(koo´gәl-berg va´lahn-dәr) a hereditary form of muscular atrophy due to lesions of the anterior horns of the spinal cord, with onset usually between 2 and 17 years of age; it is marked by atrophy and weakness of the proximal muscles of the lower limbs and pelvic girdle, and later of the distal muscles with muscular twitchings. Called also juvenile spinal muscular atrophy .
