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Biomedical subjects

T Shimpo

Publications and source records attributed to T Shimpo.

32 records · Page 2Linked to original sources
PubMed1987

Susceptibility to pressure neuropathy distal to a constricting ligature in the guinea-pig.

Silk ligatures were tied round the sciatic nerve in guinea-pigs and left in place in order to produce persistent nerve constriction. Serial nerve conduction studies over the following 9 weeks showed a reduction in motor conduction velocity distal to the ligature. The presence of axonal atrophy in tibial nerve fibres in the leg was subsequently confirmed by histological studies. These changes were not seen in a second group of animals in which similar ligatures were tied but removed after 6 hours. When the ligatures were left in place, the animals developed local plantar nerve lesions in the sole of the foot on the affected side, which were thought to be due to pressure from the floor of the cage. Local pressure changes of varying severity were seen in the foot in all the constricted nerves, but were only occasionally found in control nerves from the opposite foot, or in nerves which had been constricted for a few hours by ligatures which were then removed. These results suggest that atrophic nerve fibres distal to a persistent constriction may be particularly sensitive to local pressure.

Action Potentials↗
PubMedDate not supplied

Posterior cervical N13 in median nerve SEP has two components.

Somatosensory evoked potentials (SEPs) to median nerve stimulation were investigated in normal controls and patients with cervical lesions. Attention was paid primarily to the N13 and P13 components in the posterior and anterior cervical records with non-cephalic references. In normal subjects the CV2 and CV6 electrodes registered N13 with almost the same amplitude. Dissociation between N13 at the CV2 electrode (ucN13) and N13 at the CV6 electrode (lcN13) was observed in the patients. In 4 patients with cervical dorsal column lesions, lcN13 was preserved but ucN13 was almost completely absent. Anterior cervical P13 (acP13) was preserved. In a patient with syringomyelia, lcN13 and acP13 were greatly attenuated while ucN13 was relatively well preserved. These results suggested that the origins of ucN13 and lcN13 are different. The generator of lcN13-acP13 was assumed to be the postsynaptic potential of the dorsal horn interneurons. Upon comparison with previous animal studies and intraoperative studies, it was concluded that the generator of ucN13 is the postsynaptic potential of the cuneate nucleus.

Adult↗
PubMedDate not supplied

Somatosensory evoked potential recovery (SEP-R) in myoclonic patients.

Recovery of somatosensory evoked potentials (SEPs) was studied by paired stimulation of the median nerve in patients with various kinds of myoclonus. This technique revealed the hyperexcitability of the central nervous system (CNS) which could not be detected by the conventional SEP technique using a single stimulus. This technique would be useful for studying the excitability of the CNS.

Adult↗
PubMedDate not supplied

Widespread N18 in median nerve SEP is preserved in a pontine lesion.

Widespread N18 potential to median nerve stimulation was preserved in a patient who had profound unilateral disturbance of deep sensation and a lesion of the pontine medial lemniscus confirmed by MRI. It was concluded from this result that at least a significant part of the N18 potential was generated caudal to the pontine level or at higher levels via extralemniscal pathways. Careful review of studies in man with intraoperative recordings seemed to support that the N18 potential already exists at the medullary level. We suggested that the potential generated at the cuneate nucleus which was described in cats may correspond to part of the N18 potential.

Brain Diseases↗
PubMedDate not supplied

SEPs in two patients with localized lesions of the postcentral gyrus.

Scalp distributions of median nerve SEPs were studied in normal controls and 2 patients with localized lesions of the postcentral gyrus. In controls, parieto-occipital electrodes registered N20-P27 while frontal electrodes registered P20-N27. Other small components, parieto-occipital P22 and frontal N22, were recognized in about half of the control records. The wave forms at a frontal and a parieto-occipital electrode, both distant from the central region, formed exact mirror images of each other concerning N20-(P22)-P27 and P20-(N22)-N27. Electrodes near the central region contralateral to the stimulation registered cP22-cN30 (central P22 and central N30). When the postcentral gyrus was damaged, N20/P20-P27/N27 and cP22-cN30 were eliminated and the only remaining components were a frontal negative wave (frN) and a contralateral parieto-occipital positive wave (poP). Digital nerve stimulation also evoked poP and frN in both cases. In case 2, poP coincided with P22 of the non-affected side. The following generators were proposed; N20/P20-P27/N27: area 3b, cP22-cN30: areas 1 and 2, poP/early frN (= P22/N22): area 4 at the anterior wall of the central sulcus (due to direct thalamic inputs to motor cortex), late frN: uncertain (SMA?, SII?).

Adult↗