Estimation of conduction velocity of A delta fibers in humans.

Conduction velocity of A delta fibers of the human peripheral nerves was measured by using pain-related somatosensory evoked potentials following CO2 laser stimulation. It was found to be approximately 9 m/s in the forearm as well as in the lower leg. Because conventional conduction study using electric stimulation reflects only functions of large myelinated fibers related to deep proprioceptive and tactile sensations, the present noninvasive and simple, novel method is the only laboratory examination currently available to investigate physiological functions of the small diameter fibers mediating pain-temperature sensations.