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.

The nerve originates in the medulla then exits the skull through the jugular foramen with nerves IX and X.


Shrug shoulders with, and without, resistance. Turn head against resistance.


Investigations are the same as for CN IX.

In addition, the accessory nerve can also be damaged in the neck.


Metastatic disease in the neck with lymph node involvement can cause CN XI palsy.


Neck dissection surgery can cause injury as can blunt or penetrating trauma to the neck.