Accessory and Hypoglossal nerves

11th CN: Accessory Nerve• Type: Motor (SVE)• Origin : 2 rootscranial root: arises

from the medullaSpinal root : from

upper 5 cervical segments

• Emerges from : jugular foramen then the 2 roots separate

Cranial Part

• Origin: Nucleus ambiguus (NA) in the medulla oblongata

• Site of emergence: The fibers emerge from the anterior surface of the medulla oblongata between the olive and the inferior cerebellar peduncle (ICP)

Spinal Part

Origin:– Formed by the

axons of the nerve cells in the spinal nucleus which is located in the ventral grey horn in the upper 5 cervical segments

The nucleus ambiguus and the

spinal nucleus receive bilateral corticonuclear

fibers (from both cerebral

hemispheres)

CourseThe cranial root : joins the vagus nerve and

distributed with its pharyngeal and laryngeal branches

Spinal part: fibers emerge from the spinal cord, form a nerve trunk that ascends into the cranial cavity through the foramen magnum, pass laterally and join the cranial root.

Spinal part ctd.: • Descends first in the carotid

sheath (bet. I.C.A. and I.J.V. )• Then emerges from the sheath,

pass backwards, to pierce the sternomastoid m., cross the posterior triangle of the neck to end in the trapezius

Supply both muscles

Function: Movements of the soft palate,

larynx, pharynx. Controls the movements of

neck

Course

• Lesion results into: – Difficulty in

swallowing and speech

– Inability to turn the head

– Inability to shrug (raise) the shoulder

– Winging of scapula

Lesion

12th CN: Hypoglossal Nerve

• Type: Motor (GSE)• Origin: Hypoglossal

nucleus of the medulla (in the floor of 4th ventricle)

• Foramen of exit from skull: Hypoglossal canal

Also receives afferent fibers from nucleus solitarius and trigeminal sensory nucleus.

The hypoglossal nucleus receives corticonuclear fibers from both cerebral hemispheres EXCEPT the region that supplies genioglossus muscle (it receives contralateral supply only)

Site of emergence:The fibers emerge from the anterior surface of the medulla oblongata between the pyramid and the olive.

Olive

Pyramid

Descends in the carotid sheath between internal jugular vein and internal carotid artery It leaves the sheath and pass forward and medially crossing ICA &ECAIt enters the digastric triangle Finally , it pass deep to the mylohyoid muscle to reach the tongue where it breaks into terminal branches

Course

C1 fibers

Course

During its initial course, it carries C1 fibers which leave in a branch to take part in the formation of ansa cervicalis (a loop of nerves supplying neck muscles)

– Supplies motor innervation to all of the muscles of the tongue Except the palatoglossus (which is supplied by the vagus).

– Carries proprioceptive afferents from the tongue muscles.

Function: Controls the movements and shape of the tongue

during speech and swallowing

Distribution:

• Lesion of the nerve results into:– Loss of tongue movements– Difficulty in chewing and speech– The tongue paralyses,

atrophies, becomes shrunken and furrowed on the affected side (LMN paralysis)

– On protrusion, tongue deviates to the affected side

• If both nerves are damaged, person can’t protrude tongue

Normal

LESION