Details of a Researcher - AKIYAMA Yukinori

Papers - AKIYAMA Yukinori

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So-called bifocal tumors with diabetes insipidus and negative tumor markers: are they all germinoma?

Masayuki Kanamori, Hirokazu Takami, Shigeru Yamaguchi, Takashi Sasayama, Koji Yoshimoto, Teiji Tominaga, Akihiro Inoue, Naokado Ikeda, Atsushi Kambe, Toshihiro Kumabe, Masahide Matsuda, Shota Tanaka, Manabu Natsumeda, Ken-Ichiro Matsuda, Masahiro Nonaka, Jun Kurihara, Masayoshi Yamaoka, Naoki Kagawa, Naoki Shinojima, Tetsuya Negoto, Yukiko Nakahara, Yoshiki Arakawa, Seiji Hatazaki, Hiroaki Shimizu, Atsuo Yoshino, Hiroshi Abe, Jiro Akimoto, Yu Kawanishi, Tomonari Suzuki, Atsushi Natsume, Motoo Nagane, Yukinori Akiyama, Dai Keino, Tadateru Fukami, Takahiro Tomita, Kohei Kanaya, Tsutomu Tokuyama, Shuichi Izumoto, Mitsutoshi Nakada, Daisuke Kuga, Shohei Yamamoto, Ryogo Anei, Takeo Uzuka, Junya Fukai, Noriyuki Kijima, Keita Terashima, Koichi Ichimura, Ryo Nishikawa

Neuro-oncology 23 ( 2 ) 295 - 303 2021.02 [International journal]

BACKGROUND: The Delphi consensus statements on the management of germ cell tumors (GCTs) failed to reach agreements on the statement that the cases with (i) pineal and neurohypophyseal bifocal lesion, (ii) with diabetes insipidus, and (iii) with negative tumor markers can be diagnosed as germinoma without histological verification. To answer this, multicenter retrospective analysis was performed. METHODS: A questionnaire on clinical findings, histological diagnosis, and details of surgical procedures was sent to 86 neurosurgical and 35 pediatrics departments in Japan. RESULTS: Fifty-one institutes reported 132 cases that fulfilled the 3 criteria. Tissue sampling was performed in 91 cases from pineal (n = 44), neurohypophyseal (n = 32), both (n = 6), and distant (n = 9) lesions. Histological diagnosis was established in 89 cases: pure germinoma or germinoma with syncytiotrophoblastic giant cells in 82 (92.1%) cases, germinoma and mature teratoma in 2 cases, and granulomatous inflammation in 2 cases. Histological diagnosis was not established in 2 cases. Although no tumors other than GCTs were identified, 3 (3.4%) patients had non-germinomatous GCTs (NGGCTs). None of the patients developed permanent complications after endoscopic or stereotactic biopsy. Thirty-nine patients underwent simultaneous procedure for acute hydrocephalus without permanent complications, and hydrocephalus was controlled in 94.9% of them. CONCLUSION: All patients who fulfilled the 3 criteria had GCTs or granulomatous inflammation, but not other types of tumors. However, no fewer than 3.4% of the patients had NGGCTs. Considering the safety and the effects of simultaneous procedures for acute hydrocephalus, biopsy was recommended in such patients.

Stroke Mimics and Chameleons from the Radiological Viewpoint of Glioma Diagnosis.

Ayaka Sasagawa, Takeshi Mikami, Yusuke Kimura, Yukinori Akiyama, Shintaro Sugita, Tadashi Hasegawa, Masahiko Wanibuchi, Nobuhiro Mikuni

Neurologia medico-chirurgica 61 ( 2 ) 134 - 143 2021.02 [Domestic journal]

Gliomas are sometimes difficult to differentiate from strokes and are often misdiagnosed on magnetic resonance imaging (MRI); thus, the terms "stroke mimics" and "stroke chameleons" have been introduced. In this study, we analyzed stroke mimics and stroke chameleons in glioma and discussed the diagnostic perplexity.We retrospectively reviewed cases that were removed from lesions that were considered to be brain tumors. This study enrolled 214 patients who underwent tumor resection for suspected glioma. Clinical characteristics and radiological findings of the patients were compared between the masquerade findings group, which was further divided into two groups: the stroke chameleons and stroke mimics according to their final diagnosis, and the intelligible findings group.Stroke chameleons and stroke mimics were significantly higher in age and smaller in lesion size than the intelligible findings group. In the multivariate analysis, the predictive factor of the masquerade finding group was higher age and smaller size. Stroke mimics group has a tendency to be higher rate of hyperintensity lesion on diffusion-weighted imaging (DWI) compared with stroke chameleons group. The average period from initial diagnosis to pathological diagnosis was 13.50 days in the stroke chameleons and 61.50 days in the stroke mimics, which proved significantly different.Proper diagnosis of glioma and stroke affects a patient's prognosis, and should be diagnosed as soon as possible. However, stroke mimics and stroke chameleons caused by glioma can occur. Thus, the diagnosis of a stroke should take into consideration the possibility of a glioma in real clinical situations.

