Low-rate nerve stimulation during regional ischemia in the diagnosis of muscle glycogenosis.

Five patients with muscle glycogenoses (Gly), 30 normal subjects (NS), and 52 disease controls received 3 Hz repetitive stimulation of the ulnar nerve for 4 min (P-LRNS) during regional ischemia and during normal circulation. During regional ischemia, the compound muscle action potential (CMAP) of NS showed 8.5% (SE: 1.0) facilitation after 1 min of P-LRNS and 4.8 +/- 1.5% facilitation after 4 min. Gly showed 8.1 +/- 1.0% facilitation after 1 min of P-LRNS but -58.6 +/- 6.9% depression after 4 min of P-LRNS. During normal circulation, in 18 NS and 4 Gly tested, the facilitation detected after 1 min of P-LRNS was unchanged until the end of stimulation. Compared with the mean +/- 2 SD of NS, individual values of CMAP depression were abnormal in all Gly patients already by the 3rd min of ischemic P-LRNS. Of disease controls, myasthenia gravis patients only showed a CMAP depression during ischemic P-LRNS which was distinguishable from that detected in Gly, being mainly induced by neuromuscular transmission block.