The use and interpretation of medical examinations to determine the integrity and adequate function of the accessory nerve (eleventh cranial nerve).
The accessory nerve supplies motor innervation to the sternocleidomastoid and trapezius muscles.
To assess these muscles, firstly observe the patient for any sings of atrophy, asymmetry and palpate for hyper/hypotonicty and flaccidity. Have the patient shrug, than retract their shoulders whilst resisting the movement in both directions. Than have the patient rotate their head in both directions, and resist this movement.
Test findings (inc Positive & Negative results):
Supranuclear lesions of the accessory nerve result in mild, usually transient, dysfunction of the sternocleidomastoid and trapezius muscles, due to the bilateral innervation. In the spinal cord the nuclei of the eleventh cranial nerve can be affected by Amyotrophic Lateral Sclerosis (ALS), syringomyelia, polio, and intraspinal tumors. Occlusion of the vertebral or posterior inferior cerebellar artery produces infarction of the medullary tegmentum, with deficits of V, IX, X, and XI (Wallenberg’s syndrome). The accessory nerve is also vulnerable to space occupying lesions as it travels down the jugular foramen (Vernetâ€™s syndrome).
As with other peripheral nerves, the accessory nerve may present with the associated characteristics of an upper or lower motor neuron lesion.