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Toshiro Katsuta, Hiroshi Abe, Koichi Miki and Tooru Inoue

OBJECT

The authors experienced an intriguing phenomenon in 2 adult patients with moyamoya disease. Mouth opening caused reversible occlusion of the donor superficial temporal artery (STA), and the patients exhibited transient cerebral ischemic symptoms. The aim of this study was to assess the incidence of such occlusion and the mechanism of this phenomenon.

METHODS

Twelve consecutive adult patients with moyamoya disease (15 affected sides) who underwent STA–middle cerebral artery anastomosis were included in this study. Ultrasound examination was performed more than 3 months postoperatively to determine whether mouth opening affected blood flow of the donor STA and led to any ischemic symptoms within 1 minute. Computed tomography angiography was performed during both mouth opening and mouth closing, when blood flow changes of the donor STA were recognized.

RESULTS

Under wide mouth opening, steno-occlusion of the donor STA occurred in 5 of 15 sides (33.3%). On 1 side (6.7%), complete occlusion induced ischemic symptoms. Steno-occlusion occurred by at least 2 mechanisms: either the stretched temporalis muscle pushed the donor STA against the edge of the bone window, or the redundant donor STA kinked when the muscle was stretched.

CONCLUSIONS

Even with temporary occlusion of the donor STA, ischemic symptoms seem to rarely occur. However, to avoid the “big bite ischemic phenomenon,” the authors recommend securing a sufficient distance between the donor STA and the edge of the bone window and avoiding a redundant course of the donor STA within the muscle layer.

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Tetsuya Ueba, Hiroshi Abe, Juntaro Matsumoto, Toshio Higashi and Tooru Inoue

A 19-month-old child was gradually suffering from gait disturbance and was referred by his pediatrician to the authors' institution. Spinal MRI showed Gd-enhanced spinal cord tumor and congestive myelopathy. Intraoperatively the lesion was seen to be a hemangioblastoma. Because discrimination of the arterialized draining veins from the feeding arteries was difficult, indocyanine green videography was conducted to differentiate them. Real-time evaluation by FLOW 800 revealed that the slope of the average signal intensity in the feeding artery was steeper than that of the arterialized veins. The tumor was successfully resected, and postoperative indocyanine green videography showed total removal of the tumor as a signal-negative region; the circulation time between the feeding artery and the main draining vein was prolonged from 2.5 to 5.5 seconds. Indocyanine green videography and real-time evaluation by FLOW 800 were objective and effective for the excision of a tumor retaining the arteriovenous shunt. The patient recovered from congestive myelopathy and gait disturbance.

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Tooru Inoue, Masashi Fukui, Shunji Nishio, Katsutoshi Kitamura and Hitoshi Nagara

✓ To test the results of blood-brain barrier (BBB) disruption in the treatment of brain tumor, RG-C6 glioma was transplanted into the brains of rats. Intracarotid infusions of normal saline and hyperosmotic mannitol were then made, followed by intravenous injection of Evans blue dye plus albumin (EB, MW 68,000), horseradish peroxidase (HRP, MW 40,000), and 5-fluorouracil (5-FU, MW 130). Uptake of the drug and the consistency of drug levels in the normal brain and tumor varied widely among these three agents. Both EB and HRP penetrated the brain tumors but did not stain the normal brain tissues. After BBB opening, penetration of EB and HRP into the normal brain was drastically increased; however, the uptake of EB and HRP in the tumor was not increased. The concentration of 5-FU in the tumor was higher than that in the serum and, although it increased 1.5-fold after BBB opening, the increase was not statistically significant. Conversely, there was a progressive increase in concentrations of 5-FU in the tumor-free brain regions (p < 0.05). These observations suggest that an intracarotid infusion of hyperosmotic mannitol may increase neurotoxicity because it allows greater delivery of anticancer drugs into the normal brain tissue than into the tumor tissues.

