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Cranial nerve XI - the Spinal Accessory nerve


Signs and Symptoms of Cranial Nerve XI Paralysis

A unilateral peripheral lesion: depressed and winged scapula; atrophy of trapezius, causing shoulder depression of affected side; inability to shrug symmetrically; atrophy of the sternocleidomastoid of the affected side resulting in inability to rotate head to non-affected side.

Nuclear or peripheral nerve lesion (bilateral): an expressed inability to shrug or elevate chin; atrophy of the trapezius. 

If the lesion is peripheral atrophy usually ensues however, if it is central spasticity usually ensues. If it is unilateral there will be similar restrictions of movement as in the peripheral lesion however resulting in Spasmodic Torticollis.


Spinal Accessory Nerve Test

SCM: to examine cervical rotation and the strength of the sternocleidomastoid, have the individual rotate their head as far as possible to the right to test the right SCM. The practitioner places their hand on the individualís cheek and while applying moderate resistance request that the individual rotate their head towards the midline. Occasionally during this effort, the individual will attempt to drop their chin for the purpose of recruiting strength. The practitionerís other hand stabilizes this motion so that an accurate interpretation may be obtained. Repeat to the opposite side to test the left SCM with the practitioner obviously changing hand placement for monitoring and resistance, when the head is rotated to the left. The practitioner should monitor the quality of strength.

Spinal Accessory nerve test 1

Trapezius:  while more sophisticated muscle testing is utilized in the extended exam, the practitioner can screen the trapezius by placing one hand on each shoulder of the individual, and after applying moderate resistance, request the individual to shrug. As in the SCM test, monitor for strength of one side compared to the other.  A significant strength deficit is indicative of a positive finding, which would be exhibited by asymmetrical elevation of the shoulders.

Spinal Accessory nerve test 2

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