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Jean Régis, Motohiro Hayashi, Denis Porcheron, Christine Delsanti, Xavier Muracciole, and Jean Claude Peragut

Object. The technical advances associated with the model C gamma knife include a robotized system enabling automatic positioning of the stereotactic coordinates. The purpose of this study was to analyze the clinical impact of this technical modification.

Methods. The authors studied a sample of patients with vestibular schwannoma (VS). This sample included three groups treated using gamma knife radiosurgery. Group I comprised 21 patients with VS treated just before the installation of the Automatic Positioning System (APS). Group II included patients in Group I with new dose plans created using the APS (in other words, simulated dose plans). Group III consisted of a control group of 20 patients matched for tumor grade with the previous group and treated recently with the APS. Treatment times were calculated after correcting the time for each shot according to the age of the sources after reloading. The treatment times, including total time, irradiation time, and duration of the neurosurgical procedure, were analyzed. In addition, dose planning including number of isocenters, number of different collimators, malfunctions, and the conformity and selectivity indices were recorded.

The trend was to reduce the mean number of collimator runs from 7.9 to 1.2 and to increase the mean number of shots from 7.9 to 15.6, mostly by using the 4-mm collimator exclusively. The APS-related conformity and selectivity were improved from 95 to 97% and from 78 to 84%, respectively. The total treatment time was reduced by 53%, and time required to interact with the patient in the room was considerably reduced (75%), giving the neurosurgeon greater freedom to perform other tasks during the treatment period. The reduction of the time spent by the neurosurgeon at work in the room was 84%. The total radiation time was increased by 54%.

Conclusions. The preliminary results of this study indicate that the robotization of the gamma knife is likely a major advance in radiosurgery.

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Kotaro Nakaya, Motohiro Hayashi, Masahiro Izawa, Taku Ochiai, Tomokatsu Hori, and Kintomo Takakura


Stereotactic radiosurgery for brain metastasis has become one of the standard treatment options in recent years. Some patients must undergo repeated stereotactic radiosurgery for new lesions. The authors retrospectively reviewed their data to estimate how soon the patients undergo repeated radiosurgery for new lesions.


Between October 1999 and March 2006, 1081 patients with brain metastases underwent Gamma Knife surgery (GKS) at Tokyo Women's Medical University. One hundred and forty-nine patients in whom GKS had been performed two or more times were evaluated. There were 68 men and 81 women with a median age of 61 years (range 29–90 years). The authors analyzed data on patient age, number of treated lesions, and period between GKSs. Follow-up imaging was performed in almost all patients every 2 to 3 months after GKS.

The number of lesions treated in a single session varied from one to 35. The median interval between GKSs was 26 weeks (range 3–175 weeks) for patients with breast cancer and 23 weeks (range 4–179 weeks) for patients with non–small cell lung carcinoma.


It would appear that follow-up imaging studies should be obtained every 2 to 3 months after GKS to monitor patients for tumor recurrence.

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Jean Régis, Fabrice Bartolomei, M. Rey, Motohiro Hayashi, Patrick Chauvel, and Jean-Claude Peragut

Object. Gamma knife radiosurgery (GKS) allows precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without causing significant radiation damage to adjacent tissues. Almost all the well-documented cases of radiosurgery for epilepsy are for epilepsies associated with space-occupying lesions. These results prompted the authors to investigate the use of radiosurgery as a new way of treating epilepsy not associated with space-occupying lesions.

Methods. To evaluate this new method, 25 patients who presented with drug-resistant mesial temporal lobe epilepsy (MTLE) were selected. A follow up of more than 24 months is now available for 16 patients. The preoperative evaluation was performed as it usually is in patients selected for microsurgery for MTLE. In lieu of microsurgery, the treatment of amygdalohippocampal structures was performed using GKS.

Thirteen (81%) of these 16 patients are seizure free, and two are improved. The median latent interval from GKS to seizure cessation was 10.5 months (range 6–21 months). Two patients were immediately seizure free. The median latency in aura cessation was 15.5 months (range 9–22 months). Morphological changes on magnetic resonance imaging were visible at 11 months (median) after GKS (range 7–22 months). During the onset period of these radiological changes, three patients experienced headache associated, in two cases, with nausea and vomiting. In these three patients the signs resolved immediately after prescription of low doses of steroids. No cases of permanent neurological deficit (except three cases of nonsymptomatic visual field deficit), or morbidity, or mortality were observed.

Conclusions. This initial experience indicates that there is short- to middle-term efficiency and safety when using GKS to treat MTLE. Further long-term follow up is required. It seems that the introduction of GKS into epilepsy treatment can reduce the invasiveness and morbidity.

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Jean Régis, Philippe Metellus, Motohiro Hayashi, Philippe Roussel, Anne Donnet, and Françoise Bille-Turc


Stereotactic radiosurgery is an alternative to conventional surgery for the treatment of trigeminal neuralgia. The authors conducted a prospective evaluation of the safety and efficacy of this method in a large series of patients.


A total of 100 patients presenting with trigeminal neuralgia were treated and followed up for a minimum of 12 months. The mean age was 68.2 years; 54 patients were male, and 46 were female. Seven had a history of multiple sclerosis, and 42 had already received conventional surgical treatment for trigeminal neuralgia. The intervention consisted of gamma knife surgery to the retrogasserian cisternal portion of the fifth cranial nerve. The median dose used at the maximum was 85 Gy (range 70–90 Gy). The number and intensity of pain attacks were recorded by the patient from 3 months before radiosurgery to a minimum of 12 months after treatment. Before and a minimum of 12 months after treatment, the patient completed a quality-of-life questionnaire. Neurological examination and quantitative sensory testing to evaluate sensory perception were performed by an independent neurologist over this same time period.

