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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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

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

OBJECTIVE

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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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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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, Kyousuke Kamada, Takahiro Ota, Daisuke Itoh, Kenji Ino, Hiroshi Igaki, Shigeki Aoki, Yoshitaka Masutani, Masahiro Shin and Nobuhito Saito

Object

To prevent speech disturbances after Gamma Knife surgery (GKS), the authors integrated arcuate fasciculus (AF) tractography based on diffusion tensor (DT) MR imaging into treatment planning for GKS.

Methods

Arcuate fasciculus tractography was retrospectively integrated into planning that had been previously performed by neurosurgeons and radiation oncologists. This technique was retrospectively applied to 12 patients with arteriovenous malformations adjacent to the AF. Diffusion tensor images were acquired before the frame was affixed to the patient's head and DT tractography images of the AF were created using the authors' original software. The data from DT tractography and stereotactic 3D imaging studies obtained after frame fixation were transported to a treatment planning workstation for GKS and coregistered so that the delivered doses and incidence of posttreatment aphasia could be assessed.

Results

The AF could not be depicted in 2 patients who initially presented with motor aphasia caused by hemorrhaging from arteriovenous malformations. During the median follow-up period of 29 months after GKS, aphasia developed in 2 patients: 30 Gy delivered to the frontal portion of the AF caused conduction aphasia in 1 patient, and 9.6 Gy to the temporal portion led to motor aphasia in the other. Speech dysfunction was not observed after a maximum radiation dose of 10.0–16.8 Gy was delivered to the frontal fibers in 4 patients, and 3.6–5.2 Gy to the temporal fibers in 3.

Conclusions

The authors found that administration of a 10-Gy radiation dose during GKS was tolerated in the frontal but not the temporal fibers of the AF. The authors recommend confirmation of the dose by integration of AF tractography with GKS, especially in lesions located near the temporal language fibers.

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Kanako Kunishima, Harushi Mori, Daisuke Itoh, Shigeki Aoki, Hiroyuki Kabasawa, Tomoyuki Koga, Keisuke Maruyama, Tomohiko Masumoto, Osamu Abe and Kuni Ohtomo

Object

Although conventional catheter angiography is commonly used in the evaluation of intracranial arteriovenous malformations (AVMs), less invasive tools are more suitable for screening or follow-up. Older MR angiography techniques cannot provide high enough temporal and spatial resolution for assessing AVMs. Threetesla time-resolved imaging of contrast kinetics (TRICKS)—a time-resolved, contrast-enhanced 3D MR angiography technique—achieves subsecond time resolution without sacrificing spatial resolution. The purpose of this study was to assess the accuracy of TRICKS at 3 T in the evaluation of AVMs.

Methods

Between November 2006 and November 2007, 31 patients who were known to have AVMs underwent evaluation in a 3-T unit with the TRICKS technique. The TRICKS images were then evaluated independently by 2 radiologists for nidus detection, early venous filling detection, and Spetzler-Martin classification, and these results were compared with the results of catheter angiography.

Results

Time-resolved imaging of contrast kinetics achieved 96% sensitivity and 100% specificity both in nidus detection and early venous filling detection. The Spetzler-Martin grades also showed excellent correlation with catheter angiography findings (κ= 0.89).

Conclusions

Although this is a preliminary study, the authors' results indicate that time-resolved contrast-enhanced 3D MR angiography at 3 T is a good tool to assess AVMs, and has the potential to replace catheter angiography in screening or follow-up examinations of patients with AVMs.

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

Object

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.

Methods

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.

Results

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.

Conclusions

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.

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Keisuke Maruyama, Kyousuke Kamada, Masahiro Shin, Daisuke Itoh, Yoshitaka Masutani, Kenji Ino, Masao Tago and Nobuhito Saito

Object

No definitive method of preventing visual field deficits after stereotactic radiosurgery for lesions near the optic radiation (OR) has been available so far. The authors report the results of integrating OR tractography based on diffusion tensor (DT) magnetic resonance imaging into simulated treatment planning for Gamma Knife surgery (GKS).

