Introduction

There are 12 pairs of Cranial nerves in human body.

NUCLIE OF THE CRANIAL NERVES

1st & 2nd Cerebral cortex
3rd & 4th Midbrain
5th, 6th, 7th, 8th Pons
9th, 10th, 11th, 12th Medulla Oblongata


PURE SENSORY NERVES

1st Olfactory nerve:
Sense of smell
2nd Optic nerve:
Sense of vision
8th Vestibulocochlear nerve:
Balance & Hearing


PURE MOTOR NERVES

3rd Occulomotor :
It is motor to all the extra ocular muscles of eye except Superior Oblique and Lateral Rectus Muscle. It is also supplying ciliary muscles and sphincter pupillae with parasympathetic fibers.

4th Trochlear :
Motor to Superior oblique

6th Abducent:
Motor to Lateral Rectus

11th Accessory:
Motor to Sternomastoid and Trapezius muscles

12th Hypoglossal:
Motor to muscles of tongue


MIXED MOTOR AND SENSORY NERVES

5th Trigeminal:
Motor to muscles of mastication
Sensory to face, anterior part of head and inside mouth.

7th Facial :
Motor to Muscles of facial expression and Stapedius muscle
Sensory to Part of external ear and taste to anterior two thirds of tongue.



9th Glossopharyngeal :
Motor to Stylopharyngeus
Sensory to Pharynx, Soft palate; Taste to Posterior one third of the tongue.


10th Vagus:
Motor to muscles of Pharynx, soft palate and larynx.

NERVES CARRYING PARASYMPATHETIC FIBERS

3rd Occulomotor :
Ciliary muscles and Sphincter Pupillae

7th Facial:
Lacrimal Gland
Submandibular Gland
Sublingual Gland

9th Glossopharyngeal:
Parotid Gland

10th Vagus:
Thorax & Abdomen

OLFACTORY NERVE

Olfactory nerve or nerve of smell is the first cranial nerve.


ORIGIN

It originates as the central process of olfactory receptor nerve cells in the mucous membrane of upper part of the nose(above the superior concha).

OLFACTORY BULB

Bundles of these nerve fibers pass through openings in the cribriform plate of ethmoid bone and end in the olfactory bulb in the anterior cranial fossa.


OLFACTORY TRACT
Emerging from the posterior end of olfactory bulb is a white band the olfactory tract which passes backward to the olfactory area of cerebral cortex.


PRIMARY OLFACTORY CORTEX

The second order neurons (mitral cells) project centrally together with pyramidal cells of olfactory nucleus down olfactory tracts and stria to Primary olfactory cortex (medial temporal lobe) and ipsilateral amygdaloid body anterior perforated substance and septial area.

The primary olfactory cortex has numerous connections with hypothalamus reticulatr system, limbic lobe.

TESTING THE SENSE OF SMELL

· Check that nasal passages are clear
· Test sense of smell for each nostril separately
· Occlude one nostril by digital pressure
· Ask patient with closed eyes to sniff and identify the substance

INTERPRETATION
ANOSMIA:
It means loss of sense of smell; commonest cause is obstruction of nasal passages. If due to neurological lesion it may be due to
· Head injury
· Tumors of anterior cranial fossa
· Tuberculous meningitis
PAROSMIA:
It is the perversion of smell. Offensive smells are perceived as pleasant and vice versa.
Cause
Psychogenic in origin

HALLUCINATION:
Sometimes occur in temporal lobe palsy.

OPTIC NERVE

It is the 2nd Cranial Nerve.

ORIGIN
The optic nerve arises from cells of the ganglionic layer of retina.
The optic nerve leaves the eye ball in the orbital cavity passes through the optic canal to enter the middle cranial fossa.

OPTIC CHIASMA
It unites with the optic nerve of opposite side to form the optic chiasma. In the optic chiasma the fibers from the medial half of retina cross the midline and enter optic tract of opposite side
Fibers of lateral half pass posteriorly to the same side tract.

Most fibers of optic tract terminate by synapsing with the nerve cells in the lateral Geniculate body (a small projection from posterior thalamus)

A few fibers pass to pretectal nucleus and superior colliculus of midbrain however are concerned with light reflexes.

The axons of nerve cells of lateral geniculate body pass posteriorly as optic radiation and terminate in visual cortex of cerebral hemisphere.

EFFECT OF LESION OF DIFFERENT PARTS OF VISUAL PATHWAY

LESION AT RETINA
Scotoma (small area of blindness)

LESION OF THE OPTIC NERVE
Total loss of vision in one eye; consensual reflex is retained


LESION OF OPTIC CHIASMA
a) Central Lesion
Bitemporal Hemianopia

b) Bilateral peripheral Lesion
Binasal Hemianopia

LESION OF OPTIC TRACT, LATERAL GENICULATE BODY AND OPTIC RADIATION
Homonymous hemianopia on opposite side without macular sparing. Lesions of optic radiation usually produce quadrantic visual defects


LESION OF THE VISUAL CORTEX
Homonomous hemianopia with macular sparing

OCCULOMOTOR NERVE

It is the 3rd Cranial Nerve.

It’s a motor nerve
It supplies the following extrinsic muscles of the orbit
Levator palpebrae superioris
Superior, Medial, Inferior Rectus
Inferior Oblique
Also
Sphincter pupillae and Ciliary muscles with parasympathetic fibers. (Arising from Edinger Westphal nucleus)


FUNCTIONAL COMPONENTS

Somatic Efferent for the movements of eye ball. Fibers arise from the Occulomotor nucleus which is situated in ventromedial part of central grey matter of the midbrain at the level of superior colliculus.

General Visceral Efferent (parasympathetic), for contraction of the pupil and accommodation. Fibers arise from the Edinger Westphal nucleus (that lies in mid brain close to Occulomotor nucleus) passes through the Occulomotor nerve to the ciliary ganglion to supply Sphincter pupillae and ciliary muscle.

General Somatic Afferent for the proprioceptive impulses from the muscles of the eyeball. These impulses are relayed to the mesencephalic nucleus of trigeminal nerve.



ORIGIN
It emerges from the anterior aspect of midbrain medial to the cerebral peduncle, passes close to and between posterior cerebral and superior cerebellar arteries, runs forward in the lateral wall of cavernous sinus and divide into the superior and inferior ramus.
It enters the orbit through the superior orbital fissure.

Superior Ramus
Supply superior rectus muscle, then it pierces and supplies overhanging levator palpebrae superioris.

