The trigeminal nerve is the fifth cranial nerve that has both sensory and motor functions. It has three main divisions - the ophthalmic, maxillary, and mandibular nerves. Clinically, it is important to assess the trigeminal nerve's function through motor and sensory examinations including tests of the corneal reflex, jaw jerk reflex, and lacrimal reflex. Dysfunction of the trigeminal nerve can result in conditions like trigeminal neuralgia, cluster headaches, and Wallenberg syndrome.

1. TRIGEMINAL
NERVE
JOEL.SONY

2. TRIGEMINAL NERVE
THE TRIGEMINAL NERVE IS SO CALLED BECAUSE OF ITS THREE MAIN
DIVISIONS I.E. THE OPHTHALMIC, MAXILLARY & MANDIBULAR NERVES.
THE ORIGIN OF THE TRIGEMINAL NERVE IS THE ANNULAR
PROTUBERANCE AT THE LIMIT OF THE CEREBELLAR PEDUNCLES. IT
ORIGINATES FROM THREE SENSORY NUCLEI (MESENCEPHALIC, PRINCIPAL
SENSORY, SPINAL NUCLEI OF TRIGEMINAL NERVE) AND ONE MOTOR
NUCLEUS (MOTOR NUCLEUS OF THE TRIGEMINAL NERVE) EXTENDING
FROM THE MIDBRAIN TO THE MEDULLA
• 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.

4. DISTAL ROOTS
THE SENSORY NUCLEI MERGE TO FORM THE SENSORY ROOT AT THE
LEVEL OF THE PONS AND THE MOTOR NUCLEUS CONTINUES TO FORM THE
MOTOR ROOT. AS A RESULT THE SENSORY ROOT IS LARGE (MADE UP OF
ABOUT 50 FASCICLES), WHILE THE MOTOR ROOT IS MORE SLENDER
(COMPOSED OF SIX OR SEVEN FASCICLES). THESE ROOTS ARE ANALOGOUS TO
THE DORSAL AND VENTRAL ROOTS OF THE SPINAL CORD.
THE SENSORY ROOT THEN EXPANDS INTO THE TRIGEMINAL GANGLION,
IN THE MIDDLE OF THE CRANIAL FOSSA. THE TRIGEMINAL GANGLION
IS LOCATED LATERAL TO THE CAVERNOUS SINUS, IN A DEPRESSION OF THE
TEMPORAL BONE, KNOWN AS THE TRIGEMINAL CAVE.
THE SPINAL TRIGEMINAL TRACT COMES UP FROM THE SENSORY ROOT IN
THE PONS AND TRAVELS DOWNWARD INTO THE UPPER CERVICAL CORD. THE
FIBERS THEN END IN THE SPINAL TRIGEMINAL NUCLEUS, WHICH MERGES
ANTERIORLY WITH THE PRINCIPAL SENSORY NUCLEUS

5. PERIPHERAL DIVISONS OFTHETRIGEMINAL NERVE
THE TRIGEMINAL NERVE DIVIDES INTO 3 NERVES DISTAL TO THE TRIGEMINAL
GANGLION
•THE OPHTHALMIC NERVE (V1), PASSES FORWARD IN THE LATERAL WALL TO
THE CAVERNOUS SINUS. IT THEN ENTERS THE ORBIT VIA THE SUPERIOR
ORBITAL FISSURE.
•THE MAXILLARY NERVE (V2), LEAVES THE SKULL BASE THROUGH THE
FORAMEN ROTUNDUM OSSIS SPHENOIDALIS, INFEROLATERAL TO THE
CAVERNOUS SINUS. IT THEN ENTERS THE PTERYGOPALATINE FOSSA, GIVING OFF
SEVERAL BRANCHES. THE MAIN TRUNK THEN CONTINUES ANTERIORLY IN THE
ORBITAL FLOOR AND EMERGES ONTO THE FACE AS THE INFRAORBITAL NERVE
•THE MANDIBULAR NERVE (V3), RUNS LATERALLY ALONG THE SKULL BASE THEN
EXITS THE CRANIUM BY DESCENDING THROUGH THE FORAMEN OVALE INTO
THE MASTICATOR SPACE. THE MOTOR ROOT OF THE TRIGEMINAL NERVE
BYPASSES THE TRIGEMINAL GANGLION AND REUNITES WITH THE MANDIBULAR
NERVE IN THE FORAMEN OVALE BASIS CRANII. HENCE THE V3 IS THE ONLY
BRANCH WHICH CONTAINS BOTH SENSORY AND MOTOR COMPONENTS:THE
OPTHALMIC (V1) AND MAXILLARY (V2) NERVES CONTAIN ONLY SENSORY
FIBRES.

