Electromyography and clinical neurophysiology
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Electromyogr Clin Neurophysiol · Apr 2002
On the evaluation of muscle fiber conduction velocity considering waveform properties of an electromyogram in M. biceps brachii during voluntary isometric contraction.
The surface myoelectric signal during 20% maximum voluntary contraction was measured in m. biceps brachii using array electrodes for ten subjects in order to evaluate the distribution of muscle fiber conduction velocity (MFCV) in a whole muscle. MFCV was estimated by two calculating methods of the peak maximum method and the cross-correlation method from the myoelectric signals which were processed by techniques of the averaging and the non-averaging. It was found that the values of MFCV depended on the location irrespective of the kind of calculating method used and the kind of processing technique of myoelectric signal. ⋯ The values of MFCV significantly increased in the regions of the motor end-plate zone and the tendon zone, where the maximum correlation coefficient and amplitude ratio significantly decreased. The values of the coefficient of variance (CV) of three parameters in those regions were larger than those in other regions, i.e., the regions other than the motor end-plate zone and the tendon zone. A high maximum correlation coefficient and a high amplitude ratio were necessary for a reliable measurement of the MFCV.
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Autonomic neuropathy is a complication of diabetes mellitus (DM) in substantial proportion of cases and may cause definite autonomic symptoms. Because conventional electrophysiological methods do not assess the autonomic nervous system, simple reproducible tests were developed. One of them is sympathetic skin response (SSR) which provides useful information about the status of sympathetic postganglionic function. ⋯ An absent response in at least one tested lower extremity (50%) and prolonged foot with normal hand latency (20%). 6 patients (30%) demonstrated no abnormalities. Foot and hand latencies in diabetics did not differ significantly from those of normal controls (p: 0.4, p: 0.1) and no correlation could be found with latencies and duration of sickness, patient's age and HbA1c values. We believe latency measurement is an objective measure of conduction in multineural pathways and can detect subclinical involvement of sympathetic nervous system in diabetics who do not manifest symptoms or signs referable to autonomic system dysfunction.
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Electromyogr Clin Neurophysiol · Apr 2002
Inhibitory and excitatory circuits of cerebral cortex after ischaemic stroke: prognostic value of the transcranial magnetic stimulation.
The motor cortex excitatory responses and inhibitory effects after transcranial magnetic stimulation were studied in 20 patients with hemiparesis after ischaemic stroke in the MCA territory within 24 hours from the beginning of the symptomatology, in order to evaluate prognostic utility of these techniques and to compare they with the conventional MEP examination. Central motor conduction time was abnormal in two patient. ⋯ The motor cortex threshold measurement is easily performed and the most sensitive parameter in our group of patients with hemispheric infarct. Our study suggested that the evaluation of the modifications in the intrinsic excitatory properties rather than in the inhibitory cortical circuits may offer a prognostic tool for predicting functional outcome following ischaemic stroke.