The weakness often affects elevation of the eyelids and movement of the extraocular muscles, which causes a characteristic asymmetric ptosis and diplopia. The neck extensors are often weak and the head droops. Weakness of facial and bulbar muscles may result in a facial snarl when a patient attempts to smile, nasal or dysarthric and low-volume dysphonic speech, and dysphagia, which can result in regurgitation and choking. Proximal skeletal muscle weakness and fatigue produce difficulty in walking, climbing steps, combing hair, and carrying objects. Respiratory muscle weakness can be significant.
Symptoms fluctuate and are often better in the morning.
Fatigability is usually worse at the end of the day or after repeated activity. If a patient is asked to keep the arms abducted, a gradual decline is noted. If a patient is asked to talk continually, the voice may become husky, nasal, slurred, and finally inaudible. Sensation and cognition are normal. Tendon reflexes, especially from nonatrophic muscles, tend to be brisk or normally active.