Laser evoked potentials for assessing sensory neuropathy in human patients

Abstract

Sensory neuropathy usually impairs tactile sensations related to large myelinated afferents (Aβ) as well as thermal-pain sense related to small myelinated (Aδ) and unmyelinated (C) afferents. By selectively affecting large or small fibres, some sensory neuropathies may also provoke a dissociated sensory loss. Standard nerve conduction studies and somatosensory evoked potentials assess Aβ-fibre function only. Laser pulses selectively excite free nerve endings in the superficial skin layers and evoke Aδ-related brain potentials (LEPs). From earlier studies and new cases we collected data on 270 patients with sensory neuropathy. LEPs often disclosed subclinical dysfunction of Aδ fibres and proved a sensitive and reliable diagnostic tool for assessing small-fibre function in sensory neuropathy.