title: Ultrasound-Guided Glossopharyngeal Nerve Block: A Cadaver and a Volunteer Sonoanatomy Study.
abstract: OBJECTIVE
  Glossopharyngeal nerve (GPN) blocks are usually performed by topical, intraoral, or peristyloid approaches, which carry significant complication risks due to the proximity of important neurovascular structures. This study presents a proof of concept for a new ultrasound (US)-guided technique, which would block the GPN distally, in the parapharyngeal space, away from the immediate vicinity of high-risk collateral structures.
  
  
  METHODS
  Five cadaver heads were dissected, and the location of the GPN was explored bilaterally. In 40 healthy volunteers (20 men and 20 women; median age, 35.5 years [range, 24-69 years]) parapharyngeal sonograms were obtained, saved, and analyzed. To assess the technical feasibility of a distal GPN block in the parapharyngeal space, unilateral US-guided dye injections were performed in 3 fresh cadavers, followed by dissections.
  
  
  RESULTS
  The GPN was consistently identified between the stylopharyngeal and middle pharyngeal constrictor muscles in all cadaver specimens. The median distance between the GPN and the ipsilateral greater horn of the hyoid bone was 2.4 cm (range, 2.3-2.7 cm) on the right and 2.6 cm (range, 2.3-2.9 cm) on the left. The mean skin-to pharyngeal wall distances in the volunteers were 2.03 (SD, 0.41) cm on the right and 2.02 (SD, 0.45) cm on the left. The mean hyoid bone-to-pharyngeal wall distances were 2.04 (SD, 0.35) cm (right) and 2.07 (SD, 0.35) cm (left). The fresh cadaver dissections demonstrated dye deposition adjacent to the GPN in the parapharyngeal space in all specimens.
  
  
  CONCLUSIONS
  Based on our anatomical results in cadavers and healthy volunteers, we submit that successful and safe blockade of the distal GPN at the pharyngeal wall level is technically feasible under US guidance.
authors.affiliation: From the *Department of Anesthesiology and ICU, Rijeka University Hospital, Rijeka, Croatia; †Department of Anesthesia and Intensive Care, University Hospital Linköping, Linköping, Sweden; ‡Clinical Department of Anesthesiology and Intensive Therapy, University Medical Centre Ljubljana; and §Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and ∥Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital/Harvard Medical School, Boston, MA.
authors.forename: Josip
authors.initials: J
authors.lastname: Ažman
authors.forename: Tatjana
authors.initials: T
authors.lastname: Stopar Pintaric
authors.forename: Erika
authors.initials: E
authors.lastname: Cvetko
authors.forename: Kamen
authors.initials: K
authors.lastname: Vlassakov
mesh_terms: D000328:Adult; D000368:Aged; D059925:Anatomic Landmarks; D002102:Cadaver; D005240:Feasibility Studies; D005260:Female; D005930:Glossopharyngeal Nerve / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D064368:Healthy Volunteers; D006801:Humans; D006928:Hyoid Bone / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010614:Pharynx / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011446:Prospective Studies; D018084:Ultrasonography, Interventional; D055815:Young Adult