Nation-wide Brain Tumor Registry-based Study of Intracranial Meningioma in Japan: Analysis of Surgery-related Risks.

Soichi Oya, Fusao Ikawa, Nao Ichihara, Masahiko Wanibuchi, Yukinori Akiyama, Hirofumi Nakatomi, Nobuhiro Mikuni, Yoshitaka Narita

Neurologia medico-chirurgica 61 ( 2 ) 98 - 106 2021.02 [Domestic journal]

Although surgical resection is the most preferred treatment for intracranial meningiomas, a detailed analysis of the surgery-related risks based on large population data has not been conducted to date. In this study, we analyzed the nation-wide brain tumor registry to assess the surgical risk factors for intracranial meningiomas to provide information for an optimal treatment strategy. Data of 4081 meningioma patients who underwent initial resection between 2001 and 2008 were extracted from the Brain Tumor Registry of Japan (BTRJ) database and reviewed for postoperative mortality, aggravation of Karnofsky Performance Score (KPS), and complications. The total in-hospital mortality rate was 0.59%. Male sex and tumor size ≥30 mm were independent risk factors for mortality. Among 4081 cases, 4.4% of patients had KPS that were lowered by 20 or more points at the time of discharge after surgery. Age ≥65 years, higher WHO grading, tumor location at the skull base, tumor size ≥30 mm, and non-gross total resections were associated with lowering of KPS scores by 20 or more points. The overall incidence of surgical complications was 19.3%. The rate of occurrence of new postoperative seizure in patients with supratentorial meningioma was 10.9%. All complications except for vascular complications occurred with significantly lower frequencies in asymptomatic patients than in symptomatic patients. Our results provide useful information regarding the surgical risks when surgical intervention is being considered for intracranial meningiomas. Surgery is an important option for asymptomatic meningiomas as the mortality rate and complication rate in the current study were sufficiently low.

COVID-19 infection in Hokkaido, Japan might depend on the viscosity of atmospheric air.

Yukinori Akiyama, Kyoya Sakashita, Masayasu Arihara, Yusuke Kimura, Katsuya Komatsu, Takeshi Mikami, Nobuhiro Mikuni

Virus research 293 198259 - 198259 2021.02 [International journal]

BACKGROUND: The large number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has plunged the world into fear in recent times. In Japan, 18,769 novel coronavirus disease 2019 (COVID-19) cases have been reported as of June 30, 2020. This study aimed to assess whether cluster infection prevention is possible by evaluating the association between viral transmission and meteorological factors. METHODS: This study included 1263 people who were successively diagnosed with COVID-19 in Hokkaido, Japan between January 24, 2020 and June 30, 2020. After obtaining the values from the Japanese Meteorological Agency, the average scores of air temperature and humidity were calculated and compared with COVID-19 reproduction numbers, and the association between COVID-19 incidence or reproduction number and meteorological factors was assessed. RESULTS: The COVID-19 reproduction number in Hokkaido had three peaks that came several days before the surge in COVID-19 cases. The peaks are indicative of cluster infections. There was a strong negative correlation between the kinematic viscosity of atmospheric air and the reproduction number. DISCUSSION AND CONCLUSION: Analysis of the reproduction number is important for predicting or suppressing COVID-19 infection clusters. The authors found a strong association between meteorological factors, such as kinematic viscosity of atmospheric air and the incidence of COVID-19 infection. Meteorological forecasts could provide foreknowledge about COVID-19 infection clusters in the future.

Preoperative Prediction of Communication Difficulties during Awake Craniotomy in Glioma Patients: A Retrospective Evaluation of 136 Cases at a Single Institution.

Tomoyoshi Kuribara, Yukinori Akiyama, Takeshi Mikami, Yusuke Kimura, Katsuya Komatsu, Rei Enatsu, Yasuyuki Tokinaga, Nobuhiro Mikuni

Neurologia medico-chirurgica 61 ( 1 ) 21 - 32 2021.01 [Domestic journal]

