Trigeminal Neuralgia (TN)

• Trigeminal Neuralgia (TN) is a disorder of the trigeminal nerve (CN V) that produces severe pain in the lower face, jaw, around the nose, and above the eye

Trigeminal Neuralgia Overview

• Also known as Tic Douloureux, which translates to "facial spasm" in French
• TN is usually limited to one side of the face
• It most often occurs in people over age 50, and is more common in women than men in a 3:2 ratio
• The incidence of trigeminal neuralgia is approximately 12 cases per 100,000 people per year

Trigeminal Nerve Details

• The trigeminal nerve is the largest and most complex nerve, containing both motor and sensory fibers known as a mixed nerve
• Ophthalmic branch carries sensory information from the scalp, forehead, upper eyelid, conjunctiva, cornea, nose, nasal mucosa, frontal sinuses, and parts of the meninges (dura and blood vessels)
• Maxillary branch carries sensory information from the lower eyelid, cheek nares, upper lip, upper teeth/gums, nasal mucosa, palate, roof of pharynx, maxillary/ethmoid/sphenoid sinuses, and parts of meninges
• Mandibular branch is the largest branch and carries sensory information from the lower lip, lower teeth, gums, chin, jaw, parts of the external ear, and other parts of the meninges

Etiology and Pathophysiology

• Primary Trigeminal Neuralgia (TN) involves vascular compression where an artery or vein comes into contact with the trigeminal nerve at the base of the brain
• Secondary TN can be caused by trauma, multiple sclerosis, vestibular schwannoma (acoustic neuroma), meningioma, cyst, saccular aneurysm, or arterio-venous malformation
• Demyelination, vascular and degenerative changes in the sensory ganglion may lead to ectopic impulse generation, causing adjacent nerve fibers to exchange ions, resulting in a transmission of impulse known as ephaptic transmission

Clinical Presentation

• TN presents as recurrent paroxysms of pain unilaterally in one or more branches of the CN V, described as burning, stabbing, sharp, penetrating, or electric (shock-like)
• Severe pain episodes can last from seconds up to 15 minutes
• Trigger zones may be present, where light contact initiates an attack, such as applying makeup, brushing teeth, smiling, or grimacing
• Trigeminal Neuralgia has been described as the most excruciating pain in humanity
• The condition is usually unilateral, and bilateral cases should raise suspicion for Multiple Sclerosis

Physical Exam

• The physical exam involves checking the head, neck, and all cranial nerves
• Crucially, you must assess the ears, mouth, teeth, and TMJ for possible causes of facial pain
• Finding trigger zones supports a diagnosis of TN
• Patients generally have normal examination, and deficits are rare

Diagnostics

• Diagnosis is typically made from history and presentation
• Pain on TN lasts more than 15 minutes without radiation
• Pain is characterized by at least three instances of intense, sharp, burning, superficial, or stabbing sensations precipitated by a trigger event
• Absence of neurological deficits is typical
• There should be no other attributable cause
• CT or MRI imaging is required if secondary TN is suspected
• A referral to a neurologist is necessary

Differential Diagnosis

• Consider Cluster Headache, Dental Pain, Giant Cell Arteritis, Glossopharyngeal Neuralgia, Intracranial Tumors, Migraine, Multiple Sclerosis, Otitis Media, Paroxysmal Hemicrania, Postherpetic Neuralgia, Sinusitis, SUNCT syndrome, and TMJ syndrome as differential diagnoses

Management - Pharmacological

• Carbamazepine is the initial treatment at 100-200mg PO twice daily, with a dose increased by 200mg daily, up to a maximum dose of 1200 mg daily
• Other agents include Baclofen, Lamotrigine, Phenytoin, and Gabapentin (off label) to be added if symptoms persist

Management - Non-Pharmacological

• Avoid stimulation of trigger areas i.e. breeze, heat, or cold
• Avoid activities that may initiate pain
• Surgical decompression involves craniotomy and vascular separation
• Surgical ablation involves lesioning of the trigeminal ganglion by radiofrequency thermoregulation, mechanical balloon compression, or chemical injection
• Peripheral Neurectomy or Nerve block carries the risk of muscle weakness, loss of facial sensation, and recurrent neuralgia
• If pain is uncontrolled, consider issues such as weight loss, dehydration, poor dental hygiene, and depression

Prognosis

• Recurrence of Trigeminal Neuralgia is common
• Episodes may last weeks or months and are followed by pain-free intervals
• Complications are usually related to pharmacologic treatment, such as aplastic anemia, drowsiness, dizziness, and cognitive changes