Nervus accessorius

Nervus Accessorius (also known as the Accessory Nerve or Cranial Nerve XI) is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is unique among the cranial nerves as it is the only one that originates from both the brain and the spinal cord.

Anatomy

The Nervus Accessorius is composed of two parts: the cranial part and the spinal part. The cranial part originates from the medulla oblongata, while the spinal part originates from the upper segments of the spinal cord. These two parts join to form the Nervus Accessorius, which then exits the skull through the jugular foramen.

Function

The Nervus Accessorius is a motor nerve that controls the movements of the sternocleidomastoid and trapezius muscles. The sternocleidomastoid muscle is involved in rotating and flexing the neck, while the trapezius muscle moves the scapula and supports the arm.

Clinical Significance

Damage to the Nervus Accessorius can result in weakness or paralysis of the sternocleidomastoid and trapezius muscles. This can cause difficulties in moving the neck and shoulders, and may result in a condition known as torticollis.

See Also

• Cranial nerves
• Sternocleidomastoid muscle
• Trapezius muscle
• Torticollis