Trigeminal Nerve

Dr. Nazim Nasir Department of Anatomy Jawahar Lal Nehru Medical College A.M.U., Aligarh INDIA

Definition

The fifth vertebrate

peripheral nerve that emerges from within the skull. It is sensory from the head, but motor to the jaw muscles. L. trigerninus, three-

fold. Trigeminal nerve has three divisions. It was described by Fallopius and again by Meckel in 1748. The name trigeminal was

The sensory

Functio n

function of the trigeminal nerve is to provide the tactile, proprioceptive, and nociceptive afference of the face and mouth. The motor function

activates the muscles of the mastication, the

Peripheral 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. 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.

General Consideration Arising from the anterior border of the

trigeminal ganglion are the three terminal divisions of the trigeminal nerve, which in descending order are: Ophthalmic (V1), Maxillary (V2), and Mandibular (V3) Fibers run from the face to the pons via the

superior orbital fissure (V1), the foramen rotundum (V2), and the foramen ovale (V3) Conveys sensory impulses from various areas

of the face (V1) and (V2), and supplies motor fibers (V3) for mastication

Various Components Sensory

component Branchial Motor

component Visceral motor

component

SENSORY COMPONENT Ophthalamic

division Maxillary division Mandibular division

Division Enters the middle

cranial fossa through the superior orbital fissure and courses within the lateral wall of the cavernous sinus on its way to the trigeminal ganglion. Branches of the ophthalmic nerve (V1) {frontal nerve, nasociliary nerve, and lacrimal nerve} convey sensory information from the

Division Enters the middle cranial

fossa through foramen rotundum and may or may not pass through the cavernous sinus en route to the trigeminal ganglion. Branches of the maxillary nerve (V2) {zygomatic nerve and infraorbital nerve}convey sensory information from the lower eyelids, zygomae,

division Enters the middle cranial

fossa through foramen ovale, coursing directly into the trigeminal ganglion Branches of the mandibular nerve (V3) {buccal nerve, lingual nerve, inferior alveolar nerve, and auriculotemporal nerve}convey sensory information from the lateral scalp, skin anterior to the ears, lower cheeks,

BRANCHIAL MOTOR COMPONENT Consists of lower motor neurons whose cell bodies

are located in the motor nucleus of the trigeminal nerve in the brainstem. These nerves exit the mid-lateral aspect of the

pons, course within the trigeminal nerve, pass through the trigeminal ganglion, and within the mandibular nerve before branching. The muscles innervated-

temporalis, masseter, medial and lateral pterygoids, tensor veli palatini, tensor tympani, anterior belly of diagastric and

VISCERAL MOTOR COMPONENT Visceral motor nerves are not a true component of

the trigeminal nerve, but “hitchhike” . Vidian nerve (a.k.a. nerve of the pterygoid canal)

emerges from the pterygoid canal carrying preganglionic fibers to the pterygopalatine ganglion. After synapse, post-ganglionic fibers exit the ganglion and hitchhike along trigeminal nerve branches en route to the lacrimal gland and minor salivary glands of the palate and mouth.

Chorda tympani exits the skull through the

petrotympanic fissure, courses extracranially to join the lingual nerve. It carries pre-ganglionic fibers to the submandibular ganglion which "hangs" from the lingual nerve. After synapse, postganglionic fibers exit the ganglion to innervate the submandibular gland and sublingual gland.

The lesser petrosal nerve after exiting the skull

through or near the foramen ovale, carries preganglionic fibers to the otic ganglion. After synapse, post-ganglionic fibers exit the ganglion, hitchhiking along the auriculotemporal nerve to

Nuclei The sensory trigeminal nerve nuclei are the

largest of the cranial nerve nuclei, and extend through whole of the brainstem. The nucleus is divided into three parts, from

rostral to caudal (top to bottom in humans): The mesencephalic nucleus The chief sensory nucleus (or "pontine

nucleus" or "main sensory nucleus" or "primary nucleus") The spinal trigeminal nucleus

The

mesencephalic nucleus is involved with proprioception. Neurons of this nucleus are pseudounipolar cells receiving proprioceptive information from the jaw, and sending projections to the motor trigeminal

The principal sensory nucleus (or chief sensory

nucleus) receives information about discriminative sensation and light touch of the face as well as conscious proprioception of the jaw.

