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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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Yasuaki Abe, Keisuke Maruyama, Shigeomi Yokoya, Akio Noguchi, Eishi Sato, Motoo Nagane, and Yoshiaki Shiokawa


Chronic subdural hematoma (CSDH) is widely treated by drainage through a bur hole opening. However, whether and how preexisting comorbidities causing disturbance of consciousness affect patient outcomes remains unclear.


The authors analyzed 188 consecutive patients with CSDH who were surgically treated at the Neurosurgery Institute of the Kyorin University School of Medicine between 2010 and 2012 and followed them for more than 90 days. The mean patient age was 77.0 years (range 33–101 years) and 56 were women. Patient outcomes including modified Rankin Scale (mRS) score, postoperative morbidity and mortality, and recurrence 90 days after initial surgery were analyzed according to preexisting comorbidities causing disturbance of consciousness. The comorbidities observed in 46 patients (24%) included dementia (30 patients), history of ischemic stroke (10 patients), psychiatric disorders (3 patients), and others (3 patients).


Background characteristics of patients with comorbidities showed older patient age (p < 0.001), lower preoperative Glasgow Coma Scale score (p < 0.001), and higher preoperative mRS score (p < 0.001). The mean mRS score 90 days after the neurosurgical procedure was 1.2 in all 188 patients, which was significantly higher in those with comorbidities (p < 0.001). By 1-way ANOVA with repeated measures, interaction existed between the presence of comorbidities and mRS score, and improvement of mRS score was observed in smaller proportions of patients with comorbidities (p = 0.002). By multivariate logistic regression analysis, the presence of comorbidities, patient age, reoperation for recurrence, and preoperative mRS score were significantly related to poor outcomes, defined as mRS score of 3 or more at 90 days after surgery. Postoperative morbidity (p < 0.01) and mortality (p < 0.01) were significantly higher in those with comorbidities, whereas the rate of recurrence of CSDH was not significantly different.


The preexistence of comorbidities causing disturbance of consciousness affected severity and outcomes 90 days after surgical treatment of CSDH, and comorbidities were also correlated with aging.

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Keisuke Maruyama, Douglas Kondziolka, Ajay Niranjan, John C. Flickinger, and L. Dade Lunsford

Object. Management options for arteriovenous malformations (AVMs) of the brainstem are limited. The long-term results of stereotactic radiosurgery for these disease entities are poorly understood. In this report the authors reviewed both neurological and radiological outcomes following stereotactic radiosurgery for brainstem AVMs over 15 years of experience.

Methods. Fifty patients with brainstem AVMs underwent gamma knife surgery between 1987 and 2002. There were 29 male and 21 female patients with an age range of 7 to 79 years (median 35 years). Anatomical locations of these AVMs included the midbrain (39 lesions), pons (20 lesions), and medulla oblongata (three lesions). The radiation dose applied to the margin of the AVM varied from 12 to 26 Gy (median 20 Gy). Forty-five patients were followed up from 5 to 176 months (mean 72 months). The angiographically confirmed actuarial obliteration rate was 66% at the final follow-up examination. Two patients experienced a hemorrhage before obliteration. The annual hemorrhage rate was 1.7% for the first 3 years after radiosurgery and 0% thereafter. Patients who had received irradiation at two or fewer isocenters had higher obliteration rates (80% compared with 44% for > two isocenters, p = 0.006), and this was related to a more spherical nidus shape. The rate of persistent neurological complications in patients treated using magnetic resonance imaging—based dose planning after 1993 was 7%, compared with 20% in patients treated before 1993. An older patient age, a lesion located in the tectum, and a higher radiosurgery-based score were significantly associated with greater neurological complications.

Conclusions. Stereotactic radiosurgery provided complete obliteration of AVMs in two thirds of the patients with a low risk of latency-interval hemorrhage. Better three-dimensional imaging studies and conformal dose planning reduced the risk of adverse radiation effects. Younger patients harboring more spherical AVMs that did not involve the tectal plate had the best outcomes.

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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, Nobutaka Kawahara, Keisuke Maruyama, Masao Tago, Keisuke Ueki, and Takaaki Kirino

Object. Radiosurgery has been widely adopted for the treatment of cerebral arteriovenous malformations (AVMs) in which the practical endpoint is angiographic evidence of obliteration, presumed to be consistent with elimination of the risk of hemorrhage. To test this unverified assumption, the authors followed 236 radiosurgery-treated AVMs between 1 and 133 months (median 77 months) after angiographic evidence of obliteration.

Methods. Four patients experienced hemorrhage between 16 and 51 months after angiographic confirmation of AVM obliteration, and two underwent resection. The histological findings in these patients showed occlusion of the AVM by thickening of the intimal layer with dense hyalinization as well as a small amount of residual AVM vessels and a tiny vasculature. The risks of hemorrhage from these presumaby obliterated AVMs were 0.3% for the annual bleeding risk and 2.2% for the cumulative risk over 10 years. Continuous enhancement of the nidus on computerized tomography (CT) or magnetic resonance (MR) imaging was the only significant factor positively associated with hemorrhage in the statistical analysis (p = 0.0212).

Conclusions. Because the study was based on limited follow-up data, its significance for defining predictive features of hemorrhage after angiographic evidence of obliteration is still indeterminable. Nevertheless, disappearance of the AVM on angiography after radiosurgery does not always indicate total elimination of the disease, especially when CT or MR imaging continues to demonstrate an enhancing lesion. The authors therefore recommend continual follow up even after evidence of AVM obliteration on angiography.