Awake craniotomy has been widely performed in patients with glioma in eloquent areas to minimize postoperative brain dysfunction. However, neurological examination in awake craniotomy is sometimes problematic due to communication difficulties during the intraoperative awake period. We evaluated preoperative predictors of these difficulties in awake craniotomy for patients with glioma. In all, 136 patients with glioma who underwent awake craniotomy at our institution between January 2012 and January 2020 were retrospectively evaluated. Patients were divided into two groups (appropriately awake group and inappropriately awake group) depending on their state during the intraoperative awake period, and the relationship between communication difficulties in awake craniotomy and both clinical and radiological characteristics were assessed. The appropriately awake group included 110 patients, and the inappropriately awake group included 26 patients. Reasons for inclusion in the inappropriately awake group were insufficient wakefulness in 15 patients, restless state in 6, and intraoperative seizures in 5. In multivariate analysis, the likelihood of being inappropriately awake was inversely correlated with preoperative seizures (odds ratio [OR], 0.23; 95% confidence interval [CI], 0.06-0.89; p = 0.033) and positively correlated with left-sided lesions (OR, 7.31; 95% CI, 1.54-34.62; p = 0.012). Both lack of preoperative seizures and left-sided lesions were identified as risk factors for intraoperative difficulties in awake craniotomy for patients with glioma. Understanding these risk factors may lead to more appropriate determination of eligibility for awake craniotomy.

Preoperatively estimated graft flow rate contributes to the improvement of hemodynamics in revascularization for Moyamoya disease.

Tomoyoshi Kuribara, Takeshi Mikami, Katsuya Komatsu, Yusuke Kimura, Sangnyon Kim, Kei Miyata, Yukinori Akiyama, Rei Enatsu, Toru Hirano, Nobuhiro Mikuni

Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 30 ( 1 ) 105450 - 105450 2021.01 [International journal]

OBJECTIVES: Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass operation is an effective treatment for patients with Moyamoya disease, and the hemodynamic parameters are reported to be improved after operation. However, there is no report concerning hemodynamic changes from the viewpoint of the preoperative anatomical structure of grafts. In this study, we evaluated the correlation between the preoperatively estimated blood flow of the graft obtained through image-based computational fluid dynamics (CFD) analysis and the hemodynamic changes in the acute phase after revascularization. MATERIALS AND METHODS: A total of 30 hemispheric sides of 23 patients were examined. The blood flow, that is, flow rate (FR) of the STA branches that were anastomosed to the MCA was evaluated using CFD analysis based on computed tomography (CT) angiography imaging data. The correlations between the FR and the hemodynamic changes in the acute phase after revascularization obtained through CT perfusion were assessed. RESULTS: The preoperatively estimated FR of the graft was moderately correlated with the changes in the mean transit time significantly and weakly correlated with those in the cerebral blood flow and cerebral blood volume. In addition, the FR was strongly correlated with age and the diameter of the STA from the origin to the bifurcation. CONCLUSION: The preoperatively estimated FR of the graft obtained through image-based CFD analysis contributed to the improvement of the mean transit time after revascularization. Because the FR of the graft was associated with the diameter of the STA, the size of the STA might be an important factor in postoperative hemodynamic changes. This might lead to the risk assessment of acute drastic hemodynamic changes as cerebral hyperperfusion, and consequently, better surgical outcomes might be expected.

Necessity for craniospinal irradiation of germinoma with positive cytology without spinal lesion on MR imaging-A controversy.

Masayuki Kanamori, Hirokazu Takami, Tomonari Suzuki, Teiji Tominaga, Jun Kurihara, Shota Tanaka, Seiji Hatazaki, Motoo Nagane, Masahide Matsuda, Atsuo Yoshino, Manabu Natsumeda, Masayoshi Yamaoka, Naoki Kagawa, Yukinori Akiyama, Junya Fukai, Tetsuya Negoto, Ichiyo Shibahara, Kazuhiro Tanaka, Akihiro Inoue, Mitsuhiro Mase, Takahiro Tomita, Daisuke Kuga, Noriyuki Kijima, Tadateru Fukami, Yukiko Nakahara, Atsushi Natsume, Koji Yoshimoto, Dai Keino, Tsutomu Tokuyama, Kenichiro Asano, Kenta Ujifuku, Hiroshi Abe, Mitsutoshi Nakada, Ken-Ichiro Matsuda, Yoshiki Arakawa, Naokado Ikeda, Yoshitaka Narita, Naoki Shinojima, Atsushi Kambe, Masahiko Nonaka, Shuichi Izumoto, Yu Kawanishi, Kohei Kanaya, Sadahiro Nomura, Kohei Nakajima, Shohei Yamamoto, Keita Terashima, Koichi Ichimura, Ryo Nishikawa

Neuro-oncology advances 3 ( 1 ) vdab086 2021 [International journal]

