Biomedical subjects

Shozo Tobimatsu

Publications and source records attributed to Shozo Tobimatsu.

13 recordsLinked to original sources

PubMed2003

Interhemispheric functional desynchronization in the human vibratory system.

We examined the differences in interhemispheric functional correlation in the somatosensory system using coherence (Coh) analysis. Ten healthy adult volunteers served as subjects for this experiment. Vibratory stimulation (modulation frequency, 21 Hz) was given to each palm to record vibratory steady-state somatosensory evoked potentials (S-SEPs). S-SEPs were recorded from four electrodes placed at 2 cm posterior and anterior to C3 and C4, referred to an electrode at Fpz, respectively. For comparison, unstimulated S-SEPs were also recorded. A total of 50 responses of 1-s epochs was averaged and subjected to discrete fast Fourier transforms to yield the amplitudes of major harmonic components and Coh value. The Coh value between the two signals, x and y at each frequency f, was calculated as [Coh(xy)(f)](2)=[S(xy)(f)](2)/[S(xx)(f)xS(yy)(f)]. The amplitude at 21 Hz in the contralateral somatosensory area was significantly larger than that in the other electrodes. The interhemispheric Coh of the somatosensory area at 21 Hz was significantly lower than that in the unstimulated condition or intrahemispheric Coh. The initial somatosensory information is desynchronized. These findings indicate less significance of interhemispheric correlation as the first step of the vibratory information processing in the somatosensory cortex.

Adult↗

PubMed2003

Reappraisal of the motor role of basal ganglia: a functional magnetic resonance image study.

The importance of the basal ganglia in controlling motor function is well known. However, neuroimaging studies have failed to show either movement-rate dependence or different activation patterns caused by self-initiated (SI) and externally triggered (ET) movements in the basal ganglia-thalamo-motor loop. We herein report the functional magnetic resonance image (fMRI) mapping of sequential left-hand finger movements at five different rates under SI and ET conditions. Significant movement-rate dependence was found in the whole right basal ganglia-thalamo-motor loop only during the SI task. Network analysis also showed strong interactions within this loop during SI movement, whereas interactions were present only from the premotor cortex to the putamen via the sensorimotor cortex during the ET task. Furthermore, psychophysiological interaction analysis confirmed the different modulation between the two tasks in the putamen. fMRI provides evidence that the basal ganglia-thalamo-motor loop plays a key role in controlling the rate of sequential finger movements in SI movement but not in ET movement.

Adult↗

PubMed2003

Middle latency auditory-evoked potentials in myotonic dystrophy: relation to the size of the CTG trinucleotide repeat and intelligent quotient.

OBJECTIVE: Major components of MLAEPs are thought to originate in the temporal lobe. Absence of the Pb potential has been demonstrated in MLAEPs in Alzheimer's disease and demented Parkinson's disease patients. To validate usefulness of middle latency auditory-evoked potentials (MLAEPs) in evaluating the central nervous system (CNS) involvement of myotonic dystrophy (MyD). METHODS: MLAEPs were recorded in eight patients with MyD and nine normal control subjects. In the patient group, the size of the CTG triplet repeat expansion within the dystrophia myotonica protein kinase (DMPK) gene and the revised Wechsler Adult Intelligence Scale (WAIS-R) were also assessed. RESULTS: The latency of the Nb potential showed a significant correlation with the size of the CTG repeat expansion (r=0.734, P=0.036). The Pb latency also tended to prolong according to CTG amplification (r=0.644, P=0.087). The amplitudes of Na and Pa significantly increased compared with those of normal control subjects (P=0.024 and 0.016, respectively). However, they did not correlate with IQ or CTG amplification. CONCLUSIONS: Abnormal MLAEPs may indicate CNS involvement in MyD. Although the precise generating mechanisms of Nb are unclear, the correlation of Nb latency with CTG amplification suggests that MLAEPs can reflect the extent of genetic abnormality.

Adult↗

PubMed2003

The long-term effects of antiepileptic drugs on the visual system in rats: electrophysiological and histopathological studies.

