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CNXI (Accessory Nerve)
Siddhartha Gaddamanugu, MD; H. Ric Harnsberger, MD
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TERMINOLOGY

  • Abbreviations

    • Accessory nerve: CN 11, CNXI
  • Synonyms

    • 11th CN
  • Definitions

    • CNXI: Pure motor CN, supplying sternocleidomastoid, trapezius muscles (through spinal component) and palatal, pharyngeal, laryngeal muscles (through cranial component)
    • Comment: There is some controversy regarding fundamental anatomy of spinal accessory nerve; recently, some authors have argued that nerves that arise from caudal aspect of postolivary sulcus of medulla have variable interaction with adjacent CNs; these fibers may join vagus nerve directly
      • In some cases, these fibers remain as distinct nerves in cistern, ultimately merging with vagus nerve in jugular foramen or just below it to supply palate, larynx, and pharynx; in this circumstance, bulbar (cranial) components never actually merge with spinal component of CN XI

IMAGING ANATOMY

  • Overview

    • Intraaxial Segment

      • Cisternal Segment

        • Skull Base Segment

          • Extracranial Segment

            ANATOMY IMAGING ISSUES

            • Imaging Recommendations

              • Imaging Sweet Spots

                • Imaging Pitfalls

                  CLINICAL IMPLICATIONS

                  • Clinical Importance

                    • Function & Dysfunction

                      Related Anatomy
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                      Related Differential Diagnoses
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                      References
                      Tables

                      Tables

                      TERMINOLOGY

                      • Abbreviations

                        • Accessory nerve: CN 11, CNXI
                      • Synonyms

                        • 11th CN
                      • Definitions

                        • CNXI: Pure motor CN, supplying sternocleidomastoid, trapezius muscles (through spinal component) and palatal, pharyngeal, laryngeal muscles (through cranial component)
                        • Comment: There is some controversy regarding fundamental anatomy of spinal accessory nerve; recently, some authors have argued that nerves that arise from caudal aspect of postolivary sulcus of medulla have variable interaction with adjacent CNs; these fibers may join vagus nerve directly
                          • In some cases, these fibers remain as distinct nerves in cistern, ultimately merging with vagus nerve in jugular foramen or just below it to supply palate, larynx, and pharynx; in this circumstance, bulbar (cranial) components never actually merge with spinal component of CN XI

                      IMAGING ANATOMY

                      • Overview

                        • Intraaxial Segment

                          • Cisternal Segment

                            • Skull Base Segment

                              • Extracranial Segment

                                ANATOMY IMAGING ISSUES

                                • Imaging Recommendations

                                  • Imaging Sweet Spots

                                    • Imaging Pitfalls

                                      CLINICAL IMPLICATIONS

                                      • Clinical Importance

                                        • Function & Dysfunction