In this longitudinal study multichannel MEG was used to localize and to quantify focal pathological spontaneous neuromagnetic activity in six patients with transient ischemic attacks (TIA) and two patients with transient global amnesia (TGA). Slow (2–6 Hz) and beta (14–30 Hz) activity were monitored up to 10 weeks. Results were compared with normative data, and changes over time were statistically analyzed. MEG detected pathological activity that persisted clinical symptoms. Focal slow activity originating from sensorimotor (TIA) and mesiotemporal (TGA) cortices exceeded normal values up to 14 times during the first hours after the attack and recovered to normal within 11 days. Focal beta activity was not useful to monitor the time course of TIA or TGA.

FUNCTIONAL magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were performed in six subjects during self-paced finger movement performance, tactile somatosensory stimulation and binaural auditory stimulation using identical stimulation paradigms. Both functional imaging modalities localized brain activity in adjacent areas of anatomically correct cortex. The mean distances measured between fMRI activity and the corresponding MEG dipoles were 10.1 mm (motor), 10.7 mm (somatosensory), 13.5 mm (auditory right hemisphere) and 14.3 mm (auditory left hemisphere). The distances found may reflect the correlation between electrophysiological and hemodynamic responses due to the different underlying substrates of neurophysiology measured by fMRI and MEG: BOLD contrast vs neuronal biomagnetic activity.

Benign epilepsy of childhood with rolandic spikes (BECRS) is an electroclinical syndrome characterized by partial sensorimotor seizures with centrotemporal spikes. We report a detailed localization analysis of spontaneous magnetic brain activities in seven BECRS patients using magnetoencephalography (MEG). All patients had BECRS diagnosis with typical seizures and electroencephalographic findings and five patients had minor psychomotor deficits. MEG was recorded over both parieto-temporal regions using a 2×37-channel biomagnetic system. The collected data were digitally bandpass-filtered (2–6, 14–30, or 1–70 Hz) to analyze slow- and fast-wave magnetic activities and rolandic spikes. Slow-wave activity was increased in four hemispheres of three patients. Increased fast-wave activity was found in all five patients with minor neuropsychological deficits. The presence of increased fast-wave magnetic brain activity appeared to cause functional anomalies in the higher brain function processes. In the spike analysis, the dipoles of rolandic spikes which constantly manifested anterior positivity in direction were concentrated in the superior rolandic region in four cases and the inferior rolandic region in three cases. The localizations of increased slow- and fast-wave activities were identical with those of the spikes. The seizure profiles were frequently characterized by the spike locations. Source localizations of the focal brain activities and rolandic spikes by MEG will contribute to the different diagnosis and pathophysiological elucidation of BECRS.

INTRODUCTION: Magnetoencephalography (MEG) offers a non-invasive way to map evoked cortical activity with a high spatiotemporal resolution. The localization of the precentral motor cortex (Brodmann's area 4) is of great clinical interest because, especially in cases of presurgical diagnostics of pericentral masses in the brain, imaging procedures such äs MRI often cannot render sufficient Information about the lesion's exact local relation to the precentral gyrus [1]. For clinical usefulness, e. g. in a neuronavigating System, MEG results of measuring motor activity have to be consistently reproducible (reliable) when localized in the precentral gyrus (valid). The purpose of the present study was to establish a motor field source localization protocol in a neurologically normal subject population and to use this protocol in a clinical environment with patients undergoing presurgical magnetic source imaging (MSI).

INTRODUCTION: Multiple sclerosis (MS) is a demyelinating disease of the central nervous System. The underlying inflammatory infiltrations cause white matter lesions which can be visualized äs "plaques" in magnetic resonance imaging (MRI). Magnetoencephalography (MEG) offers the opportunity to localize pathological activity in neuronal areas with a high spatio-temporal resolution [1]. A preliminary investigation of our laboratory using a single-dewar biomagnetic System showed abnormal magnetic activity associated with white matter lesions (MS, lacunar infarctions) to be concentrated in adjacent cortical areas [2]. In this study, we investigated patients with MS simultaneously recording biomagnetic activity from both hemispheres to find if abnormal cortical activity is caused by MS lesions and, in case of such acti-

Article Precise Pre- and Intraoperative Assessment of Functional Cortex by Magnetoencephalography (MEG) was published on January 1, 1996 in the journal Biomedical Engineering / Biomedizinische Technik (volume 41, issue s1).