BACKGROUND: Cerebrospinal fluid (CSF) cytology and spinal MR imaging are routinely performed for staging before treatment of intracranial germinoma. However, the interpretation of the results of CSF cytology poses 2 unresolved clinical questions: (1) Does positive CSF cytology correlate with the presence of spinal lesion before treatment? and (2) Is craniospinal irradiation (CSI) necessary for patients with positive CSF cytology in the absence of spinal lesion? METHODS: Multicenter retrospective analyses were performed based on a questionnaire on clinical features, spinal MR imaging finding, results of CSF cytology, treatments, and outcomes which was sent to 86 neurosurgical and 35 pediatrics departments in Japan. Pretreatment frequencies of spinal lesion on MR imaging were compared between the patients with positive and negative cytology. Progression-free survival (PFS) rates were compared between patients with positive CSF cytology without spinal lesion on MR imaging treated with CSI and with whole brain or whole ventricular irradiation (non-CSI). RESULTS: A total of 92 germinoma patients from 45 institutes were evaluated by both CSF cytology and spinal MR images, but 26 patients were excluded because of tumor markers, the timing of CSF sampling or incomplete estimation of spinal lesion. Of the remaining 66 germinoma patients, spinal lesions were equally identified in patients with negative CSF cytology and positive cytology (4.9% and 8.0%, respectively). Eleven patients treated with non-CSI had excellent PFS comparable to 11 patients treated with CSI. CONCLUSION: CSI is unnecessary for germinoma patients with positive CSF cytology without spinal lesions on MR imaging.

PHASE I/II STUDY OF TEMOZOLOMIDE PLUS NIMUSTINE CHEMOTHERAPY FOR RECURRENT MALIGNANT GLIOMAS: KYOTO NEURO-ONCOLOGY GROUP

Tomokazu Aoki, Yoshiki Arakawa, Tetsuya Ueba, Masashi Oda, Namiko Nishida, Yukinori Akiyama, Tomokazu Aoki, Koichi Iwasaki, Nobuhiro Mikuni, Susumu Miyamoto

NEURO-ONCOLOGY ( OXFORD UNIV PRESS INC ) 22 49 - 50 2020.11

Recurrence Interval Within 1 Year Leads to Death in Patients with Grade 2 Meningioma.

Ryo Ukai, Masahiko Wanibuchi, Katsuya Komatsu, Yusuke Kimura, Yukinori Akiyama, Takeshi Mikami, Nobuhiro Mikuni

World neurosurgery 142 e58-e65 2020.10 [International journal]

OBJECTIVE: Grade 2 meningioma is more likely to recur than grade 1 meningioma. Recurrence decreases overall survival in patients with grade 2 meningioma. However, the clinical course of grade 2 meningioma with several repeated recurrences is poorly understood. The purpose of this study was to clarify the clinical characteristics of grade 2 meningioma with repeated recurrences. METHODS: This study included 28 patients with grade 2 meningioma treated at our institution from January 1994 to December 2017. The relationship between survival and factors including age, sex, number of recurrences, malignant transformation, radiation therapy, tumor location, MIB-1 labeling index, Simpson grade, Karnofsky Performance Status, and surgical interval were analyzed. RESULTS: The average age at the initial operation was 53.4 years. The number of recurrences was 3.7 times on average during the follow-up of 113.9 months after the initial operation. An increasing number of recurrences resulted in shortening of the surgical interval, increase in the MIB-1 labeling index, and decrease in Karnofsky Performance Status. In fatal cases, the average surgical interval before death was approximately 1 year. Three factors were related to poor prognosis: number of recurrences (odds ratio, 1.620; P = 0.030), malignant transformation (odds ratio, 10.625; P = 0.019), and high MIB-1 labeling index (odds ratio, 1.089; P = 0.044). CONCLUSIONS: Shortening of the surgical interval within 1 year because of multiple recurrences led to death in patients with grade 2 meningioma. Malignant transformation was the most potent among the poor prognostic factors.

Deep Learning-Based Approach for the Diagnosis of Moyamoya Disease.

Yukinori Akiyama, Takeshi Mikami, Nobuhiro Mikuni

Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 29 ( 12 ) 105322 - 105322 2020.09 [International journal]

OBJECTIVES: Moyamoya disease is a unique cerebrovascular disorder that is characterized by chronic bilateral stenosis of the internal carotid arteries and by the formation of an abnormal vascular network called moyamoya vessels. In this stury, the authors inspected whether differentiation between patients with moyamoya disease and those with atherosclerotic disease or normal controls might be possible by using deep machine learning technology. MATERIALS AND METHODS: This study included 84 consecutive patients diagnosed with moyamoya disease at our hospital between April 2009 and July 2016. In each patient, two axial continuous slices of T2-weighed imaging at the level of the basal cistern, basal ganglia, and centrum semiovale were acquired. The image sets were processed by using code written in the programming language Python 3.7. Deep learning with fine tuning developed using VGG16 comprised several layers. RESULTS: The accuracies of distinguishing between patients with moyamoya disease and those with atherosclerotic disease or controls in the basal cistern, basal ganglia, and centrum semiovale levels were 92.8, 84.8, and 87.8%, respectively. CONCLUSION: The authors showed excellent results in terms of accuracy of differential diagnosis of moyamoya disease using AI with the conventional T2 weighted images. The authors suggest the possibility of diagnosing moyamoya disease using AI technique and demonstrate the area of interest on which AI focuses while processing magnetic resonance images.