Inferior Ramus
It enters the orbit, gives off branches to inferior rectus, medial rectus, and inferior oblique.
Nerve to inferior oblique gives off a branch that passes to the ciliary ganglion and carries parasympathetic fibers to sphincter pupillae and ciliary muscles



PARALYSIS

COMPLETE PARALYSIS
In complete and total paralysis of 3rd nerve eye cannot move upward, downward or inward..It results in ptosis (i.e. drooping of the upper eyelid), lateral squint, dilation of the pupil; loss of accommodation; slight proptosis (i.e. forward projection of the eye); diplopia (double vision)

External Strabismus or Lateral Squint
At rest eye looks laterally because of activity of lateral rectus and downwards because of superior oblique.

SUPRANUCLEAR PARALYSIS OF 3rd NERVE
It causes loss of conjugate movement of eyes

WEBER’S SYNDROME
A midbrain lesion causing contra lateral hemiplagia and ipsilateral paralysis of 3rd nerve is known as Weber’s Syndrome.

SQUINT OR STRABISMUS
It may be concomitant or paralytic.
Concomitant Squint
Concomitant squint is congenital; there is no limitation of movement or no diplopia.
Paralytic Squint
In paralytic squint movement of eye ball is limited, diplopia and vertigo are present. The head is turned in the direction of function of paralyzed muscle. There is false orientation of field of vision.

DIPLOPIA
Patient sees double

PTOSIS
Drooping of upper eyelid due to paralysis of levator palpebrae superioris.

LOSS OF ACCOMODATION
Pupil is widely dilated and non reactive to light because of paralysis of sphincter pupillae and unopposed action of dilator pupillae (supplied by Sympathetic)

CILIARY GANGLION
· It is a peripheral parasympathetic ganglion placed in the course of occulomotor nerve.
· It lies near the apex of the orbit between optic nerve and lateral rectus.
· It has motor, sensory and sympathetic roots

MOTOR ROOT

It arises from nerve to inferior oblique, contains preganglionic fibers that begin in Edenger Westphal nucleus.
The fibers relay in ganglion, pass through short ciliary nerves and supply sphincter pupillae and ciliaris muscle .

SENSORY ROOT
It comes from the nasociliary nerve contains sensory fibers from eyeball.
The fibers do not relay in the ganglion.

SYMPATHETIC ROOT
It arises from the internal carotid plexus, contains post ganglionic fibers arising in the superior cervical sympathetic ganglion. The fibers do not relay in the ciliary ganglion. They pass out of the ganglion in short ciliary nerves and supply the blood vessels of the eye ball. They may also supply dilater pupallae.

BRANCHES

Ganglion gives 8 – 10 short Ciliary nerves that divide to 15 – 20 branches. They pierce sclera around the entrance of optic nerve; contain fibers from all the three roots of the ganglion.

TROCHLEAR NERVE & ABDUCENT NERVE

TROCHLEAR NERVE

It is a motor nerve
It is the most slender of the cranial nerves
It supplies Superior Oblique Muscle in the orbit

FUNCTIONAL COMPONENTS

Somatic Efferent for movement of the eye ball.

General Somatic Afferent for Proprioceptive impulses from superior oblique muscle. These impulses are relayed to the mesencephalic nucleus of the trigeminal nerve.

ORIGIN
It emerges from posterior surface of the midbrain just below the inferior colliculi, then curves forward around lateral side of cerebral peduncle, runs forward in the lateral wall of cavernous sinus slightly below the occulomotor nerve. It enters the orbit through superior orbital fissure, runs forward and medially across the origin of levator palpebrae superioris and enter the superior oblique muscle.


PARALYSIS
In case of paralysis of the nerve there double vision on looking straight down. This is because the superior oblique is paralyzed and eye turns medially as well as downwards. Vision is single so long as the eye looks above the horizontal plane.

The patient will adopt a compensatory head tilt.

Isolated nerve lesions are not common.

ABDUCENT NERVE

It’s a small motor nerve that supplies the lateral rectus of eye ball.

FUNCTIONAL COMPONENTS

Somatic Efferent for lateral movements of the eye ball.

General Somatic Afferent for Proprioceptive impulses from the lateral rectus muscle. These impulses reach the mesencephalic nucleus of trigeminal nerve.

ORIGIN:

It emerges from the anterior surface of brain between lower border of pons and medulla oblongata. It lies first in the posterior cranial fossa then turns sharply forward crossing superior border of petrous part of temporal bone; having entered the cavernous sinus it runs forward with Internal Carotid Artery and enters the orbital cavity through superior orbital fissure. It runs forward and supplies the Lateral Rectus.

PARALYSIS
Isolated lesions are common.
In case of paralysis of this nerve eye ball cannot be turned laterally when looking straight ahead the lateral rectus is paralyzed and unopposed medial rectus pulls the eye ball medially causing INTERNAL STRABISMUS or MEDIAL SQUINT or CONVERGENT STRABISMUS

TRIGEMINAL NERVE

It is the largest Cranial nerve, 5th in order.

It contains both Sensory & Motor fibers

Sensory fibers to Skin of
· Scalp
· Face
· Mouth
· Teeth
· Nasal Cavity
· Para nasal Sinuses

Motor fibers to
· Muscles of Mastication
· Tensor TympaniTensor Veli palatine

FUNCTIONAL COMPONENTS:

General Somatic Afferent Nuclei:

· Main sensory nucleus of the trigeminal nerve lies in the upper part of the pons.
· The Spinal nucleus of trigeminal nerve descends from the main nucleus into the medulla. It reaches the upper two segments of the spinal cord.
· The mesencephalic nucleus of the trigeminal nerve extends upwards from the main sensory nucleus into the midbrain.

These nuclei receive the following fibers
· Exteroceptive sensations (Touch, pain, temperature) from the skin of face through the trigeminal nerve.
· Proprioceptive sensations from muscles of mastication reach the mesencephalic nucleus through the trigeminal nerve.

Special Visceral Efferent:

· Motor nucleus of the trigeminal nerve lies in the upper part of pons. It supplies the muscles of mastication through the mandibular nerve.

ORIGIN:
It emerges from anterior surface of pons by a large sensory and a small motor root. (Motor root medial to sensory root)

Nerve passes out of posterior cranial fossa below the superior petorsal sinus and carries with it a pouch derived from meningeal layer of dura matter.
On reaching the apex of petrous part of temporal bone in the Middle Cranial Fossa the large Sensory root expands to form trigeminal (Gasserian) ganglion.
Ganglion lies in the pouch of the dura matter called Trigeminal Cave.
The motor root lies below the ganglion and is completely separate from it.

