Axon-reflex reactions in affected and homologous contralateral skin after unilateral peripheral injury of thoracic segmental nerves in humans.

Transection and regeneration of a rat peripheral nerve on one side reduces the ability of the contralateral nerve to evoke plasma extravasation after antidromic excitation of afferent C-fibers induced by electrical nerve stimulation (afferent axon reflex). An unknown transneuronal signalling substance was postulated. In humans, axon-reflex vasodilatation was studied using cutaneous iontophoresis of histamine for C-fiber stimulation and laser Doppler flowmetry for measuring vasodilatation. As a model of peripheral nerve lesion with regeneration, patients with severe unilateral zoster neuropathy of thoracic segmental nerves were examined. Axon-reflex reactions were considerably impaired within the affected dermatome compared with the unaffected side and compared with controls. In contrast, no significant differences could be found between the unaffected corresponding sites of patients and similar dermatomes of healthy controls, indicating that this type of nerve injury does not influence the ability of the contralateral nerve to evoke axon-reflex vasodilatation.