title: [Origin of N(18) median nerve somatosensory evoked potentials studied in patients with hemispherectomy].
abstract: OBJECTIVE
  To probe into the neural generators of the median nerve (MN) somatosensory evoked potentials (SEP) in patients after hemispherectomy, especially with regard to N(18).
  
  
  METHODS
  SEP induced by median nerve stimulation with both cephalic and noncephalic references were recorded in 20 patients with hemispherectomy entailing massive retrograde degeneration of thalamocortical, midbrain and pontine neurons documented by MRI evidence. Twelve dga and Aex matclod healty persons were used as controls.
  
  
  RESULTS
  No additional focal response (cortical N(20)) was detected over the hemisphere-ectomized lateral scalp in all patients. The positive P(14) and negative N(18) scalp far-fields were preserved and the latencies of with the 12.5 +/- 0.8 ms and 17.6 +/- 1.6 ms respectively. The preserved N(18) response reflected the neural activity below the pons.
  
  
  CONCLUSIONS
  The N(18) neural generators are located in the medulla.
authors.affiliation: Department of Neurosurgery, Tiantan Hospital Affiliated to Capital University of Medical Sciences, Beijing 100050, China.
authors.forename: Yulun
authors.initials: Y
authors.lastname: Xu
authors.forename: Shuling
authors.initials: S
authors.lastname: Liu
authors.forename: Jizong
authors.initials: J
authors.lastname: Zhao
authors.forename: Yingfu
authors.initials: Y
authors.lastname: Pan
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D038421:Hemispherectomy; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008526:Medulla Oblongata / Q000503:physiopathology; D011149:Pons / Q000503:physiopathology; D011930:Reaction Time