峯 清一郎

Dipole sources of interictal epileptiform activities recorded by conventional electroencephalogram (EEG) were estimated using the dipole tracing method. Four cases of temporal lobe epilepsy with medial temporal lesions were studied. Two patients with hippocampal sclerosis, one patient with granulation in the hippocampus and one patient with cavernous angioma were involved in the study. Interictal epileptiform activities were classified into two patterns according to the topography of spikes. They were widespread spikes over the parasagittal electrodes (parasagittal spikes) and restricted spikes at the temporal electrodes (temporal spikes). Dipole sources of parasagittal spikes were localized in the medio-basal temporal lobe with vertically orientated vector moment. Dipole sources of temporal spikes were localized in the medio-basal temporal lobe with horizontally orientated vector moment. Locations of dipoles and directions of vector moments were consistent with topography and polarity of spikes. The difference in the two patterns of interictal epileptiform activities was derived from the difference in the direction of the vector moment of dipole sources. There was no difference in the location of dipole sources. Both the dipole sources and the lesions were localized in the same medio-basal temporal lobe. Dipole tracing was very useful in localizing the dipole sources of interictal epileptiform activities and in understanding the neurophysiological background.

This study was conducted to determine risk factors for poor outcome in the natural history of arteriovenous malformation (AVM). We statistically analysed the correlation between clinical or angiographical findings and clinical outcomes for 55 cases of untreated AVM. Subsequent haemorrhage from AVMs was the only significant risk factor for poor outcome (P &lt 0.0001). The odds ratio was 44.56 with a 95% confidence interval (CI) from 4.80 to 413.90. Risk factors for subsequent haemorrhage from AVMs were also determined. The size (P = 0.0483) and location (P = 0.0147) of an AVM were significant risk factors for subsequent haemorrhage. The odds ratios were 3.97 with a 95% CI from 1.18 to 13.33 and 3.89 with a 95% CI from 1.10 to 13.72, respectively. AVMs of more than 60 mm, and deep or infratentorial AVMs had more chance of subsequent haemorrhage, and hence of a poor outcome. We propose using an aggressive multidisciplinary approach to treating these AVMs. (C) 2000 Harcourt Publishers Ltd.

The expressions of mRNAs encoding G protein α subunits were analyzed in the cerebral cortex of amygdaloid kindled rats. A remarkable increase in G(sα) mRNA were observed on the bilateral cerebral cortex at 24 h after the last generalized seizure and persisted 3 weeks on the unstimulated side. G(i2α) mRNA level was also increased on the stimulated side at 24 h and persisted 3 weeks. These result suggest that dysfunction of G(s) and G(i2) might relate to the basic mechanisms of seizure generation and the maintenance of epileptogenesis.

34 patients with indirect traumatic optic neuropathy were studied to identify factors affecting outcome and surgical indications. 12 cases (13 eyes = group A) underwent surgery and 24 patients (24 eyes = group B) were managed without surgery. Age, optic canal fracture, visual acuity before treatment (initial visual acuity) and days until surgery (only group A) were employed as variables. Visual acuity improved significantly more in patients with initial visual acuity, hand movement (HM) or better than in those with initial visual acuity for light perception (LP) only or worse. When initial visual acuity was HM or better, vision improved significantly more in patients with surgery than in those without surgery (p = 0.0003 by Mann-Whitney U test). Days until surgery were correlated with visual improvement in patients with visual acuity HM or better. Age and optic canal fracture did not affect visual improvement or influence the decision for or against surgery.

DIPOLE Source localization of ictal epileptiform activity recorded by scalp EEG was performed in patients prior to surgical treatment. The dipole tracing method combined with the scalp-skull-brain head model was used to locate epileptogenic foci. A digital EEG system was used for data collection. The accuracy of dipole source localization was evaluated by comparing the focus location with that obtained by chronic subdural electrocorticography. In a case of frontal lobe epilepsy with epileptogenic focus in the frontoparietal convexity, the results of dipole source localization agreed well with those obtained with chronic subdural electrocorticography. In a case of lateral temporal lobe epilepsy, the results of dipole source localization were consistent with those obtained with chronic subdural electrocorticography, but a small localization error was observed. The clinical usefulness of and suggestions for improving this method are discussed. (C) 1998 Lippincott Williams & Wilkins.

The aim of the present study was to explore the utility of dipole tracing (DT) of a scalp-skull-brain (SSB) head model in preoperative functional localization of the human brain. Nine patients who underwent surgery of mass lesions around the central sulcus (CS) were employed. By using SSB/DT, dipole source location of early cortical components of the somatosensory evoked potential (SEP) was estimated before surgery. Motor cortex, CS and primary somatosensory cortex were determined by cortical SEP during surgery. After surgery precise functional mapping was reproduced in MRI, and the accuracy of DT was evaluated by measuring the distance between estimated dipole source and the posterior bank of the CS. We defined this distance as localization error of DT. In 4 cases without structural change around the sensorimotor cortex, localization error ranged from 1 to 4 mm with an average of 2 mm, In 5 cases with structural alteration of sensorimotor cortex, localization error ranged from 6 to 10 mm with an average of 8 mm. The difference in localization error between the two groups was statistically significant, and may have been caused by changes of conductance near sensorimotor cortex in the latter group. Functional localization by DT was accurate and useful. But localization error could not be ignored in cases with structural alteration in the sensorimotor cortex. (C) 1998 Elsevier Science Ireland Ltd.

We studied the functional properties of rotation-sensitive (RS) neurons of the posterior parietal association cortex in detail. We classified 58 neurons as RS neurons on the basis of statistical analysis, to indicate that their responses to rotary movement were significantly greater (P <0.01) than those to linear movement of the same stimulus. We calculated rotation index, 1-(L/R), in 82 cells, where L/R is the ratio of net response to linear movement to that to rotary movement. All the RS neurons had rotation index greater than or equal to 0.3. The recording site of these RS neurons was localized in the posterolateral part of area PG (area 7a of Vogt), on the anterior bank of the caudal superior temporal sulcus (STS), in the region partly overlapping the medial superior temporal (MST) area. We compared the response of RS neurons to rotation with that to shearing movement as well as to linear movement. In the majority of RS neurons the ratio of shearing response to rotation response (S/R) was smaller than the ratio of linear response to rotation response (L/R), indicating that the response to rotation was not due to a simple combination of linear movements in the opposite direction. Most of the RS neurons responded to the rotary movement of a single spot as well as that of a slit, although the response was smaller (average 70%) for the former. Most of the RS neurons had large receptive fields (60-180 degrees in diameter) and their responses were independent of the position within the receptive field. The responses of most RS neurons increased monotonically with the increase in angular velocity and were also dependent on the size of the stimulus, although the rate of increase was small when the length was more than 10 degrees. The majority of RS neurons (37/58) responded better to rotation in depth than to that in the frontoparallel plane. Some of them (12/37) responded to diagonal rotation rather than to sagittal or horizontal rotation. We found that some depth RS neurons showed reversal in the preferred direction when we used a trapezoidal window-like plate as the rotating stimulus in the monocular viewing condition, just as occurs in the case of the Ames window illusion. The response of some RS neurons (5/7) was enhanced by tracking eye movement. The enhanced responses were observed during rotary tracking but not during linear tracking. Other RS neurons (n=2) showed maximum response to the rotation of the monkey chair in the light, as a result of convergence of visual and vestibular signals. We concluded that the continuous change of direction of movement was the most important cue for RS neurons to respond selectively to rotary movement in contrast to linear translational movement, and that these neurons were likely to discriminate the direction and orientation of the plane of rotation of the object in space.