ELECTROMYOGRAM FROM ORBICULARIS OCULI IN NORMAL PERSONS AND IN PATIENTS WITH MYASTHENIA GRAVIS

ELECTROMYOGRAPHY usually consists in recording action potentials from resting or voluntarily contracted muscles. In 1941 Harvey and Masland1introduced another procedure, in which potentials are recorded when the muscle is made to contract by supramaximal stimulation of the motor nerve. This method has the advantage of eliminating the vagaries of voluntary effort and so permits an objective analysis of the function of the peripheral nerve, neuromuscular junction, and muscle. One limitation of the procedure is that only muscles supplied by nerves accessible to electrical stimulation can be studied, so that to date only the muscles of the extremities have been tested. An early sign of myasthenia gravis is weakness of the extraocular and facial muscles, which is not necessarily accompanied by any subjective or objective evidence of weakness of the extremities. In a series of 21 patients with myasthenia gravis studied by us,2all had facial weakness and