INTRODUCTION

COMPONENTS

COURSE OF CRANIAL ROOT

COURSE OF SPINAL ROOT

DISTRIBUTION OF SPINAL ACCESSORY NERVE

CLINICAL FINDINGS

LESIONS

XI- CRANIAL NERVE

(ACCESSORY)

• The Accessory nerve [XI] carries GSE ( General Somatic

Efferent) fibers.

• Innervates the STERNOCLEIDOMASTIOD and TRAPEZIUSmuscles.

• Unique cranial nerve - - - roots arise from motor neurons of the

UPPER FIVE SEGMENTS [C1-C5] OF THE CERVICAL SPINAL CORD.

COMPONENTS:

I- Cranial Root. (Nucleus Ambiguous)

II- Spinal Root. ( Spinal Nucleus of Ant. Grey

columns b/w C1 - C5)

CRANIAL ROOT:

• Arises from the lower part of NucleusAmbiguous.

• Accessory to the Vagus nerve [X].

• Distributed through the Branches of Vagus nerve.

Course of Cranial Root:

• Rootlets arising from Caudal part of the Medulla Oblongata on the

Anterolateral surface, just inferior to the rootlets arising to form Vagus

Nerve.

• Leaving the Medulla, Cranial roots course with the “spinal” root of

Accessory nerve into the Jugular foramen, and again separates outside

the foramen.

• Join the Vagus nerve [Inf. Ganglion] after exiting the Jugular

foramen, supplying the pharyngeal musculature supplied by Vagus Nerve.

Course of the Spinal Root:

• Fibers arising from the motor cells in the lateral part of the Anterior

column of grey substance of the medulla spinalis as low as fifth cranial

nerve[C1-C5].

• Joining together as they ascend.

• Enters the Cranial Cavity through Foramen Magnum.

• Continues through the Posterior Cranial Fossa, laterally towards

Jugular foramen

Extra-cranially:

• Exits through Jugular foramen.

• Descends in the neck, Medial to the Int. Jugular Vein.

• B/w the Angle of Mandible and Mastoid process.

• Lies under the Stylohyoid and Post. Belly of Digastric muscle.

• Crosses the Int. Jugular Vein laterally in 66%, and passes behind in

33.3% of cases.

• Disappear either into or beneath the Ant. Border of

Sternocleidomastoid muscle.

[NO BRANCHES IN ANT. TRIANGLE OF THE NECK]

• Continues its descend & Enters the Post. Triangle of the Neck.

• Still moving obliquely and downward, within the Investing layer of the

Cervical fascia.

• Reaches the Ant. Border of Trapezius muscle, terminates by

innervating the muscle.

Distribution:

→ Motor Innervation to;

• Sternocleidomastoid muscle.

• Trapezius muscle.

CLINICAL FINDINGS:

• Paralysis of Sternocleidomastoid and Trapezius muscle.

• Drooping of the Shoulder.

• Inability to turn chin to opposite side.

• Inability to draw head forward.

• Irritation of the nerve during biopsy of enlarged caseous lymph

nodes, may produce TORTICOLLIS or WRY NECK.

LESIONs:

• Penetrating injury to the Posterior Triangle of the Neck.

• Superficial location of the nerve in Post. Triangle of the neck makes it

susceptible to injury.