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Abstract:
The effect of proximal nerve crush on regeneration after unrepaired nerve transection was studied in feline cutaneous nerves. Delays between the initial transection and the subsequent nerve crush varied between 0 (immediate crush) and 13 months. A survival time of 6 to 12 months after the crush was allowed for regeneration to complete. Data from these animals was compared with data from animals in which the nerve was simply transected. Four measures of regeneration success were used to assess the degree of functional recovery: (i) the number of fibers crossing the neuroma and regenerating down the distal stump; (ii) the conduction velocity and diameter of individual fibers in the distal stump relative to their conduction velocity and diameter in the proximal stump; (iii) the number of fibers reinnervating cutaneous mechanoreceptors; and (iv) the number of cutaneous type I mechanoreceptors present after regeneration. As a whole, the data showed a statistically significant increase in the number of fibers entering the distal stump and in the number of fibers reinnervating the skin when the nerve was crushed 6 months after transection compared with nerves that were only transected. There was also an increase in the size and conduction velocity of fibers in the distal stump of nerves that had been crushed 4 to 6 months after transection.