Accessory and Hypoglossal nerves

11th CN: Accessory Nerve Type: Motor (SVE) Origin : 2 roots cranial root: arises from the medulla Spinal 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)

Course The 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.

Course Function: 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

Lesion Lesion results into: Difficulty in swallowing and speech Inability to turn the head Inability to shrug (raise) the shoulder Winging of scapula

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

The hypoglossal nucleus receives corticonuclear fibers from both cerebral hemispheres EXCEPT the region that supplies genioglossus muscle (it receives contralateral supply only) Also receives afferent fibers from nucleus solitarius and trigeminal sensory nucleus.

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

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

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) C1 fibers

Distribution: Function: 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

LESION 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