trigeminal nerve

TRIGEMINAL NERVE

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It is V and Largest cranial nerve

Mixed -- Small motor root

Large sensory root

Nerve of the first pharyngeal arch

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Exteroceptive fromSkin of the face & forehead;Mucous membrane of the

nasal cavity;Oral cavity;Nasal sinus;Floor of mouth, teeth;Anterior 2/3 of tongue;Cranial dura

Proprioception from Teeth; Periodontium; Hard palate; TMJ

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Attached to lateral part of ponsSensory root (portio major)Motor root (portio minor)

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Fibers arise from Semilunar

Ganglion

Semilunar ganglion– Develops from neural crest– Crescent shaped– Unipolar neurons– Location- Meckel’s cavity;

superior to petrous part of temporal bone

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Afferent station

Afferent fibers accompany fibers of motor root

Proprioception from TMJ, periodontal membrane, teeth, hard

palate

Afferent impulses from stretch receptors in the muscles of

mastication

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Located at midpontine level

Medial to main sensory nucleus

Fibres distribute to muscles of mastication,

mylohyoid, anterior belly of digastric, tensor

tympani, tensor veli palatini.

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Location – midpons

Forms dorsal trigeminothalamic tract

Ascending fibers terminate in this nucleus

Convey light touch, tactile discrimination,

sense of position and passive movements

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True sensory ganglion

Contains cells that are structurally and

functionally ganglion cells

Convey impulses from the muscles innervated by

the trigeminal nerve and the extraocular muscles,

as well as from the periodontal ligament of the

teeth14

Largest nucleus

Extends caudally from main nucleus to level C3 of

spinal cord

Forms ventral trigeminothalamic tract

Conveys pain and temperature

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extends to the pontomedullaryjunction inferiorly

pontomedullaryjunction to obex

Obex(medulla) to C3 level of spinal cord

Tactile sense Pain and temperature16

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Smallest division

From anterior medial part of semilunar ganglion lateral wall of cavernous sinus

Sensory fibres from Scalp, skin of forehead, upper eyelid lining frontal sinus, conjunctiva of eyeball, lacrimal gland, skin of the lateral angle of eyeball & lining of ethmoid cell 19

Ophthalmic division

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Long ciliary n.Short

ciliary nerves

Infratrochlear

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LACRIMAL NERVE (n. lacrimalis) Smallest branch.

Enters the orbit through the narrowest part of the superior orbital fissure

Runs along the upper part of the lateral rectus

Communicates with zygomatic branch of maxillary nerve.

Enters the lacrimal gland – gives of several filaments

Finally pierces the orbital septum & ends in supplying the skin of upper eyelid.

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Largest branch. Enters the orbit through the superior orbital fissure.

Runs forward between levator palpebrae superioris and periosteum

Divides into two branches in the midway between the apex and base of the orbit

Supratrochlear Supraorbital

FRONTAL NERVE (n. frontalis)

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•Supraorbital Smaller than supratrochlear. Gives filament to join the infratrochlear.

Supplies – Skin over the lower forehead. Conjunctiva Skin of the upper eyelid.

Supratrochlear Passes through the supraorbital foramen. Branches into medial & lateral.

Supplies – Conjunctiva. Skin of the upper eyelid. Twigs to pericranium.

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Nasociliary Nerve (n. nasociliaris)

Intermediate in size and more deeply placed.

Enters the orbit between the two heads of rectus lateralis.

Further passes through anterior ethmoidal foramen.

Supplies internal nasal branches to mucous menbrane.

Emerges as external nasal branch supplying the skin of the ala and apex of the nose.

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SensoryFrom lower eyelid, side of the nose,

upper lip;All maxillary teeth & gingivae, mucous

membrane of most of nasal cavity, hard and soft palate;

Tonsillar region and region of pharynx

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Sphenopalatine ganglion 29

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Zygomaticotemporal:

Exits the zygomatic bone on its medial surface

Pierces the temporal fascia to supply skin over temple

Receives a branch from lacrimal nerve

Communicates with facial nerve and auriculotemporal branch

Zygomaticofacial :

Leaves zygomatic bone on its lateral surface

Supplies skin over malar prominence

Communicate with facial nerve & with inferior palpebral branch of maxillary

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Posterior superior alveolar nerves

• Arise in the pterygopalatine fossa

• Leaves maxillary nerve in pterygopalatine fossa

• Enters the posterior alveolar canals

Branches to

Sinus lining

Three twigs to Molars

Gingiva

Adjoining part cheek

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Middle superior alveolar nerves• Arise from the nerve in the posterior part of the infraorbital canal

• Runs in infraorbital groove on the lateral wall max sinus

• Supply premolars, gingiva & adjoining part cheek

• Forms a superior dental plexus with anterior and posterior superior alveolar branches

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ANTERIOR SUPERIOR ALVEOLAR NERVES• Given off just before exiting from the infraorbital foramen.

• Supplies the incisor and canine teeth.

• Descends in canalis sinosus in anterior wall of maxillary sinus.

• Gives off a nasal branch to supply the mucous membrane of the anterior part of inferior meatus and nasal floor.

• Communicates with the nasal branches of the sphenopalatine ganglion.

