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Biomedical subjects

S Tobimatsu

Publications and source records attributed to S Tobimatsu.

At least 73 records · Page 4Linked to original sources
PubMed1993

Primary progressive versus relapsing remitting multiple sclerosis in Japanese patients: a combined clinical, magnetic resonance imaging and multimodality evoked potential study.

Thirty-five Japanese patients with relapsing remitting multiple sclerosis (RRMS) and 11 Japanese patients with primary progressive MS (PPMS) were compared by a combined clinical, magnetic resonance imaging (MRI) and multimodality evoked potential (MEP) study. Patients with PPMS showed a more common occurrence of gait disturbance as the initial symptoms as well as a more common occurrence of cerebellar symptomatology than did those with RRMS, while spinal cord symptomatology was frequently observed in both conditions. On brain MRI, patients with PPMS had 3 times more lesions than did those with RRMS (P < 0.001, chi 2-test). The percentage of infratentorial lesions was also significantly higher in PPMS than in RRMS on MRI. Moreover, we found a significantly higher frequency of abnormal records in visual, brainstem auditory and somatosensory evoked potentials in PPMS than in RRMS. Interestingly, clinically unexpected abnormalities were significantly more common in PPMS than in RRMS throughout all modalities of MEPs. Thus, in Eastern MS, there exists a distinction between PPMS and RRMS in the MRI and MEP findings as well as in the clinical findings. Our result therefore suggest that there may be two distinct subtypes in MS.

Adult↗
PubMed1993

Effect of spatial frequency on transient and steady-state VEPs: stimulation with checkerboard, square-wave grating and sinusoidal grating patterns.

We recorded VEPs to the alteration of checkerboard, square-wave grating and sinusoidal grating patterns to evaluate the contribution of the fundamental spatial frequency and higher harmonic components in 12 normal subjects. Their fundamental spatial frequencies were equated and ranged from 0.5 to 8.0 c/deg. Both the transient VEP (T-VEP) and steady-state VEP (S-VEP) were obtained. The latency and amplitude of P100 of T-VEPs were measured. S-VEPs were Fourier analyzed, and phase and amplitude of the second harmonic response were measured. The mean P100 latency and the mean phase had a U-shaped function with a peak at a fundamental spatial frequency of 2.0 c/deg irrespective of the stimulus patterns, while the mean P100 amplitude and the mean amplitude of S-VEPs did not show such spatial selectivity. At low and medium spatial frequencies, differences in P100 latency, phase and amplitude between pattern types were more pronounced. However, this difference became insignificant at high spatial frequencies. These results indicate that VEP responses are predominantly determined by the fundamental spatial frequency, and that the contribution of higher harmonics to VEP responses is not negligible. Our results are consistent with the concept that the human visual system may use spatial frequency-domain information.

Adult↗
PubMed1993

[The variation of human contrast sensitivity with age and optic nerve disease].

Contrast sensitivity function (CSF) was measured in 85 normal subjects and in 23 patients with optic neuropathy, using a personal computer and video monitor system. CSF in normal controls showed an inverted U-shaped function against spatial frequency with a peak at about 4-6 cycles/degree. At higher spatial frequencies, contrast sensitivity decreased with increasing age. CSF in patients was compared with Snellen acuity, visual field examination, critical flicker fusion frequency (CFF) and pattern VEP (P-VEP). CSF and P-VEP were more sensitive than the others in detecting visual dysfunction in optic nerve disease. These results suggest that ranges of normal values should be established for each of several age groups, and that CSF is useful for evaluating visual dysfunction.

Adult↗
PubMed1992

[Adverse effect of antiepileptic drugs on the visual recognition--a contrast sensitivity function study].

Contrast sensitivity function (CSF) was measured in 16 patients (14-60 yr.) with epilepsy to investigate adverse effect of antiepileptic drugs on the central nervous system. Eight patients were treated with phenytoin, while 8 were given polytherapy (phenytoin in combination with phenobarbital, carbamazepine or valproic acid). Thirty-one normal controls (19-59 yr.) were also subjected to this study. Vertical sinusoidal gratings with various spatial frequencies (0.5-20.0 c/deg) were presented on a video monitor. Contrast sensitivity (reciprocal of threshold contrast) was determined at each spatial frequency. CSF of normal subjects showed an inverted U-shaped function against the spatial frequencies with a peak at 6 c/deg (medium size pattern). There was no significant difference in CSF values between normal controls and patients with epilepsy. However, 3 patients with polytherapy showed the significant reduction of contrast threshold. Since these patients did not complain of visual disturbance with normal visual acuity, CSF abnormality was considered as having subclinical visual dysfunction. These results suggest that CSF is useful for evaluating the adverse effect of antiepileptic drugs on the visual recognition, and that polytherapy is responsible for CSF abnormality. Therefore, monotherapy should be scheduled from the onset of therapy.

Adult↗
PubMed1992

The neurophysiologic significance of frontal negativity in pattern-reversal visual-evoked potentials.

