The trigeminal nerve is so called because of its threemain divisions i.e. the Ophthalmic, Maxillary & Mandibularnerves. 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.
MOTOR ROOT It arises separately from the sensory root in the motornucleus of pons. At the semilunar ganglion it passesinferolaterally under the ganglion towards for.ovale, throughwhich it leaves the middle cranial fossa along with theman.div. After it exits the skull, it unites with the sensoryroot and forms a single nerve trunk. It supplies thefollowing muscles:1. Muscles of mastication2. Mylohyoid3. Ant belly of the diagastric4. Tensor tympani5. 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 theconcave surface to enter the pons. The peripheral branchesare grouped to form the ophthalmic and maxillary nervesand sensory part of the mandibular nerve.
THE TRIGEMINAL GANGLION Sensory root fibres of the trigeminal nervecomprise the centralprocess of cells located in the trigeminalganglion.2 ganglion ,one inervating each side of face.located inmeckel’s cavity,on the anterior surface of the petrous portion oftemporal bone.measures arprox. 1.0x2.0cm. It lies at depth of4.5 –5 cm from the lateral aspect of the head near theposterior part of the zygomatic arch. It is cresentic 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 theganglionic branches of the ICA & the accesory meningealartery which enters through the for.ovale.
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. Leaves the cranium and enters the orbit through superior orbital fissure. 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 nerve1. Lacrimal nerve: It is the smallest. It supplies the lacrimal gland & the conjuntiva. It pireces 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 & pericraniumii. 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.
MAXILLARY NERVEThis is the second & intermediate division of the trigeminalnerve.It is wholly sensory.Course: It begins at the middle of the trigeminal ganglionas a flattened, plexiform band, passes horizontally forwardsalong the lateral wall of the cavernous sinus. It leaves theskull through the foramen rotundum & becomes morecylindrical & firmer in texture.It crosses the upper part of thepterygopalatine fossa, inclines laterally on the posterior partof the orbital process of the maxilla & enters the orbit throughthe inferior orbital fissure.It is now termed as the infraorbital nerve. It passes through the infra orbital groove &canal in the floor of the orbit & appears on the face throughthe infra orbital foramen.
The branches of the maxillary nerve can be divided into the following 4 groups:1) In the cranium: Meningeal2) In the pterygopalatine fossa: Ganglionic, Zygomatic, Post.superior alveolar3) In the infra orbital canal: Middle sup. alveolar, Anterior superior/ Greater alveolar4) On the face: Palpebral, nasal, superior labial
I. Branch given off on the cranium1. Meningeal branch: It is given off near the foramenrotundum. It supplies the duramater of the anterior & middlecranial fossae.II. Branches in the pterygopalatine fossa.1. The ganglionic branches: They connect the maxillarynerve to the pterygopalatine ganglion.They contain secretomotorfibres to the lacrimal gland. They provide sensory fibres to theorbital periosteum & mucous membrane of the nose, palate &pharynx.2. The zygomatic nerve: It arises in the pterygopalatinefosssa from the maxillary nerve and travels anteriorly ,entering through the inferior orbital fissure where it divides into 2branches. The Zygomaticofacial nerve perforates the facialsurfaces & supplies the skin over the zygomatic bone..
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 theorbicularis oculi & pierce the muscle, supplying the skin overthe lower eyelid& lateral angle of the eye along with theZygomaticofacial & 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 thecheek & upper lip including the mucous membrane & labialglands. They are joined by the facial nerve & form theinfraorbital 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 justin 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 withits cells. The branches are: -
The branches of the Pterygopalatine ganglion are:-I. Orbital branches:II.Palatine branches: 1.Anterior/greater palatine 2.Middle palatine 3.Posterior palatineIII.Nasal branches: 1.Posterior superior lateral 2.Nasopalatine/SphenopalatineIV.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:- continuedi. 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 theyposterior part of the nasal conchae ii. Nasopalatine(Sphenopalatine) nerve: It passesdownwards & forwards between the periosteum &mucousmembrane in the region of the vomer, continues downwards &forwards, reachs the floor of the nasal cavity.Descends intothe 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 themucous membrane of the nasopharynx. It arises from passesthrough the palatovaginal canal along with thepharyngeal branch of the maxillary artery.
