Spinal accessory nucleus

Spinal Accessory Nucleus

The spinal accessory nucleus is located in the medulla oblongata. Image courtesy of Wikimedia Commons.

The Spinal Accessory Nucleus is a collection of neurons in the medulla oblongata of the brainstem that is part of the cranial nerve system. It is specifically associated with the accessory nerve, also known as the eleventh cranial nerve (CN XI).

Structure

The spinal accessory nucleus is located in the lateral aspect of the anterior horn of the spinal cord. It extends from the level of the fifth cervical vertebra (C5) to the level of the first thoracic vertebra (T1). The nucleus is composed of both large and small neurons, with the larger neurons giving rise to the motor fibers of the accessory nerve.

Function

The spinal accessory nucleus is responsible for innervating the sternocleidomastoid muscle and the trapezius muscle, which are both involved in head and shoulder movements. The sternocleidomastoid muscle allows for rotation and flexion of the head, while the trapezius muscle is involved in moving and stabilizing the scapulae.

Clinical Significance

Damage to the spinal accessory nucleus or the accessory nerve can result in a condition known as accessory nerve disorder. This can lead to weakness or paralysis of the sternocleidomastoid and trapezius muscles, resulting in difficulties with head rotation and shoulder elevation.

See Also

• Cranial nerves
• Accessory nerve
• Medulla oblongata