Cranial Nerves VII - XII

The vestibulocochlear nerve originates from the pons-medulla junction in the brainstem.
It passes through the internal acoustic meatus (IAM) in the temporal bone, traveling with the facial nerve (CN VII) and the labyrinthine artery.
Within the IAM, it divides into the vestibular and cochlear branches.
Arises from the spiral ganglion in the cochlea.
Auditory signals travel through the lateral lemniscus to the inferior colliculus, then to the medial geniculate nucleus (MGN) of the thalamus, and finally reach the primary auditory cortex (temporal lobe, Brodmann area 41 & 42).

Arises from Scarpa’s ganglion (vestibular ganglion) in the internal acoustic meatus.
Vestibular apparatus:
- Superior branch: Utricle, anterior & lateral semicircular canals.
- Inferior branch: Saccule & posterior semicircular canal.

The glossopharyngeal nerve originates from the medulla oblongata and has four functional components, each associated with a specific nucleus:
1. Motor (Branchial Efferent) – Nucleus Ambiguus: Supplies the stylopharyngeus muscle, which elevates the pharynx during swallowing and speech.
2. Parasympathetic (Visceral Efferent) – Inferior Salivatory Nucleus: Sends preganglionic fibers to the otic ganglion, which innervates the parotid gland for saliva production.
3. General Sensory (Somatic Afferent) – Spinal Trigeminal Nucleus: Carries sensory input from the posterior third of the tongue, pharynx, middle ear, and external ear.
4. Special Sensory (Taste) & Visceral Sensory (Baroreception) – Nucleus Solitarius
  1. Taste from the posterior third of the tongue.
  2. Baroreceptor (blood pressure) and chemoreceptor ( $O<em>2$ & $CO</em>2$ ) input from the carotid sinus and carotid body.
Functional components:
- GVE: Secretomotor fibers to the parotid gland.
- SVE: Soft palate.
- SVA: Taste and general sensation from posterior 1/3rd of tongue including circumvallate papillae.
- GVA: Carotid sinus and carotid body.

A 55-year-old male presents to the clinic with complaints of difficulty swallowing, loss of taste on the posterior third of his tongue, and diminished sensation in his throat. He also reports occasional sharp, shooting pain in his throat and ear, especially when swallowing or talking. His gag reflex is absent on the right side, and he has mild hoarseness.
The glossopharyngeal nerve (CN IX) is likely affected because it controls sensation in the posterior third of the tongue, oropharynx, tonsils, and middle ear, as well as contributing to the gag reflex and swallowing.
Specific branches involved:
- Lingual Branch → Loss of taste and sensation from the posterior third of the tongue.
- Tonsillar Branch → Loss of sensation in the palatine tonsils.
- Pharyngeal Branches → Impaired swallowing (dysphagia) due to loss of sensory innervation in the oropharynx.
- Carotid Branch → Possible baroreceptor dysfunction (though not reported by the patient).
- Tympanic Nerve (Jacobson’s Nerve) → Pain in the ear due to loss of sensation in the middle ear.

Difficulty of swallowing.
Impairment of taste sensation over the posterior one-third of the tongue, palate, and pharynx.
Absent gag reflex.
Dysfunction of the parotid gland.

Innervation:
1. Pharynx
2. Left Lung
3. Right Lung
4. Heart
5. Stomach
6. Liver
7. Spleen
8. Pancreas
9. Right Kidney
10. Small Intestine
11. Large Intestine
Mixed nerve (motor, sensory, parasympathetic).
Name means wandering (it goes all the way to the abdomen).
Longest and most widely distributed cranial nerve.
Principal role: provide parasympathetic supply to organs throughout the thorax and upper abdomen.
Gives sensory and motor supply to the pharynx and larynx.

Origin: arises from the medulla.
Leaves the skull through the jugular foramen.
Occupies the posterior aspect of the carotid sheath between the internal jugular vein laterally and the internal and common carotid arteries medially.
Two ganglia:
- Superior ganglion in the jugular foramen.
- Inferior ganglion, just below the jugular foramen.
Lies on the prevertebral muscles and fascia.
Enters thorax through its inlet:
- Right Vagus descends in front of the subclavian artery.
- Left Vagus descends between the left common carotid and subclavian arteries.

Meningeal to the dura.
Auricular nerve to the external acoustic meatus and tympanic membrane.
Pharyngeal to muscles and mucous membrane of the pharynx.
To carotid body.
Superior Laryngeal:
- Internal Laryngeal: Supplies the mucous membrane of the larynx as far as the vocal folds.
- External Laryngeal: Supplies the cricothyroid muscle.
Recurrent Laryngeal: Supplies all the muscles of the larynx (except cricothyroid), the mucous membrane below the vocal folds, and the mucous membrane of the upper part of the trachea.
Cardiac.

On the right side, the nerve hooks around the first part of the subclavian artery and then ascends in the groove between the trachea and the esophagus.
On the left side, the nerve hooks around the arch of the aorta and then ascends into the neck between the trachea and the esophagus.
The nerve is closely related to the inferior thyroid artery.
Supplies:
- All the muscles of the larynx, except the cricothyroid m.
- The mucous membrane of the larynx below the vocal cords.
- The mucous membrane of the upper part of the trachea.

Type: Motor.
Has two parts (roots):
- Cranial part carries fibres that originate in the caudal part of nucleus ambiguus.
- Spinal part arises from motor neurones in ventral horn of the spinal gray matter at levels C1-C5 (spinal nucleus).
Foramen of exit from skull: Jugular foramen.
SVE: Muscles of palate, pharynx and larynx (cranial root).
GSE: Sternocleidomastoid and trapezius (spinal root).

Produces atrophy and weakness of trapezius.
Unilateral paralysis of trapezius is evident by inability to elevate & retract the shoulder, difficulty in elevating the arm & Winging of scapula.
Dropping of the shoulder is an obvious sign of injury of the nerve.
The lesion also causes difficulty in swallowing and speech.
Inability to turn the head.

Type: Motor.
Origin: Hypoglossal nucleus of the medulla (in the floor of the 4th ventricle).
The fibers emerge from the anterior surface of the medulla oblongata through the sulcus between the pyramid and the olive.
Foramen of exit from skull: Hypoglossal canal.

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 nerve).
Controls the movements and shape of the tongue during speech and swallowing.
Carries proprioceptive afferents from the tongue muscles.

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