THE PERMANENT RESULTS OF DENERVATION OF A CUTANEOUS AREA

¹ Department of Physiology, Edinburgh University

In a cutaneous area which has been completely denervated by section of all the nerve fibres distributed to it, i.e. an area in which there is no overlapping or accessory supply of uncut nerve-fibres and in which sufficient time has elapsed for regeneration of the cut nerves to take place, those fibres which subserve pain are permanently hypersensitive and confer a disagreeable character upon any sensation evoked by mechanical stimuli. The ordinary sensation of touch is not properly appreciated, being obscured by this hypersensitiveness to pain. A stimulation such as would produce a pleasant sensation of tickling on a normal cutaneous surface causes an unpleasant sensation of tingling over the denervated area. If the blunt point of a heated or cooled metal rod is allowed to come in contact with the area, the warm or cold feeling is complicated by the concomitant disagreeable sensation caused by contact of the rod with the skin. But if the rod is not allowed to touch the skin, the sensations of warmth or cold are felt without such concomitant disagreeable sensation.

Stated briefly, the following is the permanent condition of the original denervated area, as tested three years after section of the nerve supplying the area:—

The sensation of touch is abolished or is at any rate obscured by a concomitant sensation of pain.

Appreciation of warmth and cold has returned but in a somewhat diminished degree as compared with a normal area.

Sensation of pain is increased over the originally denervated area as compared with that felt over a normal area.

Trophic conditions are less favourable than in parts where the nerve-supply has not been interfered with.