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Kazuo Mizol, Akira Takahashi, Takashi Yoshimoto, Takayuki Sugawara and Keiichi Saito

✓ The authors present two cases of giant cerebellar hemispheric arteriovenous malformation (AVM) managed with staged preoperative embolization and surgical resection. A new embolization technique is described, combining injection of estrogen alcohol and polyvinyl acetate into AVM's by superselective catheterization of feeding arteries. Polyvinyl acetate proved to be an ideal liquid embolic material; because it polymerizes quickly and remains in a gelatinous state after injection, there was no difficulty in cutting and retracting the obliterated AVM during surgery. Intraoperative digital subtraction angiography was useful for confirming complete excision of the large and complex AVM.

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Takashi Handa, Yoshio Suzuki, Kiyoshi Saito, Kenichiro Sugita and Sunil J. Patel

✓ The case is presented of an isolated intramedullary posterior spinal artery aneurysm at the C-2 level in a 3-year-old girl. Quadriplegia related to probable intramedullary hemorrhage was the presenting symptom. Magnetic resonance imaging revealed findings consistent with an intramedullary vascular lesion, and vertebral angiography confirmed this to be an aneurysm of the posterior spinal artery. No associated vascular abnormalities were noted, and the aneurysm was successfully resected. Previous reports of isolated spinal aneurysms are reviewed.

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Takashi Watanabe, Nobuhito Saito, Junko Hirato, Hidetoshi Shimaguchi, Hiroya Fujimaki and Tomio Sasaki

✓ Complete facial palsy (House—Brackmann Grade VI) developed in a 63-year-old man with a vestibular schwannoma 25 months after he had undergone two gamma knife surgeries performed 33 months apart and involving a cumulative dose of 24 Gy directed to the tumor margin at the 50% isodose line. Magnetic resonance imaging demonstrated tumor enlargement with central nonenhancement, which initially had been recognized 21 months after the second radiosurgery. Microsurgery was performed to achieve total removal of the tumor. Histological and immunohistochemical examinations of the facial nerve specimen removed from the edge of the tumor revealed a loss of axons, proliferation of Schwann cells, and microvasculitis. In this case, microvasculitis and axonal degeneration were probably the major causes of the radiation-induced facial neuropathy.

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Takashi Inoue, Hiroaki Shimizu, Miki Fujimura, Atsushi Saito and Teiji Tominaga

Object

In this paper, the authors' goals were to clarify the characteristics of growing unruptured cerebral aneurysms detected by serial MR angiography and to establish the recommended follow-up interval.

Methods

A total of 1002 patients with 1325 unruptured cerebral aneurysms were retrospectively identified. These patients had undergone follow-up evaluation at least twice. Aneurysm growth was defined as an increase in maximum aneurysm diameter by 1.5 times or the appearance of a bleb.

Results

Aneurysm growth was observed in 18 patients during the period of this study (1.8%/person-year). The annual rupture risk after growth was 18.5%/person-year. The proportion of females among patients with growing aneurysms was significantly larger than those without growing aneurysms (p = 0.0281). The aneurysm wall was reddish, thin, and fragile on intraoperative findings. Frequent follow-up examination is recommended to detect aneurysm growth before rupture.

Conclusions

Despite the relatively short period, the annual rupture risk of growing unruptured cerebral aneurysms detected by MR angiography was not as low as previously reported. Surgical or endovascular treatment can be considered if aneurysm growth is detected during the follow-up period.

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Katsushige Watanabe, Takashi Watanabe, Akio Takahashi, Nobuhito Saito, Masafumi Hirato and Tomio Sasaki

✓ The feasibility of high-frequency transcranial electrical stimulation (TES) through screw electrodes placed in the skull was investigated for use in intraoperative monitoring of the motor pathways in patients who are in a state of general anesthesia during cerebral and spinal operations.

Motor evoked potentials (MEPs) were elicited by TES with a train of five square-wave pulses (duration 400 µsec, intensity ≤ 200 mA, frequency 500 Hz) delivered through metal screw electrodes placed in the outer table of the skull over the primary motor cortex in 42 patients. Myogenic MEPs to anodal stimulation were recorded from the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. The mean threshold stimulation intensity was 48 ± 17 mA for the APB muscles, and 112 ± 35 mA for the TA muscles. The electrodes were firmly fixed at the site and were not dislodged by surgical manipulation throughout the operation. No adverse reactions attributable to the TES were observed.

Passing current through the screw electrodes stimulates the motor cortex more effectively than conventional methods of TES. The method is safe and inexpensive, and it is convenient for intraoperative monitoring of motor pathways.