6. FUNCTION
IT IS A MIXED NERVE - THE SENSORY PART OF THE NERVE SUPPLIES THE FACE
(INCLUDES TOUCH, PAIN, AND TEMPERATURE) AND THE MOTOR PART IS FOR
MUSCLES OF MASTICATION.
THE SENSORY INFORMATION IS SENT FORTH THROUGH THE MAIN
TRIGEMINAL NUCLEUS AND NUCLEI OF THE THALAMUS BEFORE IT TRAVELS
TO THE CEREBRAL CORTEX AND SYNAPSES IN THE POST-CENTRAL GYRUS.
JUST LIKE ANY OTHER SENSORY INFORMATION OF THE BODY, THE
INFORMATION FROM THE FACE CROSSES OVER (DECUSSATES) TO THE
CONTRALATERAL BRAIN HEMISPHERE.

7. MOTOR
•THE MOTOR ROOT OF THE TRIGEMINAL NERVE BYPASSES THE
TRIGEMINAL GANGLION AND REUNITES WITH THE MANDIBULAR NERVE
IN THE FORAMEN OVALE BASIS CRANII.
•THE MOTOR ROOT OF THE MANDIBULAR NERVE INNERVATES THE FOUR
MUSCLES OF MASTICATION
1.MASSETER,
2.TEMPORALIS MUSCLE,
3.THE LATERAL PTERYGOIDS AND
4.THE MEDIAL PTERYGOIDS.
•THE MUSCLES OF MASTICATION PRODUCE ELEVATION, DEPRESSION,
PROTRUSION, RETRACTION, AND THE SIDE-TO-SIDE MOVEMENTS OF THE
MANDIBLE.
•ADDITIONALLY, THE MOTOR COMPONENT OF THE V3 ALSO INNERVATES
THE TENSOR VELI PALATINI, THE MYLOHYOID, THE TENSOR TYMPANI, AND
THE ANTERIOR PORTION OF THE DIGASTRIC MUSCLE

8. SENSORY
 THE SENSORY COMPONENTS OF THE 3 BRANCHES CARRY PAIN,
TEMPERATURE AND TOUCH INFORMATION FROM THE SKIN OF THE FACE;
MUCOSA OF OF THE SINUSES. NOSE AND MOUTH; THE TEETH AND PORTION
OF DURA.
 THEY ALSO CARRY PROPRIOCEPTIVE INFORMATION FROM THE TEETH, HARD
PALATE, TEMPOMANDIBULAR JOINT AND THE MUSCLES OF MASTICATION.
 THE OPHTHALMIC NERVE IS RESPONSIBLE FOR SENSORY INNERVATION OF
THE FACE AND SKULL, DERIVED FROM THE FRONTONASAL PROMINENCE, AS
WELL AS THE EYE AND PORTIONS OF THE NASAL CAVITY. IT ALSO CONTAINS
SYMPATHETIC NERVE FIBERS RESPONSIBLE FOR PUPIL DILATION AND
SUPPLIES THE CILIARY BODY, IRIS, LACRIMAL GLAND, CONJUNCTIVA, AND
CORNEA. ADDITIONALLY ALSO SUPPLIES THE SUPERIOR PORTION OF THE
NASAL CAVITY, THE FRONTAL SINUS, AND EVEN DEEPER STRUCTURES
INCLUDING THE DURA MATER AND PORTIONS OF THE ANTERIOR CRANIAL
FOSSA.
 THE MAXILLARY NERVE INNERVATES PORTIONS OF THE NASAL CAVITY,
SINUSES, MAXILLARY TEETH, PALATE, AND THE MIDDLE PORTION OF THE
FACE AND SKULL ABOVE THE MOUTH AND BELOW THE FOREHEAD.

