Evidence in support of collateral sprouting after sensory nerve resection.

The extent and time course of sensory recovery has been investigated in 13 patients who had resection of a cutaneous nerve. Seven patients were studied within 8 weeks of denervation; 6 others were studied more than 6 months after denervation. Touch sensation was evaluated using a computer-assisted measuring device that recorded the pressure thresholds for static and moving touch, and static and moving two-point discrimination within a continual range from 0.1 to 100 gm per square millimeter. Recovery of sensation within the autonomous zone of the resected nerve could be documented as early as 3 weeks after denervation. After 6 months, two-point discrimination had recovered in the previously denervated areas. Thresholds for all test modalities were found to be elevated within the sensory distribution of adjacent nerves, which suggests that these areas have been the donor source for reinnervation of the chronically denervated territory. Anesthetic block of these adjacent donor nerves resulted in loss of the recovered sensation.