Atypical propriospinal myoclonus with possible relationship to alpha interferon therapy.

We report on a man who received interferon-alpha 2a therapy for kidney cancer and who subsequently developed propriospinal myoclonus. The myoclonus was noted at rest and during movement. The jerks were reinforced by cutaneous stimuli and tendon taps and spread to the spinal cord via polysynaptic propriospinal pathways. Cerebrospinal fluid analysis, spinal cord magnetic resonance imaging, electroencephalogram with back-averaging, and somatosensory-evoked potentials were normal. No antineuronal antibodies were found. Although the mechanism of interferon neurotoxicity remains unclear, the possible responsibility of interferon was considered, as no focal lesion or paraneoplastic pathology were disclosed.