9.  THE SENSORY FIBRES OF THE MANDIBULAR NERVE ARE RESPONSIBLE FOR
PAIN AND TEMPERATURE INFORMATION FROM THE MANDIBULAR TEETH,
BUCCAL MUCOSA, TEMPOROMANDIBULAR JOINT, THE FACE BELOW THE
DISTRIBUTION OF THE MAXILLARY NERVE AND THE ANTERIOR TWO-THIRDS
OF THE TONGUE; THIS IS DIFFERENTIATED FROM TASTE WHICH IS PRODUCED
BY CN VII.
THE SYMPATHETIC AND PARASYMPATHETIC FIBERS, ALONG WITH THE 3
BRANCHES, ARE DISTRIBUTED TO THE NASAL MUCOSA CAUSING MUCUS
SECRETION, TO THE PUPIL, TO THE SUBLINGUAL GLANDS, THE LACRIMAL, THE
SUBMAXILLARY GLANDS AND TO THE ARTERIOLES OF THE FACE.

10. CLINICAL RELEVANCE
• TRIGEMINAL NEURALGIA - IS DEFINED AS SUDDEN, BRIEF, AND
EXCRUCIATING FACIAL PAIN ATTACKS IN ONE OR MORE OF THE V BRANCHES.
AS A RESULT, IT LEADS TO A SEVERE REDUCTION IN THE QUALITY OF LIFE OF
AFFECTED PATIENT. ITS AETIOLOGY CAN BE CLASSIFIED INTO IDIOPATHIC,
CLASSIC AND SECONDARY.
• CLUSTER HEADACHES - DEFINED AS UNILATERAL HEADACHES THAT AFFECTS
THE DISTRIBUTION OF THE TRIGEMINAL NERVE. ALONG WITH THE PAIN,
THEY CAN BE ACCOMPANIED WITH NASAL CONGESTION, SWELLING, AND
LACRIMATION ON THE AFFECTED SIDE.
• WALLENBERG SYNDROME (LATERAL MEDULLARY SYNDROME) - IS DEFINED
AS A CONDITION IN THE WHICH THE LATERAL PORTION OF THE MEDULLA IN
THE BRAINSTEM GETS DAMAGED, LIKE IN CASE OF A STROKE. IN THIS
SYNDROME THERE IS SENSORY LOSS IN THE DISTRIBUTION OF THE
TRIGEMINAL NERVE ON THE SAME AND CONTRALATERAL SENSORY LOSS IN
THE REST OF THE BODY.
• INFECTIONS - GENERALLY OCCUR IN THE PERIPHERAL DIVISIONS OF THE
TRIGEMINAL NERVE, MOSTLY DUE TO LOCAL TUMOURS LEADING TO DIRECT
SPREAD AND METASTASES FROM DISTANT MALIGNANCIES.

