Action-induced upper limb dystonia following a demyelinating lesion inthe cervical spinal cord

SC was a 49-year-old aircraft pilot who was admitted in our clinic on June 1996. In the previous two months he reported frequent paroxysmal muscle contraction of the left limbs causing flexion and adduction of the arm and extension of the leg. The brief spasms were sometimes preceded by cervical and brachial paresthesias. In most cases, sudden movements of the head preceded the onset of the episodes, which were as frequent as once or twice a week. Brain and cervical spinal cord MRI, performed 1 month after the onset, revealed the presence of an inflammatory, demyelinating lesion in the left hemicord (C4 level). This lesion was not detected by the MRI performed 1 month later. On examination (November 1996) we observed dystonic movements of the left hand provoked by prolonged outstretching of the limb.