Anterior border of the ganglion gives rise to
OPHTHALMIC, MAXILLARY, MANDIBULAR NERVES

OPHTHALMIC NERVE
· Purely Sensory
· Smallest division of trigeminal nerve
· Runs forward in the lateral wall of Cavernous Sinus below the Occulomotor and Trochlear nerve
· Divides into 3 branches :
Lacrimal, Frontal and Nasociliary
They enter the orbital cavity through the Superior Orbital Fissure.

LACRIMAL NERVE:
ORIGIN:
Arise in the lateral wall of Cavernous Sinus passes through Superior Orbital Fissure to enter the orbit moves on the lateral wall along the upper border of lateral rectus. Here it is joined by branch of zygomaticotemporal nerve (carries parasympathetic secretomotor fibers from Greater Petorsal nerve which is branch of facial nerve ) that later leaves it The nerve supplies Lacrimal gland. (Its own fibers to the gland are sensory)
It ends by supplying skin & Conjunctiva of lateral part of upper eyelid.

FRONTAL NERVE:
Arise in the lateral wall of Cavernous Sinus passes through Superior Orbital fissure to enter the orbit. In the orbit it passes on the Superior surface of levator palpebrae superioris (between muscle and the roof ). It divides in to two branches
1) Supraorbital
2) Supratrochlear


Supraorbital Nerve:
· Large
· Passes through supraorbital notch or foramen
· Supplies
i. Skin of forehead lateral to area by Supratrochlear
ii. Mucous membrane of frontal sinus
iii. Conjuctiva
iv. Skin of Central part of upper eyelid.

Supratrochlear Nerve:
· Passes above pulley for Superior Oblique
· Wind around the upper margin of orbital cavity
· Supply
i. Skin of forehead above root of nose
ii. Skin & Conjuctiva of upper eyelid (medial part)


NASOCILIARY NERVE

Arise in the lateral wall of Cavernous Sinus passes through the Superior Orbital Fissure above the ophthalmic artery and optic nerve to the medial wall of orbital cavity along the upper margin of medial rectus, ends at the anterior Ethmoidal foramen by dividing into
Infratrochlear nerve
Anterior Ethmoidal nerve

BRANCHES

Communicating Branch to Ciliary Ganglion:

Sensory fibers from the eye ball pass to Ciliary ganglion via short Ciliary nerves without interruption and join the Nasociliary by means of communicating branch.

Long Ciliary Nerve:
· Two or three in number
· Arise from Nasociliary nerve as it crosses the optic nerve
· It contains sympathetic fibers for dilator pupale muscle
· It passes forward with Short Ciliary Nerve pierces the sclera CLOSE TO OPTIC and continues forward between sclera and choroids to reach the Iris

Posterior Ethmoidal Nerve:
It passes through the posterior Ethmoidal foramen to supply the Ethmoidal and Sphenoidal air sinuses

Infratrochlear Nerve:
It passes below the pulley and supply the Conjuctiva and skin of medial part of upper eyelid and the adjacent part of nose

Anterior Ethmoidal Nerve:
It passes through anterior Ethmoidal foramen to anterior cranial fossa at the upper surface of cribriform plate and then through slit like opening on side of crista gali pass to the nasal cavity gives two Internal nasal branches MEDIAL & LATERAL that supply area of mucous membrane and then it appears on the face as EXTERNAL NASAL BRANCH at lower border of nasal bone, Supplies skin of nose down as far as the tip.

MAXILLARY NERVE:

· Purely Sensory
· It runs forward along the lower part of wall of cavernous sinus
· It leaves the skull through foramen rotundum to enter the pterygopalatine fossa.
· The nerve crosses the fossa and enters the orbit through the inferior orbital fissure. The nerve is now called as Infraorbital nerve.
· It runs forward in the floor of the orbit first in the infraorbital groove and then infraorbital canal.
· Appears on the face through infraorbital foramen.

BRANCHES:

· MENINGEAL BRANCH

Supply dura in the Middle Cranial Fossa

BRANCHING NERVES IN THE PTERYGOPALATINE FOSSA:

· GANGLIONIC BRANCHES

Two short nerves hold up the pterygopalatine ganglion in the pterygopalatine fossa.

They contain sensory fibers that without interruption have passed through the ganglion from the nose, palate and pharynx.

They also contain post ganglionic parasympathetic fibers that are going to the lacrimal gland.

· POSTERIOR SUPERIOR ALVEOLAR NERVE:

Arise in the pterygopalatine fossa pass down on the back of maxilla and pierce its posterior surface. Supply
Maxillary Sinus
Upper Molar Teeth
Adjoining parts of gum and cheek.

· ZYGOMATIC NERVE
Arise in pterygopalatine ganglion and enter the orbit through the inferior orbital fissure, ascends on the lateral wall of orbit give two branches that supply skin of face.
i. Zygomaticofacial
It passes on the face through a small foramen on lateral side of zygomatic bone.
Supply the Skin over the prominence of cheek.
ii. Zygomaticotemporal
Emerge on the temporal fossa through a small foramen on the posterior surface of zygomatic bone
Supply skin over temple.

· INFRAORBITAL NERVE

Branches:
i. Middle Superior Alveolar Nerve
Arise from the nerve in the infraorbital groove, descend in the lateral wall of maxillary sinus.
Supply upper molar and adjoining parts of gums & cheek.
ii. Anterior Superior Alveolar Nerve
Arise in the infraorbital canal, descends in anterior wall of maxillary sinus.
Supply Upper Canine & Incisor
Small terminal branch supplies Lateral Wall & Floor of Nose.


TERMINAL BRANCHES

· PALPEBRAL: Skin of lower eyelid
· NASAL: Side of nose
· LABIAL: Mucous membrane of upper lip

Also large area of skin of face.


PTERYGOPALATINE GANGLION

It is the largest parasympathetic peripheral ganglion.

THE MOTOR OR PARASYMPATHETIC ROOT

Preganglionic secretormotor fibers arise in lacrimal nucleus of facial nerve then in its greater petorsal branch & then nerve of pterygoid canal that enters the posterior surface of ganglion.

Postganglionic fibers are scretromotor to
Lacrimal gland
Mucous glands of nose
Paranasal sinuses
Palate
Nasophyrnx
Postganglionic fibers reach maxillary nerve by one of its ganglionic branches, run in zygomaticotemporal and then to lacrimal.

Others in palatine nerve & nasal nerve to palatine and nasal glands.


SYMPATHETIC ROOT

Sympathetic root is derived from nerve on pterygoid canal.

Postganglionic fibers in superior cervical sympathetic ganglion that pass through the internal carotid plexus & deep petorsal nerve & nerve of pterygoid canal.
They pass through the ganglion without rely and supply
Mucous membrane of nose
Paranasal Sinus
Palate
Nasopharynx

SENSORY ROOT
It is from maxillary nerve without relay.