To demonstrate that the frontal negative potential (N100) does exist in response to pattern-reversal visual stimulation and its independence of the dipole source from the major occipital positive potential (P100), modifications of P100 and N100 with changes in the check size, contrast, and luminance of the stimulus pattern were studied in healthy subjects. Eight different check sizes (10-90 min of arc), eight different contrast levels (10-85%), and six different luminance levels (11-180 cd/m2) were used. Changing the stimulus conditions modified the latencies and amplitudes of P100 and N100 in different ways. P100 latency had a band pass spatial tuning function against check size; N100 latency did not. P100 was sensitive to changes in contrast and luminance; N100 was less dependent on these parameters. These findings suggest the existence of different physiologic properties for N100. Consequently, frontal negativity is considered to be independent of P100.

Adult↗
PubMed1991

Auditory middle-latency responses in patients with localized and non-localized lesions of the central nervous system.

Auditory middle-latency responses were recorded in 45 neurological patients. In 4 patients with localized lesions in the thalamus, or subcortical white matter, the component Na was attenuated or delayed at T3, Cz and T4, exclusively on stimulation of the ear contralateral to the lesion. In 5 patients with temporal lobe lesions with receptive aphasia, the amplitude of component Pa was decreased on the lesion side (T3), regardless of the side of stimulation. These findings suggest that Na is generated from a subcortical structure and Pa is generated from the temporal cortex. In 25 patients with diffuse CNS lesions, V-Na interpeak latency was prolonged in 2 cases.

Adolescent↗
PubMed1991

Direct spinal versus peripheral nerve stimulation as monitoring techniques in epidurally recorded spinal cord potentials.

We recorded spinal cord evoked potentials (SCEPs) and spinal somatosensory evoked potentials (spinal SEPs) in 30 operations following stimulation of the epidural spinal cord and the peripheral nerve, respectively, to compare their feasibility as an intraoperative technique for spinal cord monitoring. SCEPs produced quicker responses and had larger amplitudes with simpler waveforms. SCEPs could reflect residual function of the pathological spinal cord and predict the postoperative clinical outcome, findings which are not observed with spinal SEPs. Moreover, SCEPs had a much higher sensitivity to spinal cord insult. Therefore, we conclude that the SCEPs were more appropriate indicator than the spinal SEPs as an intra-operative monitoring method for spinal cord function.

Adolescent↗
PubMed1991

Usefulness of epidurally evoked cortical potential monitoring during cervicomedullary glioma surgery.

This report describes a patient with an intramedullary ependymoma at the region of the cervicomedullary junction in whom there was an abolition of somatosensory evoked potentials following median nerve stimulation. During intraoperative monitoring of cortical potentials elicited by epidural cervical cord stimulation, the tumor was removed. Posterior epidural stimulation appeared to depolarize more ascending fibers than did stimulation of a single peripheral nerve. We recommend that, in cases of operations in this vital area, epidurally evoked cortical potentials be monitored intraoperatively.

Evoked Potentials, Somatosensory↗
PubMed1991

Frontal negativity of pattern-reversal visual evoked potentials in humans.

We investigated the nature of negative potential in the frontal region with an approximate latency of 100 ms ('frontal negativity') as a component of pattern-reversal visual evoked potential (PVEP) in healthy human subjects. It was recorded by stimulation of one-half of the visual field, with different reference electrodes and with experimental manipulations of the stimulating visual field ('central scotomata' and 'peripheral constriction'). A negative potential field was demonstrated to be localized in the frontal region, and its physiological properties detected by the visual field manipulations were shown to be different from those of the occipital positive (P100) and negative (N105) components of PVEP. We conclude, therefore, that frontal negativity of PVEP is an actual electrical event generated in the frontal region, independent of P100 and N105.

Adult↗
PubMed1991

Localization of stereotactic targets by microrecordings of thalamic somatosensory evoked potentials.

To improve the localization of stereotactic targets, somatosensory evoked potentials (SEPs) were recorded from the thalamus and subthalamic area using a specially designed semimicroelectrode in 61 patients and a conventional "macroelectrode" in 17 patients. By means of the semimicroelectrode, median nerve stimulation evoked two distinct SEPs, consisting of a diphasic wave with a huge positivity restricted to the nucleus ventrocaudalis (Vc) and a triphasic wave of lower amplitude with a major negativity in the ventral part of the nucleus ventrointermedius (Vim) and nucleus ventrooralis posterior (Vop) as well as the subthalamic lemniscal pathway. The Vim-Vc junction could thus be clearly delineated by an abrupt transition of SEPs from one type to the other with a precision of 1 mm. The parvicellular part of the Vc (Vcpc), situated in its basal region, was distinguishable from the Vc proper by a significant reduction of the positivity elicited by stimulation of the median nerve and by a rapid growth of a diphasic SEPs to stimulation of the posterior tibial nerve. In the other thalamic nuclei, stimulation of the median nerve elicited triphasic SEPs of a very small amplitude, suggesting a volume conduction current from the lemniscal pathway. With the macroelectrode, the positivity in the Vc was sensitive to electrode manipulation and the thalamic nuclei could not be distinctly outlined. SEP monitoring using the semimicroelectrode significantly improved the precision of target localization, which allowed minimizing of the volume of the therapeutic lesion without losing surgical effectiveness, while avoiding complications associated with increased penetration of the coagulating electrode. It is suggested that recording serial thalamic SEPs with the semimicroelectrode is a practical method to refine stereotactic targets in the thalamus.

