A progressive neurodegenerative condition of the central and autonomic nervous systems characterized by atrophy of the preganglionic lateral horn neurons of the thoracic spinal cord. This disease is generally considered a clinical variant of multiple system atrophy. Affected individuals present in the fifth or sixth decade with ORTHOSTASIS and bladder dysfunction; and later develop fecal incontinence; anhidrosis; ataxia; IMPOTENCE; and alterations of tone suggestive of basal ganglia dysfunction. (From Adams et al., Principles of neurology, 6th ed, p536)