Anatomy of the spinal accessory (CN XI) and hypoglossal (CN XII) nerves

Question 1

Are CN XI and XII sensory, motor or mixed nerves?

Answer 1

They are pure motor nerves

Question 2

Describe somatic motor pathway of CN XI

Answer 2

Spinal accessory nucleus (at cervical spinal cord)

• > formen magnum
• > exit jugular foramen
• > course down along internal carotid artery
• > innervate trapezius & SCM

Question 3

Describe somatic motor pathway of CN XII

Answer 3

Cerebral cortex

• > hypoglossal nucleus
• > exit through hypoglossal canal
• > course along occipital artery
• > innervate muscles of tongue except palatopharyngeus (CN X)

Question 4

Relationship between CN XII & C1 spinal nerve

Answer 4

C1 spinal nerve hitchhikes along CN XII to innervate thyrohyoid & geniohyoid