Cutaneous sensory nerve fibers are decreased in number after peripheral and central nerve damage.

Two dermatologic patients displaying peripheral and central nerve damage, respectively, are described. Cutaneous nerve fibers in both patients were studied in skin biopsy specimens taken from neuropathic areas and from the contralateral side, immunocytochemistry being applied to a pan-neuronal marker, a protein gene-product (PGP 9.5). One of the patients, suffering from compression of the ulnar nerve, had dyshidrotic eczema of the hands that was absent on areas of skin that were neuropathic. The cutaneous innervation (most of which was sensory) was reduced by 50% in the neuropathic area as compared with the contralateral side. The other patient had unilateral pruritus on the parethic side after a stroke. The cutaneous innervation of that side was reduced by 80% as compared with the other side. It seems that peripheral sensory innervation is a prerequisite for inflammation, whereas spontaneous itching may emanate from a central nervous system disorder such as a stroke and continue on in partly denervated skin.