Cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) syndrome is a neurological disorder. The syndrome gets its name from the different parts of the body it usually affects: Cerebellar ataxia: inflammation of the cerebellum, the part of the brain that helps control the coordination of muscle movement Areflexia: loss of reflexes Pes cavus: high arch in foot Optic atrophy: damage to the optic nerve of the eye Sensorinural hearing loss: damage to the nerves involved in hearing CAPOS syndrome typically begins after a fever-related illness with a sudden episode of ataxia, such as having a hard time walking or coordinating leg or arm movements. The ataxia is usually associated with generalized weakness and/or inflammation of the brain (encephalopathy). Pregnancy and delivery may also trigger episodes. Most people with CAPOS syndrome have one to three episodes during their lifetime. Other signs and symptoms during an episode may include low muscle tone, unusual eye movements (nystagmus or strabismus), problems with speech (dysarthria), difficulty swallowing (dysphagia), reduced or absent reflexes, and hearing loss. Some people may lose consciousness or go into a coma during an episode. Though many of the signs and symptoms of CAPOS syndrome get better as the fever and illness improve, some symptoms, including movement problems, may continue.