This study will use a magnetic resonance imaging technique called nuclear magnetic spectroscopy (H-MRS) to define the pathology and progression of primary lateral sclerosis, hereditary spastic paraplegia and amyotrophic lateral sclerosis and assess the usefulness of this technique in evaluating patients' response to therapy. H-MRS will be used to examine metabolic changes in the parts of the brain and spinal cord (motor cortex and corticospinal tract) involved in movement.

Normal volunteers and patients with primary lateral sclerosis, hereditary spastic paraplegia or amyotrophic lateral sclerosis between 21 and 65 years of age may be eligible for this study. Participants will have up to five H-MRS studies, including baseline and follow-up tests. For this procedure, the subject lies on a stretcher that is moved into a strong magnetic field. Earplugs are worn to muffle the loud knocking noise that occurs during switching of radio frequencies. The subject will be asked to lie still during each scan, for 1 to 8 minutes at a time. Total scanning time varies from 20 minutes to 2 hours, with most examinations lasting between 45 and 90 minutes. Communication with the medical staff is possible at all times during the scan.