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Archie Defillo and Eric S. Nussbaum

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Fuminari Komatsu, Mika Komatsu, Tooru Inoue and Manfred Tschabitscher

Object

The cavernous sinus is a small complex structure located at the central base of the skull. Recent extensive use of endoscopy has provided less invasive approaches to the cavernous sinus via endonasal routes, although transcranial routes play an important role in the approach to the cavernous sinus. The aims of this study were to evaluate the feasibility of the purely endoscopic transcranial approach to the cavernous sinus through the supraorbital keyhole and to better understand the distorted anatomy of the cavernous sinus via endoscopy.

Methods

Eight fresh cadavers were studied using 4-mm 0° and 30° endoscopes to develop a surgical approach and to identify surgical landmarks.

Results

The endoscopic supraorbital extradural approach was divided into 4 stages: entry into the extradural anterior cranial fossa, exposure of the middle cranial fossa and the periorbita, exposure of the superior cavernous sinus, and exposure of the lateral cavernous sinus. This approach provided superb views of the cavernous sinus structures, especially through the clinoidal (Dolenc) triangle. The lateral wall of the cavernous sinus, including the infratrochlear (Parkinson) triangle and anteromedial (Mullan) triangle, was also clearly demonstrated.

Conclusions

An endoscopic supraorbital extradural approach offers excellent exposure of the superior and lateral walls of the cavernous sinus with minimal invasiveness via the transcranial route. This approach could be an alternative to the conventional transcranial approach.

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Yoko Hirata, Noriyuki Sakata, Tooru Inoue, Kotaro Yasumori, Masahiro Yasaka and Yasushi Okada

Object

This study describes clinicopathological characteristics of pseudo-occlusion of the internal carotid artery with regard to its possible mechanisms.

Methods

The authors retrospectively reviewed 17 patients with pseudo-occlusion and 23 with high-grade stenosis (North American Symptomatic Carotid Endarterectomy Trial criteria ≥ 90%, but no collapsed distal internal carotid artery) who underwent carotid endarterectomy. Atherosclerotic risk factors, clinical presentation, angiographic findings, and histological features of plaque obtained from the carotid endarterectomy were investigated and comparisons were made between groups.

Results

Plaques obtained in the pseudo-occlusion group were significantly more fibrous and less atheromatous than those in the high-grade stenosis group. Old, organized thrombi were more frequently found in pseudo-occlusion group plaques than in high-grade stenosis group plaques. Plaques acquired in the pseudo-occlusion group had 2 different histological features: the presence or absence of the original lumen. The pseudo-occlusion plaques with total occlusion and recanalization (8 patients) were composed of thrombotic total occlusion with lumen recanalization by large neovascular channels, whereas those with severe stenosis (9 patients) were fibrous or fibroatheromatous and had severe stenosis of the original lumen. In patients with pseudo-occlusion and total occlusion and recanalization, the authors observed a significantly higher incidence of transient ischemic attack and anterior communicating artery–posterior communicating artery collateral flow than those with high-grade stenosis and pseudo-occlusion with severe stenosis.

Conclusions

Plaques of the pseudo-occlusion group were more fibrous than those of the high-grade stenosis group and had 2 different histological features: pseudo-occlusion with total occlusion and recanalization or pseudoocclusion with severe stenosis. This difference in plaque histology may be related to the clinical features of pseudoocclusion, such as symptoms and collateral flow patterns.

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Toshiro Katsuta, Tooru Inoue, Hiroyuki Nakagaki, Morishige Takeshita, Ken Morimoto and Toru Iwaki

✓ The authors present a rare case of pituicytoma. A dynamic magnetic resonance study performed after Gd injection revealed a markedly, homogeneously enhanced, early-phase pituitary lesion in a 32-year-old woman with a 1-year history of amenorrhea. The tumor bled easily during transsphenoidal resection. The lesion consisted of plump spindle cells and lacked Rosenthal fibers and granular bodies, and thus was different from ordinary pilocytic astrocytoma or any other form of this tumor. Although pituicytoma is often confused with pilocytic astrocytoma when it appears in the sellar region, these two kinds of gliomas should be distinguished on the basis of histological differences.

