ACESSORY NERVE

It is the eleventh cranial nerve.

FUNCTIONAL COMPONENTS

Cranial root is Special visceral efferent. It arises from the lower part of nucleus ambiguous.

Spinal root is also a Special visceral efferent.It arises from a long spinal nucleus situated in lateral part of anterior grey column of the spinal cord extending between segments C1 to C5.

CRANIAL ROOT:

Introduction:
· Small
· It is accessory to the vagus s
· Distributed through branch of vagus to muscles of soft palate, larynx and pharynx.

Origin & Pathway:
It emerges from anterior surface of upper part of medulla oblongata by 4 or 5 rootlets b/w olive & inferior cerebellar peduncle (postrolateral sulcus of medulla), lies below the vagus & runs laterally beneath the cerebellum in the post cranial fossa ; joins the spinal root and passes through the jugular foramen& then the spinal root separates from the cranial root. The cranial root becomes adherent to the inferior ganglion of vagus. Fibers of Cranial root are distributed through the pharyngeal & recurrent laryngeal branch of vagus.

SPINAL ROOT:
It arises from nerve cells in the anterior grey column of upper five segments of cervical part of spinal cord. The nerve fibers emerge on the lateral surface of spinal cord & form a nerve trunk. The nerve ascends on the side of spinal cord & enters the skull from foramen magnum, then turns laterally to join the cranial root, pass through the jugular foramen & then the spinal rootseparates from the cranial root. Spinal root runs backward crossing the IJV reach upper part of sternocliedomastoid enters its deep surface & supplies it; emerges above the middle of post border of sternocliedomastoid crosses posterior triangle of neck on levator scapular to supply trapezius muscle

EXAMINATION OF ACCESSORY NERVE

FOR STERNOMASTOID

Ask the patient to bend the head downwards against resistance:

This is the action of both Sternomastoid

Ask the patient to turn head towards left against resistance to test Right Sternomastoid:
This is because each Sternomastoid pushes head towards opposite side; contracted muscle can also be seen and palpated.

FOR TRAPEZIUS
Inspect the patient from behind.If muscle is paralyzed
Upper part of scapula is displaced away from the spine
Lower part of scapula towards spine.
The whole arm droops and fingers on that side are nearer the ground compared with normal side.

Ask the patient to shrug his shoulders against resistance to test the power of trapezius.

INTERPRETATION
Accessory nerve is paralyzed along with other nerves in bulbar palsy.

Irritation of the nerve by enlarged lymph node may produce torticollis or wry neck.