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Keisuke Maruyama, Masahiro Shin, Hiroki Kurita, Masao Tago, and Takaaki Kirino

✓The authors present a case of ruptured dural arteriovenous fistula primarily draining into the superior sagittal sinus, which was successfully treated by gamma knife radiosurgery.

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Keisuke Takai, Hiroki Kurita, Takayuki Hara, Kensuke Kawai, and Makoto Taniguchi

OBJECTIVE

The microvascular anatomy of spinal perimedullary arteriovenous fistulas (AVFs) is more complicated than that of dural AVFs, and occlusion rates of AVF after open microsurgery or endovascular embolization are lower in patients with perimedullary AVFs (29%–70%) than they are in those with dural AVF (97%–98%). Reports of intraoperative blood flow assessment using indocyanine green (ICG) video angiography in spinal arteriovenous lesions have mostly been for spinal dural AVFs. No detailed reports on spinal perimedullary AVFs are available.

METHODS

Participants were 11 patients with spinal perimedullary AVFs (Type IVa in 5 patients, Type VIb in 4, and Type IVc in 2). Intraoperative ICG video angiography was assessed by measuring the number of cases in which this modality was judged essential by the surgeon to correctly occlude the fistula.

RESULTS

In all patients, arterial feeders were identified and intravenous ICG video angiography was performed before and after blocking the feeders. In one patient, selective intraarterial ICG video angiography was also performed. The findings provided by ICG video angiography significantly changed the surgical procedure in 4 of 11 patients (36%). Postoperatively, complete occlusion of the AVF was achieved in 10 of the 11 patients (91%).

CONCLUSIONS

Intraoperative ICG video angiography can have a significant impact on deciding surgical strategy in the microsurgical treatment of spinal perimedullary AVF.

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Masao Tago, Atsuro Terahara, Keiichi Nakagawa, Yukimasa Aoki, Kuni Ohtomo, Masahiro Shin, and Hiroki Kurita

✓ The authors describe acute deterioration in facial and acoustic neuropathies following radiosurgery for acoustic neuromas.

In May 1995, a 26-year-old man, who had no evidence of neurofibromatosis Type 2, was treated with gamma knife radiosurgery (GKS; maximum dose 20 Gy and margin dose 14 Gy) for a right-sided intracanalicular acoustic tumor. Two days after the treatment, he developed headache, vomiting, right-sided facial weakness, tinnitus, and right hearing loss. There was a deterioration of facial nerve function and hearing function from pretreatment values. The facial function worsened from House—Brackmann Grade 1 to 3. Hearing deteriorated from Grade 1 to 5. Magnetic resonance (MR) images, obtained at the same time revealed an obvious decrease in contrast enhancement of the tumor without any change in tumor size or peritumoral edema. Facial nerve function improved gradually and increased to House—Brackmann Grade 2 by 8 months post-GKS. The tumor has been unchanged in size for 5 years, and facial nerve function has also been maintained at Grade 2 with unchanged deafness.

This is the first detailed report of immediate facial neuropathy after GKS for acoustic neuroma and MR imaging revealing early possibly toxic changes. Potential explanations for this phenomenon are presented.

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Keiichiro Maeda, Hiroki Kurita, Tsuneo Nakamura, Masaaki Usui, Kazuo Tsutsumi, Tadashi Morimoto, and Takaaki Kirino

✓ The authors present two rare cases of severe cerebral vasospasm following the rupture of arteriovenous malformations (AVMs). Computerized tomography revealed intracerebral hemorrhage in the thalamus in one case and in the putamen in the other, both accompanied by cast formation of intraventricular clots without radiological evidence of subarachnoid hemorrhage. Initial angiograms showed arterial narrowing of the bilateral internal carotid arteries in the supraclinoid portion but failed to demonstrate an arteriovenous shunt. Subsequent angiograms clearly demonstrated the existence of an AVM. Radiological features and possible mechanisms are discussed.

