Nobuyuki Hayashi

Nagasaki University Hospital, Nagasaki, Nagasaki, Japan

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Publications (5)9.67 Total impact

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    ABSTRACT: Cyst formation is a well-known complication following radiosurgery for arteriovenous malformations (AVMs). In this retrospective study, the authors studied predictors for AVMs using magnetic resonance imaging (MRI) to assess the mechanism of cyst formation after linac-based radiosurgery (LBRS). From April 1993 to April 2008, LBRS was performed on 109 patients with cerebral AVMs at our institution. Six patients (5.5%) were diagnosed with cyst formation after LBRS, and 5 of them underwent regular MRI follow-up every 3-4 months for 2 years post-LBRS, and every 6-12 months thereafter. Time from initial LBRS until cyst formation ranged from 8 months to 10.5 years. MRI showed contrast changes at the irradiated site and its periphery within a period of 4 months to 7 years after the initial LBRS. Moreover, the emergence of a high-intensity area (HIA) was observed on T2-weighted MRI (T2W-MRI) during the same period when changes were found on contrast-enhanced imaging. The emergence of a low-intensity area on T2W-MRI was observed prior to cyst formation or expansion, which was believed to be due to a subclinical hemorrhage near the irradiated region in all patients. Histological examination of the cyst nodule revealed hemosiderin deposits and microbleeding. Future cyst formation was suggested by the emergence of subclinical hemorrhage (microbleeding) in an irradiated field after gadolinium-enhanced MRI showed contrast changes and T2W-MRI showed a HIA around the irradiated field. MRI follow-up should be conducted on a regular basis in such patients, even after a complete occlusion has been diagnosed.
    Clinical neurology and neurosurgery 06/2014; 121:10-6. · 1.30 Impact Factor
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    ABSTRACT: Purpose Although radiosurgery is an accepted treatment method for intracranial arteriovenous malformations (AVMs), its long-term therapeutic effects have not been sufficiently evaluated, and many reports of long-term observations are from gamma-knife facilities. Furthermore, there are few reported results of treatment using only linear accelerator (LINAC)-based radiosurgery (LBRS). Methods and Materials Over a period of more than 12 years, we followed the long-term results of LBRS treatment performed in 51 AVM patients. Results The actuarial obliteration rates, after a single radiosurgery session, at 3, 5, 10, and 15 years were 46.9%, 54.0%, 64.4%, and 68.0%, respectively; when subsequent radiosurgeries were included, the rates were 46.9%, 61.3%, 74.2%, and 90.3%, respectively. Obliteration rates were significantly related to target volumes ≥4 cm3, marginal doses ≥12 Gy, Spetzler-Martin grades (1 vs other), and AVM scores ≥1.5; multivariate analyses revealed a significant difference for target volumes ≥4 cm3. The postprocedural actuarial symptomatic radiation injury rates, after a single radiation surgery session, at 5, 10, and 15 years were 12.3%, 16.8%, and 19.1%, respectively. Volumes ≥4 cm3, location (lobular or other), AVM scores ≥1.5, and the number of radiosurgery were related to radiation injury incidence; multivariate analyses revealed significant differences associated with volumes ≥4 cm3 and location (lobular or other). Conclusions Positive results can be obtained with LBRS when performed with a target volume ≤4 cm3, an AVM score ≤1.5, and ≥12 Gy radiation. Bleeding and radiation injuries may appear even 10 years after treatment, necessitating long-term observation.
    International journal of radiation oncology, biology, physics 01/2014; · 4.59 Impact Factor
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    ABSTRACT: A 63-year-old woman presented with right hearing disturbance and vertigo. Magnetic resonance (MR) imaging revealed the presence of right vestibular schwannoma (VS). Stereotactic radiosurgery (SRS) was performed with a tumor marginal dose of 14 Gy using two isocenters. She was followed up clinically and neuroradiologically using three-dimensional spoiled gradient-echo MR imaging. She experienced temporal neurological deterioration due to peritumoral edema in her right cerebellar peduncle and pons for a few months beginning 1.5 years after SRS, when she experienced transient right facial dysesthesia and hearing deterioration. Ten years after SRS, the patient presented with sudden onset of vertigo, gait disturbance, diplopia, dysarthria, and nausea. MR imaging demonstrated a new lesion in the right cerebellar peduncle, which was diagnosed as radiation-induced stroke. The patient was followed up conservatively and her symptoms disappeared within a few months. Multiple delayed onset radiation injuries are possible sequelae of SRS for VS.
