title: Electrophysiological diagnosis using sensory nerve action potential for the intraforaminal and extraforaminal L5 nerve root entrapment.
abstract: BACKGROUND
  The diagnosis of lumbar intraforaminal and extraforaminal stenosis (lumbar foraminal stenosis) is sometimes difficult. However, sensory nerve action potential (SNAP) decreases in amplitude when the lesion is at or distal to the dorsal root ganglion. Therefore, the amplitude of SNAP with lumbar foraminal stenosis should be decreased. In this cohort study, the usefulness of SNAP for the preoperative diagnosis of L5/S foraminal stenosis was assessed.
  
  
  METHODS
  In 63 patients undergoing unilateral L5 radiculopathy, bilateral SNAPs were recorded for the superficial peroneal nerve (L5 origin). The patients were divided into two groups according to the results of imaging examinations. Group A (37 patients) included patients whose lesion was located only at the intraspinal canal. In group B (26 patients), the lesion was located only at the intra- or extraforaminal area. All patients received surgery and the symptoms were diminished. The ratios of the amplitudes of SNAPs on the affected side to that on the unaffected side were compared between groups A and B.
  
  
  RESULTS
  SNAPs could not be elicited bilaterally in four patients. The amplitude ratio for group B (median 0.42, max 1.17, min 0) was significantly lower than that in group A (median 0.85, max 1.43, min 0) (p < 0.001 by Mann-Whitney U test). Using a cut-off value of 0.5 for the amplitude ratio, the sensitivity for the diagnosis of lumbar foraminal stenosis was 91.3 % with a specificity of 85.7 %.
  
  
  CONCLUSIONS
  Measurement of SNAP could be useful to diagnose a unilateral L5/S foraminal stenosis.
authors.affiliation: Department of Orthopedic Surgery, Wakayama Rosai Hospital, 93-1 Kinomoto, Wakayama city, 640-8505 Wakayama, Japan. mando@gaia.eonet.ne.jp
authors.forename: Muneharu
authors.initials: M
authors.lastname: Ando
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tamaki
authors.forename: Mamoru
authors.initials: M
authors.lastname: Kawakami
authors.forename: Akihito
authors.initials: A
authors.lastname: Minamide
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Maio
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Enyo
authors.forename: Munehito
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000368:Aged; D015331:Cohort Studies; D019299:Decompression, Surgical; D004594:Electrophysiology / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D005727:Ganglia, Spinal / Q000503:physiopathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000294:innervation* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009408:Nerve Compression Syndromes / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D011843:Radiculopathy / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D012680:Sensitivity and Specificity; D011984:Sensory Receptor Cells / Q000502:physiology*; D013115:Spinal Canal / Q000000981:diagnostic imaging / Q000473:pathology; D013126:Spinal Nerve Roots / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D013130:Spinal Stenosis / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D014057:Tomography, X-Ray Computed