Trigeminal Nerve( V )

Abbas A. A. Shawka

Medical student

2nd grade

Trigeminal nerve

Nerve Modality Nucleus location Distribution

Trigeminalnerve

GSA

Main Sensory nucleus of V nerve

Pons ( posterior part )

Touch and pressure

Spinal nucleus of V nerve

Pons – C2 level Pain and temperature

Mesencephalic nucleus of V nerve

Pons –midbrain level

Proprioception

SVE Motor nucleus of V nerve

Pons ( medial to main sensory nucleus )

Motor to muscles of mastication, mylohyoid, anterior belly ofdigastric, tensor veli palatini, and tensor tympani

Nuclei of trigeminal nerve V

Mainmotor

Anatomy • The trigeminal nerve exits

from the anterolateral surface of the pons as a large sensory root and a small motor root .

• These roots continue forward out of the posterior cranial fossa and into the middle cranial fossa by passing over the medial tip of the petrous part of the temporal bone .

• In the middle cranial fossa the sensory root expands into the trigeminal ganglion , which contains cell bodies for the sensory neurons in the trigeminal nerve and is comparable to a spinal ganglion.

V

Anatomy • The ganglion is in a depression

(the trigeminal depression) on the anterior surface of the petrous part of the temporal bone, in a dural cave (the trigeminal cave ) .

• The motor root is below and completely separate from the sensory root at this point.

• Arising from the anterior border of the trigeminal ganglion are the three terminal divisions of the trigeminal nerve, which in descending order are:

• the ophthalmic nerve V1

• the maxillary nerve V2

• the mandibular nerve V3

• Note how the trigeminal nerve and its divisions pass through the lateral wall of cavernous sinus !!

• Other nerves also pass through the lateral wall of cavernous sinus !!?

Ophthalmic nerve V1• Purely sensory.

• From trigeminal ganglion courses in lateral wall of cavernous sinus interior to CN IV, enters orbit through superior orbital fissure (SOF)

Branches • Befor leaving cavernous sinus it will give :-

1. Meningeal branch :- to close related structures ( not leave through SOF )

2. Frontal nerve :- enters orbit above the common tendinous ring then divides into supra-orbital and supratrochlear nerves

3. Lacrimal branch :- enters orbit above the CTR and receive parasympathetic fibers from the great petrosal nerve of CN VII through the zygomatic branch of CN V2

4. Nasociliary nerve :- enters the orbit through the CTR then divided to ( 6 ) branches !!

• Nasociliary nerve branches = ( 6 branches ) !!

1. Infratrochlear nerve

2. Anterior and posterior ethmoidal nerves

3. Internal nasal nerve

4. External nasal nerve

5. Long ciliary nerve ( sensory + sympathetic to DPM )

6. Short ciliary nerve ( sensory + parasympathetic from CN III through ciliary ganglion to sphincter papillae and )

Maxillary nerve V2• Purely sensory

• MMN is given directly after exit from the trigeminal ganglion and accompanies the MMA

• Corse in inferiolateral way in CS inferior to V1

• Exit cranial cavity through foramina rotundum to enter the pterygopalatine fossa

Branches 1. Infraorbital nerve :- enter orbit through IOF and gives :-

- Posterior superior alveolar nerve - Middle superior alveolar nerve

- Anterior superior alveolar nerve - Inferior palpebral branch

- External nasal branch - Labial branch

2. Zygomatic nerve :- ( IOF ) then divided into :-

- Zygomaticotemporal n.

- Zygomaticofascial n.

