Trigeminal nerve (nx power lite) /certified fixed orthodontic courses by Indian dental academy

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The trigeminal nerve is so called because of its three
main divisions i.e. the Ophthalmic, Maxillary & Mandibular
nerves. It is derived from the combination of 2 Latin words,
tres meaning three + geminus meaning twin i.e. three born
together (bilaterally)
 It is the largest of the cranial nerves.
 It is the fifth cranial nerve
 It is a mixed nerve.
 It is sensory to the greater part of the scalp, the teeth,
and the oral and nasal cavities.
 Motor supply is to the MOM. Proprioceptive nerve
fibres arise from the masticatory and extra-ocular
muscles.

THE TRIGEMINAL GANGLION
The trigeminal nerve is continuous with the
ventral surface of the pons near its upper border by a
large sensory and a small motor root. The ganglion
occupies a recess (Trigeminal or Meckel’s cave) in the
dura mater in front of the apex of the petrous temporal
bone. It lies at depth of 4.5 –5 cm from the lateral aspect
of the head near the posterior part of the zygomatic arch.
It is crescentic or semilunar in shape. Medially it
is related to I.C.A & cavernous sinus, inferiorly with the
motor root and the greater petrosal nerve & the apex of
the petrous temporal bone and for.lacerum.
Blood supply to the ganglion is through the
ganglionic branches of the ICA & the accesory
meningeal artery which enters through the for.ovale.

MOTOR ROOT
It arises separately from the sensory root in the motor
nucleus of pons. At the semilunar ganglion it passes
inferolaterally under the ganglion towards for.ovale, through
which it leaves the middle cranial fossa along with the
man.div. After it exits the skull, it unites with the sensory
root and forms a single nerve trunk. It supplies the
following muscles:

1. Muscles of mastication
2. Mylohyoid
3. Ant belly of the diagastric

4. Tensor tympani
5. Tensor veli palatini

SENSORY ROOT
The fibres of the sensory root arise from the cells of the
trigeminal ganglion. The branches of the unipolar cells
of the trigeminal ganglion are divided into central and
peripheral branches. The central branches leave the
concave surface to enter the pons. The peripheral
branches are grouped to form the ophthalmic and
maxillary nerves and sensory part of the mandibular
nerve.


Various nuclei associated with the fifth nerve are situated
within the pons. They are:
1. Motor nucleus

2. Sensory nucleus
3. Mesencephalic nucleus
4. Spinal nucleus
The 3 Main divisions of the trigeminal nerve are
V1 Opthalmic division.
V2 Maxillary division.
V3 Mandibular division.

OPTHALMIC NERVE
 It is the superior division of the V nerve & is the smallest.
 It is wholly sensory.
 It has 3 branches. All 3 of them pass through the sup. orbital
fissure into the orbit. They are;
1.Lacrimal nerve
2.Frontal nerve
3.Nasocilliary nerve
1. Lacrimal nerve: It is the smallest. It supplies the lacrimal
gland & the conjuntiva. It pieces the orbital septum and ends
in the skin of the upper eyelid.

2) Frontal nerve:
It is the largest branch & appears to be the direct
continuation of the ophthalmic division. It enters the orbit
through the SOF divides into 2 branches.
i.

The supra orbital branch: It is larger & more laterally
placed. It supplies the skin of the forehead & scalp as far
back as the vertex. It also supplies the mucous membrane of
the frontal sinus & pericranium

ii. The supra trochlear branch: It is smaller & more medially
placed. It curves upward on the forehead , close to the bone.
It supplies the skin of the upper eyelid & lower part of the
forehead.

3) Nasocilliary nerve: It is intermediate in size & runs more
deeply. Its branches are divided as following;
i.

Branches in the Orbit

ii. Branches in the Nasal cavity

iii. Branches on the face
(I) Branches in the Orbit:
i.

Long root of the cilliary ganglion: It is sensory &
passes through the ganglion without synapsing and
supplies the eyeball.

ii. Long ciliary nerve: Supplies the Iris & Cornea.

iii. Posterior ethmoidal nerve: It enters the post.ethmoidal
canal & supplies to the mucous membrane lining of
the Post. Etmoidal & Sphenoidal paranasal air cells.

iv. Anterior ethmoidal nerve: It supplies to the
Ant.ethmoidal & frontal paranasal air cells. In the upper
part of the nasal cavity, it further divides into:
1) Internal nasal branches: It has
medialseptal branches to the septal membrane.
It also has lateral branches, which supply the
nasal conchae & the ant. nasal wall
2) External nasal branches: supplies the skin on
the tip & ala of the nose.


