The effect of succinylcholine on denervated skeletal muscle

Succinylcholine, commonly used in anesthesia, paralyzes normal skeletal muscles by blocking transmission at the myoneural junction, but in denervated muscle, it produces sustained muscle contractions lasting several minutes. This denervation hypersensitivity, believed to be due to the progressive enlargement of the receptor area, begins within 2 to 3 weeks and may last for months. Three patients with denervation hypersensitivity were studied: one with isolated denervation of the flexor pollicis longus and two with combined median and ulnar nerve palsy. Within 1 to 2 minutes after administration of succinylcholine, sustained contraction of the denervated muscles occurred and lasted 4 to 5 minutes. Succinylcholine, due to its ability to produce sustained muscle contraction in denervated muscles, may be a useful diagnostic aid in distinguishing loss of function due to nerve injury from tendon disruption.