title: Ultrasound examination and localization of the sciatic nerve: a volunteer study.
abstract: BACKGROUND
  Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.
  
  
  METHODS
  In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded.
  
  
  RESULTS
  The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion.
  
  
  CONCLUSIONS
  These preliminary data show that a curved 2- to 5-MHz ultrasound probe provides good quality sciatic nerve imaging in the gluteal, infragluteal, and proximal thigh locations. Ultrasound-assisted sciatic nerve localization is potentially valuable for clinical sciatic nerve blocks.
authors.affiliation: Department of Anesthesia and Pain Management, Toronto Western Hospital, University Health Netwprk, 399 Bathurst Street, Toronto, Ontario, Canada M5T 2S8. vincent.chan@uhn.on.ca
authors.forename: Vincent W S
authors.initials: VW
authors.lastname: Chan
authors.forename: Hugo
authors.initials: H
authors.lastname: Nova
authors.forename: Sherif
authors.initials: S
authors.lastname: Abbas
authors.forename: Colin J L
authors.initials: CJ
authors.lastname: McCartney
authors.forename: Anahi
authors.initials: A
authors.lastname: Perlas
authors.forename: Da Quan
authors.initials: DQ
authors.lastname: Xu
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D008297:Male; D009339:Needles; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D012018:Reflex / Q000502:physiology; D012584:Sciatic Nerve / Q000000981:diagnostic imaging*; D014463:Ultrasonography