Peripheral neuropathy associated with polycythemia vera.

The aim of this study was to determine the frequency and characteristics of peripheral neuropathy associated to polycythemia vera. A prospective clinical and electrophysiological study was performed of 28 patients with polycythemia vera. Other causes of neuropathy were excluded. Eleven patients experienced paresthesiae, which were usually mild. In 13 (46%) patients, clinical examination revealed features suggesting polyneuropathy. Nerve conduction indexes were abnormal in 20 (71%) patients, suggesting the presence of a predominantly sensory axonal polyneuropathy. In the somatosensory evoked potentials a delay of the P40 wave was seen in 17 patients, while 11 exhibited a delay of the N20 wave. Three of these patients also showed bilateral increases in the I-III, I-V and III-V intervals of brain-stem evoked potentials. In most cases, the delay was moderate and symmetrical. No differences in sex, age, duration of disease, hematocrit values, or platelet counts were found between patients with or without clinical or electrophysiological polyneuropathy. A high percentage of patients with polycythemia vera present clinical or electrophysiological signs of predominantly sensory axonal polyneuropathy which is probably secondary to ischemia, due to increased blood viscosity and platelet dysfunction.