Myasthenia gravis is a chronic disease characterized by weakness and abnormal fatigability of skeletal muscle. The muscles innervated by the cranial nerves are particularly affected, and usually those of the neck, trunk, and extremities. In severe cases, weakness of the muscles of respiration occurs. Smooth and cardiac muscles are not involved. The disease usually becomes generalized, but in a minority of cases it remains localized to the extraocular muscles. The symptoms are commonly ameliorated, although to a variable degree, by anticholinesterase compounds. This response serves as the basis for diagnosis and management of the disease. Mechanism of Neuromuscular Block in Myasthenia Gravis Normal Neuromuscular Transmission Resting muscle fibers normally have a potential difference of approximately 90 mv. between the two sides of the surface membrane, the inner surface being negative with respect to the outer. They are therefore said to be in a state of "polarization." When a nerve impulse