Adult↗
PubMed1989

Electroretinograms to checkerboard pattern reversal in cats: physiological characteristics and effect of retrograde degeneration of ganglion cells.

Pattern electroretinograms (P-ERGs) evoked by alternating checks were studied in cats. Spatial frequency functions for transient and steady-state P-ERG waves showed a bimodal distribution with a preferred frequency at 0.6-0.75 c/deg and a second amplitude increase at frequencies lower than 0.5 c/deg. Decreasing the pattern luminance by 0.5 log units produced a shift of the spatial tuning curve toward lower spatial frequencies. No temporal tuning was noted in the temporal frequency functions. The bimodal distribution suggests that at spatial frequencies higher than 0.5 c/deg, the tuning reflects a 'contrast response' originating in cells with center surround organization. At spatial frequencies below 0.5 c/deg, the 'luminance response' becomes predominant and is generated in cells sensitive to mean luminance changes. Transient and steady-state P-ERGs to medium and high spatial frequencies were abolished by section of the optic nerve, while low spatial frequency stimuli at or below 0.3 c/deg continued to evoke P-ERGs at 1, 5 and 10 months after surgery. Quantitative whole mount retina microscopic examination confirmed the retrograde degeneration of the ganglion cells. It is concluded that both transient and steady-state P-ERGs to small and medium spatial frequencies checks are predominantly related to ganglion cell activity, while P-ERGs to low spatial frequencies reflect preganglionic cell activity.

Animals↗
PubMed1986

Nonfamilial prealbumin-type amyloid polyneuropathy.

A 53-year-old man with nonfamilial prealbumin-type amyloid polyneuropathy had severe motor, sensory, and autonomic polyneuropathy, beginning at age 48 years. These clinical features closely resembled familial amyloid polyneuropathy (FAP), but abnormal serum prealbumin levels, specific to FAP (Japanese type), were not detected by radioimmunoassay; DNA sequence for prealbumin was normal. Thus, the diagnosis of FAP was excluded. A possible diagnosis of systemic senile amyloidosis was also considered.

Amyloidosis↗
PubMed1986

Adrenoleukodystrophy and variants. Clinical, neurophysiological and biochemical studies in patients and family members.

Clinical, neurophysiological and biochemical studies were performed in patients with various forms of adrenoleukodystrophy (ALD) and their family members. The patients showed an abnormality in saturated very long chain fatty acids and in the somatosensory and brain stem auditory or visual evoked potentials. Female presumptive carriers without abnormal neurological manifestations also showed abnormality in the somatosensory or brain stem auditory evoked potentials and in saturated very long chain fatty acids. One ALD patient and his mother, a female carrier, had the decreased beta-galactosidase activity. The increase in saturated very long chain fatty acids was found, not only in sphingomyelin, but also in phosphatidylcholine and phosphatidylserine. Our results suggest that a generalized abnormal metabolism of VLFA and an abnormality in the central nervous system exist in our patients and female carriers.

Adrenoleukodystrophy↗
PubMed1986

Electroencephalographic correlates of myoclonus.

Fifty-five consecutive cases of myoclonus owing to various etiologies were studied by conventional EEG-EMG polygraphic recordings and/or jerk-locked or back averaging. The technique of back-averaging was shown to be useful not only for detecting EEG correlates of myoclonus that are not recognizable on the routine polygraph but also for investigating the temporal and topographic relationship between the EEG activities and myoclonus. Thirteen of 17 cases of PME and related disorders, in whom back-averaging and SEP were studied, were shown to have both a myoclonus-related cortical spike over the contralateral central area, preceding the myoclonus of an upper extremity by 6 to 22 msec, and a giant SEP accompanied by an enhanced C reflex. In these cases of "cortical reflex myoclonus," the myoclonus-related spike was similar to the P25-N33 components of the giant SEP in its wave form, scalp topography, temporal relationship to myoclonus or to C reflex, succeeding cortical excitability, and drug effect. All of this suggests participation of common physiological mechanisms in those two activities. In two cases of PME, in which myoclonus involved bilateral proximal muscles synchronously, the myoclonus-related spike was maximal near the vertex, and there was no giant SEP. The significance of this subgroup remains undetermined. In six cases of the PME group, back-averaging was inapplicable because of rare occurrence of myoclonus, but they showed a typical giant SEP accompanied by an enhanced C reflex. In CJD, back-averaging demonstrated a sharp wave or PSD over the contralateral hemisphere, preceding the myoclonus by 50 to 85 msec. This form of myoclonus seems to be subcortical in origin. In essential myoclonus and oculopalatal-somatic myoclonus, there was neither myoclonus-related cortical spike nor giant SEP. Electrical stimulation of the peripheral nerve at variable intervals after the myoclonus onset (jerk-locked-SEP paradigm) was shown to be useful for investigating the influence of myoclonus on cortical excitability.

Brain Diseases, Metabolic↗