Arterial transit artifacts observed by arterial spin labeling in Moyamoya disease.

Ryo Ukai, Takeshi Mikami, Hiroshi Nagahama, Masahiko Wanibuchi, Yukinori Akiyama, Kei Miyata, Nobuhiro Mikuni

Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 29 ( 9 ) 105058 - 105058 2020.09 [International journal]

OBJECTIVES: Arterial spin labeling (ASL) is a magnetic resonance imaging (MRI) technique used to assess cerebral perfusion. When tissue perfusion is impaired, such as in Moyamoya disease, a hyperintense band called the arterial transit artifact (ATA) may occur, which interferes with accurate measurements on ASL-MRI. In this study, we evaluated the correlation of ATAs with magnetic resonance angiography (MRA) and single-photon emission computed tomography (SPECT) imaging results in Moyamoya disease. The aim of our study was to elucidate the pathophysiology of ATAs and risk factors for high ATA scores. MATERIALS AND METHODS: This retrospective study included 28 patients (56 hemispheres) with Moyamoya disease treated at our institution. MRI, MRA, ASL perfusion, and N-isopropyl-[123I] b-iodoamphetamine (123I-IMP) SPECT were performed. In order to semi-quantitatively evaluate the degree of ATA, the ATA scores were measured according to the number of hyperintense signal bands in the cerebral cortex. The relationship between the ATA scores and clinical and radiological factors were analyzed. RESULTS: Regional cerebral blood flow (rCBF) determined with ASL weakly correlated with that determined by 123I-IMP SPECT (ρ=0.31, p=0.027). There was no significant association between the ATA scores and rCBF values determined with 123I-IMP SPECT (p=0.872, 0.745, 0.743 at PLD1000 (post-labeling delay), 1500, and 2000, respectively). However, there was a significant correlation between ATA scores and MRA scores (ρ=0.427 p=0.001; ρ=0.612 p=0.001; ρ=0.563 p=0.001 at PLD1000, 1500, and 2000, respectively). An analysis of patient background characteristics revealed a significantly higher incidence of high ATA scores in female patients, patients with high MRA scores, and patients with a distinguishable ivy sign. A multivariate analysis confirmed that female sex, high MRA score, and presence of an ivy sign were risk factors for high ATA scores. CONCLUSION: ATA scores were moderately correlated with MRA scores, and presence of an ivy sign was the most predictive factor for high ATA scores. A high ATA score determined using ASL in a patient with Moyamoya disease might suggest an advanced disease stage and a reduction in cerebrovascular reserve capacity.

Natural Y-shaped radial artery graft bypass for a complex middle cerebral artery aneurysm: A case report.

Ryota Sato, Takeshi Mikami, Hime Suzuki, Akinori Yamamura, Yusuke Kimura, Ryo Ukai, Tomoaki Tamada, Yuka Kawata, Yukinori Akiyama, Nobuhiro Mikuni

Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 29 ( 7 ) 104853 - 104853 2020.07 [International journal]

Giant thrombosed middle cerebral artery (MCA) aneurysms are difficult to treat and sometimes require complex revascularization using allografts. We describe a technical method using revascularization with a natural Y-shaped graft that provides a normal variation for a complex MCA aneurysm. A 65-year-old man with a giant thrombosed MCA aneurysm presented with right hemiparesis and aphasia. The patient had a history of clipping surgery for the ipsilateral side of the MCA aneurysm 25 years before, and a de novo aneurysm developed over the previous 18 years. For the giant thrombosed aneurysm, trapping and revascularization were performed. A natural radial artery Y-graft was used as the graft and anastomosed to both M2 trunks. The symptoms improved after surgery, and the patient was discharged 3 weeks later. This is the first report of a double-barrel bypass using a natural Y-graft. This method attained a normal variation, and the flow of the Y-graft was physiological. For the radical cure of giant thrombosed MCA aneurysms, multiple revascularizations might be required. With this natural Y-graft, complex transpositions could be avoided.

Ischemic Tolerance Evaluated by Computed Tomography Perfusion during Balloon Test Occlusion.