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Masahiro Shin, Keisuke Maruyama, Hiroki Kurita, Shunsuke Kawamoto, Masao Tago, Atsuro Terahara, Akio Morita, Keisuke Ueki, Kintomo Takakura, and Takaaki Kirino

Object. A large number of clinical studies have been made on treatment outcomes of radiosurgery for arteriovenous malformations (AVMs), but the reported obliteration rates following this treatment vary significantly, perhaps reflecting the different methods and timings of the imaging studies used.

Methods. The authors retrospectively analyzed their experience with gamma knife surgery in 400 patients with AVMs (follow-up period 1–135 months, median 65 months), with special reference to the imaging modality used in each case. The calculated obliteration rates varied from 68.2 to 92%, depending on imaging modality and timing of evaluation. When only unquestionable imaging data such as demonstrations of a residual nidus on computerized tomography (CT) or magnetic resonance (MR) images or findings on angiograms were used in the calculation, the obliteration rates were 72% at 3 years and 87.3% at 5 years. Factors leading to a better obliteration rate were previous hemorrhage (p = 0.0084), smaller nidus (p = 0.0023), and higher radiation dose to the lesion's margin (p = 0.0495), as determined in a multivariate analysis. Factors leading to an earlier obliteration of the nidus were male sex (p = 0.0001), previous hemorrhage (p = 0.0039), smaller nidus diameter (p = 0.0006), and dose planning using angiography alone (p = 0.0201).

Conclusions. After the introduction of CT and MR images into dose planning, the conformity and selectivity of dosimetry improved remarkably, although the latency intervals until obliteration were prolonged. Imaging outcomes for AVMs should be evaluated using data provided by longer follow-up periods. The timing of additional treatments for residual AVMs should be decided cautiously, considering the size of the AVM, the patient age and sex, and the history of hemorrhage before radiosurgery.

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Yuma Okamura, Keisuke Maruyama, Shin Fukuda, Hiroshi Horikawa, Nobuyoshi Sasaki, Akio Noguchi, Motoo Nagane, and Yoshiaki Shiokawa


While cerebrospinal fluid (CSF) shunt surgery plays an essential role in the treatment of hydrocephalus, postoperative infection due to the implantation of foreign materials is still one of the most common and potentially serious complications of this procedure. Because no previously reported protocol has been proven to prevent postoperative infection after CSF shunt surgeries in adults, the authors investigated the effectiveness of a protocol introduced in their institution.


A detailed standardized surgical protocol to prevent infection in patients undergoing CSF shunt surgeries was introduced in the authors’ institution in December 2011. The protocol included a series of detailed rules regarding the surgical procedure, the surgical environment to minimize contamination from air, double gloving, local injection of antibiotics, and postoperative management. The rate of CSF shunt infection during the 3 years after surgery before and after implementation of the protocol was compared in patients undergoing their first CSF shunt surgeries. The inclusion periods were from January 2006 to November 2011 for the preprotocol group and from December 2011 to December 2014 for the postprotocol group.


The study included 124 preprotocol patients and 52 postprotocol patients. The mean patient age was 59 years in both groups, ranging from 40 days to 88 years. Comparison of patient background factors, including known risk factors for surgical site infections, showed no significant difference between the patient groups before and after implementation of the protocol. While 9 patients (7.3%) developed shunt infections before protocol implementation, no shunt infections (0%) were observed in patients who underwent surgery after protocol implementation. The difference was statistically significant (p = 0.047).


The authors’ detailed protocol for CSF shunt surgeries was effective in preventing postoperative infection regardless of patient age.

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Letter to the Editor

High-definition fiber tractography and language

Juan C. Fernandez-Miranda, Sudhir Pathak, and Walter Schneider

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Keisuke Maruyama, Tomoyuki Koga, Masahiro Shin, Hiroshi Igaki, Masao Tago, and Nobuhito Saito


Optimal timing of Gamma Knife surgery (GKS) after hemorrhage from brain arteriovenous malformations (AVMs) is unclear and of concern to neurosurgeons because GKS is usually performed after absorption of the hematoma. The authors investigated whether waiting for hematoma absorption is beneficial and aimed to clarify the optimal treatment timing.


The authors retrospectively studied 211 patients with AVMs who presented with hemorrhage and underwent GKS as the initial treatment. Patients were categorized into 3 groups according to the interval between the time of first hemorrhage and GKS, as follows: Group 1, 0–3 months (70 patients); Group 2, 3–6 months (62 patients); and Group 3, > 6 months (79 patients). The obliteration rates, number of hemorrhages before and after GKS, and complication rates were compared between these 3 groups. The authors also analyzed a subgroup of 127 patients who presented with intracerebral hemorrhage (ICH) to identify the influence of ICH on outcome.


After a median follow-up of 6.3 years, the rates of obliteration, hemorrhage after treatment, and complication were not significantly different between the 3 groups even though the patients with a longer interval before GKS (Group 3) had more AVMs in eloquent areas and neurological deficits. However, the numbers of patients with preoperative hemorrhage in the interval before GKS was significantly higher in Group 3 (1, 3, and 20 patients in Group 1, 2, and 3, respectively). These results were similar in the analyses of 127 patients presenting with ICH.


No benefit was detected in waiting for hematoma absorption until GKS after hemorrhage from AVM. Because of higher hemorrhagic risk until GKS > 6 months after hemorrhage, the authors recommend GKS within 6 months after hemorrhage.