Reversible motor neuron disease.

We investigated a 69-year-old male with a clinical syndrome resembling amyotrophic lateral sclerosis characterized by fasciculation, wasting of the limb muscles and increased deep tendon reflexes in the lower limbs. Electromyographic (EMG) studies showed abundant positive sharp waves and fibrillation potentials with decreased recruitment in the limbs and paraspinal muscles. The patient recovered almost completely in approximately 1.5 years, and follow-up EMG studies showed no positive sharp waves or fibrillation potentials in the limb muscles except for some polyphasic motor units in the bilateral intrinsic hand muscles. No known systemic disease, malignancy or heavy metal intoxication was found during the course of his illness. So far, there are only few cases reported with spontaneous remission of motor neuron disease; however, the possibility should always be considered.