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Yoshio Miyasaka, Kenzoh Yada, Takashi Ohwada, Takao Kitahara, Masataka Endoh, Motoyoshi Saito, Akira Kurata and Hirotoshi Ohtaka

✓ Five cases of retrograde thrombosis of former feeding arteries after removal of an arteriovenous malformation (AVM) are reported. The clinical features of these patients were studied and compared to those of 71 patients without this complication. The following characteristics were found to correlate with retrograde thrombosis: 1) advancing age of the patient; 2) large AVM size; and 3) markedly dilated and elongated feeders. It is suggested that the slow flow in the former feeding arteries that was observed immediately after AVM removal and pathological changes in these vessels due to long-standing hemodynamic stresses contributed to the development of retrograde thrombosis. Neurological manifestations related to retrograde thrombosis were noted in three of the five cases. Although infrequent, this complication should be considered as a serious possibility following removal of an AVM.

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Atsuhiro Nakagawa, Yasuko Kusaka, Takayuki Hirano, Tsutomu Saito, Reizo Shirane, Kazuyoshi Takayama and Takashi Yoshimoto

Object. Shock waves have not previously been used as a treatment modality for lesions in the brain and skull because of the lack of a suitable shock wave source and concerns about safety. Therefore, the authors have performed experiments aimed at developing both a new, compact shock wave generator with a holmium:yttrium-aluminum-garnet (Ho:YAG) laser and a safe method for exposing the surface of the brain to these shock waves.

Methods. Twenty male Sprague—Dawley rats were used in this study. In 10 rats, a single shock wave was delivered directly to the brain, whereas the protective effect of inserting a 0.7-mm-thick expanded polytetrafluoroethylene (ePTFE) dural substitute between the dura mater and skull before applying the shock wave was investigated in the other 10 rats. Visualizations on shadowgraphy along with pressure measurements were obtained to confirm that the shock wave generator was capable of conveying waves in a limited volume without harmful effects to the target. The attenuation rates of shock waves administered through a 0.7-mm-thick ePTFE dural substitute and a surgical cottonoid were measured to determine which of these materials was suitable for avoiding propagation of the shock wave beyond the target.

Conclusions. Using the shock wave generator with the Ho:YAG laser, a localized shock wave (with a maximum overpressure of 50 bar) can be generated from a small device (external diameter 15 mm, weight 20 g). The placement of a 0.7-mm-thick ePTFE dural substitute over the dura mater reduces the overpressure of the shock wave by 96% and eliminates damage to surrounding tissue in the rat brain. These findings indicate possibilities for applying shock waves in various neurosurgical treatments such as cranioplasty, local drug delivery, embolysis, and pain management.

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Masayuki Nitta, Yoshihiro Muragaki, Takashi Maruyama, Hiroshi Iseki, Takashi Komori, Soko Ikuta, Taiichi Saito, Takayuki Yasuda, Junji Hosono, Saori Okamoto, Shunichi Koriyama and Takakazu Kawamata

OBJECTIVE

In this study on the effectiveness and safety of photodynamic therapy (PDT) using talaporfin sodium and a semiconductor laser, the long-term follow-up results of 11 patients with glioblastoma enrolled in the authors’ previous phase II clinical trial (March 2009–2012) and the clinical results of 19 consecutive patients with newly diagnosed glioblastoma prospectively enrolled in a postmarket surveillance (March 2014–December 2016) were analyzed and compared with those of 164 patients treated without PDT during the same period.

METHODS

The main outcome measures were the median overall survival (OS) and progression-free survival (PFS) times. Moreover, the adverse events and radiological changes after PDT, as well as the patterns of recurrence, were analyzed and compared between the groups. Kaplan-Meier curves were created to assess the differences in OS and PFS between the groups. Univariate and multivariate analyses were performed to identify the prognostic factors, including PDT, among patients with newly diagnosed glioblastoma.

RESULTS

The median PFS times of the PDT and control groups were 19.6 and 9.0 months, with 6-month PFS rates of 86.3% and 64.9%, respectively (p = 0.016). The median OS times were 27.4 and 22.1 months, with 1-year OS rates of 95.7% and 72.5%, respectively (p = 0.0327). Multivariate analyses found PDT, preoperative Karnofsky Performance Scale score, and IDH mutation to be significant independent prognostic factors for both OS and PFS. Eighteen of 30 patients in the PDT group experienced tumor recurrence, including local recurrence, distant recurrence, and dissemination in 10, 3, and 4 patients, respectively. Conversely, 141 of 164 patients in the control group experienced tumor recurrence, including 101 cases of local recurrence. The rate of local recurrence tended to be lower in the PDT group (p = 0.06).

CONCLUSIONS

The results of the present study suggest that PDT with talaporfin sodium and a semiconductor laser provides excellent local control, with few adverse effects even in cases of multiple laser irradiations, as well as potential survival benefits for patients with newly diagnosed glioblastoma.

