OPHTHALMOPLEGIA

also called Extraocular Muscle Palsy, paralysis of the extraocular muscles, which control the movements of the eye and of the pupil. Ophthalmoplegia usually involves either the third (oculomotor), fourth (trochlear), or sixth (abducent) cranial nerves. In oculomotor paralysis, the muscles controlling one pupil are affected so that the pupil drifts outward and cannot turn inward (i.e., toward the nose) past the midline point. Abducent nerve paralysis affects another ocular muscle so that one eye turns inward and cannot turn outward past the midline. Trochlear paralysis, involving still another muscle, causes a vertical deviation of the affected eye. Double vision is the characteristic symptom in all three conditions. Ophthalmoplegia is usually caused by disorders that affect the nervous system, including multiple sclerosis, cerebral tumours, and cerebrovascular disease. It can also occur as a complication of muscle disorders such as myasthenia gravis, in which it is usually associated with other muscular symptoms.