11. • NEOPLASMS - JUST AS INFECTION, MORE COMMON IN THE PERIPHERAL
DIVISIONS OF CNV. EXTRINSIC DISEASE OF THE MECKEL'S CAVITY (WHICH
USUALLY INVOLVES BONY METASTASIS, CHORDOMA, OR CHONDROSARCOMA)
DESTROY ADJACENT BONE AS THEY EXTEND TOWARD THE MECKEL’S CAVITY
AND THE INTRINSIC DISEASE OF THE SAME CAVITY SIMPLY EXPANDS IT.
PRIMARY TUMOURS OF THE MECKEL’S CAVITY INCLUDE EPIDERMOID CYST,
TRIGEMINAL SCHWANNOMA AND MENINGIOMA.
• TRIGEMINAL SENSORY NEUROPATHY - UPPER CERVICAL DISC HERNIATIONS
PATIENTS CAN PRESENT WITH THIS KIND OF NEUROPATHY WITH CERVICAL
EXTENSION OF THE SPINAL TRACT DUE TO ITS ANATOMY IN THE BRAINSTEM.
COMMON BRAINSTEM AND UPPER CERVICAL CORD LESIONS WHICH CAN
LEAD TO CN V SYMPTOMS INCLUDE MULTIPLE SCLEROSIS, GLIOMA, AND
INFARCTION. LESSER COMMON LESIONS INCLUDE METASTASIS,
HAEMORRHAGE, CAVERNOUS HAEMANGIOMAS AND ARTERIOVENOUS
MALFORMATION. RARELY, RHOMBENCEPHALITIS MAY DEVELOP AS A RESULT
OF RETROGRADE EXTENSION OF HERPES SIMPLEX VIRUS TYPE 1 FROM THE
TRIGEMINAL GANGLION INTO THE BRAINSTEM.

12. ASSESSMENT
THE CN V HAS THREE TERMINAL BRANCHES THAT INNERVATE THE SKIN OF
THE FACE AND NECK, MUCOUS MEMBRANES AND PARANASAL SINUSES OF
THE FACE, THE CORNEAS, AND THE MUSCLES OF MASTICATION, THEREFORE
TRIGEMINAL REFLEX CAN BE USED TO ASSESS THE PROPER FUNCTIONING OF
THE NERVE FOR EACH OF THE AREA ITSERVES.
A TRIGEMINAL NERVE REFLEX IS A NATURAL RESPONSE TO STIMULI
INDICATING THE PROPER FUNCTIONING OF THE NERVE. AS IT HAS BOTH
SENSORY AND MOTOR FIBERS, CLINICAL ASSESSMENT/EXAMINATIONS
SHOULD EVALUATE THE RESPONSE OF EACH STRUCTURE. WHEN THE REFLEX
IS PRESENT, EG JAW REFLEX OR CORNEAL REFLEX, IT IS SAFE TO SAY THE CN V
TRACT IS FUNCTIONING WITH IN ITS NORMAL NATURAL PARAMETERS.
HOWEVER, THE ABSENCE OF OR VARIATION IN THE STRENGTH OF THE
REFLEX ASSISTS IN LOCALIZING THE LESION AND ASSESSING THE SEVERITY
OF THE ABNORMALITY WITHIN THE CN V TRACT.

13. MOTOR EXAMINATION.
IT IS PERFORMED TO TEST THE SUPERFICIAL MUSCLES OF MASTICATION,
MAINLY THE TEMPORALIS AND MASTER MUSCLES.
• MUSCLE MASS - THE SUBJECT IS ASKED TO CLENCH THEIR TEETH, WHILE THE
EXAMINER PALPATES THE TEMPORALIS AND THE MASSETER MUSCLE TO
ASSESS ITS MUSCLE MASS.
• MUSCLE STRENGTH - CAN BE ASSESSED BY PLACING THE FINGERS OF THE
EXAMINING HAND BENEATH THE CHIN AND ASKING THE PATIENT TO OPEN THE
MOUTH AND RESIST CLOSURE.
• MOTOR NUCLEUS FUNCTION - THE SUBJECT IS ASKED TO OPEN THEIR MOUTH
AND DEVIATE THE JAW FROM LEFT TO RIGHT. UNINTENTIONAL JAW DEVIATION
TOWARD ONE SIDE PIN POINTS TOWARDS A LESION OF THE TRIGEMINAL
NERVE NUCLEI INNERVATING THE PTERYGOID MUSCLE ON THE AFFECTED SIDE.

