Painful alcoholic polyneuropathy with predominant small-fiber loss and normal thiamine status

Background: Although polyneuropathy related to chronic alcoholism has been reported frequently, its clinical features and pathogenesis remain to be clarified. Objective: To determine the clinicopathologic features and pathogenesis of alcoholic polyneuropathy associated with pain in patients with normal thiamine status, particularly in comparison to beriberi neuropathy. Patients and methods: Clinical, electrophysiologic, and histopathologic findings were assessed in 18 patients with painful alcoholic polyneuropathy and normal thiamine status. Results: Symmetric sensory-dominant polyneuropathy predominantly involving the lower limbs was the major clinical pattern. Painful sensations with or without burning quality represented the initial and major symptom. Progression of symptoms usually was gradual, continuing over months or years. Electrophysiologic and pathologic findings mainly indicated an axonal neuropathy. Densities of small myelinated fibers and unmyelinated fibers were more severely reduced than the density of large myelinated fibers, except in patients with a long history of neuropathic symptoms and marked axonal sprouting. Conclusions: The clinicopathologic features of painful symptoms and small axon loss are distinct from those of beriberi neuropathy. Sensory-dominant involvement with prominent neuropathic pain is characteristic of alcoholic neuropathy when thiamine deficiency is not involved, supporting the view of direct neurotoxic effect by alcohol or its metabolites.