Peripheral neuropathy associated with the hypereosinophilic syndrome.

This case report documents the natural history of the peripheral polyneuropathy associated with persistent hypereosinophilia after treatment with corticosteroids. The neuropathy was documented by nerve conduction studies which revealed reduced amplitude of the sensory and motor evoked responses and slowed conduction velocities that were consistent with axon loss. Sural nerve biopsy revealed mild axonal loss distally without eosinophilic infiltration. The patient was treated with high-dose corticosteroids with a rapid normalization of his eosinophil count. Neurologic examination six months later revealed a slight improvement in his motor strength and reflexes but no change in sensory functions. Follow-up electromyographic evaluation demonstrated an average 89% improvement in evoked potential amplitudes and a slight improvement in distal latencies and conduction velocities. These findings suggest that the neuropathy associated with hypereosinophilia is axonal in nature and that there is a temporal relationship between reduction in the absolute eosinophil count and the improvement of the neuropathy.