The cause of the cervical spondylotic amyotrophy (CSA) is thought to be the nerve root damage, the impairment of the anterior horn of spinal cord, or the mixed type of both lesions. In CSA patients, measured were the compound muscle action potentials (CMAP), central motor conduction time (CMCT) and F wave. CMAP stimulated at supramaximal Erb point were recorded from the proximal (deltoid and biceps) and distal muscles (extensor digitorum and abductor digiti minimi). The aim of this study was to determine the clinical usefulness of these electrophysiological tests for the pathophysiological analyses and the prediction of prognosis of CSA patients. Fourteen patients with proximal type CSA and 3 with distal type CSA were examined. CMAP were recorded from the above muscles, while CMCT was calculated from the motor evoked potentials (MEP) and F wave. All of the atrophied muscles showed decreased CMAP amplitude. Not only the affected muscles but also the healthy muscles as well as proximal muscles in distal type CSA patients showed the decreased amplitude. CMAP ratio to the reference value was correlated with manual muscle testing (MMT). Interestingly there found patients with full MMT score whose CMAP amplitudes were decreased. Even in the patients with full MMT, CMAP evoked by Erb point stimulation was able to detect the preclinical abnormalities, and the decrease in CMAP from the several spinal cord segments suggests that wide range of the segments was affected. The delayed CMCT and the F wave abnormalities were found in 36% of proximal type CSA patients and all distal type CSA patients. Furthermore, the patients with postoperative poor prognosis were the cases that myelopathy across a wide range was suggested by preoperative CMCT and F wave abnormalities. Thus, these electrophysiological tests on CSA patients can be useful both in the evaluation of the affected regions and the prediction of the postoperative prognosis.

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[in Japanese]

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We present the comparison of somatosensory evoked potentials (SEPs) and somatosensory evoked magnetic fields (SEFs) following median nerve stimulation. We describe new knowledge about a magnetic M15 component and its electric counterpart, P15 both of which reflect action potentials traveling along the thalamocortical fibers, and about somatic 600 Hz high frequency oscillations. Also, we mention that middle and long latency SEPs derived from the primary somatosensory cortex are modified by the difference in interstimulus intervals and that the middle and long latency SEP waveforms change into a crescendo pattern but do not disappear when N20 is lost or equivocal in patients developing dysfunction of the peripheral or central somatosensory pathways. Thus, we propose that bilateral disappearance of the middle and long latency SEPs under an appropriate recording condition is essential to confirm a severe brain damage such as a hypoxic ischemic encephalopathy when N20 is equivocal or lost.

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Recently, the cerebral mechanism of itch has been investigated using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). These studies have identified brain regions associated with itch. However, no study has investigated the temporal aspect of the cerebral mechanism of itch because of no itch stimulus useful for EEG and MEG recordings. Thus, we developed a new itch stimulus (i.e., electrical itch stimulus). We confirmed that the electrical itch stimulus evoked itch sensation and that itch stimulus-related brain response can be observed using electroencephalography (EEG) and the stimulus. In addition, the conduction velocity related to the electrical itch stimulus estimated by EEG data was about 1 m/sec, indicating that itch sensation evoked by the electrical itch stimulus would be associated with C-fibers. We also performed magnetoencephalography (MEG) recording using the electrical itch stimulus and observed parts of the temporal aspect of itch stimulus-related brain processing. For example, it was suggested that neural information related to itch was transmitted from the contralateral secondary somatosensory cortex/insula (SII/insula) to the ipsilateral SII/insula. In addition, we also observed the activation of the precuneus. This region was not observed in previous pain studies using EEG and MEG, speculating that the precuneus may be selective for itch. These findings indicate that EEG and MEG recordings using the electrical itch stimulus would be useful to investigate the temporal aspect of the cerebral mechanism of itch.

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[in Japanese]

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