Sodium channel accumulation in humans with painful neuromas

Painful neuromas from 16 patients were examined using site-specific antisodium channel antibodies employed in immunocytochemical and radioimmunoassay methods. Normal sural nerves from six of these patients served as controls. Immunocytochemistry showed abnormal segmental accumulation of sodium channels within many axons in the neuromas. Dense immunolocalization was especially apparent within the axonal tips. Radioimmunoassay confirmed a significantly greater density of sodium channels in the neuromas as compared with the sural nerves. Thus, sodium channels accumulate abnormally within the axons of neuromas in humans. This alteration of the sodium channels may underlie the generation of axonal hyperexcitability and the resulting abnormal sensory phenomena (pain and paresthesias), which freequently occur after peripheral nerve injury.