Branches

ORBITAL BRANCHES
They pass through Inferior Orbital fissure and supply Periosteum of the Orbit and Orbitalis muscle. They are actually the branches of maxillary and carry parasympathetic and sympathetic fibers from the ganglion.

PALATINE BRANCHES
Greater and lesser palatine nerve supply mucous membrane of palate, tonsil and nasal cavity

NASAL BRANCHES
Enter through sphenopalatine foramen

Lateral posterior superior nasal nerve
Medial posterior superior nasal nerve

Nasopalatine largest descending up to anterior part of hard palate through incisive foramen.

PHYRNGEAL BRANCH
It supplies mucous membrane of roof of nasal part of phyrnx.

MANDIBULAR NERVE

· Motor & Sensory nerve
· Largest division of Trigeminal Nerve
· Large sensory nerve leaves the lateral part of trigeminal ganglion, pass almost at once through Foramen Ovale
· Small motor root passes beneath the ganglion
· Immediately after emerging motor root joins sensory root
· The Mandibular nerve now descends & divides into
Ø Small anterior division
Ø Large posterior division


BRANCHES
FROM MAIN TRUNK

· MENINGEAL BRANCH
It enters the skull through foramen ovale and supply meningies in Middle Cranial Fossa.

· NERVE TO MEDIAL PTERYGOID
It’s a small branch that supplies to pterygoid muscle.
Two branches pass to otic ganglion without interruption to supply Tensor tympani & Tensor veli palatine.


FROM ANTERIIOR DIVISION
Anterior division gives four branches including
Three Motor Branches
One Sensory Branch
They are described as follows
· MASSETERIC BRANCH:
It runs laterally to supply the massetor muscle.

·TWO DEEP TEMPORAL BRANCHES:
They run upward and enter deep surface of
Temporalis.

·NERVE TO LATERAL PTERYGOID
It enters deep surface of the muscle and supplies it.

·BUCCAL NERVE
It is the sensory nerve. It emerges on the cheek from the anterior border of masseter.
It supplies
Skin over cheek
The mucous membrane lining the cheek.
Buccal nerve does not supply the buccinator.

FROM POSTERIOR DIVISION
· Two Sensory
· One containing sensory as well as motor fibers (The Inferior alveolar nerve.


· AURICULOTEMPORAL NERVE:
Two roots embrace the Middle Meningeal artery, run backward and ascend behind TMJ in accompany with superficial temporal vessels, receive postganglionic parasympathetic secretormotor fibers from otic ganglion and convey to parotid gland; in front of auricle supply skin of
Auricle
External auditary meatus
Tympanic Membrane
Parotid gland (sensory)
TMJ
Skin of Scalp

· LINGUAL NERVE
It is sensory to anterior 2/3rd of tongue and floor of mouth.
It runs down anterior to Inferior alveolar nerve passes forward and medially beneath lower border of superior constrictor muscle, lateral to the lower third molar runs forward on the lateral surface of hyoglossus in submandibular region. At lower border of lateral pterygoid it is joined by Chorda tympani and also by a branch from Inferior alveolar nerve/


· INFERIOR ALVEOLAR NERVE

It has motor and sensory nerve fibers.
It descends on the lateral surface of sphenomandibular ligament, enters the mandibular canal through the mandibular foramen runs forward below the teeth, emerges through the mental foramen.
Mental nerve supplies lower lip and chin

Branches

Mylohyoid nerve
It is branch of Inferior alveolar nerve.
It arises just above mandibular foramen, runs forward on the medial surface of body of mandible below the Mylohyoid line superficial to mylohyoid muscle.
It supplies Mylohyoid muscle & anterior belly of digastric muscle.

Communicating Branch To Lingual Nerve.

OTIC GANGLION:
The otic ganglion is a small parasympathetic ganglion that is functionally associated with the Glossopharyngeal nerve. It is situated just below foramen ovale in the infratemporal fossa and is medial to the mandibular nerve. The ganglion adheres to the nerve to medial pterygoid, but functionally it is completely separate from it

The Motor or Parasympathetic Root
The preganglionic parasympathetic fibers originate in the inferior salivatory nucleus of the Glossopharyngeal nerve. They leave the Glossopharyngeal nerve by its tympanic branch and then pass via the tympanic plexus and the lesser petorsal nerve to the otic ganglion. Here the fibers synapse and the postganglionic fibers leave the ganglion and join the auriculotemporal nerve. They are conveyed by this nerve to the parotid gland and serve as secretomotor fibers.

The Sympathetic Root
It is derived from the plexus on the middle Meningeal artery. It contains post ganglionic fibers arising in the superior cervical sympathetic ganglion. The fibers pass through the ganglion without relay and reach the parotid gland via auriculotemporal nerve. They are vasomotor in function.
The Sensory Root
It comes from the auriculotemporal nerve and is sensory to the parotid gland.

CLINICAL CORELATES

· Trigeminal Neuralgia

Episodic facial pain is the most common disease of the 5th nerve. In common idiopathic variety, there are no signs. If signs are present, it is likely that there is structural lesion e.g. multiple sclerosis, tumor involving the 5th nerve. Herpes zoster commonly affects the ophthalmic division and postherpatic neuralgia may occur. There will be a scar and sensory loss over the forehead. The ophthalmic branch is not involved in idiopathic trigeminal neuralgia.

· Fifth nerve is involved in cerebello-pontine angle tumors along with 7th and 8th cranial nerves and cerebellum.
· Ophthalmic division is involved in the lesions of cavernous sinus along with 3rd , 4th and 6th cranial nerves.
· Bilateral motor paralysis may occur in bulbar palsy (there is wasting of muscles of mastication and fasciculations are present) and pseudobulbar palsy (jaw jerk is brisk).

FACIAL NERVE:

It is the 7th Cranial Nerve.
It has a medial motor root and a lateral sensory root, the nervous intermedius.

FUNCTIONAL COMPONENTS

Special Visceral (brachial) Efferent

· Nucleus of the facial nerve lies in the lower part of Pons supplies various muscles innervated by facial nerve. The part of nucleus that supplies muscles of the upper part of the face receives corticonuclear fibers from the motor cortex of both the right and left sides. In contrast the part of nucleus that supplies muscles of the lower part of the face receive corticonuclear fibers only from the opposite side of cerebral hemisphere.

