3. Anatomy:
• Largest & one of most complex cranial nerves
• Mixed nerve
• Large sensory part (portio major) & much smaller motor part (portio
minor)
• Sensory component has 3 divisions : ophthalmic, maxillary,
mandibular.
4. Function:
• The sensory function of the trigeminal nerve:
- provide the tactile, proprioceptive, and nociceptive afferent of the
face and mouth.
• The motor function:
- activates the muscles of mastication, the tensor tympani, tensor veli
palatini, mylohyoid, and anterior belly of the digastric.
5. Peripheral Anatomy:
• The three major branches converge on
the trigeminal ganglion (also called the
semilunar ganglion or gasserian
ganglion), located within Meckel's cave,
and contains the cell bodies of incoming
sensory nerve fibers.
• The trigeminal ganglion is analogous to
the dorsal root ganglia of the spinal
cord, which contain the cell bodies of
incoming sensory fibers from the rest of
the body.
6. • From the trigeminal ganglion, a single
large sensory root enters the brainstem
at the level of the pons. Immediately
adjacent to the sensory root, a smaller
motor root emerges from the pons at
the same level.
• Motor fibers pass through the
trigeminal ganglion on their way to
peripheral muscles, but their cell bodies
are located in the nucleus of the fifth
nerve, deep within the pons.
7. Sensory Branches of the Vth nerve:
Ophthalmic div
• Skull foramen : superior orbital
fissure
• Terminal br: : frontal , lacrimal,
nasociliary, meningeal
• Cutaneous innervation : bridge &
side of nose, upper eyelid,
forehead, scalp back to vertex,
eyeball, lacrimal gland, nasal
septum, lat wall of nasal cavity,
ethmoid sinus, tentorium
cerebelli
8. Sensory Branches of the Vth nerve:
Maxillary div
• Skull foramen : foramen
rotundum
• Terminal br : infraorbital,
zygomatic, sup.alveolar,
pterygopalatine, meningeal
• Cutaneous innervation : cheek,
lat.forehead, side of nose, upper
lip, upper teeth & gums, palate,
nasopharynx, post.nasal cavity,
meninges of ant & middle
cranial fossae
10. Motor branches of Vth nerve:
• Distributed in the mandibular nerve.
• These fibers originate in the motor nucleus of the fifth nerve, which is
located near the main trigeminal nucleus in the pons.
• The motor branches of the trigeminal nerve control the movement of
eight muscles, including the four muscles of mastication.
-Masseter
-Temporalis
-Medial pterygoids
-Lateral pterygoids
11. • Others:
-tensor veli palatine
-mylohyoid
-anterior belly of digastric
-tensor tympani
• With the exception of tensor tympani, all of these muscles are involved in
biting, chewing and swallowing.
• All have 'bilateral' cortical representation.
• A unilateral central lesion (e.g., a stroke), no matter how large, is unlikely to
produce any observable deficit.
• Injury to the peripheral nerve can cause paralysis of muscles on one side of
the jaw. The jaw deviates to the paralyzed side when it opens.
• This direction of the mandible is due to the action of normal pterygoids on
the opposite side.
12. Trigeminal nucleus
• The trigeminal nucleus extends throughout the entire brainstem, from the
midbrain to the medulla, and continues into the cervical cord, where it merges
with the dorsal horn cells of the spinal cord.
• The nucleus is divided anatomically into three parts, visible in microscopic
sections of the brainstem.
• They are the spinal trigeminal nucleus, the main trigeminal nucleus, and the
mesencephalic trigeminal nucleus.
• The three parts of the trigeminal nucleus receive different types of sensory
information.
-The spinal trigeminal nucleus receives pain/temperature fibers.
-The main trigeminal nucleus receives touch/position fibers.
-The mesencephalic nucleus receives proprioceptor and mechanoreceptor fibers
from the jaws and teeth
13.
14. Clinical examination
sensory functions
• Pain, touch, heat, cold – tested on face & mucous membranes
• Each of the 3 divisions of Vth.N is tested individually and compared
with the opposite side.
15. Clinical examination
motor functions
• Bulk & power of masseters & pterygoids – palpating as pt clinches the
jaw
• Ask pt – to protrude & retract the jaw
• Pt bite on tongue depressors with molar teeth
• U/L Trigeminal motor weakness –
deviation of jaw towards the weak side on opening
pt will be unable to move the jaw contralaterally.
Lesion inv brainstem, gasserian ganglion, motor root
16. Clinical examination
motor functions
• B/L Weakness of muscles of
mastication with inability to close
the mouth ( dangling jaw ) –
motor neuron ds, neuromuscular
transmission disorder, myopathy
18. • Trigeminal neuralgia (TN) is named
for the nerve (the fifth cranial
nerve) that is affected.
• Trigeminal neuralgia causes brief,
intense, severe pain, usually on one
side of the face or the jaw or near
the eye.
• Trigeminal neuralgia is a type
of neuropathic pain (pain caused
by nerves).
19. Trigeminal Neuralgia
• Initiating pathologic events include:
• nerve compression by tortuous arteries of the posterior fossa blood vessels
• demyelinating plaques
• herpes virus infection
• infection of teeth and jaw
• a brainstem infarct
21. Clinical manifestations
• Abrupt onset with excruciating pain!!
• Pain described as burning, knifelike, or lightinglike shock in the lips,
upper or lower gums, cheek, forehead, or side of the nose.
• Patient may twitch, grimace, frequent blinking and tearing of eye (tic)
may occur.
22. Clinical manifestations
• Attacks may be brief (2 or 3 minutes)
• Unilateral
• Episodes may be initiated by triggering mechanism of light cutaneous
stimulation as a specific point (trigger zone) along nerve branches.
23. Precipitating stimuli
• Chewing, brushing teeth, hot or cold blast of air on the face, washing
the face, yawning, or talking.
• Patient may eat improperly, neglect hygiene practices, wear cloth
over face, withdraw from interaction with others.
24. Diagnostic studies
• Need to rule out other neurological causes of facial and cephalic pain.
• CT scan will rule out brain lesions, vascular malformations. LP and
MRI will r/o MS.
• There is no specific diagnostic test for TN.
25. Drug Therapy
• Antiseizure meds may prevent and acute attack or promote
remission-mechanism unknown.
• Carbamazeprine (Tegretol)…most common
• Phenytoin (Dilantin)
• Valproate (Depakene)
26. Drug Therapy
• Carbamazeprine has side effects:
• Bone marrow suppression leading to blood abnormalities (CBC counts
needed)
• Pain relief not permanent
28. Surgery
• Percutaneous radiofrequency rhizotomy (electrocoagulation)- placing
a needle into the trigeminal nerve to destroy the area by
radiofrequency currents.
• May lose corneal reflex
• Easily performed; minimal risk
• Pain relieved, but face is numb
29. Microvascular decompression
• Most common surgical procedure
• Blood vessels that are compressing the nerve are displaced and
repositioned. This relieves pain without residual sensory loss.
• Long-term success rate
• Safe without residual sequelae
• Recurrence occurs in 30% of patients within 6 years
Sympathetic and parasympathetic fibers join the three divisions and are distributed to the pupil, to the nasal mucosa causing mucus secretion, to the lacrimal, submaxillary, and sublingual glands, and to the arterioles of the face.
Motor root: Passes forward in posterior fossa Pierces the duramater beneath attachment of tentorium to tip of petrous part of temporal bone. Enters the meckel’s cave leaves skull via Foramen Ovale. It joins the mandibular div of Vth N to form mandibular nerve – supplies masticatory muscles .
