Accessory Nerve (XI)
The accessory nerve is a motor nerve supplying the sternocleidomastoid and the upper part of the trapezius.
Injury causes weakness of shoulder elevation and head rotation.
Anatomy
The nerve originates in the medulla then exits the skull through the jugular foramen with nerves IX and X.
Testing
Shrug shoulders with, and without, resistance. Turn head against resistance.
Investigations
Investigations are the same as for CN IX.
In addition, the accessory nerve can also be damaged in the neck.
Medical
Metastatic disease in the neck with lymph node involvement can cause CN XI palsy.
Trauma
Neck dissection surgery can cause injury as can blunt or penetrating trauma to the neck.