General Visceral efferent (parasympathetic)

· Superior salivatory nucleus lies in lower part of pons. It sends fibers through the facial nerve and its chorda tympani branch to the Submandibular ganglion for the supply of Submandibular and sublingual salivary glands.
· Lacrimatory nucleus lies near the salivatory nuclei gives fibers that pass through facial nerve and its branches relay in the pterygopalatine ganglion and supply the lacrimal gland.

Special Visceral afferent

· Nucleus of tractus solitarius (gustatory) carries taste sensation from anterior 2/3rd of the tongue and from the palate.

General Somatic Afferent fibers

They probably innervate a part of skin over the ear. The nerve does not give any direct branches to the ear but some fibers may reach it through communication with vagus nerve. Proprioceptive impulses from muscles of the face are believed to travel through branches of trigeminal nerve to reach the mesencephalic nucleus of the nerve

MOTOR ROOT
Supplies Muscles of face, scalp, auricle, buccinator, platysma, Stapedius, stylohyoid & posterior belly of diagastric

SENSORY ROOT
It carries the taste fibers from anterior two thirds of tongue, floor of mouth and palate.
It also conveys parasympathetic secretromotor fibers to Submandibular and sublingual salivary glands, lacrimal gland and glands of nose and palate.

ORIGIN
The two roots of facial nerve emerge from the anterior surface of brain between the pons and medulla oblongata. They pass laterally forward in the posterior cranial fossa with the Vestibulocochlear nerve to the opening of internal acoustic meatus. At the bottom of the meatus the nerve enters the facial canal runs laterally above the vestibule of labyrinth until it reaches the medial wall of tympanic cavity. (Middle ear)Here the nerve expands to form sensory Geniculate ganglion. The nerve then bends sharply backwards above the promontory, on arriving at the posterior wall of the middle ear, it curves downward. On the medial side of the aditus of the mastoid antrum. It descends in the posterior wall of middle ear, behind the pyramid and finally emerges through the stylomastoid foramen.

IMPORTANT BRANCHES OF INTRAPETROUS PART OF FACIAL NERVE:

GREATER PETORSAL NERVE

It arises from facial nerve at the geniculate ganglion. It contains preganglionic parasympathetic fibers that pass to the pterygopalatine ganglion and are there relayed through the zygomatic & lacrimal gland; other post ganglionic fibers pass through nasal & palatine nerves to the glands of mucous membrane of nose and palate. It also contains taste fibers from the nose and palate. It also contains many taste fibers from the mucous membrane of the palate.

The nerve emerges on the superior surface of petrous part of temporal bone and runs forward in a groove. It runs below the trigeminal ganglion and enters the foramen lacerum.

It is here joined by the deep petorsal nerve from sympathetic plexus on the Internal Carotid Artery and forms nerve of pterygoid canal. This passes forward and enters the pterygopalatine fossa where it ends in the pterygopalatine ganglion.

THE NERVE TO STAPEDIUS
It arises from the facial nerve as it descends in the facial canal behind the pyramid. It supplies the muscle with in the pyramid.

CHORDA TYMPANI
It arises from the facial nerve above the stylomastoid foramen. It enters the middle ear close to posterior border of tympanic membrane. It then runs forward over the tympanic membrane and crosses the root of the handle of the malleus. It lies in the interval between the mucous membrane and the fibrous layer of tympanic membrane.
Taste fibers
The nerve leaves the middle ear through petrotympanic fissure and enters infratemporal fossa where it joins the lingual nerve. Chorda tympani contain many taste fibers from the mucous membrane covering the anterior two thirds of tongue. (not the vallate papillae)
Taste fibers are the peripheral processes of the cells in the Geniculate ganglion.
Parasympathetic secretomotor fibers
The nerve also contains pre ganglionic parasympathetic secretomotor fibers that reach the Submandibular ganglion and are there relayed to the Submandibular and sublingual salivary gland.
As the nerve runs forward in the substance of parotid gland. It divides into 5 terminal branches

BRANCHES AT ITS EXIT FROM THE STYLOMASTOID FORAMEN

THE POSTERIOR AURICULAR NERVE:
It arises just below the stylomastoid foramen. It ascends between the mastoid process and the external acoustic meatus and supplies the
· Auricularis posterior
· The Occipitalis
· Intrinsic muscles on the back of the auricle

THE DIAGASTRIC BRANCH
It arises close to the previous nerve. It is short and supplies the posterior belly of diagastric muscle.

THE STYLOHYOID BRANCH
It may arise with the diagastric branch. It is long and supplies the stylohyoid muscle.

TERMINAL BRANCHES WITH IN THE PAROTID GLAND

THE TEMPORAL BRANCH
It emerges from the upper border of the gland and supplies
The anterior and superior auricular muscles
The frontal belly of occipitofrontalis
The orbicularis occuli
The corrugator supercilli

THE ZYGOMATIC BRANCH
It emerges from the anterior border of the gland and supplies the orbicularis occuli

THE BUCCAL BRANCH
It emerges from the anterior border of gland below the parotid duct and supplies the buccinator muscle and muscles of upper lip and nostril.

THE MANDIBULAR BRANCH
It emerges from the anterior border of the gland and supplies the muscles of lower lip.

THE CERVICAL BRANCH
It emerges from the lower border of the gland and passes forward in the neck below the mandible to supply depressor anguli oris muscle.

The facial nerve is the nerve of second arch and supplies all muscles of facial expression. It does not supply skin but its branches communicate with branches of trigeminal nerve.

EXAMINATION
Routinely only the motor function of the 7th nerve is tested.

MOTOR FUNCTION
· When 7th nerve is paralyzed, the patient may complain of inability to close the eyelid, collection of food in the mouth and dribbling of saliva on the affected side of the mouth and deviation of the angle of the mouth towards the opposite side.


On inspection, palpebral fissure may be wide and nasolabial fold may be flattened on theparalyzed side.
· Ask the patient to frown or wrinkle the forehead.
There would be no wrinkling on the affected side.

· Ask the patient to close the eyes; the affected side will remain open and there will be brisk upward rolling of the eye ball (Bell’s phenomenon). To test the power of orbicularis occuli ask the patient to close the eyes as strongly as possible while you try to open the upper eyelids. The affected side will be weak.
· Ask the patient to inflate the cheek and tap on both sides with finger. The weak side will be deflated easily.
· Ask the patient to show the teeth. The angle of mouth will be deviated towards the healthy side.
· The patient cannot whistle as air escapes from the paralyzed side.
· The patient will complain of unusually loud sounds on paralyzed if nerve to Stapedius is involved.

