Subacute, reversible motor neuron disease.

Four patients with a clinical syndrome closely resembling amyotrophic lateral sclerosis recovered completely, without treatment, 5 to 12 months after onset. Electrodiagnostic tests revealed acute and chronic denervation, with normal motor and sensory nerve conduction studies. The CSF was normal, and tests for paraproteinemia, heavy metal intoxication, and systemic illness were negative. Although such cases are rare, the possibility of spontaneous recovery should always be considered when counseling patients with suspected ALS.