OBJECTIVE: We quantified the long-term effects of antiepileptic drugs (AEDs) on the visual system of rats using electroretinograms (ERGs) and visual evoked potentials (VEPs). METHODS: Twenty adult Sprague-Dawley rats were divided into 4 groups (n=5). Each animal was treated by monotherapy of phenytoin (PHT), valproic acid (VPA), zonisamide (ZNS) or physiological saline as control. The AEDs were injected intraperitoneally daily for 180 days. ERGs and VEPs were recorded before the medication and on Days 30 and 180. RESULTS: There were no significant changes in the 4 groups on Day 30. On Day 180, the amplitudes of a- and b-waves of dark-adapted (DA) ERGs were reduced in the PHT group compared with those of the control group. In the VPA group, the amplitudes of the DA ERG a- and b-waves, light-adapted ERG b-wave and the DA VEP were reduced. No significant changes were observed in the ZNS group. There were no histopathological changes of the retina and visual cortex in all groups. CONCLUSIONS: Our results indicate that neurons along the visual pathways have different sensitivity to each AED. This may result from the differential pharmacological actions of each AED on visual neurons. SIGNIFICANCE: Our findings suggest that epileptic patients on long-term use of AEDs might have subclinical influences to the visual systems.

Adaptation, Ocular↗

PubMed2003

[Electrophysiolgical diagnosis for multiple sclerosis].

Evoked potentials(EPs) in daily practice contain brainstem auditory evoked potentials (BAEPs), short-latency somatosensory evoked potentials(SSEPs), pattern-reversal visual evoked potentials(PVEPs) and motor evoked potentials(MEPs) with transcranial magnetic stimulation(TMS). In this review, we summarize the EP findings in Caucasian and Japanese MS. EPs can confirm the presence of lesions in patients with suspected involvement, and document the presence of clinically unsuspected lesions. In addition, the combined use of these EPs in each patients, so-called multimodality EPs, enables us to evaluate multiple aspects of sensory and motor systems. In 73 Japanese MS, the abnormality rates were 10.3% in median nerve SSEP, 37.1% in posterior tibial nerve SSEP, 35.6% in upper limb MEP, 56.1% in lower limb MEP, 39.3% in PVEP and 34.3% in BAEP. The frequency of clinically unsuspected lesions was about 30% in each EP. These findings are in good agreement with the recent fact that conventional MS have been increased in Japan. Other electrophysiological methods such as multimodality VEPs, pain-related SEPs, paired TMS and event related potentials(P300) may be useful for the diagnosis or evaluation of MS.

Asian People↗

PubMed2002

Cerebral metabolic changes in early multiple system atrophy: a PET study.

Previous positron emission tomography (PET) studies have shown widespread hypometabolism in the brain of advanced MSA but the time course of these metabolic abnormalities is largely unknown. In order to clarify the principal disease processes in multiple system atrophy (MSA) in the early stage, we investigated regional cerebral glucose metabolism (rCMGglc) and nigral dopaminergic function in nine patients with early stage of MSA using [(18)F]fluorodeoxyglucose (FDG) and 6-L-[(18)F]fluorodopa ((18)F-Dopa) positron emission tomography (PET) (two men and seven women; age, 59.3+/-5.4 years; disease duration, 29.7+/-14.6 months). The rCMRglc in the early MSA patients significantly decreased in the cerebellum, brainstem, and striatum compared with that in nine normal subjects. A significant correlation was found between the severity of autonomic dysfunction and rCMRglc within the brainstem. The severity of extrapyramidal signs also correlated with the decline of F-Dopa uptake but not that of rCMRglc within the striatum. The degree of atrophy on MRI has correlated with neither the clinical symptoms nor rCMRglc at the cerebellum and the brainstem. Our PET studies demonstrated widespread metabolic abnormalities except for the cerebral cortex in the brain of MSA even in the early stage. The hypometabolism in the brainstem was tightly linked to the autonomic dysfunction. Not the striatal dysfunction but the nigral damage may be responsible for the extrapyramidal symptoms in early MSA.

Aged↗

PubMed2002

Persistent hypertension does not alter the cerebral blood flow and glucose utilization in young-adult Dahl salt-sensitive rats.