TASTE
Test taste of the anterior two third of the tongue by following technique.
· Get solutions of four common tastes- sweet, salt, sour and bitter.
· Instruct the patient to identify the taste, either by writing or raising fingers, e.g. one finger if taste is sweet, two fingers if salty and so on.
· Ask the patient to protrude the tongue. Hold it with a gauze, dry it and test each side separately.
· Put a drop of each solution one by one and ask for response.
· Test bitter at the end.

SECRETOMOTOR FUNCTION
Lacrimation and salivation can be tested by various tests but it is not done routinely.

INTERPRETATION

The facial nerve is the most commonly affected cranial nerve by lesion of both upper motor neuron and lower motor neuron.

UPPER MOTOR NEURON LESION
Manifestations are on the opposite side. Upper half of the face (wrinkling of the forehead, closure of the eyelid) is less severely affected because the part of the facial nerve nucleus which supplies muscles of the upper half of the face is connected with both cerebral hemispheres; the part of the facial nerve nucleus which supplies muscles of lower half of the face is connected only with the contra lateral cerebral hemispheres. Smiling and other emotional movements are usually preserved in UMN lesion because there is a separate path for these movements.

LOWER MOTOR NEURON LESION
Whole of the ipsilateral half of the face is affected. Bell’s palsy is the most common cause of isolated lower motor neuron facial palsy. Etiology is unknown. The lesion is in the facial canal.

As facial nerve has a long route and gives off branches at various sites, the site of lesion can be localized with considerable precision.

· If the lesion is after the nerve exits from the skull, there is only weakness of the facial muscles.
· If the lesion is in the facial canal, between the chorda tympani and branch to Stapedius, in addition to motor weakness, there is loss of taste as well.
· If the lesion is between the branch to Stapedius and internal auditory meatus, there is hyperacusis on the affected side, in addition to motor weakness and loss of taste.
· Geniculate ganglion can be affected by herpes zoster(Ramsay Hunt syndrome). In addition to other features of facial palsy, there are vesicles in that part of external auditory meatus which gets sensory supply from the facial nerve.
· If the lesion is in the internal auditory meatus, in addition to the features of facial nerve palsy, 8th nerve is also paralyzed.
· If the lesion is in the cerebello-pontine angle, there are signs of cerebellar dysfunction and 5th, 6th, 7th, and 8th nerves are also involved.
· In pontine lesion, along with the facial nerve, the 6th nerve is also paralyzed and there is upper motor neuron hemiplagia on the opposite side.

VESTIBULOCOCHLEAR NERVE

This nerve consist of two sets of sensory fibers; Vestibular and Cochlear

The vestibular fiber which are concerned with equilibrium, represent the central processes of nerve cells of the vestibular ganglion. This is located in the outer part of the internal acoustic meatus.

The cochlear fibers which are concerned with hearing represent the central process of nerve cells of the spiral ganglion of the cochlea.

FUNCTIONAL COMPONENTS

Special Somatic Afferent Nuclei

The Cochlear nuclei (dorsal and ventral) that receive impulses of hearing through cochlear nerve.

The Vestibular nuclei (superior, inferior, medial and lateral) that receive fibers from the semicircular canals, the utricle, and the saccule through the vestibular nerves.

ORIGIN
The two parts of the nerve leave the anterior surface of the brain between the lower border of the pons and the medulla oblongata. They cross the posterior cranial fossa and enter the internal acoustic meatus with the facial nerve.

On reaching the bottom of the internal acoustic meatus the nerve divides into vestibular and cochlear portions.

VESTIBULAR GANGLION
The vestibular nerve is expanded to form the vestibular ganglion. The branch of the nerve then pierces the internal acoustic meatus and gain entrance to the membranous labyrinth where they supply the utricle, the saccule and the ampullae of the semicircular ducts

SPIRAL GANGLION
The cochlear nerve divides into branch which enters the foramina at the base of the modiolus. The sensory ganglion of this takes the form of an elongated spiral ganglion that is lodged in a canal winding around the modiolus in the base of the spiral lamina.
The peripheral branch of this nerve passes from the ganglion to the spiral organ of corti.

Auditory Receptors
The auditory receptors are the hair cells of the organ of corti, situated in the cochlear duct of the internal ear. They are innervated by the peripheral processes of bipolar neurons of the spiral ganglion.


CLINICAL CORELATES

Lesions of this nerve cause hearing defects. Hearing power can be tested by means of a watch, one ear at a time. If there is any impairment of hearing one must determine whether it is really due to disease of the nerve (nerve deafness), or merely due to disease of the middle ear (conductive deafness). This is done by Rinne’s test and Weber’s test.

Principle of the Tests
The tests are based on the principle that normally aerial conduction of sound is better than bony conduction. In conductive deafness bony conduction becomes better than aerial conduction. In nerve deafness both types of conduction are lost.

Rinne’s test
In Rinne’s test a vibrating tuning fork is held opposite the ear and then placed on the mastoid process. The patient is asked to compare the loudness of the fork in the two instances.

Weber’s test
In Weber’s test the vibrating tuning fork is placed on the centre of the forehead. The fork is heard better on the side of middle ear disease than on the normal side.

THE GLOSSOPHARYNGEAL NERVE

It is the 9th Cranial Nerve.

It is a motor and sensory nerve.
Motor fibers supplies Stylopharyngeus
Parasympathetic secretromotor supply to parotid salivary gland.
Sensory fibers including the taste fibers pass to the posterior third of the tongue and the pharynx.

FUNCTIONAL COMPONENTS

Special Visceral Efferent
Fibers arise in nucleus ambiguus and supply Stylopharyngeus. Nucleus ambiguus lies in the medulla.

General Visceral Efferent
Fibers arise in the inferior salivatory nucleus and travel to the Otic ganglion. Postganglionic fibers arising in the ganglion supply the parotid gland.

General Visceral Afferent
Fibers are peripheral processes of cells in the inferior ganglion of the nerve. They carry general sensations (touch, temperature, pain) from the pharynx and the posterior part of the tongue to the ganglion. The central processes convey these sensations to the nucleus of solitary tract.

Special Visceral Afferent
These fibers are also peripheral processes of cells in the inferior ganglion. They carry sensations of taste from the posterior one third of the tongue to the ganglion. The central processes convey these sensations to the nucleus of the solitary tract.

ORIGIN:
It emerges from the anterior surface of upper part of medulla oblongata by three or four rootlets between olive and inferior cerebellar peduncle.
It passes forward and laterally beneath the cerebellum in the posterior cranial fossa and leaves the skull by passing downward through the central part of Jugular foramen.
Superior and inferior sensory ganglia are located on the nerve as it passes through the jugular foramen. It descends in the neck within the carotid sheath. It then winds forward around the stylopharyngeus muscle and passes between superior and middle constrictor muscles.
The lingual branch of nerve enters the submandibular region.