2) Branches in the nasal cavity:

The branches arising here supply the mucous membrane of
the nasal cavity.
3) Terminal branches on the face:
They supply sensory nerves to the skin of the medial parts
of the both eyelids, the lacrimal sac. They also supply skin
on the bridge of the nose.


MAXILLLARY NERVE
This is the second & intermediate division of the trigeminal
nerve.
It is wholly sensory.

Course: It begins at the middle of the trigeminal ganglion
as a flattened, plexiform band, passes horizontally forwards
along the lateral wall of the cavernous sinus. It leaves the
skull through the foramen rotundum & becomes more
cylindrical & firmer in texture.It crosses the upper part of the
pterygopalatine fossa, inclines laterally on the posterior part
of the orbital process of the maxilla & enters the orbit through
the inferior orbital fissure.It is now termed as the infra
orbital nerve. It passes through the infra orbital groove &
canal in the floor of the orbit & appears on the face through
the infra orbital foramen.

The branches of the maxillary nerve can be divided into the
following 4 groups:

1) In the cranium:

Meningeal

2) In the pterygopalatine fossa: Ganglionic, Zygomatic,
Post.superior alveolar

3) In the infra orbital canal:

Middle sup. alveolar,Anterior
superior/ Greater alveolar

4) On the face:

Palpebral, nasal, superior labial


I. Branch given off on the cranium

1.

Meningeal branch: It is given off near the foramen
rotundum. It supplies the duramater of the anterior &
middle cranial fossae.

II. Branches in the pterygopalatine fossa.
1.

The ganglionic branches: They connect the maxillary
nerve to the pterygopalatine ganglion.They contain
secretomotor fibres to the lacrimal gland. They provide
sensory fibres to the orbital periosteum & mucous
membrane of the nose, palate & pharynx.

2.

The zygomatic nerve: It arises in the pterygopalatine
fosssa from the maxillary nerve.the nerve then enters the
zygomatic bone & then divides into 2 branches. The
Zygomaticofacial nerve perforates the facial surfaces &
supplies the skin www.indiandentalacademy.com bone..
over the zygomatic

The Zygomaticotemporal nerve perforates the temporal
surface of the zygomatic bone , pierces the temporalis
fascia, & supplies the skin over the anterior temporal fossa
region.
3. Posterior superior alveolar nerve: It begins in the
pterygopalatine fossa but divides into 3 branches which
emerge through the pterygomaxillary fissure.2 branches
enter the posterior wall of the maxilla above the tuberosity
& supply the 3 molar teeth(except the mesiobuccal root of
first molar). The third branch pierces the buccinator &
supplies the adjoining part of the gingiva & cheek along the
buccal side of the upper molar teeth.


III. Branches in the Infraorbital canal( Infraorbital nerve)
1.

Middle superior alveolar nerve: It arises from the Infra
orbital nerve & runs downwards & forwards along the
infraorbital groove along the lateral wall of the maxillary
sinus. It divides into branches which supply the maxillary
premolars & mesiobuccal root of the first molar teeth.

2.

Anterior superior alveolar nerve: It also arises in the
infraorbital canal near the mid point. It runs in the anterior
wall of the maxillary antrum. It runs inferiorly & divides
into the branches, which supply the canine & incisors. A
nasal branch from this nerve, given off from the superior
dental plexus supplies the mucous membrane of the anterior
part of the lateral wall & floor of the nasal cavity. It ends in
the nasal septum.

IV. Branches given on the face:
1.

The palpebral branches: They arise deep to the
orbicularis oculi & pierce the muscle, supplying the skin
over the lower eyelid& lateral angle of the eye along with
the Zygomaticofacial & Facial nerves.

2.

The nasal branches: They supply the skin of the nose &
tip of the nasal septum & join the External nasal branch of
the anterior ethmoidal nerve.

3.

The superior labial branches: These are large &
numerous. They supply the skin over the anterior part of
the cheek & upper lip including the mucous membrane &
labial glands. They are joined by the facial nerve & form
the infraorbital plexus.

