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H Shigeto

Publications and source records attributed to H Shigeto.

27 records · Page 2Linked to original sources
PubMed1998

Visual evoked cortical magnetic responses to checkerboard pattern reversal stimulation: a study on the neural generators of N75, P100 and N145.

In an attempt to elucidate the neural generators of pattern reversal visual evoked potentials (PR-VEPs), we measured the visual evoked magnetic fields (PR-VEFs) using a 37-channel magnetoencephalography in six healthy young adults. A half-field checkerboard pattern was phase-reversed at a rate of 1 Hz to stimulate the right or left visual half-field, thus yielding 12 PR-VEFs in total from the six subjects. The simultaneously recorded scalp PR-VEPs showed three distinct components of N75, P100 and N145. Three corresponding components were also identified in the PR-VEFs with similar peak latencies (N75m, P100m and N145m). P100m and N145m were clearly identified in all 12 PR-VEFs, whereas N75m was observed in only nine of 12 PR-VEFs. The equivalent current dipoles (ECDs) of N75m, P100m and N145m were located closely to each other in the occipital cortex around the calcarine fissure contralateral to the stimulated visual field, when they were overlaid on the MRI. The reliability of dipole estimation was highest in P100m, followed by N145m while N75m showed the least reliability. The direction of the current flow of ECDs of N75m and N145m was from the medial to the lateral in the occipital cortex when viewed in a coronal section, whereas that for P100m was toward the medial. The ECD location of P100m changed according to the retinotopic organization when the upper or lower quadrant of the visual field was stimulated, with the ECDs being located in the lower or upper part, respectively, of the visual cortex. Our results therefore indicate that the neural origins of N75m, P100m and N145m of PR-VEFs are in the primary visual cortex on the contralateral side of the stimulated visual half-field, while the three components are physiologically distinct.

Adult↗
PubMed1998

Three-dimensional localization of subclinical ictal activity by magnetoencephalography: correlation with invasive monitoring.

BACKGROUND: Although magnetoencephalography (MEG) provides accurate information on the spatial distribution and temporal patterns of the "interictal" epileptic activities, it is interictal in nature and therefore also prone to all the problems associated with interictal data. METHODS: We investigated the subclinical "ictal" epileptic activity with a 37-channel, large-array biomagnetometer and mapped the data onto a three-dimensional image in a patient with intractable frontal lobe epilepsy. Dipole source localization was calculated based on magnetic fields for both the interictal and subclinical ictal activities. RESULTS: The current dipoles of the interictal MEG spikes (MEG irritative zone) were revealed to be scattered in the left anterior frontal lobe, whereas that of the subclinical ictal onset (MEG subclinical ictal onset zone) was surrounded by the interictal dipole cluster. The dipole source localization of the propagating activities was not calculated with a single dipole model. The MEG subclinical ictal onset zone correlated well with the ictal onset zone subsequently recorded by invasive subdural electrophysiological monitoring. After multiple subpial transection of the deduced epileptogenic area, a dramatic reduction of the seizures occurred. CONCLUSION: These results illustrate the potential of MEG for localizing the epileptogenic foci with high spatial and temporal resolution.

Adolescent↗
PubMed1998

Magnetic source imaging of the sensory cortex on the surface anatomy MR scanning.

Surgery for lesions either within or close to the central sulcus of the brain always carries the risk of inducing iatrogenic motor or sensory deficits. We performed advanced magnetic source imaging (MSI) of the somatosensory cortex combined with 3-dimensional (3-D) surface anatomy scanning (SAS) of magnetic resonance imaging on 9 patients who had peri-Rolandic lesions, including 7 tumor cases, 1 arteriovenous malformation and 1 focal cortical dysplasia. 3-D MSI mapped out the entire somatosensory homunculus and localized the lesion on a cortical surface image. The results were then used for developing an appropriate surgical strategy and also as a reference in the operating room. This relationship and deduced localization were both confirmed by a cortical recording of the somatosensory evoked potentials at the time of surgery. Case histories of selected patients are briefly reported to demonstrate how the method can be used to improve the safety of surgical excisions of peri-Rolandic lesions. MSI on SAS including the cortical veins, was thus found to provide a readily interpretable presurgical road map of the cortical surface which compares favorably to that of intraoperative brain mapping.

Adolescent↗
PubMed1997

Jerk-locked back averaging and dipole source localization of magnetoencephalographic transients in a patient with epilepsia partialis continua.

