Neuromyopathy during chronic amiodarone treatment. A case report

Clinical, electrophysiological, and the nerve and muscle biopsy findings from a case treated with amiodarone are reported. Marked distal motor and sensory impairment and distal muscular atrophy were observed clinically. The electrophysiological examination revealed normal motor and sensory conduction velocities in the median nerve; the sensory action potentials were polyphasic and reduced in amplitude. Electromyography revealed denervation potentials and severe loss of motor units in the M. extensor digitorum brevis and in the M. tibialis anterior. The light and electronmicroscopical study of a N. suralis biopsy displayed total loss of large myelinated fibers and an almost total reduction of small myelinated fibers. The number of unmyelinated axons was markedly reduced. Fibrocytes and degenerative axons polymorphous inclusion bodies were present in Schwann cells. The muscle biopsy revealed both neurogenic and myopathic changes. Lipid storage was also present in the muscle fibers. Physical and chemical analysis of the nerve and muscle biopsy revealed the content of iodine to be more than 40 times increased. The findings indicate damage of axons, schwann cells and muscle fibers. It is suggested that the lipid storage in nerve and muscle tissue might be related to the accumulation of the drug or its metabolites.