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 TRAPEZIUS muscles.

• 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 Nucleus Ambiguous.

• 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.