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Kenji Fukuda, Toshio Higashi, Masakazu Okawa, Mitsutoshi Iwaasa, Tsutomu Yoshioka and Tooru Inoue

OBJECTIVE

The white-collar sign (WCS) is known as a thick neointimal tissue formation at the aneurysm neck after endovascular coil embolization of cerebral aneurysms, which may prevent aneurysm recanalization. The purpose of this study was to evaluate factors involved in the appearance of WCS and to identify radiological and clinical outcomes of treated aneurysms with WCS.

METHODS

The study included 140 patients with 149 aneurysms in which it was possible to confirm the aneurysm neck between the aneurysm sac and parent artery by using conventional angiography. The WCS was defined as a radiolucent band at the aneurysm neck on the angiogram at 6 months after initial embolization. The radiological outcome was evaluated using MR angiography.

RESULTS

In 23 of 149 aneurysms (15.4%), a WCS appeared. The WCS-positive group had a significantly smaller neck size (3.3 ± 0.8 mm vs 4.2 ± 1.1 mm, p < 0.001) and smaller aneurysm size (4.3 ± 0.9 mm vs 6.0 ± 2.1 mm, p < 0.001) than the WCS-negative group. Multivariate analysis revealed that WCS appearance was associated with small neck size (OR 0.376, 95% CI 0.179–0.787; p = 0.009). In 106 of 149 aneurysms, the rate of complete occlusion was significantly higher in the WCS-positive group (18/18, 100%) than in the WCS-negative group (n = 54/88, 61.4%; p = 0.001) in the mean follow-up period of 31.0 ± 9.7 months (range 5–52 months). Neither major recanalization nor rupture of the aneurysm occurred in the WCS-positive group.

CONCLUSIONS

Appearance of the WCS was associated with complete occlusion and good clinical outcome after endovascular coil embolization. The WCS would help to determine the prognosis of cerebral aneurysms after endovascular treatment.

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Toshio Matsushima, Tooru Inoue, Takanori Inamura, Yoshihiro Natori, Kiyonobu Ikezaki and Masashi Fukui

Object. The purpose of the present study was to refine the transcerebellomedullary fissure approach to the fourth ventricle and to clarify the optimal method of dissecting the fissure to obtain an appropriate operative view without splitting the inferior vermis.

Methods. The authors studied the microsurgical anatomy by using formalin-fixed specimens to determine the most appropriate method of dissecting the cerebellomedullary fissure. While dissecting the spaces around the tonsils and making incisions in the ventricle roof, the procedures used to expose each ventricle wall were studied. Based on their findings, the authors adopted the best approach for use in 19 cases of fourth ventricle tumor.

The fissure was further separated into two slit spaces on each side: namely the uvulotonsillar and medullotonsillar spaces. The floor of the fissure was composed of the tela choroidea, inferior medullary velum, and lateral recess, which form the ventricle roof. In this approach, the authors first dissected the spaces around the tonsils and then incised the taenia with or without the posterior margin of the lateral recess. These precise dissections allowed for easy retraction of the tonsil(s) and uvula and provided a sufficient view of the ventricle wall such that the deep aqueductal region and the lateral region around the lateral recess could be seen without splitting the vermis. The dissecting method could be divided into three different types, including extensive (aqueduct), lateral wall, and lateral recess, depending on the location of the ventricle wall and the extent of surgical exposure required.

Conclusions. When the fissure is appropriately and completely opened, the approach provides a sufficient operative view without splitting the vermis. Two key principles of this opening method are sufficient dissection of the spaces around the tonsil(s) and an incision of the appropriate portions of the ventricle roof. The taenia(e) with or without the posterior margin of the lateral recess(es) should be incised.