myasthenia gravis, an abnormal condition characterized by chronic fatigability and muscle weakness, especially in the face and throat, as a result of a defect in the conduction of nerve impulses at the neuromuscular junction. ▪ OBSERVATIONS: Muscular fatigability in myasthenia gravis is caused by the inability of receptors at the myoneural junction to depolarize because of a deficiency of acetylcholine; hence the diagnosis may be made by administering an anticholinesterase drug and observing improved muscle strength and stamina. The onset of symptoms is usually gradual, with ptosis of the upper eyelids, diplopia, and weakness of the facial muscles. The weakness may then extend to other muscles innervated by the cranial nerves, particularly the respiratory muscles. Muscular exertion aggravates the symptoms, which typically vary over the course of the day. The disease occurs in younger women more often than in older women and in men over 60 years of age more often than in younger men. ▪ INTERVENTIONS: Anticholinesterase drugs are given. The edrophonium test is used to determine the optimal maintenance dose. Neostigmine or pyridostigmine is the drug most often used. ▪ PATIENT CARE CONSIDERATIONS: Physical activity is restricted and rest encouraged. Anticholinesterase drugs are usually administered before meals, and the patient is monitored for toxic side effects. Myasthenic crisis may require emergency respiratory assistance. The patient’s diet may have to be adjusted if the ability to chew and swallow is affected.
