Magnetoencephalographic analysis of rolandic discharges and somatosensory evoked potentials in benign childhood epilepsy with centrotemporal spikes

Society Proceedings/Electroencephalography and clinical Neurophysiology 95 (1995) 86P-94P sponses was the same as that of electrical responses. In the other 3 ALS and in 2 KAS patients, the time course of suppression was within the normal range. We conclude that lack of later phase (8-10 msec) facilitation is due to dysfunction of the corticospinal tract and that lack of early phase (1-5 msec) inhibition is just secondary to the magnetic response produced by direct activation of the corticospinal tract (delta wave) in the late-stage ALS patients. 16. Myotomai MEP by magnetic stimulation; the concept and clinical application to spinal disorders. - T. Iizuka, Z. Lee and N. Tsuzuki (Saitama) Like the dermatomal SEP in sensory pathway measurement, myotomal MEP in motor pathway was introduced for segmental and level diagnosis of spinal disorders. In addition to the conventional MEPs from upper and lower extremities, MEPs from trunk muscles (intercostal, rectus abdominis, pyramidalis) and anal sphincter were recorded with multi-channel and facilitation methods in 30 patients with spinal disorders and in 10 healthy volunteers as controls. MEPs from facial, buccal muscles or diaphragm were also measured in some cases. The double cone coil was useful for eliciting myotomal MEPs from trunk and anal sphincter muscles as well as lower extremity muscles. In case of difficulty to obtain clear MEPs from intercostal muscles because they overlapped those from pectoris major muscles, facilitation by inspiration was useful to detect the former MEPs. Results from a uro-dynamic study and MEPs from anal sphincter in patients with or without a neurogenic bladder correlated well. No side effects were encountered by magnetic brain and spine stimulation. Myotomal MEP concluded to be useful for the segmental and level diagnosis of cervical to sacral spinal cord lesions, especially in patients with thoracic multiple lesions of OPLL and OYL. 17. Evaluation of motor pathways in orthopedic neurological disorders by magnetic stimulation with new methods. - T. Iizuka, K. Saiki and N. Tsuzuki (Saitama) Motor evoked potentials (MEPs) from hand, foot, and trunk muscles were measured by magnetic stimulation over the scalp, cervical, thoracic and lumbar areas, and central motor conduction time (CMCT) was calculated in 76 healthy persons and 210 patients with orthopedic neurological disorders. Non-invasive methods of measuring the spinal cord motor conduction velocity, cauda equina conduction velocity, and our original new methods of "myotomal MEP" and "dynamic MEP" were introduced. In 120 patients with cervical myeropathy, pre- and postoperative studies were performed. Intraoperative studies by epidural recording were also performed in 20 cases. CMCTs from head to neck and to lumbar were significantly prolonged in the patient group. Motor function and CMCT correlated well in patients with cervical myelopathy. MEPs were successfully recorded intraoperatively (n = 18). Postoperative CMCT and motor function also showed good correlation. Dynamic MEPs were useful to detect dynamic and subclinical lesions in lumbar spinal stenosis with cauda equina syndrome and in Hirayama disease. No side effect was encountered, in conclusion, these new methods are reliable and useful for measuring the motor function of spinal disorders and peripheral neuropathies. 18. Evaluation of epileptogenic focus by implantation of subdural strip electrodes in patients with refractory epilepsies without clear lateralization. - H. Onishi, N. Yamaguchi, T. Emori, K. Tsukada and A. Okada (Kanazawa) We report 4 patients who were surgical candidates for intractable seizures. No patient showed a clear lateralization on scalp EEG, neurological and radiographic findings. In these 4 patients we implanted subdural strip electrodes on the frontal and temporal lobes bilaterally through the burrhole craniectomies. The first patient was a 20-year-old male with generalized tonic-clonic seizures. The ictal discharges recorded from subdural strip electrodes

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started from the right frontal lobe. Subsequent implantation of an additional subdural grid electrode disclosed the epileptogenic focus in the right supplementary motor area. Focal resection resulted in complete seizure reduction. The second patient was a 41-year-old male having falling spells. The ictal discharges started from the left mesial temporal lobe. Left temporal lobectomy resulted in good seizure control. In the other 2 patients, the subdural strip electrodes provided no definitive information with regard to epileptogenic focality, and corpus callosotomies were performed. There were no complications associated with implantation of the electrodes. The implantation of subdural strip electrodes is a relatively less invasive method for presurgical evaluation of the epilepsies and offers adequate information to determine the epileptogenic focus. 19. Estimation of electrical sources of focal spike and slow wave complex by means of the 3-shell model dipole tracing (scalpskull-brain model dipole tracing, SSB-DT). - T. Shibata, H. Iwasa, K. Koseki, T. Ito and T. Sato (Chiba) We examined the electrical source generators of the focal spike and slow wave complex by means of dipole tracing with the 3-shell head model, the so-called scalp-skull-brain model dipole tracing (SSB-DT, Homma et al.). Two-dipole analysis was applied to estimate the equivalent current dipoles (ECD). Single ECD corresponding to the peak of the spike component was estimated in the mesial part of the temporal lobe and another single ECD corresponding to the trough component was observed near the region of the ECD of the spike component. The ECDs corresponding to the slow wave component were estimated in 2 separate regions. One of the 2 ECDs of the slow wave component was located in the mesial temporal lobe near the region where the ECD of the spike component was estimated, and the other was located in the frontal and temporal cortices. These results suggest that spike and trough components might be related to the activity of the mesial part of the temporal lobe and that the slow wave component might reflect the wide-spread electrical activities of cerebral cortex including mesial temporal lobe. 20. Magnetoencephalographic analysis of rolandic discharges and somatosensory evoked potentials in benign childhood epilepsy with centrotemporal spikes. - T. Minami, K. Gondo, S. Yanai, T. Yamamoto and K. Ueda (Fukuoka) Rolandic discharge (RD) and somatosensory cvoked magnetic field (SEF) in benign childhood epilepsy with centrotemporal spikes (BCECS) were closely analysed using 37-channel magnetoencephalography with 3-dimensional dipole neuromagnetic localization. Dipoles of the prominent negative sharp waves of RD appeared as tangential dipoles in the rolandic region with positive poles situated anteriorly. Negative sharp waves showed a relatively limited localization and regular directions compared with other components. Dipoles of the positive waves following negative sharp waves appeared in the vicinity of negative sharp waves. Dipoles of the SEF stimulated at the lower lip were located in the same gyrus from which the prominent sharp negative waves of RD originated. Magnetic field strengths were compared between a group of BCECS patients and a group with other epilepsies. Responses of the BCECS patients were 3 times higher than those of the other patients. These findings suggest that RDs are basically generated through the same or a similar mechanism to that of the late components of somatosensory evoked responses. 21. Electroencephalographic and histological studies on a newly developed genetically epileptic rat. - S. Amano, S. Uemura, M. Ikeda and N. Ihara (Otsu) A new epileptic mutant rat with spontaneous seizures was developed by N. Ihara by successive mating and selection from rats with inherited cataract. Epileptic attacks were investigated on these male mutants (6-12