Friday, November 6, 2009

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).

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