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Nobukazu Nakasato

Publications and source records attributed to Nobukazu Nakasato.

6 recordsLinked to original sources
PubMed2004

Comparison of magnetoencephalographic spikes with and without concurrent electroencephalographic spikes in extratemporal epilepsy.

Interictal spikes in patients with epilepsy may be detected by either electroencephalography (EEG) (E-spikes) or magnetoencephalography (MEG) (M-spikes), or both MEG and EEG (E/M-spikes). Localization and amplitude were compared between E/M-spikes and M-spikes in 7 adult patients with extratemporal epilepsy to evaluate the clinical significance of MEG spikes. MEG and EEG were simultaneously measured using a helmet-shaped MEG system with planar-type gradiometers and scalp electrodes of the international 10-20 system. Sources of E/M-spikes and M-spikes were estimated by an equivalent current dipole (ECD) model for MEG at peak latency. Each subject showed 9 to 20 (mean 13.4) E/M-spikes and 9 to 31 (mean 16.3) M-spikes. No subjects showed significant differences in the ECD locations between E/M- and M-spikes. ECD moments of the E/M-spikes were significantly larger in 2 patients and not significantly different in the other 5 patients. The similar localizations of E/M-spikes and M-spikes suggest that combination of MEG and EEG is useful to detect more interictal spikes in patients with extratemporal epilepsy. The smaller tendency of ECD amplitude of the M-spikes than E/M-spikes suggests that scalp EEG may overlook small tangential spikes due to background brain noise. Localization value of M-spikes is clinically equivalent to that of E/M-spikes.

Adolescent↗
PubMed2003

Ipsilateral area 3b responses to median nerve somatosensory stimulation.

Magnetoencephalography investigation of the somatosensory evoked fields for median nerve stimulation detected ipsilateral area 3b responses in 18 hemispheres of 14 (1 normal subject and 13 patients with brain diseases) among 482 consecutive subjects. The major three peaks in the ipsilateral response were named iP50m, iN75m, and iP100m, based on the current orientation in the posterior, anterior, and posterior directions and the latency of 52.7 +/- 6.2, 74.1 +/- 9.4, and 100.2 +/- 15.8 ms (mean +/- standard deviation), respectively. The moment of the iP50m dipole (9.4 +/- 5.7 nAm) was significantly smaller than that of the N20m dipole of the contralateral response (cN20m, 27.5 +/- 10.5 nAm, P < 0.0001). Dipoles of iP50m and cN20m were similarly localized on the posterior bank of the central sulcus. iP50m in the present study had the same current orientation as and peak latency similar to that of the first ipsilateral primary somatosensory response to lip stimulation in our previous report. Therefore, the somatosensory afferent pathway from the hand may reach directly to the ipsilateral area 3b at least in part of the human population.

Adult↗
PubMed2003

Focal magnetoencephalographic spikes in the superior temporal plane undetected by scalp EEG.

Temporal lobe spikes were detected by magnetoencephalography (MEG), but not by standard scalp electroencephalography (EEG), in a patient with intractable complex partial seizures. Simultaneous recording of scalp EEG and MEG revealed 2 different types of spike discharges: sporadic single spikes detected by both EEG and MEG which were localised diffusely in the right temporal lobe; and rhythmic MEG spike discharges that were not detected by scalp EEG, focally localised in the posterior part of the superior temporal plane. The tangential current orientation to the scalp may explain the different sensitivity of scalp EEG and MEG to rhythmic discharges. This study shows the unique sensitivity of MEG to epileptic activity in the superior temporal plane.

Adult↗
PubMed2002

Surgical implications of neuromagnetic spike localization in temporal lobe epilepsy.

PURPOSE: To investigate the clinical usefulness of magnetoencephalography (MEG) as a guide to the surgical treatment of temporal lobe epilepsy (TLE). METHODS: Preoperative spike localization by MEG was compared with seizure outcome and postoperative spike localization at 12 months after resective surgery in 16 patients with TLE. Spike localization was classified into anterior temporal (AT) and non-AT localization in 11 patients without neocortical lesion treated with anterior temporal lobectomy (ATL); and lesion and lobar localization in five patients with neocortical lesion treated with lesionectomy (n = 3) or lesionectomy with medial temporal resection (n = 2). RESULTS: All five patients with AT localization became seizure free and spike free after surgery. Among the six patients with non-AT localization, two became seizure free and spike free, two became seizure free with residual spikes, one had residual seizures but no spikes, and one had both residual seizures and spikes. All three patients with lesion localization and two with lobar localization had favorable seizure outcome and became spike free after surgery. CONCLUSIONS: MEG spike localization can identify neocortical sources remote from the presumed epileptogenic area. Favorable seizure outcome can be expected in patients with AT localization after ATL and patients with lesion localization after lesionectomy. In contrast, non-AT localization indicates either nonmedial TLE or spike propagation to the posterior and extratemporal neocortex. Similarly, lobar localization indicates spike propagation from an epileptogenic lesion or extensive epileptogenicity. Patients with non-AT localization or lobar localization should undergo intensive evaluations, such as intracranial EEG, for improved seizure outcome.

Action Potentials↗
PubMed2002

[Magnetoencephalographic localization of multiple seizure foci for surgical treatment of intractable frontal lobe epilepsy: confirmation with intra-operative electrocorticography].

A successfully treated case of intractable FLE, of which preoperative magnetoencephalography (MEG) provided multiple spike localization and intraoperative corticogram (ECoG) confirmed the resection area. A 22-year-old male patient, with a history of subdural abscess at the age of 14 years, had suffered frequent simple (SPSs) and complex partial seizures (CPSs) and falling attacks since the age of 16 years. Although he underwent corpus callosotomy at the age of 17 years, additional surgical treatment was considered because of intractable and more frequent SPSs and CPSs. Magnetic resonance (MR) imaging demonstrated diffuse lesions in the right frontal lobe. Although, both interictal and ictal electroencephalography (EEG) failed to show focal epileptogenic localization, interictal MEG localized several clusters over the multiple anatomical lesions in the right prefrontal and frontal opercular regions. The patient underwent right fronto-temporal craniotomy, and anterior frontal lobectomy, followed by lesionectomy of the premotor area based on the intraoperative ECoG findings. The ECoG localized frequent spike discharges over the right prefrontal, frontal operculum and premotor cortices, which showed good correspondence with the MEG findings. MEG can be a useful noninvasive method for presurgical evaluation of intractable FLE.

Adult↗