title: A clear map of the lower cranial nerves at the superior carotid triangle.
abstract: BACKGROUND
  The lower cranial nerves must be identified to avoid iatrogenic injury during skull base and high cervical approaches. Prompt recognition of these structures using basic landmarks could reduce surgical time and morbidity.
  
  
  METHODS
  The anterior triangle of the neck was dissected in 30 cadaveric head sides. The most superficial segments of the glossopharyngeal, vagus and its superior laryngeal nerves, accessory, and hypoglossal nerves were exposed and designated into smaller anatomic triangles. The midpoint of each nerve segment inside the triangles was correlated to the angle of the mandible (AM), mastoid tip (MT), and bifurcation of the common carotid artery.
  
  
  RESULTS
  A triangle bounded by the styloglossus muscle, external carotid artery, and facial artery housed the glossopharyngeal nerve. This nerve segment was 0.06 ± 0.71 cm posterior to the AM and 2.50 ± 0.59 cm inferior to the MT. The vagus nerve ran inside the carotid sheath posterior to internal carotid artery and common carotid artery bifurcation in 48.3% of specimens. A triangle formed by the posterior belly of digastric muscle, sternocleidomastoid muscle, and internal jugular vein housed the accessory nerve, 1.90 ± 0.60 cm posterior to the AM and 2.30 ± 0.57 cm inferior to the MT. A triangle outlined by the posterior belly of digastric muscle, internal jugular vein, and common facial vein housed the hypoglossal nerve, which was 0.82 ± 0.84 cm posterior to the AM and 3.64 ± 0.70 cm inferior to the MT.
  
  
  CONCLUSIONS
  Comprehensible landmarks can be defined to help expose the lower cranial nerves to avoid injury to this complex region.
authors.affiliation: Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Cavalcanti
authors.forename: Ulises
authors.initials: U
authors.lastname: Garcia-Gonzalez
authors.forename: Abhishek
authors.initials: A
authors.lastname: Agrawal
authors.forename: Paulo L M S
authors.initials: PL
authors.lastname: Tavares
authors.forename: Robert F
authors.initials: RF
authors.lastname: Spetzler
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
mesh_terms: D000055:Accessory Nerve / Q000473:pathology / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D003391:Cranial Nerves / Q000473:pathology* / Q000601:surgery; D005260:Female; D005930:Glossopharyngeal Nerve / Q000473:pathology / Q000601:surgery; D006801:Humans; D007002:Hypoglossal Nerve / Q000473:pathology / Q000601:surgery; D007823:Laryngeal Nerves / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000294:innervation* / Q000601:surgery*; D012016:Reference Values; D019291:Skull Base / Q000294:innervation* / Q000601:surgery*