Fig. 22.2 Axial thin CISS MRI image at the level of the medulla shows the cranial root of CN11 (arrows) emerging from the post-olivary sulcus just inferior to CN10. The cranial root travels anterolaterally through the basal cistern with CN9 and CN10.
22.2 Function
Branchial motor function (GSE): Motor fibers innervate the sternocleidomastoid muscle to turn the head and the trapezius muscle to raise the scapula and shrug the shoulders.
22.3 Pathology
Individual symptoms: Damage to the spinal accessory nerve results in the following symptoms depending on the location:
Upper cervical spinal lesions: Isolated lesions of the upper cervical spinal cord can result in spinal accessory neuropathy, such as ischemia, neoplasm, and demyelinating pathologies.
Cisternal lesions: Lesions within the premedullary cistern may present with spinal accessory neuropathy, such as meningiomas and metastatic disease.
Jugular foramen lesions: Lesions centered at the jugular foramen can present with spinal accessory dysfunction. At this location, a thin-bone algorithm (edge enhancement) CT and a thin-section contrasted MRI can distinguish pathologies. A jugular foramen paraganglioma causes permeative destructive (decreased density) changes to the jugular foramen walls, has variable phleboliths and/or slow flow and high-velocity flow voids leading to a salt and pepper (bright T1 and dark T1) appearance on MRI, and will have a superolateral vector of spread into the middle ear cavity. A jugular foramen meningioma will cause permeative sclerotic (increased density) to the surrounding osseous walls, has dural tails on contrasted MRI, and a centrifugal spread in all directions from the jugular foramen. A jugular foramen schwannoma will cause smooth, scalloped changes to the jugular foramen, shows intratumoral cysts when larger, and has a vector of spread along the expected course of cranial nerves 9–11 superiorly and medially toward the midbrain and inferiorly and laterally into the carotid sheath (carotid space).
Cervical soft tissue lesions: Traumatic changes and pathologies of the cervical soft tissues may also present with spinal accessory nerve dysfunction. Isolated CN11 dysfunction or injury is most commonly caused by neck dissection due to the close association of CN11 with the spinal accessory nodal chain [6]. The initial presentation of CN11 neuropathy is downward and lateral rotation of the scapula with the shoulder droop from loss of trapezius muscle tone [7]. With time, ipsilateral sternocleidomastoid and trapezius muscle atrophy progresses with compensatory hypertrophy of ipsilateral levator scapulae muscle. Hypertrophic levator scapulae muscle related to CN11 dysfunction should not be confused for a cervical mass.
Others: Other pathologies within the cervical soft tissues that may lead to CN11 dysfunction include nerve sheath tumors, such as glomus vagale paragangliomas, schwannomas, and neurofibromas, as well as squamous cell carcinoma nodal disease or primary lateral extension, carotid artery dissection. Spinal accessory nerve schwannomas not associated with neurofibromatosis are very rare. When they do occur, they can involve either intrajugular or intracisternal portions of CN11 [8–10].Related posts:
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