The Dahl- Iwai salt-sensitive (DS) rat develops hypertension due to a high-salt diet without any structural alterations of the brain arteries and arterioles. We investigated the effect of persistent hypertension on the regional cerebral blood flow (rCBF) and regional cerebral glucose utilization (rCGU) in the DS rats. The rats were fed either a high-salt diet (HSD; 8% NaCl, n = 5) or a low-salt diet (LSD; 0.3% NaCl, n = 6) from 8 to 16 weeks of age, and the HSD group developed hypertension lasting for 1 month. At 16 weeks of age, the rCBF was measured in the sensorimotor and visual cortices using the hydrogen clearance method, and the rCGU was measured in 26 different brain structures using the [(14)C]deoxyglucose method. The mean arterial pressure was significantly higher in the HSD group (168+/-7 mm Hg) than in the LSD group (139+/-3 mm Hg) (P < 0.01). The mean rCBF and the rCGU values tended to be lower in the HSD group than in the LSD group; however, there were no statistically significant differences except for the reduced rCGU value in the nucleus accumbens. These results suggest that hypertension itself does not alter either the rCBF or the rCGU in young-adult DS rats. This indicates that the functional / structural changes of the cerebral arteries and arterioles that are associated with hypertension appear to be responsible for altered rCBF and rCGU in other animal models of hypertension.

Animals↗

PubMed2002

Paradoxical lateralization of parasagittal spikes revealed by back averaging of EEG and MEG in a case with epilepsia partialis continua.

Our aim was to localize the generator site of parasagittal epileptiform discharges in a patient with epilepsia partialis continua (EPC) in the right leg. We examined a 32-year-old woman with EPC whose conventional EEG did not show any epileptic discharge. We performed the jerk-locked back averaging (JLA) of EEG and magnetoencephalography (MEG) to localize the dipole source of sharp transients. The myoclonic discharges in the right soleus muscle were used as a trigger pulse. JLA revealed consistent EEG and MEG sharp transients that coincided consistently and constantly preceded the myoclonic jerks. JLA of EEG demonstrated sharp waves paradoxically distributed over the vertex and right hemisphere. However, the estimated dipoles of MEG were localized in a restricted area in the primary leg motor area in the left hemisphere, which was closely located in the abnormal lesion on the brain MRI. JLA of MEG is considered to be a useful non-invasive method for localizing the epileptogenic area in EPC even when paradoxical lateralization of electroencephalographic discharges was noted.

Action Potentials↗

PubMed2002

Different patterns of excitation and inhibition of the small hand and forearm muscles from magnetic brain stimulation in humans.

OBJECTIVES: The objective of the present study is to quantify the effects of voluntary muscle contraction of the small hand (abductor pollicis brevis, first dorsal interosseus (FDI)) and forearm muscles (extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU)) on motor evoked potentials (MEPs). METHODS: MEPs were recorded in 12 healthy subjects by a circular coil placed over the vertex at 1.2 times the resting motor threshold at different levels of the muscle contraction (0-100% of maximum voluntary contraction (MVC)). The effects of transcranial magnetic stimulation (TMS) on the onset latency, MEP area and silent period (SP) as a function of the %MVC were evaluated using a piecewise linear regression analysis. RESULTS: The MEP areas for the small hand muscles were almost completely saturated at 20% of MVC. In contrast, the MEP areas for radial muscles (ECR, FCR) had a dual increase at 40% of MVC while the ulnar muscles (ECU, FCU) had a dual increase at 20% of MVC. A uniform latency shift (1.5-3 ms reduction) was observed in all muscles with a changing point at 10% of MVC. The SPs were the longest for FDI and were not significantly influenced by MVC for any muscles. CONCLUSIONS: The excitatory and inhibitory effects of TMS on the MEPs differed for the small hand and forearm muscles and also between the ulnar and radial muscles. These results probably resulted from the different degrees of direct corticomotoneuronal inputs to each muscle and the inherent properties of the spinal motoneurons.

Adult↗

PubMed2002

Delayed effects of the microvascular decompression on hemifacial spasm: a retrospective study of 131 consecutive operated cases.

We reviewed 131 consecutive cases operated for hemifacial spasm (HFS) by the same surgeon between January 1983 and April 1999. Microvascular decompression (MVD) was performed via lateral suboccipital approach. Post-operative follow-up ranged from 1.5 to 10 years (average 34 months). The final outcome divided into three categories, excellent (total recovery) in 120 cases (91.6%), partial (> 75% recovery) in 4 cases (3.1%), and unchanged or recurrent in 7 cases (5.3%). Only 2 cases were re-operated, and final outcome of both was excellent. Based on these data, we aimed to determine a period of the final judgement of MVD effect and the causative factors of delayed effects on HFS retrospectively. There were 102 complete recovered cases without hemifacial paralysis; immediate recovery from HFS was observed in 78 cases (76.5%), after 1 month in nine cases, 1-3 months in 5 cases, 3-6 months in 3 cases, 6-10 months in 2 cases, and 10-12 months in 5 cases. Thus, most cases were completely recovered within one year of observation. On the other hand, there was no statistically significant difference between immediate and delayed relief cases in clinical histories or operative observations. Therefore, our results suggest that the final judgement of the MVD effect could be made at least one year after surgery.