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Masayuki Nitta, Yoshihiro Muragaki, Takashi Maruyama, Soko Ikuta, Takashi Komori, Katsuya Maebayashi, Hiroshi Iseki, Manabu Tamura, Taiichi Saito, Saori Okamoto, Mikhail Chernov, Motohiro Hayashi and Yoshikazu Okada

OBJECT

There is no standard therapeutic strategy for low-grade glioma (LGG). The authors hypothesized that adjuvant therapy might not be necessary for LGG cases in which total radiological resection was achieved. Accordingly, they established a treatment strategy based on the extent of resection (EOR) and the MIB-1 index: patients with a high EOR and low MIB-1 index were observed without postoperative treatment, whereas those with a low EOR and/or high MIB-1 index received radiotherapy (RT) and/or chemotherapy. In the present retrospective study, the authors reviewed clinical data on patients with primarily diagnosed LGGs who had been treated according to the above-mentioned strategy, and they validated the treatment policy. Given their results, they will establish a new treatment strategy for LGGs stratified by EOR, histological subtype, and molecular status.

METHODS

One hundred fifty-three patients with diagnosed LGG who had undergone resection or biopsy at Tokyo Women's Medical University between January 2000 and August 2010 were analyzed. The patients consisted of 84 men and 69 women, all with ages ≥ 15 years. A total of 146 patients underwent surgical removal of the tumor, and 7 patients underwent biopsy.

RESULTS

Postoperative RT and nitrosourea-based chemotherapy were administered in 48 and 35 patients, respectively. Extent of resection was significantly associated with both overall survival (OS; p = 0.0096) and progression-free survival (PFS; p = 0.0007) in patients with diffuse astrocytoma but not in those with oligodendroglial subtypes. Chemotherapy significantly prolonged PFS, especially in patients with oligodendroglial subtypes (p = 0.0009). Patients with a mutant IDH1 gene had significantly longer OS (p = 0.034). Multivariate analysis did not identify MIB-1 index or RT as prognostic factors, but it did identify chemotherapy as a prognostic factor for PFS and EOR as a prognostic factor for OS and PFS.

CONCLUSIONS

The findings demonstrated that EOR was significantly correlated with patient survival; thus, one should aim for maximum tumor resection. In addition, patients with a higher EOR can be safely observed without adjuvant therapy. For patients with partial resection, postoperative chemotherapy should be administered for those with oligodendroglial subtypes, and repeat resection should be considered for those with astrocytic tumors. More aggressive treatment with RT and chemotherapy may be required for patients with a poor prognosis, such as those with diffuse astrocytoma, 1p/19q nondeleted tumors, or IDH1 wild-type oligodendroglial tumors with partial resection.

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Taiichi Saito, Yoshihiro Muragaki, Manabu Tamura, Takashi Maruyama, Masayuki Nitta, Shunsuke Tsuzuki, Satoko Fukuchi, Mana Ohashi and Takakazu Kawamata

OBJECTIVE

Resection of gliomas in the precentral gyrus carries a risk of severe motor dysfunction. To prevent permanent, severe postoperative motor dysfunction, reliable intraoperative predictors of postoperative function are required. Since 2005, the authors have removed gliomas in the precentral gyrus with combined functional mapping and estimation of intraoperative voluntary movement (IVM) during awake craniotomy and transcortical motor evoked potentials (MEPs). The purpose of the current study was to evaluate whether intraoperative findings of combined monitoring of IVM during awake craniotomy and transcortical MEP monitoring were useful for predicting postoperative motor function of patients with gliomas in the precentral gyrus.

METHODS

The current study included 30 patients who underwent resection of precentral gyrus gliomas during awake craniotomy from April 2000 to January 2018. All tumors were removed with monitoring of IVM during awake craniotomy and transcortical MEPs. Postoperative motor function was classified as stable or declined, with the extent of decline categorized as mild, moderate, or severe. We defined moderate and severe deficits were those that hindered daily life.

RESULTS

In 28 of 30 cases, available waveforms were obtained with transcortical MEPs. The mean extent of resection (EOR) was 93%. Relative to preoperative status, motor function 6 months after surgery was considered stable in 20 patients and was considered to show mild decline in 7, moderate decline in 2, and severe decline in 1. Motor function 6 months after surgery was significantly correlated with IVM (p = 0.0096), changes in transcortical MEPs (decline ≤ or > 50%) (p = 0.0163), EOR, and ischemic lesions on postoperative MRI. Six patients with no change in IVM showed stable motor function 6 months after surgery. Only 2 patients with a decline in IVM and a decline in MEPs ≤ 50% had a decline in motor function 6 months after surgery (18%; 2/11 patients), whereas 11 patients with a decline in IVM and a decline in MEPs > 50% had such a decline in motor function (73%; 8/11 patients) including 2 patients with moderate and 1 with severe deficits. Three patients with moderate or severe motor deficits showed the lowest MEP values (< 100 µV).

CONCLUSIONS

Combined judgment from monitoring of IVM during awake craniotomy and transcortical MEPs is useful for predicting postoperative motor function during removal of gliomas in the precentral gyrus. Maximum resection was achieved with an acceptable morbidity rate. Thus, these tumors should not be considered unresectable.