Spinal muscular atrophy: the natural course of disease.

The infantile form of spinal muscular atrophy (Werdnig-Hoffmann disease) is thought to be progressive and usually fatal by age three. The intermediate and juvenile forms (Kugelberg-Welander disease) have been reported to be static in many cases. A review of 48 patients, 50% of whom had been followed for more than 10 years, were placed into four groups according to the maximum motor function attained. Progression of muscle weakness was assessed using functional criteria, including inability to walk, inability to use a manual wheelchair and inability to raise the hands above the head. The results of this analysis suggest that all patients with spinal muscular atrophy have a progressive disease and that the course of the deterioration is predictable in each of the four groups. This information allows one to offer realistic counseling and a rational rehabilitation program.