14. SENSORY EXAMINATION
THE 2 MAIN SENSORY SENSATIONS THAT ARE EXAMINED IN RELATION TO THE
CN V ARE PAIN AND LIGHT TOUCH. THE METHOD OF CHOICE FOR LIGHT TOUCH
TESTING IS USING A COTTON WISP, WHERE THE EXAMINER GIVES
INSTRUCTIONS TO THE PATIENT TO CLOSE THEIR EYES AND SAY "YES" EACH
TIME THEY FEEL A TOUCH. THIS TEST IS FIRST PERFORMED ON AREAS NOT
SUPPLIED BY THE CN V AS IT FORMS A BASELINE REFERENCE POINT, ASSUMING
THAT THERE ARE NO SENSORY DEFICITS IN THAT AREA. ONCE THE SUBJECT
CLOSES THEIR EYES, THE EXAMINER PROCEEDS TO LIGHTLY TOUCH THE AREA
SUPPLIED BY THE NERVE WITH THE COTTON WISP. THE NERVE IS ALWAYS
TESTED BILATERALLY TO CHECK FOR UNILATERAL OR BILATERAL (B/L) LESIONS.
FOR TESTING NOCICEPTION, THE SAME PROCEDURE IS FOLLOWED AS ABOVE,
BUT THIS TIME THE TESTING OBJECT IS A SHARP OBJECT RATHER THAN A
COTTON WISP.

15. • CORNEAL REFLEX - INVOLVES B/L INVOLUNTARY BLINKING OF THE EYELIDS
STIMULATED BY THERMAL, PAINFUL OR TACTILE STIMULATION OF THE
CORNEA. THE ABSENCE OF THIS REFLEX IS INDICATIVE OF
TNR/OPHTHALMIC NERVE OR FACIAL NERVE DAMAGE AS THE OPHTHALMIC
NERVE IS THE AFFERENT LIMB AND THE FACIAL NERVE IS THE EFFERENT
LIMB. PERIPHERAL DAMAGE CAUSES IPSILATERAL REFLEX DEFICITS, WHILE
CENTRAL DAMAGE TENDS TO BE ASSOCIATED WITH BILATERAL DEFICITS.
OTHER DISORDERS AND ENVIRONMENTAL FACTORS AFFECTING THE
CORNEA CAN ALSO INFLUENCE THIS REFLEX EG GLAUCOMA AND DIABETES
• JAW JERK REFLEX- PERFORMED TO CHECK THE INTEGRITY OF THE UPPER
MOTOR NEURONS, WHICH PROJECT INTO THE TRIGEMINAL MOTOR
NUCLEUS. THE EXAMINER PLACES A FINGER IN BETWEEN THE LOWER LIP
AND THE CHIN OF THE SUBJECT, WITH THE MOUTH SLIGHTLY OPEN. THE
EXAMINER THEN TAPS ON THE FINGER IN A DOWNWARD ANGLE.
NORMALLY THE REFLEX IS SLIGHT OR ABSENT. HOWEVER, IN A UPPER
MOTOR NEURON LESIONS THE REFLEX IS EXAGGERATED AS THE MASSETER
MUSCLES JERK THE MANDIBLE UPWARDS.

16. • LACRIMAL REFLEX - IN THIS REFLEX ARC, IRRITATION OF THE CORNEA AND
CONJUNCTIVA LEADS TO PRODUCTION OF TEARS. THE CILIARY FIBERS OF
THE NASOCILIARY BRANCH OF V1 IN THE TRIGEMINAL NERVE IS THE
AFFERENT LIMB OF THE REFLEX ARC AND THE FACIAL NERVE (CN VII) AND
THE SUPERIOR SALIVARY NUCLEUS ARE CNS COMPONENT OF THE REFLEX
ARC. IN AN EVENT OF AN ABNORMAL REFLEX ARC, LEADS TO WATERING OF
THE EYES WITH OUT AN APPROPRIATE STIMULUS.

17. THANK YOU!!!