TRIGEMINAL NEURALGIA

R.Nandinii

Part 1:Trigeminal nerve

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.

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.

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.

• 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.

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

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

Sensory Branches of the Vth nerve: Mandibular div

• Skull foramen : foramen ovale • Terminal br : buccal, lingual,

inf.alveolar, auriculotemporal, meningeal • Cutaneous innervation : Inner

cheek, temple, lateral scalp, ext.aud.meatus, tympanic membrane, TMJ, mandible, lower teeth & gums, ant.2/3 tongue, lower lip, meninges of ant & middle cranial fossae

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

• 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.

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

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.

Clinical examinationmotor 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

Clinical examinationmotor functions

• B/L Weakness of muscles of mastication with inability to close the mouth ( dangling jaw ) – motor neuron ds, neuromuscular transmission disorder, myopathy

Part 2: Trigeminal neuralgia

• 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).

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

Trigeminal neuralgia

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.

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.

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.

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.

Drug Therapy

• Antiseizure meds may prevent and acute attack or promote remission-mechanism unknown.• Carbamazeprine (Tegretol)…most common• Phenytoin (Dilantin)• Valproate (Depakene)

Drug Therapy

• Carbamazeprine has side effects:• Bone marrow suppression leading to blood abnormalities (CBC counts

needed)• Pain relief not permanent

Conservative Therapy

• Nerve block• Biofeedback

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

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

Glycerol rhizotomy

• Injecting glycerol near the root of the nerve• Safer and fewer risks that percutaneous types.