Methods

Data from imaging studies performed in 10 patients who underwent GKS for treatment of arteriovenous malformations (AVMs) located adjacent to the OR were used for the simulated treatment planning. Diffusion tensor images performed without the patient's head being secured by a stereotactic frame were used for DT tractography, and the OR was visualized by means of software developed by the authors. Data from stereotactic 3D imaging studies performed after frame fixation were coregistered with the data from DT tractography. The combined images were transferred to a GKS treatment-planning workstation. Delivered doses and distances between the treated lesions and the OR were analyzed and correlated with posttreatment neurological changes.

Results

In patients presenting with migraine with visual aura or occipital lobe epilepsy, the OR was located within 11 mm from AVMs. In a patient who developed new quadrantanopia after GKS, the OR had received 32 Gy. A maximum dose to the OR of less than 12 Gy did not cause new visual field deficits. A maximum dose to the OR of 8 Gy or more was significantly related to neurological change (p < 0.05), including visual field deficits and development or improvement of migraine.

Conclusions

Integration of OR tractography into GKS represents a promising tool for preventing GKS-induced visual disturbances and headaches. Single-session irradiation at a dose of 8 Gy or more was associated with neurological change.

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Keisuke Maruyama, Masahiro Shin, Masao Tago, Hiroki Kurita, Nobutaka Kawahara, Akio Morita and Nobuhito Saito

Object

Appropriate management of hemorrhage after Gamma Knife surgery (GKS) for arteriovenous malformations (AVMs) of the brain is poorly understood, although a certain proportion of patients suffer from hemorrhage.

Methods

Among 500 patients observed for 1 to 183 months (median 70 months) after GKS, 32 patients (6.4%) suffered a hemorrhage. Hemorrhage developed even after angiographically documented obliteration of the AVM in five (2%) of 250 patients followed for 1 to 133 months (median 75 months) post-GKS. These patients had been treated according to their pathological condition. Treatment of these patients and their outcomes were retrospectively reviewed. As a management strategy in patients with preobliteration hemorrhage, the intracerebral hematoma and the AVM nidus were removed in four patients, and chronic encapsulated hematoma was removed in three. Among 11 patients who were conservatively treated, AVMs were ultimately obliterated in five, including three patients who underwent repeated GKS. Intracerebral hematoma from angiographically documented obliterated AVMs was radically resected in two patients, including one who also underwent aspiration of an accompanying symptomatic cyst. Intraoperative bleeding was easily controlled in these patients. Outcomes after hemorrhage, measured with the modified Rankin Scale, were significantly better in patients with postobliteration hemorrhage than in those with preobliteration hemorrhage (p < 0.05).

Conclusions

Various types of hemorrhagic complications after GKS for AVMs can be properly managed based on an understanding of each pathological condition. Although a small risk of bleeding remains after angiographically demonstrated obliteration, surgery for such AVMs is safe, and the patient outcomes are more favorable. Radical resection to prevent further hemorrhage is recommended for ruptured AVMs after obliteration because such AVMs can cause repeated hemorrhages.

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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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Keisuke Maruyama, Kyousuke Kamada, Masahiro Shin, Daisuke Itoh, Shigeki Aoki, Yoshitaka Masutani, Masao Tago and Takaaki Kirino

Object. In the radiosurgical treatment of critically located lesions, the effort to minimize the risk of complication is essential. In this study the integration of diffusion-tensor (DT) imaging—based tractography was clinically applied to treatment planning for gamma knife surgery (GKS).

Methods. Seven patients with cerebral arteriovenous malformations located adjacent to the corticospinal tract (CST) underwent this technique. Data provided by DT imaging were acquired before the frame was affixed to the patient's head and the CST of the DT tractography was created using our original software. Stereotactic three-dimensional imaging studies were obtained after frame fixation and then coregistered with the data from DT tractography. After image fusion of the two studies, the combined images were transported to a GKS treatment-planning workstation. The spatial relationship between the dose distribution and the CST was clearly demonstrated within the 2 hours it took to complete the entire imaging process. The univariate logistic regression analysis of transient or permanent motor complications revealed a significant independent correlation with the volume of the CST that received 25 Gy or more and with a maximum dose to the CST (p < 0.05).

Conclusions. The integration of DT tractography into the GKS treatment planning was highly useful in confirming the dose to the CST during treatment planning.