The spinal trigeminal nucleus is a nucleus in the

medulla that receives information about deep/crude touch, pain, and temperature from the ipsilateral face. The facial, glossopharyngeal, and vagus nerves also convey pain information from their areas to the spinal trigeminal nucleus.

s

#3 – Muscle Afferents

#1 – Large Afferents

#2 – Small Afferents

Motor Trigeminal Pathway Efferents 1. Origin – Motor neurons of trigeminal motor 2. 3. 4. 5. 6. 7.

nucleus. Course – Exit via trigeminal nerve Laterality – Uncrossed. Topographical Organization – Organized by muscle group. Destination – Muscles of mastication. Function – Voluntary movement of the jaw; mastication. Dysfunction – Paralysis of the jaw

Part 1--Trigeminal Large Primary Afferents RECEPTOR TYPE

FIBER GROUP

FIBER NAME

MODALITY

Cutaneous and subcutaneous mechanoreceptors

Touch

Meissner's corpuscle

Aβ

RA

Stroking, fluttering

Merkel disk receptor

Aβ

SAI

Pressure, texture

Pacinian corpuscle

Aβ

PC

Vibration

Ruffini ending

Aα,β

SAIl

Skin stretch

Hair follicle

Aβ

Gl,G2

Stroking, fluttering

Hair-down

Aβ

D

Light stroking

Field

Aβ

F

Skin stretch

Trigeminal Large Primary Afferents Origin - Trigeminal ganglion, Aβ and Aδ fibers Course – Trigeminal nerve, enter at pons Laterality - Uncrossed Topographical Organization - yes Destination – Principal sensory nucleus of trigeminal Function – fine touch, vibration, two-point discrimination, proprioception Dysfunction – loss of above senses on half of face.

Trigeminal Lemniscus 1. Origin – Principal sensory nucleus of 2. 3. 4. 5. 6. 7.

trigeminal (nV) Course – Trigeminal lemniscus Laterality – Mostly crossed; bilateral projections for oral cavity receptive fields. Topographical Organization - yes Destination – Ventroposterior Medial nuc. (VPM) of thalamus Function – Vibration, proprioception, fine touch, two-point discrimination Dysfunction – loss of sensation mostly contralateral face.

Thalamocortical Pathway 1. Origin - VPM 2. Course – Posterior limb of internal capsule 3. Laterality - Uncrossed 4. Topographical Organization – yes; head area 5. Destination – Primary somatosensory cortex,

areas 1, 2, 3 6. Function – Fine touch, vibration, proprioception 7. Dysfunction – Loss of somatic sensations

Part 2--Small Trigeminal Primary Afferent Pathway RECEPTOR THERMAL RECEPTORS Cool receptors Warm receptors Heat Nociceptor Cold Nociceptors NOCICEPTORS Mechanical Thermal-mechanical Thermal-mechanical Polymodal Chemoreceptors

FIBER GROUP

FIBER NAME

Aδ C Aδ C

III IV III IV

Aδ Aδ C C C

III III IV IV IV

MODALITY TEMPERATURE Skin cooling (25°C) Skin warming Hot temp Cold temp PAIN Sharp pain Burning pain Freezing pain slow, burning pain Insect venom, histamine

Small Trigeminal Primary Afferent Pathway Origin - Nociceptors, small trigeminal ganglion cells; Aδ and C fibers. Course - Enter trigeminal nerve; descend in spinal trigeminal tract. Laterality – Uncrossed. Topographical Organization – Yes. Separate dermatomes are distributed in segments; most oral are rostral Destination - Spinal trigeminal nucleus. Function - Pain and temperature sensation Dysfunction – Numbness, loss of temp sense

5

3

1

Trigeminal Lemniscus, part 2 Pain and Temp Pathway 1. Origin – Neurons of spinal trigeminal 2. 3. 4. 5. 6. 7.

nucleus. Course – Axons cross in spinal cord or medulla and join the trigeminal lemniscus. Laterality - Crossed Topographical Organization - Yes Destination – VPM in thalamus Function - Information from A-delta fibers on fast pain, temp, and innocuous stimuli. Dysfunction – Numbness on opposite face

Spino-Reticular Pathway 1. Origin – Neurons of spinal trigeminal nucleus. 2. Course – Same as trigeminal lemniscus 3. Laterality – Mostly crossed 4. Topographical Organization - Poor 5. Destination – Reticular formation of medulla 6. Function – slow pain 7. Dysfunction – partial analgesia

Thalamocortical Pathway  Same as for the large afferent pathway.  Both go the head and face area of S1.