Tomoyoshi Kuribara, Takeshi Mikami, Satoshi Iihoshi, Kei Miyata, Sangnyon Kim, Yuka Kawata, Katsuya Komatsu, Yusuke Kimura, Rei Enatsu, Yukinori Akiyama, Toru Hirano, Nobuhiro Mikuni

Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 29 ( 6 ) 104807 - 104807 2020.06 [International journal]

OBJECTIVES: Balloon test occlusion (BTO) is performed to evaluate ischemic tolerance for large and giant cerebral aneurysms and head and neck tumors that may require parent artery occlusion. However, ischemic tolerance for the temporary test occlusion does not always guarantee a tolerance for permanent occlusion. In this study, we evaluated the utility of computed tomography (CT) perfusion during BTO to quantify ischemic tolerance for detecting delayed ischemic stroke. MATERIALS AND METHODS: Forty-one patients who underwent BTO for the internal carotid artery were included. The correlations between the parameters of CT perfusion and collateral angiographic appearance or stump pressure during BTO were evaluated. The cerebral blood flow (CBF), cerebral blood volume, mean transit time (MTT), and time to peak (TTP) were obtained through CT perfusion, and the asymmetry ratios were determined. Collateral angiographic appearances were categorized into 5 grades (0-4). RESULTS: The collateral angiographic appearance showed moderate correlations with CBF, MTT, and TTP that was significant. Of these, the absolute value of the correlation coefficient was the highest for MTT. MTT also showed a moderate correlation with stump pressure. CBF and MTT were significantly different between the poor collateral group (grades 2 and 3) and the good collateral group (grade 4). Based on the MTT, the good collateral group was identified with high sensitivity (75.0%) and specificity (81.2%). CONCLUSIONS: In BTO, the MTT obtained through CT perfusion showed a correlation with collateral angiographic appearance and stump pressure. Thus, the MTT might be useful to quantify ischemic tolerance for detecting delayed ischemic stroke.

The Immediate Effects of Vagus Nerve Stimulation in Intractable Epilepsy: An Intra-operative Electrocorticographic Analysis.

Rintaro Yokoyama, Yukinori Akiyama, Rei Enatsu, Hime Suzuki, Yuto Suzuki, Aya Kanno, Satoko Ochi, Nobuhiro Mikuni

Neurologia medico-chirurgica 60 ( 5 ) 244 - 251 2020.05 [Domestic journal]

The purpose of this study was to investigate whether and how vagus nerve stimulation (VNS) reduces the epileptogenic activity in the bilateral cerebral cortex in patients with intractable epilepsy. We analyzed the electrocorticograms (ECoGs) of five patients who underwent callosotomy due to intractable epilepsy even after VNS implantation. We recorded ECoGs and analyzed power spectrum in both VNS OFF and ON phases. We counted the number of spikes and electrodes with epileptic spikes, distinguishing unilaterally and bilaterally hemispherically spread spikes as synchronousness of the epileptic spikes in both VNS OFF and ON phases. There were 24.80 ± 35.55 and 7.20 ± 9.93 unilaterally spread spikes in the VNS OFF and ON phases, respectively (P = 0.157), and 35.8 ± 29.21 and 10.6 ± 13.50 bilaterally spread spikes in the VNS OFF and ON phases, respectively (P = 0.027). The number of electrodes with unilaterally and bilaterally spread spikes in the VNS OFF and ON phases was 3.84 ± 2.13 and 3.59 ± 1.82 (P = 0.415), and 8.20 ± 3.56 and 6.89 ± 2.89 (P = 0.026), respectively. The ECoG background power spectra recordings in the VNS OFF and ON phases were also analyzed. The spectral power tended to be greater in the high-frequency band at VNS ON phase than OFF phase. This study showed the reduction of epileptogenic spikes and spread areas of the spikes by VNS as immediate effects, electrophysiologically.

Predictive factors for acute thrombogenesis occurring immediately after bypass procedure for moyamoya disease.

Takeshi Mikami, Hime Suzuki, Ryo Ukai, Katsuya Komatsu, Yukinori Akiyama, Masahiko Wanibuchi, Kiyohiro Houkin, Nobuhiro Mikuni

Neurosurgical review 43 ( 2 ) 609 - 617 2020.04 [International journal]

