Miller Fisher syndrome is a rare acquired nerve disease considered to be a variant of Guillain-Barré syndrome. The main features are lack of muscle coordination (ataxia), eye muscle weakness resulting in the inability to move the eyes in several directions (ophthalmoplegia), and the absence of tendon reflexes. Symptoms often start several days after a viral illness. Other symptoms include generalized muscle weakness and respiratory failure. The cause is not known, but it is thought to be an autoimmune disease in which there are autoantibodies that attack the nerves. In most people with Miller Fisher syndrome an antibody (anti-GQ1b) is identified. The presence of these autoantibodies helps confirm the diagnosis of the syndrome.