Yoshihisa Oka

Publications (4)1.8 Total impact

• Article: Importance of neuropsychological evaluation after surgery in patients with unruptured cerebral aneurysms.

  Shiro Ohue, Yoshihisa Oka, Yoshiaki Kumon, Shinsuke Ohta, Saburo Sakaki, Takao Hatakeyama, Toshitaka Shiraishi, Sadanori Takeda, Takanori Ohnishi
  [show abstract] [hide abstract]
  ABSTRACT: We evaluated neuropsychological function before and after surgery in patients with unruptured cerebral aneurysms. Neuropsychological functions in 43 patients with unruptured cerebral aneurysms were evaluated before and 1 month after surgery. The neuropsychological examination included the Mini-Mental State examination, "Kana-hiroi" test, Kohs Block Design test, and Miyake's Memory test. Then, if scores of even a single test were decreased 1 month after surgery, the tests were performed again 5 months later. In 24 of the 43 subjects, cerebral blood flow (CBF) was measured before and 1 month after surgery by single-photon emission tomography. The outcome in all patients was evaluated as good according to the Glasgow Outcome Score (GOS). In 17 (40%) of the 43 patients, neuropsychological function had deteriorated 1 month after surgery. The most sensitive test applied was the Miyake's Memory test. Of 14 patients with neuropsychological deterioration 1 month after surgery, 6 showed complete recovery, 5 showed partial recovery, and 3 still showed cognitive deterioration 6 months after surgery. Patients over 65 years old, those with anterior communicating artery aneurysms, those operated by interhemispheric approach, or those with systemic diseases showed a greater tendency toward a decline in postoperative neuropsychological function than the other patients. The postoperative CBF and vascular response in the frontal lobe of affected-side was decreased in cases showing cognitive deterioration. These results suggested that the neuropsychological outcomes after surgery for unruptured cerebral aneurysms were not satisfactory.
  Surgical Neurology 05/2003; 59(4):269-75; discussion 275-6. · 1.67 Impact Factor
• Article: [Problems and proposals from neurosurgical practice, no. 10 in series of articles: controversy and reform proposals concerning insured medical care in neurosurgery].

  Yoshihisa Oka, Kazuhiko Sadamoto
  No shinkei geka. Neurological surgery 01/2003; 30(12):1361-3; discussion 1363-5. · 0.13 Impact Factor
• Article: [Assessment of hemodynamics of meningioma with dynamic MR imaging].

  Yoshihisa Oka, Katsusuke Kusunoki, Ichiro Nochide, Keiji Igase, Hironobu Harada, Kazuhiko Sadamoto, Kiyoshi Nagasawa
  [show abstract] [hide abstract]
  ABSTRACT: Dynamic MR imaging provides hemodynamic information about normal and pathologic tissue of the brain. The purpose of our study was to evaluate the usefulness of dynamic MR imaging in the assessment of tumor vascularity and the tumor tissue blood flow of meningiomas. We studied 13 patients with meningiomas using dynamic spin-echo MR imaging. The histological subtypes of meningioma were confirmed by the examination of surgical specimens in all patients, and tumors were meningothelial in 9 cases, fibrous in 2, transitional in 1, and psammomatous in 1. Serial images were obtained every 18-24 sec for 8 minutes and 30 seconds after rapid injection of gadolinium diethylenetriaminepentaacetic acid. Different parameters (time to peak, maximum of signal intensity and the washout ratio) were calculated directly from signal intensity curves. As an indicator of tumor vascularity, microvessel density was counted based on immunohistochemically stained sections and tumor tissue blood flow was measured using an xenon-CT system. The maximum of signal intensity corresponded to the tumor vascularity. With dynamic MR imaging, the time intensity curves (TI curves) were divided into two patterns; type 1 had a steep increase with a peak and type 2 had a slow increase to a peak followed by plateau. The maximum of signal intensity measured from TI curve of dynamic MR imaging correlated significantly with microvessel density (R2 = 0.840, p < 0.0001). Linear regression revealed a significant positive relation between the washout ratio and the tumor tissue blood flow in group showed type 1 on TI curve (R2 = 0.961, p < 0.001). There was also a significant negative correlation between the time to peak and the tumor tissue blood flow (R2 = 0.792, p < 0.01). We suggest that dynamic MR imaging is useful for evaluating hemodynamics of meningiomas.
  Nō to shinkei = Brain and nerve 07/2002; 54(7):589-93.
• Conference Proceeding: Evaluation of hemodynamics and proliferative activity of meningioma by dynamic MR imaging.

  Keiji Igase, Yoshihisa Oka, Katsusuke Kusunoki, Ichiro Nochide, Hironobu Harada, Kazuhiko Sadamoto
  CARS 2001. Computer Assisted Radiology and Surgery. Proceedings of the 15th International Congress and Exhibition, Berlin, Germany, June 27-30, 2001; 01/2001