RECOVERY OF SENSORY NERVE-FIBERS AFTER SURGICAL DECOMPRESSION IN LUMBAR RADICULOPATHY - USE OF QUANTITATIVE SENSORY TESTING IN THE EXPLORATION OF DIFFERENT POPULATIONS OF NERVE-FIBERS

Thirty nine patients with unilateral lumbar nerve root compression at one level were examined with quantitative sensory testing immediately before microdiscectomy and at six weeks, four months, and 12 months af ter surgery. Twenty one healthy volounteers were used as controls. The patients were classified as having a good or a poor result at the one year follow up. The improvement of function in small unmyelinated ner ve fibres came within six weeks in the patients with a good result. By contrast the improvement of function in small myelinated fibres was n ot found before 12 months after surgery. The function in large myelina ted fibres did not improve during the observation period. The differen ce in the time course of the recovery between large and small nerve fi bres is assumed to reflect differing severity in the damage to the fib res before surgical decompression. The preoperative warmth detection t hreshold reflecting the function in small unmyelinated C fibres was si gnificantly higher in the patients with a poor result and this may ind icate that damage to C fibres before surgery is a negative prognostic factor.