MANDIBULAR NERVE It is the third & largest division of the trigeminalnerve.It is made up of 2 roots: a large sensory rootwhich proceeds from the lateral part of the trigeminalganglion & almost immediately emerges out through theforamen ovale & a small motor root which passes belowthe ganglion, & unites with the sensory root justoutside 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 smallanterior & 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
The braches of the Mandibular nerve:-I. Branches of the undivided nerve. i. Meningeal branch/nervus spinosus. ii. Nerve to the medial pterygoidII. Branches of the divided nerve:(A) Anterior division: (B) Posterior division:1.Buccal nerve 1. Auriculotemporal nerve2.Massetric nerve 2.Lingual nerve3.Deep temporal nerve 3.Inferior alveolar nerve4.Nerve to the lateral pterygoid.
BRANCHES OF THE UNDIVIDED NERVE1.Meningeal nerve: It enters the skull through the foramen spinosumalong with MMA. It has anterior & posterior divisions that supply thedura of the middle & anterior cranial fossae.2. Nerve to the medial pterygoid: It is a slender branch that supplies to the deepsurface 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 themasseter & unites with the buccal branches of he facialnerve. 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 Division1.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 thesphenomandibular 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.
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 musclein the pterygomandibular space. ~It then passes deep to reach the side of the tongue. Here itlies in the lateral lingual sulcus against the deep surface of themandible on the medial side of the roots of the third molartooth where it is covered only by mucous membrane of thegum. ~From here it passes on to the side of the the side of thetongue where it is crosses the styloglossus & runs on the lateralsurface of the hyoglossus & deep to the mylohyoid in closerelation to the deep part of the submandibular gland &its duct. ~It gives off sensory fibres to the tonsil & the mucousmembrane 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 lateralpterygoid, it is joined from behind by the chordatympani. This nerve conveys secretory fibres from thefacial nerve. The parasympathetic secretory fibres controlthe 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 thesphenomandibular ligament & the ramus to enter themandibular foramen. ~In the canal the nerve runs alongside the inferioralveolar artery as far as the mental foramen where itemerges 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 thelingual nerve above the submandibulat salivary gland. Thepreganglionic parasympathetic fibres reach the ganglionarising from the superior salivatory nucleus, reaching through thefacial, chorda tympani & the lingual nerve. Post ganglionic fibresare conveyed through the submandibular, sublingual &anterior lingual salivary glands. The sensory nerves reach the ganglion through thelingual nerve. Sympathetic fibres are derived from the plexus around the facial artery & contain post ganglionic fibres arising in the superior cervical ganglion. They providesecretomotor fibres to the submandibular & sublingualglands.
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.Theefferent fibres pass by way of the glossopharyngeal nervethrough the jugular canal.Below the canal it passes through thetympanic branch of the glossopharyngeal nerve( Jacobson’snerve), passing through the tympanic plexus & the lesserpetrosal branch to reach the Ganglion. (the lesser superficialpetrosal 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 thepostganglionic fibres that have originated in thesuperior cervical sympathetic ganglion & theplexus of the MMA. The fibres pass through theganglion uninterrupted. These fibres reach the parotidthru the auriculotemporal nerve. Afferent of sensory nerves come from the parotidthrough the auriculotenporal nerve.
GENRAL CONSIDERATIONS OF TRIGEMINAL NERVE.
Damage to the trigeminal nerve as a complication of surgery Cancer surgeries: the tendency of squamous cellcarcinoma to affect the cutaneous branches places thesenerves at risk for injury during surgery. Similarly thetendency of salivary gland tumors (ACC) to spread alongperinueral 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 acommon complication of transantral procedures. Risk of damage to the lingual nerve is to be anticipated during procedures like removal of impacted thirdmolars, submandibular gland surgeries etc..
Trigeminal nueralgia: It is a paroxysmal, intermittant,excruciating painconfined 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.