Extracranial-to-intracranial (EC-IC) bypass surgery is an effective treatment for patients with moyamoya disease and other conditions. Some patients with moyamoya disease have a risk of acute thrombogenesis at the anastomotic site just after bypass surgery. The purpose of this study was to study risk factors of acute thrombogenesis and determine effective countermeasures. This study included 48 patients (66 EC-IC bypass procedures) with moyamoya disease and 52 controls (54 procedures) without moyamoya disease. The development of acute thrombogenesis was compared between the moyamoya disease and control groups. In the moyamoya disease group, clinical and radiological characteristics were assessed with respect to acute thrombogenesis. In the patients with acute thrombogenesis, causes of technical problems were retrospectively examined. The incidence of acute thrombogenesis was significantly higher in the moyamoya disease group than those in the control group. In the moyamoya disease group, acute thrombogenesis was observed in seven patients. In the moyamoya disease group, the magnetic resonance angiography (MRA) scores were significantly higher in patients with acute thrombogenesis than those in the patients without acute thrombogenesis. In the multivariate analysis, the predictive factor of acute thrombogenesis in moyamoya disease was a high MRA score (odds ratio, 2.336; p = 0.009). During EC-IC bypass surgery for moyamoya disease, acute thrombogenesis should be considered to obtain a high patency rate, particularly in patients with high MRA scores. Acute thrombogenesis will not influence morbidity if proper countermeasures are followed; therefore, the prediction and recognition of white thrombus are important for a successful bypass surgery.

Molecular Aberrations Associated with Seizure Control in Diffuse Astrocytic and Oligodendroglial Tumors.

Hime Suzuki, Nobuhiro Mikuni, Shintaro Sugita, Tomoyuki Aoyama, Rintaro Yokoyama, Yuto Suzuki, Rei Enatsu, Yukinori Akiyama, Takeshi Mikami, Masahiko Wanibuchi, Tadashi Hasegawa

Neurologia medico-chirurgica 60 ( 3 ) 147 - 155 2020.03 [Domestic journal]

Diffuse astrocytic and oligodendroglial tumors are frequently associated with symptomatic epilepsy, and predictive seizure control is important for the improvement of patient quality of life. To elucidate the factors related to drug resistance of brain tumor-associated epilepsy from a pathological perspective. From January 2012 to October 2017, 36 patients diagnosed with diffuse astrocytic or oligodendroglial tumors were included. Assessment for seizure control was performed according to the Engel classification of seizures. Patient clinical, radiological, and pathological data were stratified based on the following 16 variables: age, sex, location of tumor, existence of the preoperative seizure, extent of resection, administration of temozolomide, radiation therapy, recurrence, Karnofsky performance scale, isocitrate dehydrogenase 1, 1p/19q co-deletion, Olig2, platelet-derived growth factor receptor alpha, p53, ATRX, and Ki67. These factors were compared between the well-controlled group and drug-resistant seizure group. Twenty-seven patients experienced seizures; of these, 14 cases were well-controlled, and 13 cases were drug-resistant. Neither clinical nor radiological characteristics were significantly different between these two groups, though p53 immunodetection levels were significantly higher, and the frequency of 1p/19q co-deletion was significantly lower in the group with drug-resistant seizures than in the well-controlled group. In the multivariate analysis, only one item was selected according to stepwise methods, and a significant difference was observed for p53 (OR, 21.600; 95% CI, 2.135-218.579; P = 0.009). Upregulation of p53 may be a molecular mechanism underlying drug resistant epilepsy associated with diffuse astrocytic and oligodendroglial tumors.

Effectiveness of intraoperative visual evoked potential in avoiding visual deterioration during endonasal transsphenoidal surgery for pituitary tumors.

Kentaro Toyama, Masahiko Wanibuchi, Toshimi Honma, Katsuya Komatsu, Yukinori Akiyama, Takeshi Mikami, Nobuhiro Mikuni

Neurosurgical review 43 ( 1 ) 177 - 183 2020.02 [International journal]

Postoperative visual function is a major concern in transsphenoidal surgery (TSS). Although several reports have demonstrated the importance of visual evoked potential (VEP) monitoring during TSS, the usefulness of VEP monitoring have been controversial because of its reproducibility. Efficacy of VEP was analyzed in 20 consecutive cases of patients who underwent endoscopic endonasal TSS surgery. We adapted a high-power light-emitting diode stimulator with electroretinography using venous anesthesia. In addition, we used black shield patch and braided codes to obtain reproducible VEP amplitudes. Stable and reproducible VEP waveforms were obtained in 38 of 39 eyes (97.4%) before surgery. Fifteen eyes had deteriorated VEP amplitude during operation, and nine eyes had improved VEP amplitude at the end of surgery, and six eyes had not improved VEP amplitude. But no postoperative visual impairment was observed in all cases by temporary halting the surgical manipulation when the VEP was deteriorated. In conclusion, VEP monitoring could be a warning sign to avoid postoperative visual dysfunction. We recommend VEP as a routine monitoring in TSS.

Diagnosis of a Rare Intraventricular Schwannoma.