BRANCHES

TYMPANIC BRANCH

It arises from the Glossopharyngeal nerve just below the jugular foramen, passes through the floor of the middle ear and gives off lesser petorsal nerve, lesser petorsal nerve contains secretromotor fibers for parotid gland.
Having entered the skull it leaves through the foramen ovale. The nerve then joins the otic ganglion.

CAROTID BRANCH
It supplies the carotid sinus and carotid body. Carotid body is a chemoreceptor being sensitive to excess carbon dioxide and decreased oxygen.

MUSCULAR BRANCH:
It supplies the stylophyrngeus muscle.

PHARYNGEAL BRANCH:

It unites on the outer surface of middle constrictor muscle with pharyngeal branch of vagus and pharyngeal branch of sympathetic trunk to form the pharyngeal plexus.
By means of these branches the glossophyrngeal nerve gives sensory fibers to the mucous membrane of pharynx, tonsil, and soft palate.

LINGUAL BRANCH

It supplies General sensory and special taste fibers to mucous membrane of posterior third of the tongue and circumvallate papillae region of the anterior of the tongue.
The lingual branch enters the tongue below styloglossus muscle.


EXAMINATION

Most of the functions of the 9th nerve are intermingled with 10th nerve. Taste on the posterior one third of tongue is difficult to test on the bedside.

Sensory Function:

Gag Reflex
Ask the patient to open the mouth and depress the tongue with a spatula. Touch the posterior pharyngeal wall with a stick having cotton wrapped on that end, first on one side of the midline and then the other. There will be contraction and elevation of the pharyngeal wall on that side. The sensory component of this reflex arc is 9th nerve and motor component is 10th nerve.

Palatal Reflex
When soft palate is touched it moves upwards. Each side is tested separately. Pathway is the same as that of gag reflex.

Motor Function:
It cannot be tested independent of 10th nerve.

INTERPRETATION:
Isolated 9th nerve lesion is rare.

VAGUS NERVE

10TH Cranial Nerve
Both sensory & Motor Root

FUNCTIONAL COMPONENTS


Special Visceral Efferent fibers arise in the nucleus ambiguus and supply the muscles of pharynx and larynx.

General Visceral Efferent fibers arise in the dorsal motor nucleus of the vagus. These are pre ganglionic parasympathetic fibers. They are distributed to the abdominal and thoracic viscera.

General Visceral Afferent fibers are peripheral processes of the cells located in the inferior ganglion of the nerve. They bring sensations from the pharynx, larynx, trachea, esophagus, and from abdominal and thoracic viscera. These are conveyed by central processes of ganglionic cells to the nucleus of solitary tract

Special Visceral Afferent fibers are also processes of neurons in the inferior ganglion. They carry sensations of taste from the posterior most part of the tongue and the epiglottis. The central processes of the cells terminate in the upper part of nucleus of solitary tract


General Somatic Afferent Fibers are the peripheral process of neurons in the superior ganglion and are distributed to the skin of the external ear. The central processes of the ganglion cells terminate in relation to the spinal nucleus of the trigeminal nerve.

Origin:

Originates from Medulla Oblongata (ant part) b/w olive and Inferior Cerebellar peduncle.
Attach by 8-10 rootlets.
Leaves the skull through the Jugular foramen (middle part) along with the 9th & 11th CN.
Two Sensory Ganglia; Superior ganglion on the nerve within the Jugular foramen; Inferior ganglion just below the foramen.
Below the Inferior ganglion the cranial part of accessory nerve joins the vagus nerve & is distributed mainly in its pharyngeal & recurrent laryngeal branches.
Vagus nerve passes vertically down within the neck in the carotid sheath b/w IJV & ICA & later b/w IJV & CCA at the Root of the neck; lies anterior to the first part of Subclavian artery.

RIGHT VAGUS
Descends to thorax (Lateral to Brachycephalic artery,lateral to trachea),passes behind root of lung,assists the formation of Pulmonary plexus, leaves plexus moves to posterior surface of esophagus, forms esophageal plexus, through the esophageal opening of the diaphragm moves to posterior surface of the stomach


LEFT VAGUS

Descends to thorax, enters thorax between left Common carotid artery and subclavian artery, cross left side of the aortic arch, turns backward behind root of the lung, assists the formation of pulmonary plexus, leaves the plexus, moves to anterior surface of esophagus forms esophageal plexus, through the esophageal opening of the diaphragm moves to anterior surface of the stomach.

BRANCHES OF VAGUS

MENINGEAL BRANCH

Supply Dura matter in Post Cranial Fossa

AURICULAR BRANCH:
Supply
· Medial Surface of auricle
· Floor of External auditory meatus
· Adjacent part of tympanic membrane.

PHARYNGEAL BRANCH:

Contains motor fibers from Cranial part of accessory nerve .
Passes forward between External Carotid Artery & ICA to reach Pharyngeal wall, joins the branches from Glossopharyngeal nerve and sympathetic trunk to form pharyngeal plexus.

Supply
· All the muscles of pharynx EXCEPT Stylopharyngeus (Glossopharyngeal )
· All muscles of soft palate except Tensor veli Palatini (mandibular div of trigeminal nerve)
·
SUPERIOR LARYNGEAL BRANCH:
Divides into
· External Laryngeal
· Internal Laryngeal

External Laryngeal:
Lies close to Superior Thyroid artery
Supply Cricothyroid muscle

Internal Laryngeal:
Sensory to the mucous membrane of piriform fossa and larynx as far down as the vocal cords

RECURRENT LARYNGEAL NERVE

Right Side:
Hooks around 1st part of Subclavian artery & descends in the groove between trachea & esophagus

Left Side:
Hooks around the arch of aorta and descends between trachea and esophagus. Closely related to Inferior thyroid artery

Motor Supply
All the muscles of larynx except cricothyroid

Sensory supply
Mucous membrane of larynx below the vocal folds and mucous membrane of upper part of trachea

CARDIAC BRANCHES
Arise in the neck descend to thorax end in cardiac plexus

Vagus supply thorax, heart, trachea, bronchi, lungs, esophagus with parasympathetic and sensory nerve fibers


CLINICAL CORRELATES:
The vagus nerve is tested clinically by comparing the palatal arches on the two sides. On the paralyzed side there is no arching and uvula is pulled to the normal side.

DAMAGE TO EXTERNAL LARYNGEAL NERVE
Causes some weakness of phonation due to loss of the tightening effect of the cricothyroid on the vocal cord.