SphenopalatinePterygopalatine ganglion


It is the largest of the peripheral ganglia.



It is associated with the greater petrosal nerve.
( Functionally it is part of the Facial nerve). It acts as a
relay staion bn the superior salivatory nucleus in the pons
and the lacrimal gland & mucous & serous glands of the
palate, nose & paranasal sinuses.



It lies in the pterygopalatine fossa, suspended from the
maxillary division of the trigeminal nerve by 2 roots just in
front of the opening of the pterygoid canal.Branches arise
from the maxillary nerve through its ganglionic branches.
They do not establish any sympathetic connections with its
cells. The branches are: www.indiandentalacademy.com

The branches of the Pterygopalatine ganglion are:I. Orbital branches:
II.Palatine branches:

1.Anterior/greater palatine
2.Middle palatine
3.Posterior palatine
III.Nasal branches:
1.Posterior superior lateral
2.Nasopalatine/Sphenopalatine
IV.Pharyngeal branch:

1. Orbital branches:
They are made up of afferent fibres & convey sensory
impulses from the periosteum of the orbit. Others
supply the mucous membrane of the Posterior
ethmoidal & sphenoidal air cells.

2. Palatine branches:
They are distributed to the roof of the mouth,
soft palate, tonsil & lining membrane of the nasal
cavity. It gives of three branches. They are:-


Palatine branches:- continued
i.

Greater palatine nerve: it emerges from the foramen medial
to the 3 rd molar, continues forward splitting into number
of branches. It is sensory to the mucosa of the hard palate
& palatal gingiva.

ii. Middle palatine nerve: This nerve emerges from a small
foramen in the medial aspect of the pyramidal part of the
palatine bone. Sensory supply is to the mucous
membrane of the soft palate.
iii. Posterior palatine nerve: It emerges from a foramen slightly
lateral to the median palatine nerve. It contains sensory &
secretomotor fibres to the mucous membrane of the
Tonsillar area.

3. Nasal branches:

i. Posterior superior lateral nerves: they supply they
posterior part of the nasal conchae
ii. Nasopalatine(Sphenopalatine) nerve: It passes
downwards & forwards between the periosteum &mucous
membrane in the region of the vomer, continues
downwards & forwards, reachs the floor of the nasal
cavity.Descends into the incisal canal to appear in the
anterior part of the hard palate & supplies the mucous
membrane of the premaxilla.
4.Pharyngeal branches:
This branch supplies sensory & secretory fibers to the
mucous membrane of the nasopharynx. It arises from
passes through the palatovaginal canal along with the
pharyngeal branch of the maxillary artery.

MANDIBULAR NERVE


It is the third & largest division of the trigeminal
nerve.It is
made up of 2 roots: a large sensory root
which proceeds
from the lateral part of the
trigeminal ganglion & almost
immediately
emerges out through the foramen ovale & a small motor
root which passes below the ganglion, &
unites with
the sensory root just outside the foramen.



Immediately beyond the junction of the 2 roots, the nerve
sends off the meningeal branch & the nerve to the medial
pterygoid. Now the main trunk divides into a small
anterior & a large posterior trunk.



As it descends from the foramen, the mandibular nerve
lies at a distance of 4 cm from the surface & a little in
front of the neckwww.indiandentalacademy.com
of the mandible.

The braches of the Mandibular nerve:-

I. Branches of the undivided nerve.
i.

Meningeal branch/nervus spinosus.

ii.

Nerve to the medial pterygoid

II. Branches of the divided nerve:
(A) Anterior division:

(B) Posterior division:

1.Buccal nerve

1. Auriculotemporal nerve

2.Massetric nerve

2.Lingual nerve

3.Deep temporal nerve

3.Inferior alveolar nerve

4.Nerve to the lateral pterygoid.

BRANCHES OF THE UNDIVIDED NERVE
1.Meningeal nerve:
It enters the skull through the foramen spinosum
along with MMA.
It has anterior & posterior divisions that supply the
dura of the middle & anterior cranial fossae.
2. Nerve to the medial pterygoid:
It is a slender branch that supplies to the deep
surface of the muscle.
It also gives 1-2 filaments to the tensor tympani &
the tensor veli palati muscles.

