Compound muscle action potential evaluation

The electrophysiological procedure provided an evaluation of the reinnervation of plantar muscles after transection and grafting of the sciatic nerve. Electrical stimuli were applied to the nerve via percutaneous needle electrodes, both proximal and distal to the transection site, and the resulting compound muscle action potentials (CMAPs) elicited in the plantar muscles of the foot were recorded using a concentric needle. The time between the stimulation of the nerve and the onset of the elicited CMAPs, termed the distal motor latency, was measured. ... 

Assessment of neuromuscular block usually is performed by stimulation of the ulnar nerve. Responses are monitored from compound action potentials or muscle tension developed in the adductor pollicis (thumb) muscle. Responses to repetitive or tetanic stimuli are most useful for evaluation of blockade of transmission. Thus, stimulus schedules such as the train of four and the double burst or responses to tetanic stimulation are preferred procedures. Rates of onset of blockade and recovery are more rapid in the airway musculature (jaw, larynx, and diaphragm) than in the thumb. Hence, tracheal intubation can be performed before onset of complete block at the adductor pollicis, whereas partial recovery of function of this muscle allows sufficient recovery of respiration for extubation. 

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