The CN XI only contains motor fibres and innervates the sternocleidomastoid muscle and the trapezius muscle.
Procedure
Sternocleidomastoid muscle
- Stand behind the patient and hold your right hand against the patient’s lower right jaw [Figure 32].
- Ask the patient to push your hand away.
- In this way assess the strength of the left sternocleidomastoid muscle.
- Subsequently examine the strength of the right sternocleidomastoid muscle.
Figure 32
Trapezius muscle
- Have the patient lift their shoulders [Figure 33].
- Place your hands on the patient’s shoulders and try to push them down.
- Grade the strength of the trapezius muscle and the sternocleidomastoid muscle.
- Compare left and right.
Figure 33
Interpretation
Since the CN IX, CN X and CN XI all exit the skull through the jugular foramen, any pathology near this foramen (carcinoma, meningitis) often causes loss of function in all three nerves.