RECURRENT LARYNGEAL NERVE
When both recurrent laryngeal nerves are interrupted the vocal cords lie in cadeveric position and phonation is completely lost. Breathing also becomes difficult through the partially opened glottis.

PARALYSIS OF VAGUS NERVE

It produces nasal regurgitation of swallowed liquids; nasal twang in voice; hoarseness of voice; flattening of the palatal arch; cadeveric position of the vocal cords; dysphasia.

IRRITATION OF THE AURICULAR BRANCH OF VAGUS
In the external ear may reflexly cause persistent cough (ear cough), vomiting or even death due to sudden cardiac inhibition

STIMULATION OF THE AURICULAR BRANCH may reflexly produce increase appetite.


IRRITATION OF THE RECURRENT LARYNGEAL NERVE by enlarged lymph node in children may also produce a persistent cough

ACESSORY NERVE

It is the eleventh cranial nerve.

FUNCTIONAL COMPONENTS

Cranial root is Special visceral efferent. It arises from the lower part of nucleus ambiguous.

Spinal root is also a Special visceral efferent.It arises from a long spinal nucleus situated in lateral part of anterior grey column of the spinal cord extending between segments C1 to C5.

CRANIAL ROOT:

Introduction:
· Small
· It is accessory to the vagus s
· Distributed through branch of vagus to muscles of soft palate, larynx and pharynx.

Origin & Pathway:
It emerges from anterior surface of upper part of medulla oblongata by 4 or 5 rootlets b/w olive & inferior cerebellar peduncle (postrolateral sulcus of medulla), lies below the vagus & runs laterally beneath the cerebellum in the post cranial fossa ; joins the spinal root and passes through the jugular foramen& then the spinal root separates from the cranial root. The cranial root becomes adherent to the inferior ganglion of vagus. Fibers of Cranial root are distributed through the pharyngeal & recurrent laryngeal branch of vagus.

SPINAL ROOT:
It arises from nerve cells in the anterior grey column of upper five segments of cervical part of spinal cord. The nerve fibers emerge on the lateral surface of spinal cord & form a nerve trunk. The nerve ascends on the side of spinal cord & enters the skull from foramen magnum, then turns laterally to join the cranial root, pass through the jugular foramen & then the spinal rootseparates from the cranial root. Spinal root runs backward crossing the IJV reach upper part of sternocliedomastoid enters its deep surface & supplies it; emerges above the middle of post border of sternocliedomastoid crosses posterior triangle of neck on levator scapular to supply trapezius muscle

EXAMINATION OF ACCESSORY NERVE

FOR STERNOMASTOID

Ask the patient to bend the head downwards against resistance:

This is the action of both Sternomastoid

Ask the patient to turn head towards left against resistance to test Right Sternomastoid:
This is because each Sternomastoid pushes head towards opposite side; contracted muscle can also be seen and palpated.

FOR TRAPEZIUS
Inspect the patient from behind.If muscle is paralyzed
Upper part of scapula is displaced away from the spine
Lower part of scapula towards spine.
The whole arm droops and fingers on that side are nearer the ground compared with normal side.

Ask the patient to shrug his shoulders against resistance to test the power of trapezius.

INTERPRETATION
Accessory nerve is paralyzed along with other nerves in bulbar palsy.

Irritation of the nerve by enlarged lymph node may produce torticollis or wry neck.

HYPOGLOSSAL NERVE

· It is the 12th Cranial Nerve
· Motor Nerve
· Supplies all the intrinsic muscles of the tongue, and the

Styloglossus, Geniglossus, Hyoglossus.

FUNCTIONAL COMPONENTS

Somatic Efferent Nuclei

Hypoglossal nucleus lies in the medulla in the floor of the fourth ventricle deep to the hypoglossal triangle.

ORIGIN:
It emerges as a no of rootlets on anterior surface of Medulla Oblongata b/w pyramid & the olive.

COURSE:
Runs laterally in the post cranial fossa & leaves the skull through Hypoglossal Canal.
Now comes in close contact with 9th, 10th, 11th CN, ICA & IJV. Descends b/w ICA & IJV until it reaches the lower border of posterior belly of digastric where it runs forward & medially. It then curves forward crossing the loop of lingual artery just above the tip of greater cornu of hyoid bone. It runs forward lateral to hyoglossus & medial to mylohyoid. (Lies below the deep part of submandibular gland, submandibular duct & lingual nerve. It ends by curving up to the tip of the tongue supplying branches to the muscles.

In the upper part of its course it is joined by small branch from cervical plexus
(C1 & C2)
The branch later leaves the nerve as its
Descending branch
Nerve to thyrhyoid
Nerve to Genihyoid

BRANCHES:

Meningeal Branch:

Supply meningies in posterior cranial fossa.

Descending Branch:

Composed of C1 fibers, descends in front of carotid sheath joined by C2 & C3 from cervical plexus to form a loop called Ansa Cervicalis. Branches from this loop supply omohyoid, Sternohyoid, Sternothyroid

Nerve to Thyrohyoid
It is composed of C 1 fibers. It supplies the thyrohyoid muscle.

Nerve to Genihyoid:
It is composed of C1 fibers. It supplies the genihyoid muscle.

Muscular Branches:
All intrinsic muscles of tongue along with Styloglossus, Hyoglossus, Geniglossus
Except Palatoglossus supplied by pharyngeal plexus.

Communicating Branch:
Hypoglossal nerve communicates with the lingual nerve at the side of the tongue.

TESTING THE INTEGRITY OF HYPOGLOSSAL NERVE

EXAMINATION

Inspection
Ask the patient to open the mouth, inspect the tongue, as it lies on the floor of mouth for its
· Size
· Shape
· Wasting
· Fasciculations

Ask the patient to protrude the tongue
If lesion of the nerve is present tongue deviates towards paralyzed side.
The normal muscle pulls the unaffected side of tongue forward leaving the paralyzed side stationary. The tip of the tongue thus deviates to paralyzed side.

Ask the patient to press tongue against cheek while you resist with finger pressure on outside of cheek.
In unilateral paralysis movements towards normal side will be weak.

INTERPRETATION

In Bilateral Upper Motor Neuron Lesions (e.g. pseudobulbar palsy)
Tongue looks small, conical and is immobile

In Unilateral Upper Motor Neuron Lesion, the tongue may sometimes deviates towards paralyzed side when protruded. There is no wasting. It is usually seen in acute stroke and disappears over days.

In Bilateral Lower Motor Neuron Lesions (e.g. bulbar palsy), there is generalized wasting with Fasciculations.

In Unilateral Lower Motor Neuron Lesions, wasting and Fasciculations are present on the affected side only.

In Bilateral tongue paralysis there is dysarthria