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At least 1,675 records · Page 93Linked to original sources
PubMed1979

Single-fiber electromyography in myasthenia gravis.

One-hundred-sixty single-fiber EMG studies of the extensor digitorum communis muscle were performed on 127 patients with myasthenia gravis; 131 demonstrated defective neuromuscular transmission. Jitter determinations in the biceps, deltoid or frontalis muscles increased the diagnostic yield significantly. Evoked-potential EMG studies were abnormal in less than 50 percent of patients in whom they were performed. The most sensitive criterion of abnormality was the percentage of fibers with increased jitter; the sensitivity of the test was enhanced, however, if the mean jitter of the tested muscle was also used as a criterion of abnormality. Since increased jitter may also be seen in primary muscle and nerve disease, these disorders must be excluded by other means before diagnosing myasthenia gravis on the basis of the single-fiber studies.

Adult↗
PubMed1985

Electrophysiologic evaluation of lumbosacral radiculopathies: electromyography, late responses, and somatosensory evoked potentials.

We compared the diagnostic utility of EMG, F wave and H-reflex studies, and peroneal and dermatomal SEPs in evaluating 28 patients with clinically unequivocal L-5 or S-1 compressive root lesions. The single most useful electrophysiologic technique was EMG, which often provided evidence of denervation in a myotomal pattern when other electrophysiologic findings were normal. We found abnormal late responses in 14 patients, but always in association with EMG abnormalities. Peroneal-derived SEPs were always normal. Dermatomal SEPs confirmed the diagnosis in seven patients, including two in whom other electrophysiologic studies were normal.

Adolescent↗
PubMed1998

Electromyography in cervical dystonia: changes after botulinum and trihexyphenidyl.

BACKGROUND: The value of physical examination in detecting involved neck muscles in cervical dystonia (CD) is uncertain and little is known about changes in electromyographic (EMG) features after botulinum toxin type A (BTA) treatment. METHODS: In a double-blind, randomized study we recorded the EMG activities of 420 neck muscles in 42 patients with CD before and after treatment with BTA or trihexyphenidyl. We regarded any needle EMG activity higher than 100 microV as the gold standard for involuntary involvement of a muscle in the dystonic posture and compared this with the results of physical examination. We calculated EMG total scores by adding the scores of the individual muscles. RESULTS: Physical examination had a low predictive value in the detection of involved muscles. There was a significant correlation between changes in EMG total scores and changes in clinical measurements. We observed increased EMG activity in 20% of noninjected muscles after BTA treatment and in 27% of noninjected muscles after trihexyphenidyl treatment. A switch from one most active muscle to another was seen equally in both groups and had no influence on clinical response. CONCLUSION: Physical examination alone is not sufficient to detect involved muscles, and repeated, simultaneous EMG-guided application of BTA may be helpful. In addition to clinical measurements, changes in EMG activity due to treatment can be used as a physiologic measure in evaluating treatment response. Increased activity of noninjected muscles and a switch from one most active muscle to another are not related to BTA treatment, but are probably pathophysiologic phenomena of CD itself.

Botulinum Toxins, Type A↗
PubMed1998

Needle electromyography of bulbar muscles in patients with amyotrophic lateral sclerosis: evidence of subclinical involvement.

OBJECTIVE: To determine if quantitative motor unit action potential (MUAP) analysis and peak ratio interference pattern analysis of the fifth, seventh, and eleventh cranial nerve innervated muscles are helpful in the assessment of subclinical bulbar involvement in ALS. METHODS: With both electromyographic (EMG) techniques, electrical activity was recorded via needle electrodes from the right frontalis, masseter, and sternocleidomastoideus muscles of nine ALS patients without clinical bulbar signs (Frenchay score >85%) aged 40 to 87 years; 21 healthy subjects aged 27 to 74 years; and five ALS patients with clinical bulbar signs (Frenchay score <85%) aged 53 to 69 years. RESULTS: The normal mean (2 SD) MUAP duration of the frontalis muscle was 7.4 (2.2) milliseconds; masseter muscle, 9.3 (3.1) milliseconds; and sternocleidomastoideus muscle, 10.9 (4.1) milliseconds. The normal mean (2 SD) peak ratio of the frontalis was 2.3 (1.1) milliseconds; masseter, 1.2 (0.4) milliseconds; and sternocleidomastoideus, 1.5 (0.7) milliseconds. Quantitative MUAP analysis was interpreted as neuropathic if MUAP duration, MUAP amplitude, or both exceeded the mean (+2 SD). Peak ratio interference pattern analysis was interpreted as neuropathic if the peak ratio, the number of small time intervals, or both were below the mean (-2 SD). If a result of either EMG technique was neuropathic in at least one of the three investigated muscles, bulbar involvement was assumed. Subclinical bulbar involvement could be detected by quantitative MUAP analysis in six ALS patients without clinical bulbar signs, and by peak ratio interference pattern analysis in two. CONCLUSIONS: Conventional needle EMG of the fifth, seventh, and eleventh cranial nerve innervated muscles shows subclinical bulbar involvement quite frequently. Peak ratio interference pattern analysis is largely not helpful in detecting this involvement.

Accessory Nerve↗
PubMed1992

Effect of partial neuromuscular blockade on intraoperative electromyography in patients undergoing resection of acoustic neuromas.