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Greater palatine nerveLesser palatine nerve

Pterygopalatine ganglion

INNERVATION OF HARD PALATESensory innervations

Greater palatineNasopalatine

These are branches of maxillary N passing through Pterygopalatine ganglion

Lesser Palatine N ( middle & posterior ) – Uvula, tonsil, soft palate

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GANGLIONS

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Ciliary ganglion • Suspended from nasociliary nerve

• Anatomically belongs to trigeminal nerve

• Functionally belongs to oculomotor nerve

• Carries parasympathetic motor fibres from Edinger – Westphal nucleus

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OTIC GANGLION • Suspended from mandibular nerve

• Anatomically belongs to trigeminal nerve but functionally belongs to glossopharyngeal nerve

• Carries the secretomotor ( nucleus is superior salivary )fibres & distributed via lesser superficial petrosal nerve to Parotid glands.

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Suspended from lingual nerve

Anatomically belongs to trigeminal nerve but functionally belongs to facial nerve

Carries the secretomotor ( nucleus is superior salivary )fibres & distributed via chorda tymoani nerve to submandibular & sublingual salivary glands.

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PTERYGOPALATINE GANGLION • Suspended from maxillary nerve

• Anatomically belongs to trigeminal nerve but functionally belongs to facial nerve

• Carries secretomotor fibres & distributed via the great superficial petrosal nerve ( Nucleus is inferior salivary ) to the Lacrimal glands & the glands of the palate

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Surgical removal of third molars(Von Arx and Simpson, 1989; Rood, 1992)

Osteotomies (Walter and Gregg, 1979; Yoshida et al, 1989)

Trauma (De Man and Bax, 1988)Tooth extractions (Strassburg, 1967; Hansen, 1980)Pulpectomy (Holland, 1994)

Experimental Trigeminal Nerve Injury G.R. Holland CROBM 1996 7: 237

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Implant placementHydroxypatite ridge augmentationEndodontic surgeriesTumour resectionSalivary gland and duct surgeryVestibuloplastyBiopsy procedures

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• Inferior alveolar nerve injury – 0.41-7.5%

• Lingual nerve injury – 0.06-11.5%

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Risk factors for nerve injury

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Local anesthetic toxicity

Formation of epineural hematoma

Needle-barb mechanism of injury

Chemical injury

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Sagittal split osteotomy

Mandibular advancement procedure osteotomies.

Intraoral vertical ramus osteotomy (IVRO)

Genioplasty procedures

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Fracture of mandibular body and ramus

LeFort I & II fractures

Fracture of condylar segment medially

Mandibular angle, body and symphysis fracture

Inadvertent placement of screws

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Overinstrumentation

Chemical injury

Direct trauma from apicoecotomy

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TMJ exposures by preauricular approach

Damage is minimized by incision and dissecting in

close apposition to cartilagenous portion of external

auditory meatus

Fracture of neck of condyle

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Trigeminal neuralgia is defined as sudden, usually unilateral, severe, brief, stabbing, lancinating type of pain in the distribution of one or more branches of 5th cranial nerve

Specific etiology unknown

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Sudden, unilateral, intermittent paroxysmal, sharp, shooting, lancinating, like pain.

Pain is elicited by slight touching superficial ‘Trigger points’

Common triggers include touch, talking, eating, drinking, chewing, tooth brushing, etc.

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MEDICAL TREATMENTDRUGS CURENTLY USED:- 1.Carbamazepine is used as a standard drug , adult dose 200mg TDS & can be increased upto 1600 mg/day in divided doses initially started as small dose & gradually increased to prevent side effects adverse effects include dizziness, ataxia, vertigo, skin rashes . ,etc bone marrow suppression is rare but requires routine . monitoring

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2.Phenytoin sodium usually used in combination of carbamazepine dose 100-400mg/day side effects: gum hyperplasia3. Gabapentin dose is 1200-3600mg/day used with caution in patients with renal & hapatic disease4. Gaba agonist these drugs reduce the central projection of painful impulses eg. Baclofen , adult dose being 10-30 mg TDS

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Surgical treatment• Peripheral nerve block procedure: It involves blocking

of peripheral nerve by long acting LA.

• Alcohol block : 0.5 -2 ml of 95% alcohol can be used for blocking of peripheral nerve.

• Blocking of gasserian ganglion: more effective but it has hazards in sense that alcohol escape into the surrounding subarchanoid space & may cause palsy of adjacent cranial nerve.

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• Post ganglionic sectioning: peripheral neurectomy in which peripheral branch of nerve is avulsed.

• Cryotherapy: peripheral branches are subjected to application of extreme cold by using cryoprobes

In this the nerve is not sectioned but destroyed

• Percutaneous procedure: Percutaneus procedures involes mechanically or chemically damaging parts of trigeminal groove

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• Radiation therapy:

Gamma knife has been used which consists of multiple rays of high energy photon concentrated on trigeminal nerve root.

Can be used to destroy specific components of nerve

Source of radiation is Co 60

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Head neck and brain- bd chaurasiaGray’s anatomyMonheim’s local anesthesia and pain control in

dental practiceHandbook of local anesthesia - malamedPeterson’s principles of oral & maxillofacial surgeryExperimental trigeminal nerve injury g.R. Holland

crobm 1996 7: 237

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