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Toshikazu Kimura, Tetsuro Sameshima and Akio Morita

Trigeminal neuralgia is usually caused by compression of the nerve by vessels or a tumor. The authors report a case of trigeminal neuralgia not caused by vessel/tumor compression but by a constricting fibrous band around the trigeminal nerve. A 26-year-old man presented with typical trigeminal neuralgia. Although a gradient echo MR imaging demonstrated no offending vessel or a tumor, the patient agreed to undergo exploratory surgery. Intraoperatively, there were no vessels that could be the cause of the neuralgia; instead, the trigeminal nerve was constricted near the root entry zone. After the fiber was cautiously cut, the nerve expanded slightly. The neuralgia resolved without any neurological deficit, and the postoperative course was uneventful. A fibrous band around the trigeminal nerve can cause trigeminal neuralgia. When the symptom is typical and gradient echo MR imaging shows constriction of the trigeminal nerve, surgery is recommended to release the constricted the trigeminal nerve.

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Toshikazu Kimura, Daichi Nakagawa and Kensuke Kawai

A large basilar trunk aneurysm was incidentally found in a 77-year-old woman in examination for headache. Though it was asymptomatic, high signal intensity was noticed in the brainstem around the aneurysm on FLAIR image of MRI. As she was otherwise healthy, surgical clipping was performed through anterior temporal approach.

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Toshikazu Kimura, Chikayuki Ochiai, Kensuke Kawai, Akio Morita and Nobuhito Saito


To investigate the risk of bleeding from unruptured cerebral aneurysms (UCAs), previous studies have used Kaplan-Meier analyses without treating the definitive treatment as a competing risk event, which may underestimate the rupture rate. The authors analyzed the survival of patients with UCAs alongside the occurrence of aneurysm bleeding and its competing risk events.


A retrospective analysis was conducted on 722 patients diagnosed with UCAs in the period from 2000 to 2009 using an institution’s electronic medical records and telephone interviews. The cumulative incidence of aneurysm rupture was examined, and factors contributing to rupture were assessed using regression analyses.


By 2014, 19 patients had experienced aneurysm rupture, with an overall rupture rate of 0.57% per year over 3320.8 person-years. However, cumulative incidence analysis indicated that 1.3% of all patients had a rupture within 2 years after aneurysm identification, and 38.4% of the patients underwent definitive treatment in the same period. Among the patients who experienced rupture, regression analysis revealed that an aneurysm size greater than 5 mm, a location in the anterior or posterior communicating arteries, and an irregular shape contributed to aneurysm rupture, with HRs of 4.4 (95% CI 1.2–15.7), 3.5 (95% CI 1.4–8.7), and 2.1 (95% CI 0.7–6.0), respectively.


Rupture rate analyses using the person-year or standard Kaplan-Meier method are not as informative without consideration of the competing risks. The incidence of aneurysm rupture should be presented clearly with those of competing risks.

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Toshikazu Kimura, Taichi Kin, Masaaki Shojima and Akio Morita

Flow reduction therapy is sometimes utilized for difficult aneurysms, but it does not always work. A 42-year-old man presented with headache, dizziness, and slight gait disturbance due to left thrombosed giant vertebral aneurysm. Clip ligation of the VA after the PICA origin was performed for flow reduction based on the CFD analysis. Two months later, the aneurysm showed minor hemorrhage and hydrocephalus, and thrombectomy and clip reconstruction of the VA was performed. He returned to work with slight ipsilateral facial palsy (House & Brackmann grade 2).

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