Warm and cold sensory thresholds in patients with unilateral sciatica: C fibers are more severely affected than A-δ fibers

Objectives ‐ In order to evaluate if nerve root compression or inflammation is the most important pathogenetic mechanism in lumbar radicular pain, we investigated unmyelinated C‐fiber function (warm sensation) and myelinated A‐delta fiber function (cold sensation) in patients with unilateral L5 or S: sciatica. Material and methods ‐ Forty consecutive patients with clinical and radiological evidence of unilateral L5 (n=29) or S1 (n= 11) sciatica were studied. The warm and cold sensory thresholds (Somedic thermotest, method of limits) were measured on the anterolateral leg (L5 dermatome) and on the calf (S1 dermatome) on both sides. Results ‐ Warm thresholds were significantly higher on the symptomatic side compared to the non‐symptomatic side (8.4±3.0 vs 6.2±2.5°C, P