Objective: Unexplained weakness in critically ill patients is recognized with increasing frequency. However, it is debated whether the condition is a peripheral neuropathy or a myopathy. Diagnostic ...difficulties can arise from multiple sources that are not generally a factor in other neuromuscular conditions. Conventional electrodiagnostic techniques may provide only non-specific data, clinical examination is often hampered, and muscle biopsy is not a practical screening tool.
Method: To improve diagnostic yield, we studied 22 consecutive patients with critical illness associated weakness with additional electrodiagnostic techniques, including direct muscle stimulation, quantitative electromyography, and motor unit number estimation.
Results: The applied techniques supported an underlying myopathy in all the patients examined. The diagnosis was confirmed by muscle biopsy in 9 patients. Additional lesser features of neuropathy were concomitantly present in one patient who also underwent sural nerve biopsy.
Conclusions: The study suggests that myopathy is much more common than polyneuropathy in critical illness. Suspicion of this entity should be high in this setting even without exposure to corticosteroids or non-depolarizing blocking agents.
Neuromuscular disorders are increasingly recognized in the critically ill but conventional electrodiagnostic techniques often provide non-specific results or are hampered by local conditions that ...prevent adequate disease classification. Muscle fiber inexcitability is a common phenomenon in critical illness myopathy possibly secondary to disordered sodium channel fast inactivation and associated with loss of myosin staining. Direct muscle stimulation techniques, measuring evoked response amplitudes and comparison of nerve and muscle stimulated responses, are recognized methods of demonstrating this phenomenon. Other measures studied in this population include increased compound motor action potential duration, motor unit number estimates and mean step area of individual motor unit potentials during motor unit number estimate studies. An electrophysiologic approach to the study of patients with critical illness associated weakness is proposed.
In traumatic brachial plexus injuries a thorough neurological, electrodiagnostic, and radiological examination is essential to determine treatment and prognosis. The most important diagnostic ...question concerns the presence or absence of a preganglionic nerve root lesion. Electromyography and motor and sensory conduction studies were performed in 17 patients with traumatic plexus injuries who had myelographic evidence of nerve root avulsion; in 8 of these clinical and electrophysiological features confirmed the X-ray findings. However, in 9 cases there was a discrepancy between myelographic and neurophysiological data regarding the actual number and sites of roots avulsed. Thus, in 2 cases myelography showed avulsion of one more root than did conduction studies and EMG; in 2 others, there was discordance as to the specific roots avulsed; in 4 cases fewer nerve roots seem to be avulsed radiologically than predicted clinically, and in 1, none at all, although clinical and electrophysiological data were compatible with avulsion of four roots. In 6 cases recovery showed that avulsions indicated by clinical and electrophysiological considerations could not have occurred. When both EMG and myelography are misleading, surgical exploration should be considered.
We studied 26 patients with both motor neuron disease and lymphoproliferative disease (LPD). Twenty-three patients had definite or probable upper motor neuron signs; none had electrophysiologic ...evidence of motor neuropathy. LPD syndromes comprised Waldenstromʼs macroglobulinemia, multiple myeloma, chronic lymphocytic leukemia, follicular cell lymphoma, and Hodgkinʼs disease. In all but one patient, the cause of disability or death was neurologic. LPD was confined to bone marrow in 14 patients; eight of 14 had monoclonal paraproteinemia. One patient had LPD discovered at autopsy. Treatment of LPD in 20 patients resulted in neurologic improvement in 1 patient and arrest in another; both had progressive spinal muscular atrophy. Eleven patients were worse and 13 died. At least 30 cases have been reported from other centers, bringing the total to 56. Among the unusual reported concomitants were POEMS (polyneuropathy, organomegaly, endocrinopathy, myeloma, and skin changes) syndrome of myeloma and angiotropic lymphoma.
Failure to take body height into considerations in the evaluation of nerve conduction velocities (CV) has recently been deemed unacceptable. This statement prompted the present study. Besides height, ...the influence of age, gender, and temperature was studied in 92 normal subjects, half of whom were females. The CV decreased 0.9 m/s per 10 years increase in age, the same in women and men aged 15 to 44 years. Mean temperature between distal and proximal ends of the nerve segment examined increased 6.1 +/- 0.3 degree C after heating followed by a CV increase of 7.0 +/- 0.5 m/s. The CV decreased 0.15 m/s per 100-mm increase in heights. When considering 37 individuals aged 25 to 34 years only, the CV increased 0.34 m/s per 1-m increase in height. In both instances, the changes were within the experimental error (2.3%) of the method.
To assess the diagnostic value of electrophysiological tests in patients with sciatica.
The diagnostic value of electrophysiological tests were evaluated in 25 patients with monoradicular sciatica. ...The electrophysiological study included dermatomal somatosensory evoked potentials, electromyography, F-wave latencies, H-reflexes and motor and sensory nerve conduction determinations. The results of the electrophysiological examinations were evaluated blindly, and the test results were analysed separately by a receiver operating characteristic (ROC) analysis. Furthermore, the 5 modalities were evaluated jointly and analysed by a decision-analytic regret function.
A high predictive value was found for the H-reflex examination, but low for the other modalities. When the 5 modalities were evaluated jointly, a non-significant decrease in expected regret from the pre-test situation of 0.96 to a value of 0.93 in post-test situation was revealed.
Electrophysiological testing is not sufficient as stand-alone examination in patients with sciatica.
On account of EEG findings in jet pilot applicants examined during 1951-1952, the Royal Danish Air Force (RDAF) accepted EEGs as part of the routine procedures for evaluation of the applicants' ...fitness. The outlook for a successful completion of the training program was poor for those with a paroxysmal abnormal EEG. As a consequence, candidates were excluded from training on the basis of paroxysmal EEG changes regardless of their clinical findings. During 1956-1975 an EEG was obtained from 5,893 applicants for jet pilot training in the RDAF. Of these, 142 (2.4%) were excluded because of an abnormal EEG. Paroxysmal discharges were induced by intermittent photic stimulation in 90%. Generalized or focal paroxysmal changes were present at rest in 6 applicants, during hyperventilation and sleep in 4 each. Four applicants, although asymptomatic, developed epileptic seizures during intermittent photic stimulation.