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Hiroki Kurita, Tomio Sasaki, Syunsuke Kawamoto, Makoto Taniguchi, Chifumi Kitanaka, Hiroshi Nakaguchi, and Takaaki Kirino

✓ The authors report a rare case of a patient with a chronic encapsulated expanding hematoma and progressive neurological deterioration who presented 2 years after gamma knife radiosurgery for a cerebral arteriovenous malformation (AVM). A tough capsule containing multiple layers of organized hematoma resulting from previous bleeding was confirmed surgically. Histological examination revealed that the capsule consisted of a dense collagenous outer layer and a granulomatous newly vascularized inner layer with marked fibrosis. Hemosiderin deposits were frequently observed in the inner layer, which suggested recurrent minor bleeding from fragile vessels in this layer. An AVM was found in the hematoma, which had degenerated as the result of radiosurgery. A cross-section of the abnormal vessels showed various stages of obliteration due to intimal hypertrophy. The clinical course, radiological features, and histological findings in this case were compatible with those of previously reported chronic encapsulated hematomas. A possible mechanism of hematoma formation and its expansion are discussed.

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Keisuke Maruyama, Masahiro Shin, Masao Tago, Hiroki Kurita, Shunsuke Kawamoto, Akio Morita, and Takaaki Kirino

Object. The purpose of this study was to evaluate the safety and efficacy of gamma knife surgery (GKS) for the treatment of arteriovenous malformations (AVMs) involving the corpus callosum.

Methods. Thirty-two patients aged from 7 to 65 years (median 25 years) with AVMs of the corpus callosum underwent GKS between 1990 and 2002. The maximum AVM diameter was more than 3 cm in 11 patients (34%). The AVM volume ranged from 0.1 to 19.1 cm3 (median 1.6 cm3). The median dose to the AVM margin was 20 Gy (range 17–28 Gy). Patients were followed for 1 to 12 years (median 9 years). The angiographically confirmed actuarial obliteration rate was 64% and 74% at 4 and 6 years, respectively. Younger patient age (p < 0.05) and lower radiosurgery-based grading score (calculated from the patient age and AVM volume; p < 0.01) were the significant factors affecting successful AVM obliteration. No patient suffered a hemorrhage after GKS, although 28 patients (88%) had a history of hemorrhage from their AVMs. Radiation-induced neurological deficit was observed only in one patient (3%) who had undergone previous radiotherapy (50 Gy). No patient experienced complications of occlusion or stenosis of the normal vascular structures adjacent to the AVM.

Conclusions. Gamma knife surgery is a safe and effective treatment for selected patients with AVMs involving the corpus callosum, and it carries a low risk of damaging adjacent critical vascular structures. Even ruptured AVMs with relatively large diameter can be successfully treated, especially in younger patients, with minimal morbidity and a low risk of repeated hemorrhage.

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Masao Tago, Atsuro Terahara, Masahiro Shin, Keisuke Maruyama, Hiroki Kurita, Keiichi Nakagawa, and Kuni Ohtomo

Object. The authors reviewed their 14-year experience using stereotactic radiosurgery for the treatment of hemangioblastomas and define the role and the proper strategy for radiosurgery of this condition.

Methods. This is a retrospective study of 38 hemangioblastomas in 13 patients. Seven patients had von Hippel—Lindau disease. All patients have undergone at least one follow-up visit. The median and mean tumor volumes were 0.23 cm3 and 0.72 cm3 respectively (range 0.004:4.84 cm3). Twenty-eight tumors received 20 Gy to the margin, and the remainder received 18 Gy. The median clinical follow-up period was 36 months (range 3–159 months).

No patient died. The survival rate was 84.6% (11 of 13 patients). The actuarial 5- and 10-year survival rates were both 80.8%. The median radiological follow-up period was 35 months (range 7–147 months). Only one tumor increased in volume 24 months after treatment in association with an intratumoral hemorrhage. The tumor control rate was 97.4% (37 of 38 tumors). Actuarial 5- and 10-year control rates were both 96.2%. New lesions and/or those increasing in size outside the irradiated area were discovered in five patients (38.5%). Nine tumors revealed peritumoral contrast enhancement which was seen more frequently in larger tumors with a volume greater than 0.5 cm3 (p = 0.0034).