BRANCHES OF THE DIVIDED NERVE
I. Anterior division
1.The buccal nerve:



It passes between the 2 heads of the lateral pterygoid &
descends beneath or through the temporalis. It emerges
from under cover of the ramus & ant. border of the
masseter & unites with the buccal branches of he facial
nerve.



It supplies the skin over the ant. part of the buccinator
& mucous membrane lining the buccal surface of the
gum.


2.The massetric nerve:

~Passes laterally above the lateral pterygoid in
front of the TMJ & behind the tendon of
temporalis.
~It passes through the mandibular notch to sink
into the masseter muscle.
~It also gives a branch to the TMJ.
3.The deep temporal nerves:

~They are 2 in number.
~They pass above the upper head of the lateral
pterygoid, turn above the infra temporal crest &
sink into the deep part of the temporalis muscle.
4.The nerve to the lateral pterygoid.
~These are 2 in number; one supplying each muscle head.

II.Posterior Division
1.The Auriculotemporal nerve:

Course of the nerve
} The auriculotemporal nerve arises by a medial & lateral
roots, that enclircle the MMA & unite behind it just
below the foramen spinosum.
}

The united nerve passes backwards, deep to the lateral
pterygoid muscle & passes between the
sphenomandibular ligament & the neck of the condyle.

}

It then passes laterally behind the TMJ i.r.t. to the upper
part of the parotid. It emerges from behind the TMJ,
ascends posterior to the superficial temporal vessels &
crosses the posterior root of the zygomatic arch.

Communications of the Auriculotemporal nerve:

i. 2 roots of the nerve:- both these roots receive
communications from he OTIC ganglion. They are
postganglionic secretomotor fibres to the Parotid
gland.i.e. they control the secretions from the gland
ii. Communicating branches to the postganglionic
sympathetic fibres:- These are vasomotor fibres that
pass to the parotid through the auriculotemporal nerve.
iii. Communicating branches to the facial nerve: These are
purely sensory from the Auriculotemporal nerve.

Branches of the Auriculotemporal nerve:
1. Parotid branches-----secretomotor, vasomotor.

2. Articular branches--- to the TMJ.
3. Auricular branches---to the skin of the helix & tragus.
4. Meatal branches----- Meatus of the tymphanic
membrane
5. Terminal branches----Scalp over the temporal region


Lingual nerve

~It lies between the ramus of the mandible & the muscle
in the pterygomandibular space.
~It then passes deep to reach the side of the tongue. Here it
lies in the lateral lingual sulcus against the deep surface of
the mandible on the medial side of the roots of the third
molar tooth where it is covered only by mucous membrane
of the gum.

~From here it passes on to the side of the the side of the
tongue where it is crosses the styloglossus & runs on the
lateral surface of the hyoglossus & deep to the mylohyoid in
close relation to the deep part of the submandibular gland
&its duct.
~It gives off sensory fibres to the tonsil & the mucous
membrane of the posterior part of the oral cavity.

Communication of the facial nerve (Chorda
tymphani) with the lingual nerve.
As the lingual nerve passes medially to the lateral
pterygoid, it is joined from behind by the chorda
tympani. This nerve conveys secretory fibres from
the facial nerve. The parasympathetic secretory
fibres control the submandibular & sublingual
salivary glands.


Inferior alveolar nerve.

~It is the largest terminal branch of the posterior division
of the mandibular nerve.
~The nerve descends deeep to the lateral pterygoid muscle
at the lower border of the muscle, it passes b/n the
sphenomandibular ligament & the ramus to enter the
mandibular foramen.
~In the canal the nerve runs alongside the inferior alveolar
artery as far as the mental foramen where it emerges out&
gives off the mental & incisive branches.
~From here the nerve runs in the canal giving of branches
to the mandibular teeth as apical fibres & enters the apical
foramena of the teeth to supply mainly the pulp as well as
the periodontium.

Branches of the nerve :1. Mental nerve: it supplies to the skin of the chin & the
mucous membrane as well as the skin of the lower lip.

2. Incisive branch: continues anteriorly from the mental
nerve in the body of the mandible to form the incisive
plexus & supplies the canine & incisors.
3. Mylohyoid nerve: it is given of before the nerve enters the
canal & contains both sensory & motor fibres.It pierces
the sphenomandibular ligament, descends in a groove in
the medial side of the ramus & passes beneath the
mylohyoid line supplying the mylohyoid muscle as well
as the anterior belly of the digastric.