In order to localize the generator site of epileptiform discharges, we applied the techniques of jerk-locked back averaging (JBA) of magnetoencephalographic (MEG) activities and dipole source localization in a patient with epilepsia partialis continua (EPC), who showed continuous, focal myoclonic jerks in the right arm. The myoclonic discharges in the right thenar muscle were used as a trigger pulse. JBA revealed consistent EEG and MEG transients that coincided consistently and constantly preceded the myoclonic jerks. The estimated dipoles of MEG were localized in a restricted area in the left precentral area, which closely correlated with the area of epileptic discharges recorded in electrocorticography. Therefore, JBA of MEG is considered to be a useful non-invasive method for localizing the epileptogenic area in EPC.

Aged↗
PubMed1995

Comparison of magnetoencephalography, functional MRI, and motor evoked potentials in the localization of the sensory-motor cortex.

To clarify the topographical relationship between peri-Rolandic lesions and the central sulcus, we carried out presurgical functional mapping by using magnetoencephalography (MEG), functional magnetic resonance imaging (f-MRI), and motor evoked potentials (MEPs) on 5 patients. The sensory cortex was identified by somatosensory evoked magnetic fields using MEG (magnetic source imaging (MSI)). The motor area of the hand region was identified using f-MRI, during a hand squeezing task. In addition, transcranial magnetic stimulation localized the hand motor area on the scalp, which was mapped onto the MRI. In all cases, the sensory cortex was easily identified by MSI and the results of MSI correlated well with the findings obtained by the intraoperative recording of somatosensory evoked potentials. In contrast, the motor cortex could not be localized by f-MRI due to either the activated signal of the large cortical vein or the lack of any functional activation in the area of peri-lesional edema. MEPs were also unable to localize the entire motor strip. Therefore, at present, MSI is considered to be the most reliable method to localize peri-Rolandic lesions [corrected].

Adult↗
PubMed1993

Hypothalamic hamartoma: the role of surgery.

A hypothalamic hamartoma associated with true precocious puberty in a 7-month-old girl is hereby reported. Hormonal studies disclosed elevated serum levels of luteinizing hormone (LH) and follicle stimulating hormone, both of which responded well to LH-releasing hormone stimulation. Following a subtotal removal of the tumor, the clinical manifestations of precocious puberty as well as associated endocrinological abnormalities returned to normal. The role of surgery for this lesion, which appears to be safe when a planned microsurgical course is employed, is discussed.

Female↗
PubMed1992

[A case of hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome with spastic paraparesis and severe distal muscle atrophy of lower limbs].

A 16-year-old boy with hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome was reported. He was the second child of first-cousin consanguineous parents. Since childhood, he was mentally retarded and had frequent episodes of vomiting but no unconsciousness attack. Because of progressive gait disturbance since the age of 15, he was admitted to Kyushu University Hospital. Neurological examination revealed mental defect and spastic paraparesis with bilateral positive pathological reflexes. Moreover, severe muscle atrophy and moderate weakness were observed in the distal portion of lower extremities. The diagnosis of HHH syndrome was made by the examination of amino acids in the serum and urine and by the incorporation study of radioactive ornithine into cultured fibroblasts. EMG and nerve biopsy studies suggested that the muscle atrophy seen in this patient was caused by the degeneration of spinal anterior horn cells. Amino acid imbalance, especially elevation of glutamine and glutamic acid in the CSF, may cause dysfunction of neuronal system including anterior horn cells.

Adolescent↗
PubMedDate not supplied

[A case of bilateral brachial plexopathy after median sternotomy].

A 53-year-old man with bilateral brachial plexopathy after median sternotomy for cardiac surgery was described. When he was awakened six days after cardiac surgery, he experienced weakness and paresthesia of both upper limbs. Neurological examination revealed moderate to severe atrophy and weakness of right biceps, brachioradialis, left triceps, and distal muscles of both upper limbs, and paresthesia around the right thumb and the left hypothenar. Deep tendon reflex of the right biceps, triceps, brachioradialis and left triceps was absent. In addition, he showed Horner's syndrome at the left side. The results of needle EMG and nerve conduction study indicated the damage of the right upper trunk and left middle and lower trunks of the brachial plexus. Although brachial plexopathy following median sternotomy has previously been reported in Western literatures, there is only a single report of unilateral brachial plexopathy in Japan. This is the first report in Japan of the bilateral brachial plexopathy following median sternotomy, and suggests that brachial plexopathy should be recognized as a complication of median sternotomy.

Brachial Plexus↗