Conclusions. Gamma knife surgery is a safe and effective method to control hemangioblastomas for as many as 10 years. Higher doses and smaller tumors probably contribute to good outcomes. Recurrence outside the original irradiated area is common. Peritumoral contrast enhancement may be seen in larger tumors. The authors recommend regular imaging follow up and early repeated treatment in the face of new or growing tumors.

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Masahiro Shin, Hiroki Kurita, Tomio Sasaki, Masao Tago, Akio Morita, Keisuke Ueki, and Takaaki Kirino

Object. The purpose of this study is to determine the efficacy of gamma knife radiosurgery (GKS) treatment of pituitary adenomas that have invaded the cavernous sinus.

Methods. Sixteen patients were treated with GKS: three with nonfunctional adenomas and 13 with hormone-secreting (seven growth hormone [GH] and six adrenocorticotropic hormone [ACTH]) adenomas. More than 16 Gy and 30 Gy were delivered to the tumor margin for nonfunctioning tumors and functioning tumors, respectively, keeping the dose to the optic pathways below 10 Gy. The median follow up was 3 years.

Tumor growth control was achieved in all cases. In GH-producing tumors, four of six cases evaluated were endocrinologically normalized (serum GH < 10 mIU/L, somatomedin C < 450 ng/ml), and the remaining two cases also showed a steady decrease in the GH and somatomedin level. In ACTH-producing tumors, three of six cases were endocrinologically normalized (24-hour urinary-free cortisol < 90 mg/day), two were unchanged, and one showed hormonal recurrence 3 years after radiosurgery. Notably, there were no cases of permanent hypopituitarism or visual symptoms caused by radiosurgery.

Conclusions. The authors data indicate that GKS can be a safe salvage therapy for invading pituitary adenomas, with effectiveness equivalent to conventional radiation therapy but with less risk of causing radiation-induced injury to the surrounding structures.

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Naoki Nakamura, Masahiro Shin, Masao Tago, Atsuro Terahara, Hiroki Kurita, Kejichi Nakagawa, and Kuni Ohtomo

✓ A cavernous hemangioma occurring in the cavernous sinus is a rare vascular tumor that causes cranial nerve symptoms by direct compression. Surgical removal is often difficult because excessive intraoperative bleeding is expected. These lesions remain a therapeutic challenge even with state-of-the-art treatment modalities. The authors report three cases of cavernous hemangioma occurring in the cavernous sinus that were treated with gamma knife radiosurgery, with a mean patient age of 66 years and a mean tumor volume of 2.3 cm3.

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Kenichi Usami, Kensuke Kawai, Tomoyuki Koga, Masahiro Shin, Hiroki Kurita, Ichiro Suzuki, and Nobuhito Saito

Object

Despite the controversy over the clinical significance of Gamma Knife surgery (GKS) for refractory mesial temporal lobe epilepsy (MTLE), the modality has attracted attention because it is less invasive than resection. The authors report long-term outcomes for 7 patients, focusing in particular on the long-term complications.

Methods

Between 1996 and 1999, 7 patients with MTLE underwent GKS. The 50% marginal dose covering the medial temporal structures was 18 Gy in 2 patients and 25 Gy in the remaining 5 patients.

Results

High-dose treatment abolished the seizures in 2 patients and significantly reduced them in 2 others. One patient in this group was lost to follow-up. However, 2 patients presented with symptomatic radiation necrosis (SRN) necessitating resection after 5 and 10 years. One patient who did not need necrotomy continued to show radiation necrosis on MRI after 10 years. One patient died of drowning while swimming in the sea 1 year after GKS, before seizures had disappeared completely.

Conclusions

High-dose treatment resulted in sufficient seizure control but carried a significant risk of SRN after several years. Excessive target volume was considered as a reason for delayed necrosis. Drawbacks such as a delay in seizure control and the risk of SRN should be considered when the clinical significance of this treatment is evaluated.