title: The Spinal Accessory Nerve for Functional Muscle Innervation in Facial Reanimation Surgery: An Anatomical and Histomorphometric Study.
abstract: BACKGROUND
  Facial reanimation surgery is performed in severe cases of facial palsy to restore facial function. In a 1-stage procedure, the spinal accessory nerve can be used as a donor nerve to power a free gracilis muscle transplant for the reanimation of the mouth. The aim of this study was to describe the surgical anatomy of the spinal accessory nerve, provide a guide for reliable donor nerve dissection, and analyze the available donor axon counts.
  
  
  METHODS
  Dissections were performed on 10 nonembalmed cadavers (measurements of 20 nerves). Surgical anatomy of the spinal accessory nerve was described and distances to important landmarks were measured. Nerve biopsies were obtained of the main nerve trunk distal to the skull base, caudoposterior to the sternocleidomastoid muscle, proximal to the trapezius muscle and at the level of donor nerve harvest to analyze the myelinated axon count throughout the course of the spinal accessory nerve. The donor nerve length and available donor nerve axon count were the primary outcome parameters in this study.
  
  
  RESULTS
  The mean donor nerve length was 11.6 cm. The spinal accessory nerve was transferred to the mandibular angle without tension for ideal coaptation to the free muscle transplant. After retraction of the trapezius muscle, a small distal nerve branch that leaves the main nerve trunk at a 90-degree angle medially was used as a landmark to indicate the level of donor nerve transection. On average, 1400 myelinated donor axons were available for innervation of the gracilis muscle transplant.
  
  
  CONCLUSIONS
  This study gives a practical guide for spinal accessory nerve dissection for its application in facial reanimation as a motor source for the innervation of a free muscle transplant.
authors.affiliation: From the *Division of Plastic and Reconstructive Surgery, Department of Surgery, †Center for Anatomy and Cell Biology Medical University of Vienna, Vienna, Austria; and ‡Department of Plastic Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taipei, Taiwan.
authors.forename: Eva
authors.initials: E
authors.lastname: Placheta
authors.forename: Ines
authors.initials: I
authors.lastname: Tinhofer
authors.forename: Melanie
authors.initials: M
authors.lastname: Schmid
authors.forename: Lukas F
authors.initials: LF
authors.lastname: Reissig
authors.forename: Igor
authors.initials: I
authors.lastname: Pona
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weninger
authors.forename: Thomas
authors.initials: T
authors.lastname: Rath
authors.forename: David Chwei-Chin
authors.initials: DC
authors.lastname: Chuang
authors.forename: Chieh Han
authors.initials: CH
authors.lastname: Tzou
mesh_terms: D000055:Accessory Nerve / Q000033:anatomy & histology* / Q000637:transplantation*; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D004210:Dissection / Q000379:methods; D005158:Facial Paralysis / Q000601:surgery*; D005260:Female; D000071976:Gracilis Muscle / Q000294:innervation* / Q000637:transplantation*; D006801:Humans; D008297:Male; D019635:Neurosurgical Procedures / Q000379:methods*