title: Evaluation of lumbosacral nerve root lesions using evoked potentials recorded by a surface electrode technique.
abstract: METHODS
  Patients with lumbar disc herniation were studied with lumbosacral evoked potentials (EPs).
  
  
  OBJECTIVE
  To evaluate lumbosacral EPs for the functional diagnosis of nerve root lesions in patients with lumbar disc herniation.
  
  
  BACKGROUND
  No clinical studies have been conducted using lumbosacral EPs elicited by body surface leads.
  
  
  METHODS
  Lumbosacral EPs elicited by stimulating the posterior tibial nerve were recorded using surface electrodes placed over the interspinous processes of T12-S1. By subtracting the waveform recorded at NT12 (T12/L1 potential) from that at NL3 (L3/L4 potential), NL3' (residual potential) potentials were clearly identified. NT12 and NL3' potentials were classified into four groups based on the degree of the reduction of amplitude and/or the prolongation of latency.
  
  
  RESULTS
  Significant correlations were found between the NL3' score and the straight-leg raising test score (r = 0.36, P < 0.05) and between the NT12 amplitude and sensory disturbance (r = 0.37, P < 0.02). The NL3' score was 1.2 +/- 0.5 points before surgery, and it significantly improved to 2.5 +/- 0.5 points 2 months after surgery (P < 0.05). Short-term, the NT12 amplitude did not change significantly. Twelve months after surgery, the NT12 amplitude improved significantly to 1.1 +/- 0.5 microV (P < 0.05).
  
  
  CONCLUSIONS
  The results of this study indicated that the NL3' score may reflect impairment of the impulse traversing the nerve root in the acute clinical stage, whereas the NT12 amplitude reflects a neurologic deficit. The postoperative clinical course can be estimated by observing recovery of the NL3' score and NT12 amplitude.
authors.affiliation: Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kamigyo, Kyoto, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Osawa
authors.forename: Taku
authors.initials: T
authors.lastname: Ogura
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Hayashida
authors.forename: Masaki
authors.initials: M
authors.lastname: Mori
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hase
mesh_terms: D000293:Adolescent; D000328:Adult; D004558:Electric Stimulation / Q000295:instrumentation; D004566:Electrodes; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000503:physiopathology*; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000503:physiopathology; D013126:Spinal Nerve Roots / Q000473:pathology / Q000503:physiopathology*