PubMed Health⌕ Search

Biomedical subjects

Takayuki Ohira

Publications and source records attributed to Takayuki Ohira.

6 recordsLinked to original sources
PubMed2006

TMS orientation for NIRS-functional motor mapping.

Functional near-infrared spectroscopic imaging (NIRS imaging) has the potential to elucidate the relationship between neuronal activity and oxygenation responses. However, its signal specificity to the functional cortex is sometimes spoiled by its rough spatial resolution. In this study we incorporated transcranial magnetic stimulation (TMS) motor mapping into an NIRS imaging study to enhance spatial specificity to the functional cortex. Distinctive biphasic responses in the cortical oxygenation status were observed in the center of the primary motor cortex during a motor task. The early response phase, occurring within 1 to 3 seconds after task initiation, represents a cortical deoxygenation which consists of a significant increase in deoxygenated hemoglobin concentration (HbR) and a nonsignificant decreasing tendency in oxygenated hemoglobin concentration (HbO(2)). The delayed response phase represents an excess of incoming blood flow, which appears as an increase in HbO(2)/total Hb (tHb) and a decrease in HbR following the early response. In the surrounding area, cortical oxygenation change showed a monophasic response consisting of an increase in HbO(2)/tHb and a decrease in HbR. Combining TMS mapping with NIRS imaging enabled us to specify the cortex with the strongest functional activity.

Adult↗
PubMed2005

Motor-related intracortical steal phenomenon detected by multichannel functional near-infrared spectroscopy imaging.

BACKGROUND: Patients with severe cerebral ischemia may lose autoregulation to increase cerebral blood flow following neural activity. Although the steal phenomenon under conventional cerebral blood flow study has been known as a high-risk factor for stroke, the cerebral oxygen hemodynamics in ischemic patients during functional activation has not been thoroughly investigated. In this study, we present rare cases with intracortical steal phenomenon during motor tasks detected by multichannel functional near-infrared spectroscopy before and after surgery. METHODS: The relative concentration change of oxygenated, deoxygenated and total hemoglobin in and around the primary sensorimotor cortex during contralateral hand grasping was investigated in 11 patients with severe internal carotid artery stenosis. RESULTS: In 3 patients, the concentration of total hemoglobin around the primary sensorimotor cortex significantly decreased in response to motor stimulation and returned to baseline soon after termination of the motor task. This phenomenon partially disappeared postoperatively in all patients who underwent surgery. The remaining 8 patients showed no signs of total hemoglobin decrease in and around the sensorimotor cortex. In 9 patients, lack of decrease in deoxygenated hemoglobin in the center of the primary motor cortex during the motor task was observed and 3 of them showed significant increase in deoxygenated hemoglobin. CONCLUSIONS: We have demonstrated that in some patients with severe ischemia, an abnormal motor-related steal phenomenon can be observed. This phenomenon can be modulated by surgical intervention and might imply the severity of ischemia.

Aged↗
PubMed2003

Angiographic manifestations and operative findings with 70 cases of hemifacial spasm: relation of common trunk anomalies.

The relations between angiographic manifestations and operative findings of hemifacial spasm were studied in 70 cases between 1988 and 2001. Vertebral angiography was performed, and Towne, straight AP, and lateral projections were routinely examined. The dominant anterior inferior cerebellar artery (AICA) directly compressed the facial nerve root exit zone in 26 cases, the dominant posterior inferior cerebellar artery (PICA) in 20, the AICA in 13, the PICA in 2, and the vertebral artery (VA) in 9. Compression by multiple vessels was observed in 11 cases. Anatomical variations of the affected AICA and PICA were classified into 3 groups according to their origins and distributions of blood supply: normal distribution of AICA and PICA in 18%, common trunk anomaly with dominant AICA (basilar artery origin) in 48% and common trunk anomaly with dominant PICA (vertebral artery origin) in 34%. Analyses of the angiograms revealed significantly increased numbers of common trunk anomalies compared with cases with normal angiograms. In 18 of the 20 cases of unilateral common trunk anomalies, facial nerves were compressed by the dominant artery. Preoperative vertebral angiograms may clarify the offending vessels and their sites in most hemifacial spasm cases, thus increasing the safety of surgical interventions.

Adult↗
PubMed2003

[Transient dementia during hyperthyroidism of painless thyroiditis. A case report].

We report transient dementia in a 71-year-old woman, that was caused by hyperthyroidism of painless thyroiditis. Her friends, who found her very forgetful and performing abnormal behavior, brought her to our hospital. She looked alert and cooperative. There was neither goiter nor pain of the thyroid. Neurological examination revealed impairment of recent memory with a low score of memory test (MMSE: 20/30) indicating mild dementia. EEG showed slow alpha waves (8 Hz) with random theta and delta waves in the frontotemporal regions bilaterally. MRI showed mild diffuse atrophy of the brain, and SPECT revealed diffuse decrease in the cerebral blood flow most predominantly in the frontotemporal regions bilaterally. Abnormal findings included low levels of thyroid stimulating hormone (TSH), high levels of free triiodothyronine and free thyroxine. Antithyrogloblin antibody was positive and TSH receptor antibody was negative, while CRP was normal. Radioactive Tc uptake of the thyroid gland was low. A diagnosis of painless thyroiditis was made. Thyroid function turned to euthyroid state spontaneously in four weeks without antithyroid therapy, and subsequently memory disturbance and abnormal behavior disappeared. SPECT after clinical recovery showed improvement in the cerebral blood flow of the frontotemporal lobes. To our knowledge, dementia-like symptoms secondary to hyperthyroidism of painless thyroiditis have not been reported previously, and should be kept in mind as one of the causes of treatable dementia.

Aged↗
PubMed2002

Intra-arterial CT-angiography for cerebral arteriovenous malformation--initial experiences for treatment planning of radiosurgery.

PURPOSE: To clarify the feasibility and effectiveness of intra-arterial CT angiography (IACTA) for treatment planning of arteriovenous malformation radiosurgery. METHODS AND MATERIALS: A CT scanner installed in an angiographic examination room was used. Helical IACTA was performed in 22 patients during continuous intra-arterial infusion of contrast medium via the internal carotid or vertebral artery, and dynamic IACTA was performed in 20 of these patients with reconstruction at 0.2-s intervals. The dynamic IACTA was repeated for each 3- or 5-mm increment to encompass the nidus. Subtractions were performed in postembolization cases. A retrospective review of IACTA was performed to assess the effectiveness of dynamic scans. RESULTS: No complications related to the angiographic procedure or CT imaging were detected. High contrast enhancement was obtained for both helical and dynamic IACTA. In 18 of the 20 cases (90%), draining veins were separated from the nidus by using the enhancement patterns, and in 13 cases (65%), feeding arteries were separated. CONCLUSION: Dynamic IACTA added important information for target-volume determinations. Conventional CT and MRI could be omitted from the protocol, and the period that patients wore the frame was substantially shortened. We conclude that IACTA is a practical and useful method for radiosurgical treatment planning of arteriovenous malformations.

Adolescent↗