ataxia(redirected from optic ataxia)
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ataxia(ətăk`sēə), lack of coordination of the voluntary muscles resulting in irregular movements of the body. Ataxia can be brought on by an injury, infection, or degenerative disease of the central nervous system, e.g., syphilis, encephalitis, brain tumor, or multiple sclerosis. The term also designates a specific type of cerebral palsycerebral palsy
, disability caused by brain damage before or during birth or in the first years, resulting in a loss of voluntary muscular control and coordination. Although the exact cause is unknown, apparent predisposing factors include disease (e.g.
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a disturbance in the coordination of voluntary movements. The coordination of a number of muscle groups, which in turn depends on the activity of many parts of the brain (cerebellum, cortex, and so forth), is required for the proper and precise execution of movements and for the maintenance of balance in various body positions. Impulses from muscles, tendons, joints, and ligaments travel via the posterior columns of the spinal cord to the brain. Signals from the semicircular canals of the inner ear are very important for the coordination of movements.
Ataxia appears when there is a disease in one or more of the links in this system. Autonomic, cerebellar, frontal, and labyrinthic ataxias are distinguished according to the site of the condition. Static ataxia (disruption of balance when the person is standing) and locomotor ataxia (actual disruption of the coordination of movement) are distinguished according to clinical manifestations. Sensory ataxia is observed in disease of the peripheral nerves or of the posterior columns of the spinal cord. When the patient stands with his feet together and his eyes closed, his torso begins to sway. His gait is disrupted, and he moves slowly, looking at his feet and casting them far out to either side. In cerebellar ataxia (which affects the connections or structures of the cerebellum) the patient uses excessive space to execute movements; for example, in trying to touch an object, he brings his arm out too far (hypermetria). His speech loses coherence—he speaks loudly, then softly, dividing his words into syllables (scanning). When rising from a lying to a standing position without using his hands, the patient raises his legs instead of his torso. His gait resembles that of an inebriate. Frontal ataxia, which occurs with the disruption of frontal-cerebellar pathways, is similar to cerebellar ataxia in its manifestations. Labyrinthic ataxia is manifested in severe dizziness and horizontal nystagmus. The treatment of ataxia consists of eliminating the fundamental disease with which it is associated, doing therapeutic exercise, and aiding in the restoration of proper coordination of movement.
REFERENCESMnogotomnoe rukovodstvo po nevrologii, vol. 7. Edited by S. N. Davidenkov. Moscow, 1960. Page 217.
Davidenkov, S. N. Klinicheskie lektsii po nervnym bolezniam, issue 4. Leningrad, 1961.
A. M. VEIN