title: Neurophysiological assessment of spinal cord stimulation in failed back surgery syndrome.
abstract: Despite good clinical results, the mechanisms of action of spinal cord stimulation (SCS) for the treatment of chronic refractory neuropathic pain have not yet been elucidated. In the present study, the effects of SCS were assessed on various neurophysiological parameters in a series of 20 patients, successfully treated by SCS for mostly unilateral, drug-resistant lower limb pain due to failed back surgery syndrome. Plantar sympathetic skin response (SSR), F-wave and somatosensory-evoked potentials (P40-SEP) to tibial nerve stimulation, H-reflex of soleus muscle, and nociceptive flexion (RIII) reflex to sural nerve stimulation were recorded at the painful lower limb. The study included two recording sets while SCS was switched 'ON' or 'OFF' for 1h. Significant changes in 'ON' condition were as follows: SSR amplitude, H-reflex threshold, and RIII-reflex threshold and latency were increased, whereas SSR latency, F-wave latency, H-reflex amplitude, P40-SEP amplitude, and RIII-reflex area were reduced. Analgesia induced by SCS mainly correlated with RIII attenuation, supporting a real analgesic efficacy of the procedure. This study showed that SCS is able to inhibit both nociceptive (RIII-reflex) and non-nociceptive (P40-SEP, H-reflex) myelinated sensory afferents at segmental spinal or supraspinal level, and to increase cholinergic sympathetic skin activities (SSR facilitation). Complex modulating effects can be produced by SCS on various neural circuits, including a broad inhibition of both noxious and innocuous sensory information processing.
authors.affiliation: Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, EA 4391, U-PEC, Créteil, France Service de Neurochirurgie, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, Créteil, France.
authors.forename: Daniel Ciampi
authors.initials: DC
authors.lastname: de Andrade
authors.forename: Belgacem
authors.initials: B
authors.lastname: Bendib
authors.forename: Mohammed
authors.initials: M
authors.lastname: Hattou
authors.forename: Yves
authors.initials: Y
authors.lastname: Keravel
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Nguyen
authors.forename: Jean-Pascal
authors.initials: JP
authors.lastname: Lefaucheur
mesh_terms: D000328:Adult; D000368:Aged; D001416:Back Pain / Q000601:surgery; D004558:Electric Stimulation / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D012018:Reflex / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D018709:Statistics, Nonparametric; D013979:Tibial Nerve / Q000503:physiopathology