CUTANEOUS INNERVATION DENSITY IN THE ALLODYNIC FORM OF POSTHERPETIC NEURALGIA

The relationship between deafferentation, sensory function, and pain w as explored in 18 subjects with chronic postherpetic neuralgia (PHN). Subjective thresholds for warmth, cooling, and heat pain were measured quantitatively in painful skin areas and compared with normal contral ateral skin. The severity of allodynia was graded in the affected area . Two 3-mm punch biopsies were taken from the most painful skin area a nd one from unaffected contralateral mirror-image skin. Immunofluoresc ence with the axonal marker PGP 9.5 revealed a reduction in density of innervation of the epidermis, the dermal-epidermal junction, and the eccrine sweat glands in PHN skin. In painful PHN skin, the reduction i n innervation density was positively correlated with the magnitude of the thermal sensory deficits. However, loss of cutaneous innervation w as inversely correlated with allodynia, indicating that surviving cuta neous primary afferent nociceptors that are spontaneously active and/o r sensitized contribute to PHN pain and allodynia. (C) 1996 Academic P ress, Inc.