Submandibular ganglion:

It is a small ovoid body that is suspended from the
lingual nerve above the submandibulat salivary gland.
The preganglionic parasympathetic fibres reach the
ganglion arising from the superior salivatory nucleus,
reaching through the facial, chorda tympani & the
lingual nerve. Post ganglionic fibres are conveyed
through the submandibular, sublingual & anterior
lingual salivary glands.
The sensory nerves reach the ganglion through the
lingual nerve.
Sympathetic fibres are derived from the plexus around
the facial artery & contain post ganglionic fibres arising
in the superior cervical ganglion. They provide
secretomotor fibres to the submandibular & sublingual
glands.

Otic ganglion

It is a flattened ovoid body located on the medial side of
the undivided nerve. It is situated below the foramen
ovale & the MMA. It has 2 main roots:1.Parasympathetic preganglionic (secretory) fibres:
they arise from the inferior salivatory nucleus.The
efferent fibres pass by way of the glossopharyngeal nerve
through the jugular canal.Below the canal it passes
through the tympanic branch of the glossopharyngeal
nerve( Jacobson’s nerve), passing through the tympanic
plexus & the lesser petrosal branch to reach the Ganglion.
(the lesser superficial petrosal nerve is the
parasympathetic root of the otic ganglion) The
postganglionic fibres pass through the auriculotemporal
nerve.

2.Sympathetic root: It is made up of the
postganglionic fibres that have originated in the
superior cervical sympathetic ganglion & the
plexus of the MMA. The fibres pass through the
ganglion uninterrupted. These fibres reach the
parotid thru the auriculotemporal nerve.
Afferent of sensory nerves come from the parotid
through the auriculotenporal nerve.


GENRAL CONSIDERATIONS
OF TRIGEMINAL NERVE.


Damage to the trigeminal nerve as a complication of surgery

Cancer surgeries: the tendency of squamous cell
carcinoma to affect the cutaneous branches places these
nerves at risk for injury during surgery. Similarly the
tendency of salivary gland tumors (ACC) to spread
along perinueral spaces.
The ophthalmic branches( frontal, SO, ST, lacrimal &
nasal) can be injured during eye brow surgeries. All
patients in whom coronal incision was made complained
of forehead numbness & paresthesias.
Paresthesias of the upper lip, gums & teeth are a
common complication of transantral procedures.

Risk of damage to the lingual nerve is to be anticipated
during procedures like removal of impacted third
molars, submandibular gland surgeries etc..

Trigeminal nueralgia:
It is a paroxysmal, intermittant,excruciating pain
confined to one of the branches of the trigeminal nerve.

Characterised by unilateral affliction, not crossing the
midline, presence of trigger zones, cessation of pain
during sleep.
The etiology is not definitely known. Suggested causes
are viral lesions of the ganglion, demyelination of the
nerves, narrowing of the foramina & Idiopathic.
Diagnosis: Based on C/f s & diagnostic test block on the
trigger zones.
Treatment modalities include..

1. Carbamazepine(Tegretol) 100 mg od, bd or tid, depending
on the severity or frequency of pain.
2. Injection of 60 to 90% alcohol in the nerve trunk or
ganglion.
3. Peripheral nuerectomy or cryotherapy of the peripheral
trigger zone.
4. Peripheral radiofrequency thermolysis & radiofrequency
thermogangliolysis.
5. Microvascular nerve root decompression procedure. It is a
nuerosurgical procedure wherein the internal vascular loops
of the superior cerebellar artery is made to compess on the
trigeminal nerve root.

Mental nerve nueralgia.
Due to resorption of the lower alveolar ridge, the borders
of the denture flange may compress on the mental nerve,
causing pain. Radiologically, the foramen can be seen at
the level of the surface of the ridge. Shifting the foramen
down is the treatment of choice.
Similar pain is felt due to narrowing of the foramen.
Decompession of the nerve by carefully enlargening the
foramen is the treatment of choice.


List of references:
1.Grays textbook of anatomy
2.Last’s anatomy

3. Grant’s atlas of anatomy
5. Atlas of anatomy--- Frank Netter.
4. Regional anesthesia--- Hahn
5. Anatomy & Physiology– Seeley, Stephens & Tate.


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