Thermal quantitative sensory testing in lumbar disc herniation

The most frequent clinical presentation of sciatica suggests injury of sensor root fibers alone. To evaluate whether thermal quantitative sensory testing (QST) is applicable in the study of sensory dysfunction in lumbosacral disc herniations, 36 men and 30 women with L4/5 or L5/S1 disc herniations underwent thermal QST of the L4, L5, and S1 dermatomes. For both levels of disc herniation, there was a significant difference for all temperature modalities, i.e., cold, warmth and heat pain, between all dermatomes as well as between the side of the herniated disc and the corresponding asymptomatic side. However, the proportion of herniated discs classified correctly was only 48% in patients with disc herniations at the L4/5 level, while it was 71% at the L5/S1 level. We conclude that thermal QST measurements reflect and document sensory dysfunction in patients with lumbosacral disc herniation. The method offers a new means both to study the time course of a spontaneous recovery of sensory dysfunction and to evaluate the result of different treatment options. However, thermal QST seems to have the same poor predictive value for identifying the anatomic location of a herniated lumbar disc as conventional electrophysiologic methods.