Adult↗

PubMed2002

Feasibility and limitations of magnetoencephalographic detection of epileptic discharges: simultaneous recording of magnetic fields and electrocorticography.

Magnetoencephalography (MEG) is considered clinically useful in localizing the epileptogenic focus in partial epilepsy. However, the relationship between the extent of the brain involved in paroxysmal activities and the magnetic field changes at the scalp has not been fully clarified. Furthermore, whether paroxysmal activities generated in deep brain structures such as the hippocampus can be detected magnetically is uncertain. Eight patients with temporal lobe epilepsy and two with extratemporal lobe epilepsy underwent chronic recording from subdural electrodes. Magnetic and electrocorticographic discharges representing epileptic activity were recorded simultaneously. MEG recorded magnetic field changes originating from paroxysmal activity in the superiolateral cerebral cortex when the amplitudes of the electrical paroxysmal activities exceeded 100 microV and extended over more than 3 cm2 of cortical surface. MEG failed to record paroxysmal activity localized to the medial temporal lobe. MEG is often useful in identifying a spike focus in the superiolateral aspects of the cerebral hemisphere, but not discharges arising from the medial temporal lobe. Rapid decay of the magnetic field is likely to be the reason for this limited sensitivity to medial discharges.

Adolescent↗

PubMed2002

High incidence of subclinical peripheral neuropathy in myelitis with hyperIgEaemia and mite antigen-specific IgE (atopic myelitis): an electrophysiological study.

OBJECTIVE: To study subclinical involvement of the peripheral nerves in myelitis with hyperIgEaemia and mite antigen-specific IgE (atopic myelitis: AM). MATERIAL AND METHODS: We carried out a nerve conduction study of the median, ulnar, tibial, and sural nerves in 21 patients with AM and in 28 patients with clinically definite or laboratory-supported definite multiple sclerosis (MS). RESULTS: The patients with AM showed a significantly higher frequency of abnormal records than the MS patients in the sensory nerve conduction study (52.4% vs. 14.3%, p = 0.0106). The frequency of abnormal records in the motor nerve conduction study in AM patients was twice as high as in MS patients (38.1% vs. 17.9%), but the difference was not statistically significant. Abnormality in the F-wave-evoked frequency in the median nerve was also significantly more common in AM patients than in MS patients (57.9% vs. 10.7%, p = 0.0016). CONCLUSIONS: These findings suggest that subclinical peripheral neuropathy is frequent in patients with AM.

Adult↗

PubMed2002

[A case of cerebellar ataxia showing severe dystonia masquerading as myoclonic jerky movements on arm extension].

A 43-year-old man was admitted to our hospital due to unstable walking, head tilting to the left and difficulty in extending his arm. He was quite healthy until the age of 20 years, when these symptoms appeared and progressed slowly afterward. Due to his unstable walking, he started to use a wheelchair when he was 39 years old. He had no family history of similar disease. On admission, neurological examination revealed spasmodic torticollis, ataxic speech and marked limb and truncal ataxia. Myoclonic jerky flexion of the forearm was induced when he raised and extended his forearm. He also showed mild hyperreflexia in the lower limbs without pathological reflexes. He had weakness and atrophy of the left supraspinatus, infraspinatus, deltoid and biceps brachii muscles and mild superficial sensory impairment in the left axillary nerve territory due to cervical spondylotic radiculopathy of the left C5 root. MRI of the brain demonstrated severe bilateral atrophy of the cerebellar hemispheres and vermis but minimal atrophy of the cerebrum and brainstem. Because surface electromyography revealed continuous discharge with phasic components in the biceps and wrist flexor muscles on extending the upper limbs, the jerky flexion movement of the forearm was considered to be primarily dystonia. Although no giant SEP was observed, a C-response was detected in the long-loop reflex in response to right median nerve stimulation. Nuclear examinations showed diffuse hypoperfusion and decreased glucose metabolism in the cerebellum. Based on these findings, we hypothesized that cerebellar dysfunction may have induced severe dystonic movement resembling myoclonus. We would like to name this complicated involuntary movement an "arm thrust". This is the first case to be reported of sporadic, chronic, progressive cerebellar ataxia accompanied by severe dystonic movement, especially on stretching the forearms, that mimics myoclonic movement.

Adult↗