    Neurologia medico-chirurgica 01/2012; 52(12):933-6. · 0.49 Impact Factor
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    ABSTRACT: To analyses the result of linac radiosurgery (LRS) for the treatment of intracranial benign lesions and to assess possible factors related to complications. The authors retrospectively reviewed 204 patients treated with LRS between May, 1993 and December, 2003. The study determined the correlation between radiosurgical complications including imaging changes after LRS and multiple factors such as radiosurgical parameters, location, volume and shape. We divided the patients into three groups by MRI imaging changes and clinical symptoms. Group 1 (Gr. 1): Imaging change only. Group 2 (Gr. 2): Imaging change with transient symptoms. Group 3 (Gr.3): Imaging change with permanent symptoms. Ninty-three patient with AVM: Gr. 1, 8 cases (8.6%), Gr. 2, 1 case (1.1%), Gr. 3, 2 cases (2.1%). A significantly higher incidence of imaging change was noted in patients with arteriovenous malformation (AVM) volumes greater than 10 cc, irregular shape of the nidus and deep location. Fifty-eight patients with vestibulan schwannoma (VS): Gr. 1, 6 cases (10.3%), Gr. 2, 1 case (1.8%), Gr. 3, 2 cases (3.4%). Imaging changes were seen mostly in cases with tumor volume greater than 5 cc. Fifty-three patients with meningioma: Gr. 1, 4 cases (7.5%), Gr.2, 2 cases (3.7%), Gr.3, 0 case. Imaging changes were seen mostly in convexity, parasaggital, and falx meningiomas that were deeply embedded in the cortex. The symptom continued the until last serial observation in four cases. We used various interventions in these patients including steroid, anticoagulant, surgical removal, and hyperbaric oxygen therapy; but these therapies were not effective. LRS for each disease seems to be a safe and effective treatment. However, once serious radiation injuries occur there is no effective therapy, so it is important to make appropriate selection of patients for radiosurgery.
    No shinkei geka. Neurological surgery 12/2009; 37(12):1201-6. · 0.13 Impact Factor
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    ABSTRACT: The authors report on a series of 46 patients harboring vestibular schwannomas (VSs) treated using linear accelerator (LINAC) radiosurgery and an analysis of serial magnetic resonance (MR) imaging data, specifically the changes in tumor volume. Fifty-three consecutive patients underwent LINAC radiosurgery for VS between 1993 and 2002. Seven of these patients were lost to follow up. Three-dimensional (3D) spoiled gradient-echo (SPGR) MR imaging was performed at 3- to 4-month intervals after radiosurgery. Tumor volume was measured on Gd-enhanced MR images of each slice. The median duration of follow-up MR imaging studies was 56.5 months (range 12-120 months). Follow-up imaging studies were conducted for longer than 1 year in 42 of 53 patients. Tumor volume changes were categorized into four types: enlargement (eight lesions [19%]), no change (two lesions [4.8%]), transient enlargement followed by shrinkage (19 lesions [45.2%]), and direct shrinkage (13 lesions [31%]). Two cases (4.8%) with twice the initial tumor volume required repeated radiosurgery. All cases of transient enlargement had subsequent shrinkage within 2 years after radiosurgery. Nine (21.4%) of 42 patients demonstrated ventricular enlargement on MR images obtained after radiosurgery. Three patients (7.1%) required placement of a ventriculoperitoneal shunt because of symptomatic hydrocephalus, and another four cases (9.5%) spontaneously resolved. Volume measurement on 3D-SPGR MR imaging was a suitable method to assess tumor changes. Volume changes beyond twofold or continuous enlargement for longer than 2 years after radiosurgery are key criteria in rating the effects of radiation. Some cases of hydrocephalus after radiosurgery resolved spontaneously and their rates of occurrence were similar to the typical incidence of hydrocephalus associated with VS.
    Journal of Neurosurgery 08/2005; 103(1):53-8. · 3.15 Impact Factor