Intraoperative electromyographic monitoring of the facial nerve during acoustic neuroma excision provides early detection of nerve injury and improved outcome. To determine whether a useful level of peripheral neuromuscular blockade could be achieved without compromise of facial electromyographic monitoring, we studied 10 patients undergoing resection of acoustic neuroma. Facial nerve monitoring was accomplished by placement of wire electrodes in the orbicularis oris, orbicularis occuli, and mentalis muscles. Peripheral neuromuscular blockade was assessed by recording unprocessed hypothenar compound muscle action potentials (CMAPs). After induction of anesthesia, an infusion of atracurium (1.0 micrograms.kg-1.min-1) accompanied by a bolus dose of 50 micrograms/kg was administered. The infusion was then increased in increments of 0.5 micrograms.kg-1.min-1 until a 50% reduction in hypothenar single-twitch CMAP was obtained. Facial nerve function was continuously monitored by comparison of facial CMAPs produced by stimulation of the nerve proximal and distal to the tumor bed. The mean (+/- SD) infusion rate of atracurium was 2.55 +/- 0.75 micrograms.kg-1.min-1. Decrements in facial nerve CMAPs were detected in 6 of 10 patients, and all demonstrated moderate to severe facial nerve dysfunction. In no patient was an unexpected deficit present postoperatively. Moderate degrees of peripheral neuromuscular blockade can be achieved without compromising facial nerve electromyographic monitoring.

Action Potentials↗
PubMed1992

Multisegmental analyses of acoustic startle in the flying cricket (Teleogryllus oceanicus): kinematics and electromyography.

Tethered, flying Australian field crickets (Teleogryllus oceanicus) stimulated with ultrasound respond with a rapid, short-latency turn from the sound source. We analyzed the kinematics of two behavioral components of this acoustic startle response and recorded electromyograms from the muscles involved in producing them. The two behavior patterns studied were the swing of the metathoracic leg, which has been shown to elicit a short-latency turn, and a lateral swing of the antennae, for which a direct role in steering has not been demonstrated. The kinematic data showed that when a pulse of ultrasound was presented to one side of the animal (1) the contralateral metathoracic leg abducted and elevated, while the ipsilateral leg remained in place, (2) both antennae swung laterally, but the contralateral antenna moved farther than the ipsilateral antenna, (3) increases in stimulus intensity elicited larger movements of the leg and contralateral antenna, while the ipsilateral antenna showed little sensitivity to stimulus intensity, and (4) for the leg, the latency to the onset of the swing decreased and the duration of the movement increased with increasing stimulus intensity. Electromyograms were recorded from the leg abductor M126 and two antennal muscles: the medial scapo-pedicellar muscle M6 and the lateral scapo-pedicellar muscle M7. M7 moves the antenna laterally, M6 moves it medially. Upon stimulation with ultrasound (1) both M126 and M7 showed increasing spike activity with increasing intensity of the ultrasound stimulus, (2) M126 showed a decrease in latency to the first spike and an increase in the duration of spike activity with increasing stimulus intensity, (3) latencies for M6 and M7 were not correlated with stimulus intensity, but M7 had significantly shorter latencies than M6 and the contralateral M7 had significantly shorter latencies than the ipsilateral M7, and (4) the ipsilateral M126 spiked in response to ultrasound in 6 of the 10 animals tested. In these cases, however, latency to the first spike was substantially longer, and the spike frequency was lower than for the muscle's response to contralateral stimuli. We attempt to correlate these electromyogram data with the kinematic data and relate them to the relevance of the two behavior patterns to the execution of an escape response.

Acoustic Stimulation↗
PubMed1991

Comparison of evoked electromyography of the larynx to electrical and magnetic stimulation of the motor cortex of the dog.

The electromyographic and contractile properties of the laryngeal muscles upon stimulation of the laryngeal nerve have been described before. In the present investigation, we used electrical and magnetic stimulation to activate the vocalis muscle in dogs. Stimulation of the vagus nerve at the brain stem exit point resulted in evoked vocalis compound muscle action potential identical in onset latency and configuration to that obtained by the transcranial single-shock magnetic stimulation at high intensity (greater than 80%). Electrical stimulation of the laryngeal representation of the somatomotor cortex resulted in a contralateral evoked vocalis compound muscle action potential. Central delay time for the 10th cranial nerve was calculated by subtracting the latency of the vocalis recorded by stimulation of the vagus nerve as it exited the brain stem from the latency obtained by direct cortical stimulation.

Animals↗
PubMed1991

Electromyography of masticatory muscles in craniomandibular disorders.

Patients presenting to the otolaryngologist with complaints such as otalgia, dizziness, tinnitus, or fullness in the ear may be experiencing the effects of craniomandibular disorders. These disorders can involve dysfunction in the delicate interrelationship of the skull, mandible, cervical vertebrae, and neuromuscular apparatus and can present as myofacial pain. Electromyographic recordings using surface electrodes were made bilaterally on the masseter, anterior temporalis, and digastric muscles in 641 craniomandibular patients, before and after transcutaneous electrical neural stimulation, at their initial presentation and following the insertion of mandibular orthopedic appliances. In the presenting patient, muscle-resting levels significantly decreased from hyperactive levels with transcutaneous electrical neural stimulation therapy. The creation of a new occlusal position with an orthotic appliance was found to correlate with a significant reduction in otolaryngologic symptoms as well as an increase in maximum muscle activity in function and coordination of muscle groups during mandibular movement. Thus, clinical electromyographic studies are an important aid in the treatment of craniomandibular disorders.

Electromyography↗
PubMed1978

Clinical expression of neurotoxic injury and diagnostic use of electromyography.

The clinical features of neurological damage produced by acrylamide, lead, organophosphates, hexacarbon solvents, and methylmercury are described, and the differences in effects of these compounds are stressed. The characteristic pattern of electrophysiological changes for each group of substances are described and correlated with pathological findings.

Acrylamides↗