Ryohei Chiba, Yukinori Akiyama, Yusuke Kimura, Rintaro Yokoyama, Nobuhiro Mikuni

World neurosurgery 134 145 - 149 2020.02 [International journal]

BACKGROUND: Intraventricular schwannoma is extremely rare, with only 35 cases reported to date in the literature. Consequently, its etiology and pathogenesis are still unclear, and therefore require further investigations. Here, we report on and discuss a rare case of intraventricular schwannoma to elucidate on this matter. CASE DESCRIPTION: A 26-year-old man was admitted to our institution with a 1-month history of headaches and left hemianopsia. At diagnosis, magnetic resonance imaging of the brain revealed a well-demarcated mass with surrounding edema in the right lateral ventricle. Total resection of the tumor was performed by a transsulcal approach through the right parietal lobe. In surgery, it was observed that the tumor was attached to the choroid plexus without invading the wall of the right lateral ventricle. The respective histologic examination confirmed the diagnosis of intraventricular schwannoma. Six months after the surgery, there was no recurrence. Additionally, during this follow-up period, the patient did not develop any neurologic deficit, including visual field narrowing or parietal symptoms, such as acalculia and right-left, finger, and space agnosias. CONCLUSIONS: Although intraventricular schwannomas are rare, 35 cases have already been reported to date. We emphasize the importance of diagnosing such cases correctly to increase knowledge on the origin and pathogenesis of intraventricular tumors, which would facilitate disease management.

Far-anterior Interhemispheric Transcallosal Approach for a Central Neurocytoma in the Lateral Ventricle.

Shouichi Komura, Yukinori Akiyama, Hime Suzuki, Rintaro Yokoyama, Takeshi Mikami, Nobuhiro Mikuni

Neurologia medico-chirurgica 59 ( 12 ) 511 - 516 2019.12 [Domestic journal]

To describe the far-anterior interhemispheric transcallosal approach for the treatment of a central neurocytoma at the roof of the lateral ventricle. In comparison to the view obtained during the usual anterior transcallosal approach, the far-anterior approach allowed for a higher view of the lateral ventricle to be obtained without further injury or retraction of the corpus callous. Two patients with central neurocytoma in the lateral ventricle were treated with the far-anterior interhemispheric transcallosal approach. Gross-total resections were achieved in both the patients without any postoperative neurological impairments by only 2-3 cm incisions of the corpus callosum. With the anterior transcallosal approach, which was usually used for the intraventricular tumors, the surgical view was relatively downward into the lateral ventricle and suitable for the resection of the tumors located at the base of the lateral ventricle or even in the third ventricle through the foramen of Monro. However, it was relatively difficult to reach the roof of the lateral ventricle using this approach. In contrast, the surgical corridor of the far-anterior transcallosal approach reaches upward to the roof of the lateral ventricle. The far-anterior transcallosal approach provides an alternative to reach the lesions, especially those located in the upper region of the lateral ventricle near important structures, such as the pyramidal tracts.

Inflammation promotes progression of thrombi in intracranial thrombotic aneurysms.

Hime Suzuki, Takeshi Mikami, Tomoaki Tamada, Ryo Ukai, Yukinori Akiyama, Akinori Yamamura, Kiyohiro Houkin, Nobuhiro Mikuni

Neurosurgical review ( SPRINGER ) 43 ( 6 ) 1565 - 1573 2019.11 [Refereed] [International journal]

Advances in the understanding of the pathogenesis of arteriosclerosis, abdominal aorta aneurysms and dissections, and carotid artery plaques have focused on chronic inflammation. In this study, we report that inflammatory changes of thrombi contribute to the enlargement and growth of giant intracranial thrombotic aneurysms. Surgical and postmortem samples were collected from 12 cases of large or giant intracranial thrombotic aneurysms diagnosed via pathological investigations. Degeneration of the aneurysmal wall and the infiltration of inflammatory cells in the thrombi were assessed. The number of blood cells and immunohistochemical stain-positive cells was enumerated, and the inflammation and neovascularization in the thrombi were assessed. In all cases, the appearance of inflammatory cells (CD68+ cells, CD206+ cells, lymphocytes, and neutrophils) was apparent in the thrombi. The number of CD34+ cells was moderately correlated with the number of CD68+ cells, and CD34+ cells significantly and strongly correlated with the number of CD206+ cells. Based on the number of neutrophils per CD68+ cells, we classified the cases into 2 groups: a macrophage inflammation-dominant group and a neutrophilic inflammation-dominant group. The neutrophilic inflammation-dominant group had significantly more cases with previous treatments and neurological symptoms due to mass effect than the macrophage inflammation-dominant group. Chronic inflammation due to macrophages in thrombi is a fundamental mechanism in the enlargement of an intracranial thrombotic aneurysm, and neutrophilic inflammation can accelerate this process. Microvascularization in thrombi is linked to inflammation and might promote thickening of the intima and repeated intimal microbleeds.

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