Part 3 – Mesencephalic Trigeminal Afferents RECEPTOR TYPE

FIBER GROUP FIBER NAME

Muscle and skeletal mechanoreceptors

MODALITY

Limb proprioception

Muscle spindle primary

Aα

la

Muscle length and speed

Muscle spindle secondary

Aβ

II

Muscle stretch

Golgi tendon organ

Aα

Ib

Muscle contraction

Joint capsule mechanoreceptors Aβ

II

Joint angle

Stretch sensitive free endings Aδ

III

Excess stretch or force

Mesencephalic Trigeminal Afferents 1.

2.

3. 4. 5. 6.

Origin – Ganglion cells in mesencephalon; sensory endings from muscle spindles and golgi tendon organs. Course – Enter trigeminal nerve; ascend in mesencephalic division to midbrain near inferior colliculus where cell bodies are located. Fibers then descend back to pons. Laterality – Uncrossed. Topographical Organization – Organized by muscle group. Destination – Motor nucleus of trigeminal nerve. Function – Muscle stretch and tension; proprioception. Substrate for jaw stretch reflex – myotatic jaw-jerk reflex.

Clinical Consideration Wallenberg Syndrome

(Lateral Medullary Syndrome) In the medulla, the ascending spinothalamic

tract (which carries pain/temperature information from the opposite side of the body) is adjacent to the descending spinal tract of the fifth nerve (which carries pain/temperature information from the same side of the face). A stroke that cuts off the blood supply to this area (e.g., a clot in the posterior inferior cerebellar artery) destroys both tracts simultaneously. The result is loss of pain/temperature sensation (but not touch/position

Trigeminal Neuralgia Trigeminal neuralgia (TN), also known as “tic

douloureux” (pronounced “tick-doo-la-roo”), is a condition affecting the trigeminal nerve or fifth cranial nerve  characterized by sudden attacks of pain to the face, commonly described as sudden, severe, electric-shock-like, or stabbing. Because sufferers of TN may contort their face in pain or become noticeably still during an attack, the disease has sometimes been confused with a seizure disorder, hence the term “tic douloureux” which means “twitching pain.”  A patient’s description of the pain and a

Peripheral lesions----craniofacial trauma, basilar skull features,

dental trauma, maxillary sinusitis, primary or metastatic tumors, aneurysm of the internal carotid artery, cavernous sinus thrombosis, stilbamidine, trichlorethylene, lupus, scleroderma, Sjøgren's syndrome, sarcoidosis, probably amyloidosis, and a fairly common idiopathic benign sensory neuropathy. Horner's syndrome can be produced by lesions of the nasociliary nerve as it runs with the ophthalmic division.

Lesions of the ganglion: herpes zoster infection,

primary and metastatic tumors.

Trigeminal root lesions: adjacent tumors and

vascular malformations, especially acoustic

Refrences

 http://anatomyatlases.org/MicroscopicAnatomy/Appendices/Appendix5.shtml  http://www.nature.com/nrm/journal/v3/n4/glossary/nrm783_glossary.html  Grays Anatomy  Snells Neuroanatomy  Grants Anatomy  http://en.wikipedia.org/wiki/Trigeminal_nerve  http://medinfo.ufl.edu/year1/trigem/text.html  Pocket Atlas of Human Anatomy 4th edition  http://images.google.co.in/images?hl=en&q=trigeminal+pics&um=1&ie=U

TF8&ei=kyjKSbyrNJT27AO0yaytAg&sa=X&oi=image_result_group&resnum=1 &ct=title  http://www.google.co.in/imgres?imgurl=http://www.dalcross.com/staging/_i mages/trigeminal.JPG&imgrefurl=http://www.dalcross.com/trigeminal_neur algia.php&h=578&w=550&sz=70&tbnid=EZaF9XlIF137dM::&tbnh=134&tb nw=128&prev=/images%3Fq%3Dtrigeminal%2Bpics&hl=en&usg=__kvKsX C_rl0dZorPt6qpCqT4IDdA=&ei=kyjKSbyrNJT27AO0yaytAg&sa=X&oi=imag e_result&resnum=2&ct=image&cd=1  http://www.google.co.in/imgres?imgurl=http://upload.wikimedia.org/wikipe dia/commons/9/99/Gray778_Trigeminal.png&imgrefurl=http://commons.wi

