Spinal Accessory Nerve

Description

Anatomical illustration demonstrating the posterior pathways of the dorsal scapular nerve (DSN) and spinal accessory nerve (SAN)

Spinal accessory nerve. (A) Schematic drawing shows the pertinent anatomy of the spinal accessory nerve (arrowhead) that emerges underneath the sternocleidomastoid muscle (1), becomes superficial at the posterior cervical triangle (2), and then enters and supplies the trapezius muscle (3). (B) Winged scapula in a 27-year-old woman with spinal accessory nerve palsy after cervical lymph node biopsy. Winging (arrow) involves the superomedial scapula. (C) Longitudinal ultrasound image obtained over the left cervical region in the same patient shown in (B). The spinal accessory nerve (outlined arrows) is seen crossing the sternocleidomastoid muscle and ending in a small fusiform neuroma (white arrow) suggesting complete nerve transection.

Names

• Spinal Accessory Nerve
• Accessory Nerve
• Cranial Nerve XI

Spinal Component Anatomy

• Arises from the neurons of C1 to C5/C6
• Coalesce to form the spinal part of the nerve
• Runs superiorly to enter the cranial cavity at the foramen magnum
• Traverses the posterior fossa to reach the jugular foramen
• Meets with the accessory nerve before exiting the skull
• Descends along the internal carotid artery to reach the sternocleidomasteroid muscle
• Moves posterior triangle of the neck to supply the trapezius

Cranial Component Anatomy

• Arises from the lateral aspect of medulla oblongata
• Leaves the cranium via the jugular foramen
• Briefly contacts the spinal part of the spinal accessory nerve
• After leaving the skull, combines with the vagus nerve
• Distally to this point, the cranial component is considered part of the vagus nerve

Motor Function

• Sternocleidomastoid
• Trapezius

---

Clinical Significance

• Spinal Accessory Nerve Injury
• Winged Scapula

---

See Also

• Neuropathies Main
• Nerve Anatomy Main
• Physical Exam Neck

---