At the last visit 83 of 100 patients were reported to be pain free. Fifty-eight of these 83 patients had stopped taking medication during the study. All quality-of-life parameters were improved (p < 0.001). Six patients reported facial paresthesia, and four patients reported hypesthesia. These symptoms were classified as mild. None of the complications reported for other techniques were observed.


Radiosurgery is a safe and effective alternative treatment for trigeminal neuralgia and is associated with a particularly low rate of hypesthesia.

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Atsushi Shimizu, Koji Yamaguchi, Yoshikazu Okada, Takayuki Funatsu, Tatsuya Ishikawa, Motohiro Hayashi, Noriko Tamura, Ayako Horiba, and Takakazu Kawamata


Gamma Knife radiosurgery (GKRS) is a safe and effective treatment, but it has a risk of bleeding. Herein, the authors describe their experience with some patients who required surgical removal of cerebral arteriovenous malformations (AVMs) located mainly in eloquent areas of the brain after GKRS, and they consider the advantages of surgical removal after GKRS.


Twelve patients who had undergone surgical removal of AVMs after GKRS at Tokyo Women’s Medical University between April 2013 and July 2019 were selected for analysis. All participants underwent GKRS as first-line therapy for AVMs located in an eloquent region or if requested by the patient. Complete obliteration was achieved in 7 patients, and the size of the nidus decreased in 3 patients during the follow-up period. The Spetzler-Martin grade decreased in 11 patients. Three patients experienced symptomatic intracerebral hemorrhage before and after confirmation of complete obliteration of the nidus via GKRS, and 7 patients experienced some neurological deficits because of an encapsulated expanding hematoma. All patients underwent resection of the nidus without complications. The preoperative neurological deficits improved in 6 patients and remained unchanged in 6 patients.


This report indicates that performing GKRS before surgery may be useful for future multimodal therapy.

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Masahiro Izawa, Motohiro Hayashi, Kohtarou Nakaya, Hiroyuki Satoh, Taku Ochiai, Tomokatsu Hori, and Kintomo Takakura

Object. The purpose of this study was the analysis of a large series of patients treated with gamma knife radiosurgery for pituitary adenoma in a single institution.

Methods. One hundred eight patients with pituitary adenomas were treated over the last 7 years. Seventy-four patients have been followed for more than 6 months and form the basis of this report.

Conclusions. Twenty-three patients harbored nonfunctioning adenomas, and 56 harbored functioning adenomas. The mean margin dose was 22.5 Gy (nonfunctioning adenomas, 19.5 Gy; functioning adenomas, 23.8 Gy). Control of tumor growth was achieved in 91%. A significant decrease of excessive hormone production was seen in 80% of patients, and the endocrinological normalization rate was 30.3%. Postradiosurgical complications were seen in 2.5%.

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Masahiro Izawa, Motohiro Hayashi, Mikhail Chernov, Koutarou Nakaya, Taku Ochiai, Noriko Murata, Yuichi Takasu, Osami Kubo, Tomokatsu Hori, and Kintomo Takakura

Object. The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs).

Methods. Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05).

Conclusions. Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

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Motohiro Hayashi, Mikhail Chernov, Masao Usukura, Kayoko Abe, Yuko Ono, Masahiro Izawa, Sadao Hori, Tomokatsu Hori, and Kintomo Takakura

The authors conducted a study to determine a way of overcoming the poor-quality demonstration of choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD) on conventional magnetic resonance (MR) imaging studies.

The poor MR imaging demonstration of CNV in patients with AMD makes the use of gamma knife surgery more difficult. This difficulty, however, can be overcome by use of a modified time-of-flight MR imaging sequence with Gd enhancement and coronal reconstruction.

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Reirradiation spine stereotactic body radiation therapy for spinal metastases: systematic review

International Stereotactic Radiosurgery Society practice guidelines

Sten Myrehaug, Arjun Sahgal, Motohiro Hayashi, Marc Levivier, Lijun Ma, Roberto Martinez, Ian Paddick, Jean Régis, Samuel Ryu, Ben Slotman, and Antonio De Salles


Spinal metastases that recur after conventional palliative radiotherapy have historically been difficult to manage due to concerns of spinal cord toxicity in the retreatment setting. Spine stereotactic body radiation therapy (SBRT), also known as stereotactic radiosurgery, is emerging as an effective and safe means of delivering ablative doses to these recurrent tumors. The authors performed a systematic review of the literature to determine the clinical efficacy and safety of spine SBRT specific to previously irradiated spinal metastases.


A systematic literature review was conducted, which was specific to SBRT to the spine, using MEDLINE, Embase, Cochrane Evidence-Based Medicine Database, National Guideline Clearinghouse, and CMA Infobase, with further bibliographic review of appropriate articles. Research questions included: 1) Is retreatment spine SBRT efficacious with respect to local control and symptom control? 2) Is retreatment spine SBRT safe?


The initial literature search retrieved 2263 articles. Of these articles, 160 were potentially relevant, 105 were selected for in-depth review, and 9 studies met all inclusion criteria for analysis. All studies were single-institution series, including 4 retrospective, 3 retrospective series of prospective databases, 1 prospective, and 1 Phase I/II prospective study (low- or very low–quality data). The results indicated that spine SBRT is effective, with a median 1-year local control rate of 76% (range 66%–90%). Improvement in patients’ pain scores post-SBRT ranged from 65% to 81%. Treatment delivery was safe, with crude rates of vertebral body fracture of 12% (range 0%–22%) and radiation-induced myelopathy of 1.2%.


This systematic literature review suggests that SBRT to previously irradiated spinal metastases is safe and effective with respect to both local control and pain relief. Although the evidence is limited to low-quality data, SBRT can be a recommended treatment option for reirradiation.