 http://images.google.co.in/imgres?imgurl=http://wpcontent.answers.com/w

ikipedia/en/thumb/e/e3/Gray696_Trigeminal.png/300pxGray696_Trigeminal.png&imgrefurl=http://www.answers.com/topic/trigemi nalnerve&usg=__fenDtfRA3gaI08q6fuhFFSzcTwo=&h=539&w=300&sz=109& hl=en&start=10&sig2=A5FGxaBoSqBwdvbznCbNg&um=1&tbnid=yDDxms2I2Pkt2M:&tbnh=132&t bnw=73&prev=/images%3Fq%3Dtrigeminal%2Btracts%2Bpics%26hl%3De n%26sa%3DX%26um%3D1&ei=_JnDSfLSHMOSkAWNysTXDA  http://www.google.co.in/imgres?imgurl=http://www.stjosephsatlanta.org/ga

mma_knife_center/images/gamma_knife_trigeminal_neuralgia_profile.jpg&i mgrefurl=http://www.stjosephsatlanta.org/gamma_knife_center/trigeminal. html&h=327&w=300&sz=128&tbnid=hpZGcBjS1e0M2M::&tbnh=118&tbn w=108&prev=/images%3Fq%3Dtrigeminal%2Bpics&hl=en&usg=__gAs9794jtB4vt3SSeXIgy0I6o=&ei=kyjKSbyrNJT27AO0yaytAg&sa=X&oi=image_result &resnum=1&ct=image&cd=1  http://www.google.co.in/imgres?imgurl=http://zingerone.foodsci.cornell.ed

u/trigeminal/trigeminal-figure.png&imgrefurl=http://nikasculinaria.com/2006/07/09/molecular-gastronomy-101-part-2%25E2%2580%2593-the-nose-andreceptors/&h=523&w=379&sz=56&tbnid=Vvh_s28IAjlFeM::&tbnh=131&tb

 http://images.google.co.in/imgres?imgurl=http://www.ncbi.nlm.nih.gov/boo

kshelf/picrender.fcgi%3Fbook%3Dcm%26part%3DA1882%26blobname%3 Dch61f2.jpg&imgrefurl=http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi%3Fb ook%3Dcm%26part%3DA1882&usg=__wKG_QNUDpHapRzzbYrd2FRhkjo=&h=558&w=482&sz=140&hl=en&start=9&sig2=JvPvZqC8XNFHeZlV mZawxA&um=1&tbnid=G7kwKMBbvltUkM:&tbnh=133&tbnw=115&prev=/ images%3Fq%3Dtrigeminal%2Btracts%2Bpics%26hl%3Den%26sa%3DX% 26um%3D1&ei=_JnDSfLSHMOSkAWNysTXDA  http://www.ajnr.org/cgi/content-nw/full/20/6/1119/F3  http://images.google.co.in/images?hl=en&um=1&q=trigeminal+nuclei+diag  http://www.google.co.in/imgres?imgurl=http://wpcontent.answers.com/wiki

pedia/en/thumb/e/e3/Gray696_Trigeminal.png/300pxGray696_Trigeminal.png&imgrefurl=http://www.answers.com/topic/trigemi nalnerve&h=539&w=300&sz=108&tbnid=yDDxms2I2Pkt2M::&tbnh=132&tbn w=73&prev=/images%3Fq%3Dtrigeminal%2Bnuclei%2Bdiagram&hl=en&u sg=__WE6860WS0L99KYD696GFCCOJcqk=&ei=oy_KSYzzMoiO6gOZ5rm9A g&sa=X&oi=image_result&resnum=3&ct=image&cd=1  http://www.google.co.in/imgres?imgurl=http://instruct.uwo.ca/anatomy/53 0/trignuc.gif&imgrefurl=http://instruct.uwo.ca/anatomy/530/530notes.htm &h=379&w=499&sz=72&tbnid=NZaUHJ1_CbF0M::&tbnh=99&tbnw=130&prev=/images%3Fq%3Dtrigeminal%2Bnucl ei%2Bdiagram&hl=en&usg=__9eZMutXE6L3gnl5wgNojn6WYvlE=&ei=oy_K