title: Clinical application of laser evoked potentials using the Nd:YAG laser.
abstract: The clinical interest of a new type of laser evoked potentials (LEPs) using Nd:YAG laser was assessed in the diagnosis of peripheral neuropathies affecting the small-diameter nerve fibres, and of spinal cord lesions, affecting the spinothalamic tract. Twelve patients aged from 26 to 79 years with sensory neuropathies (n = 6) or spinal cord lesions (n = 6) underwent neurophysiological examination of the lower limbs comprising quantitative sensory testing, i.e., the determination of vibratory and thermal thresholds (VT and TT), somatosensory evoked potentials (SEPs) to electrical stimulation and Nd:YAG LEPs. VT and SEPs were used to assess large-diameter afferent nerve fibres and the lemniscal pathways while TT and LEPs were used to assess small-diameter afferent nerve fibres and the spinothalamic tract. In addition, patients with peripheral neuropathy underwent also standard nerve conduction studies to explore large fibres and the recording of sympathetic skin responses (SSRs) to explore small fibres, whereas motor evoked potentials were performed in patients with spinal cord lesion. LEPs were absent bilaterally in all patients with polyneuropathy, even when TT remained within the normal limits and SSRs were present. LEPs were absent after stimulation of the affected limb in all patients with a spinal cord lesion, and allowed to detect subclinical contralateral lesion in two cases. LEPs following Nd:YAG laser stimulation are sensitive in the diagnosis of peripheral and/or central nervous system disorders and they give complementary information as compared to routine electrophysiological tests.
authors.affiliation: Service de physiologie-explorations fonctionnelles, centre hospitalier universitaire Henri Mondor, 51, avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil, France. jean-pascal.lefaucheur@hmn.ap-hop-paris.fr
authors.forename: J P
authors.initials: JP
authors.lastname: Lefaucheur
authors.forename: A
authors.initials: A
authors.lastname: Brusa
authors.forename: A
authors.initials: A
authors.lastname: Creange
authors.forename: X
authors.initials: X
authors.lastname: Drouot
authors.forename: G
authors.initials: G
authors.lastname: Jarry
mesh_terms: D000368:Aged; D004594:Electrophysiology; D005071:Evoked Potentials / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D007834:Lasers; D007866:Leg / Q000294:innervation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D009460:Neurologic Examination; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis*; D012684:Sensory Thresholds / Q000502:physiology; D013118:Spinal Cord Diseases / Q000175:diagnosis*; D013133:Spinothalamic Tracts / Q000473:pathology; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013696:Temperature