Sympathetic skin response in fifth lumbar and first sacral radiculopathies.

Skin temperature changes and sympathetic skin response (SSR) changes have previously been reported in lumbosacral radiculopathy patients (6). The SSR was studied in 14 normals and in 8 radiculopathy subjects with unilateral, EMG documented active radiculopathies to assess if the SSR becomes asymmetric when measured across appropriate dermatomes. The SSR was recorded in dermatomal patterns in both feet simultaneously with active electrodes on the plantar surface and reference electrodes on the dorsum. Four wave types were identified and normal values for latency of onset, latency of peak, and amplitude are presented with the normal left/right ratios presented. In all individual subjects the amplitudes of the SSR were extremely variable and asymmetric while latencies were less variable and more symmetric. There were no significant differences in symmetry between radiculopathy and normal subjects. When using this technique the SSR is not significantly altered in L5 and S1 radiculopathies.

Quantification of gaps in the EMG interference pattern in chronic hemiparesis.

This study presents a quantification of the impersistence in the EMG interference pattern (IP) produced during maximal effort by patients with chronic hemiparesis. Monopolar needles were used to record from the flexor carpi radialis (FCR) and extensor carpi radialis longus (ECR) muscles of both the paretic and non-paretic sides of 19 patients with a history of unilateral CVA and 10 healthy control subjects during maximal voluntary isometric wrist flexion or extension. We found more gaps in the IP and fewer total seconds of EMG activity in paretic than in non-paretic or control forearm muscles. The number of gaps was similar in paretic FCR and ECR, but the reduced active time in paretic ECR indicates proportionally more gaps per second of EMG activity. This method provides quantitative measures of both the lapses (gaps in the IP during maximal effort and the inability to sustain EMG activity (total seconds) during long contractions. The latter measure is sufficiently sensitive to distinguish the greater impairment of a paretic wrist extensor than a paretic wrist flexor muscle, and both may prove to be valuable for future comparisons of the severity of paresis and the progress of recovery. These results represent the first quantitative confirmation of previous qualitative descriptions of impersistent recruitment.

Co-contraction in the hemiparetic forearm: quantitative EMG evaluation.

Co-contraction of antagonist muscles is a recognized clinical phenomenon in patients surviving a cerebrovascular accident. Yet, discrepancies persist in the literature as to whether or not antagonist electromyographic activity is increased in hemiparesis. We have developed a technique to obtain simultaneous counts of motor unit activity in a wrist flexor and extensor muscle using monopolar needle electromyography. Stable stroke patients and age/sex matched control subjects were tested during maximal voluntary isometric wrist flexion and extension. Fewer agonist events (p less than 0.05) and more antagonist events (p less than 0.10) were counted in paretic than in control muscles. A co-contraction ratio of antagonist activity to total (agonist and antagonist) activity was much greater for patients than controls (p less than 0.01). We conclude that both agonist recruitment and antagonist inhibition are impaired in the hemiparetic arm.