Papers - Akiyama, Takenori

Source analysis of the magnetic field evoked during self-paced finger movements

Niimi, Maki, Ohira, Takayuki, Akiyama, Takenori, Hiraga, Kenji, Kaneko, Yousei, Ochiai, Masato, Fukunaga, Atsushi, Kobayashi, Masahito, Kawase, Takeshi

NEUROLOGICAL RESEARCH (MANEY PUBLISHING)  30 ( 3 ) 239 - 243 2008.04

Research paper (scientific journal), Joint Work,  ISSN  0161-6412

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Objective: The aim of this study is to investigate a source of cortical magnetic fields evoked by index finger movements.
Methods: We analysed both movement-related cortical fields (MRCFs) and somatosensory-evoked fields (SEFs) by single equivalent current dipole (ECD) method in six healthy subjects. Dipole locations were superimposed on MR images of each individual subject.
Results: The first component after finger movement (movement-evoked field I, MEFI) was observed in all subjects. The dipole of MEFI was oriented posteriorly, and was located on the posterior wall of the central sulcus of the hemisphere contralateral to the movement. The SEFs showed three major components: N20m, P30m and P60m. The dipoles of P30m and P60m were orientated posteriorly, similarly to the MEFI dipole, while that of N20m was orientated anteriorly. The dipole location of MEFI was closely located to P60m, not to N20m and P30m. The mean location of the MEFI dipole was significantly (p < 0.05) superior to N20m.
Conclusion: These findings suggest that MEFI would be generated in the sensory area ( area 3b) affected by multiple afferents and activities, and that the source of the MEFI is not identical to that of the N20m component.

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Hemodynamic response following neuronal activity in cases with severe stenosis of the cervical internal carotid artery and its serial change through carotid artery stenting

AKIYAMA Takenori, OHIRA Takayuki, HIRAGA Kenji, TANIZAKI Yoshio, AKAJI Kazunori, KAWASE Takeshi

Journal of Neuroendovascular Therapy (The Japanese Society for Neuroendovascular Therapy)  2 ( 2 ) 93 - 100 2008

ISSN  1882-4072

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Objective: Regional cerebral blood flow (CBF) increasing focally at sites of neural activity is called "hemodynamic response (HDR)". In cases with severe cerebral ischemia, HDR may be disturbed and cause disruption of normal neuro-vascular coupling. HDR was measured during a motor task using functional near infrared spectroscopy (fNIRS) in cases with severe cervical internal carotid artery (ICA) stenosis before and after carotid artery stenting (CAS). Ischemia and the influence of therapy for it on HDR was analyzed.Methods: Seventeen right-handed patients with severe cervical ICA stenosis admitted for CAS were examined. fNIRS during a motor task was performed and concentration changes in oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HbR), and total hemoglobin (tHb) were calculated in these patients in addition to routine evaluations. The same measurements were repeated after CAS and serial data were evaluated. In order to analyze the relevance of HDR to CBF status, Xenon-enhanced computed tomography (Xe-CT) was performed before and after CAS.Results: Some abnormalities in the HDR curve and its recovery after CAS were detected, including a delay in peak time of tHb concentration, of more than 10 seconds during the 20 second stimulation, in 9 cases. TTP0.7 (time to peak) value, defined as the time to reach seventy percent of maximum tHb concentration, was observed to be higher in patients with low CBF at rest before CAS. In the group with a high TTP0.7 value, CBF at rest before CAS was lower than 35mL/100g/min., significantly lower than the group without a high TTP0.7 value (P<0.01). Additionally, in the group with a high TTP0.7 value, CBF increase after CAS was significantly higher than the group with a lower TTP0.7 value (P<0.01).Conclusions: In some cases with severe ICA stenosis, cortical hemodynamics, and oxygen metabolism during functional activation are disturbed, and CAS can modulate these changes. This result is important in that intervention for cervical IC stenosis can not only reduce ischemic events, but also influence cortical hemodynamics during functional activity.

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近赤外線トポグラフィーによる大脳皮質顔面一次運動野描出の試みと問題点

'AKIYAMA TAKENORI, Ohira Takayuki, Hiraga Kenji, Niimi Maki, Fukunaga Atsushi, Kawase Takeshi, Kato Toshinori'

Facial nerve research (日本顔面神経研究会)  23   51-53 2003.12

Research paper (scientific journal), Single Work

Spontaneous resolution of nontraumatic bilateral intracranial vertebral artery dissections―case report―

Fukunaga Atsushi, Tabuse Masanao, Naritaka Heiji, Nakamura Tsuneo, Akiyama Takenori

Neurol Med Chir (Tokyo) (JAPAN NEUROSURGICAL SOC)  42 ( 11 ) 491-495 - 495 2002.11

Research paper (scientific journal), Joint Work,  ISSN  0470-8105

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A 49-year-old man presented with nontraumatic bilateral intracranial vertebral artery dissections without subarachnoid hemorrhage manifesting as Wallenberg's syndrome on the right. Magnetic resonance imaging revealed an infarct in the right dorsolateral aspect of the medulla oblongata. Antiplatelet therapy was administered. Vertebral angiography performed on the 9th hospital day (Day 9) revealed pearl and string sign in the right vertebral artery and narrowing of the left vertebral artery. Second angiography performed on Day 25 showed no change, but third angiography performed on Day 74 revealed spontaneous resolution of the bilateral vertebral artery dissections. Magnetic resonance angiography performed on Day 250 showed no evidence of dissection. However, magnetic resonance imaging revealed a small infarct in the splenium of the corpus callosum. Spontaneous resolution of stenotic dissections of the bilateral vertebral arteries is extremely unusual. Serial cerebral angiography and magnetic resonance angiography are very important for monitoring the time course of changes in patients with vertebral artery dissections.