- Parasympathetic fibers from CN VII – GPN – Pterygo. Ganglia – Zygomatic nerve ( V2 ) – lacrimal nerve ( V1 )

3. Branches bass through the pterygopalatine ganglion without synapsing in it includes :-

- Orbital ( to periosteum )

- Greater and lesser palatine nerves

- Posterior superior nasal

- Nasopalatine nerve

- Pharyngeal

Mandibular nerve V3• Sensory and motor

• The largest

• The sensory root is inferior to V1 and V2 in the trigeminldepression then it exit through foramina ovale

• V3 do not enter the cavernous sinus

• Mandibular nerve lies in the infratemporal fossa

Mandibular branch V3

Nerve to medial

pterygoid

Meningeal branches

Anterior trunk

Posterior trunk

Masseteric

Deep temporal

Nerve to lateral

pterygoid

buccal

Auriculo-temporal

lingual

Inferior aleveolar

Nerve to myelohyoid

Foramina ovale

Branches

Auriculotemporal n.• Branch of V3

• Carry 2 type of fibers :

• 1- sensory fibers

• Give sensation to parotid gland, auricle , hairy temporal and TM joint.

• 2- parasympathetic ( secretomotor ) to parotid gland ( from otic ganglion –lesser petrosal nerve – tympanic nerve – IX – inferior salivatory nucleus )

• Pain from parotid fascia if felt by GRAET AURICULAR NERVE !!!

Branches of auriculotemporal nerve

• Anterior auricular

• Branches to external acoustic meatus ( EAM )

• Articular branch

• Superficial temporal branches

• Communicating branches with CN VII

lingual n.• Branch from the posterior trunk ( which is mainly sensory ) of V3.

• Carry three types of fibers

1. Sensation ( from V ) to tongue.

2. Test fibers to anterior 2/3 of the the tongue ( Chorda tympani – VII – solitary nucleus tract )

3. Secretomotor ( parasympathetic fibers ) ( chorda tympani – VII – superior salivatory nucleus )

Inferior alveolar n.• Branch of mandibular nerve ( V3 )

• Only 1 type of fibers after giving nerve to myelohyoid

• ( afferent fibers ) sensation !!

• 3 branches ( nerve to myelohyoid , mental & incisive )

Motor component of V n. • Beneath the trigeminal sensory

ganglion .

• Exits the cranial cavity through foramina ovale the joins the sensory root of CN V3 to form the mandibular nerve !

• Trigeminal nerve is motor for (8) muscles :-

1. Masseter

2. Temporalis

3. MPt

4. LPt

5. TP

6. LP

7. Mylohyoid

8. ABD

Lesions• Affections of the motor part of the fifth

nerve, whose fibres run in the mandibular branch, are very unusual. Test for contraction of masseter.

• The commonest condition affecting the sensory part of the nerve is trigeminal neuralgia (tic doloureux), of unknown cause and characterized by pain in the distribution of the maxillary and/or mandibular branches.

• The ophthalmic branch is rarely involved and, equally strangely, nor is the complete distribution of the affected main branch.

• With the maxillary nerve affected the pain is usually felt deeply in the face and nose between the mouth and orbit, and with the mandibular nerve from the mouth up to the ear and the temporal region—but not along the lower part of the mandible or the angle, where the nerve supply is by the great auricular nerve.

• Injection or electrocoagulation of the trigeminal ganglion may be necessary to abolish the pain.

Lesions• It should be noted that the sensory

distribution of the mandibular nerve extends into the external ear and on to the temporal region via the auriculotemporal branch, and that the ophthalmic nerve distribution stretches from the tip of the nose to the vertex of the skull, well beyond the hairline and as far back as a line drawn upwards from both ears.

• The appearance of herpetic vesicles on the tip of the nose should be a warning that the cornea may become involved.

• This occurs because the nasociliarybranch of the trigeminal nerve innervates both the cornea and the lateral dorsum of the nose as well as the tip of the nose

• The afferent side of the corneal reflex depends on the ciliary branches of the nasociliary part of the ophthalmic nerve. Disappearance of the reflex is often the first sign of a lesion of the ophthalmic nerve; test by gently touching the cornea (not the conjuctiva) with cotton wool.

Test • Initially test the sensory branches

by lightly touching the face with a piece of cotton wool followed by a blunt pin in three places on each side of the face:

1. around the jawline,

2. on the cheek and,

3. on the forehead.

• The corneal reflex should also be examined as the sensory supply to the cornea is from this nerve. Do this by lightly touching the cornea with the cotton wool. This should cause the patient to shut their eyelids.

Thank You