichi Harigaya

✓ A case of pineal germ-cell tumor producing human chorionic gonadotropin (HCG) and alpha-fetoprotein (AFP) is reported in a 23-year-old man. Extraneural metastasis developed during a course of combined chemotherapy after radiation therapy. Postmortem examination revealed that the metastatic pulmonary tumor was a choriocarcinoma, producing only HCG.

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Takeshi Kawase, Shigeo Toya, Ryuzo Shiobara and Toru Mine

✓ Extradural subtemporal access to the petrosal ridge and a resection of the anterior pyramidal bone produced direct observation of the lower basilar artery, with minimum retraction of the temporal lobe and preservation of the temporal bridging veins. Two patients, with lower basilar trunk aneurysms facing toward the brain stem, were operated on by the “transpetrosal approach,” with successful clipping of the aneurysms. Auditory function was preserved in one case. This approach decreases the possibility of retraction damage to the temporal lobe, brain stem, or cranial nerves, and may be helpful for surgery of aneurysms arising around the vertebrobasilar junction or at the origin of the anterior inferior cerebellar artery.

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Shuzo Sato, Shigeo Toya, Takayuki Ohira, Tohru Mine and Nigel H. Greig

✓ A real-time two-dimensional echocardiogram was used to detect the presence of an air embolism in patients undergoing neurosurgical procedures in the sitting position. The technique could with good sensitivity detect the appearance of a single air bubble intraoperatively, thus allowing early intervention to prevent development of further air emboli. Two types of air embolism could be differentiated; the single-bubble type and the “stormy-bubble” type. The single-bubble type was observed during skin and muscle incisions, craniotomy, and brain lesion excision. Further embolism development was prevented by electrocoagulation and application of bone wax. The stormy-bubble type occurred during dura and muscle incisions and was prevented by electrocoagulation, reflection of the dura, or suturing the affected muscle.

The routine use of a Swan-Ganz catheter for removal of air embolism by suction proved effective for the treatment of the stormy-bubble type of air embolism. Masking the operative field with saline-soaked cotton strips was of moderate benefit in the stabilization of the single-bubble type of air influx, but proved to be of little value in controlling the entrance of the stormy-bubble type.

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Ryuzo Shiobara, Takayuki Ohira, Jin Kanzaki and Shigeo Toya

✓ During the past 10 years, 125 operations for acoustic nerve tumors were performed on 114 patients at the authors' institution using a modified extended middle cranial fossa approach. This approach is based on a combination of King and Morrison's translabyrinthine-transtentorial approach and on the extended approach through the middle cranial fossa described by Bochenek and Kukwa. There were two hospital deaths (operative mortality 1.6%). In 102 operations on the initial tumor, total removal was performed in 89 cases (87%), and in 71 (80%) of these the facial nerve was anatomically preserved. Intracranial end-to-end anastomosis was performed on five of the 18 sacrificed facial nerves; a facial-hypoglossal anastomosis was carried out in the remaining 13 patients and in five (7%) of the 71 patients whose anatomically preserved facial nerve functioned poorly. In seven (39%) of the 18 patients in whom an attempt to preserve hearing was made, postoperative hearing was saved. In 23 operations on 17 patients for recurrent tumors, most of which had previously been removed subtotally via the suboccipital approach, total removal was accomplished in 13 (57% of the 23 reoperations and 76% of the 17 patients). At reoperation, the facial nerve was preserved in six (55%) of the 11 patients in whom the facial nerve had not been sacrificed. Postoperative leakage of cerebrospinal fluid occurred in 11 cases (8.8%), with rhinorrhea in 10 cases and otorrhea in one. Five of the fistulas were corrected by surgery and the rest healed spontaneously. Other complications were not significant.

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Mami Ishikawa, Takayuki Ohira, Jun Namiki, Masato Kobayashi, Moriichiro Takase, Takeshi Kawase and Shigeo Toya

✓ In patients with hemifacial spasm, it has been said that the spasm is due to cross compression of the facial nerve by a blood vessel and that microvascular decompression (MVD) of the facial nerve is an effective treatment. The F waves, which result from backfiring of antidromically activated motor neurons of the facial motor nucleus, are indices of the excitability of the facial motor nucleus and are enhanced in patients with hemifacial spasm. Measuring blink reflexes and abnormal muscle responses (lateral spread), a characteristic sign of hemifacial spasm, has been used to investigate the mechanism of hemifacial spasm pathophysiologically. Thus the authors measured F waves of the facial muscle, blink reflexes, and abnormal muscle responses before and after MVD in patients suffering from hemifacial spasm to investigate the excitability of the facial motor nucleus and the course of the cure of hemifacial spasm after MVD. The authors obtained facial nerve—evoked electromyograms in 20 patients with hemifacial spasm before and after the MVD procedure. On the spasm side, the F waves and blink reflexes were enhanced preoperatively compared to those on the normal side and abnormal muscle responses were recorded in all patients. In 12 patients whose hemifacial spasm had not disappeared completely for 5.1 ± 1.7 (mean ± standard error) months following the MVD procedure, F waves were still enhanced significantly and abnormal muscle responses were still recordable, albeit at lower amplitude. Within 1 month after the hemifacial spasm had disappeared completely, F waves were still significantly enhanced in 17 patients and abnormal muscle responses were recorded in seven of 15 patients. Subsequently, the enhanced F waves and abnormal muscle responses disappeared completely. The authors' study supports the hypothesis that the cause of hemifacial spasm is hyperexcitability of the facial motor nucleus and suggests that additional surgery should not be performed for at least 2 years after MVD, because that period is necessary for the disappearance of the hyperexcitability of the facial motor nucleus.