eMedicine Specialties > Neurosurgery > Functional

Trigeminal Neuralgia

Author: Kim J Burchiel, MD, FACS, John Raaf Professor and Chairman, Department of Neurological Surgery, Professor, Department of Anesthesiology and Perioperative Medicine, Oregon Health and Science University; Attending Neurosurgeon, Section of Neurosurgery, Portland Veterans Affairs Medical Center
Coauthor(s): Suzan Khoromi, MD, Fellow, Pain and Neurosensory Mechanisms Branch, National Institute of Dental and Cranial Research, National Institutes of Health; Abraham Totah, MD, Staff Physician, Department of Neurology, University of South Florida; Sally B Zachariah, MD, Associate Professor, Department of Neurology, University of South Florida; Director, Department of Neurology, Division of Strokes, Veteran Affairs Medical Center of Bay Pines
Contributor Information and Disclosures

Updated: Sep 30, 2008

Introduction

The clinical description of severe facial pain, which is now known as trigeminal neuralgia (TN), can be traced back more than 300 years. Aretaeus of Cappadocia, known for one of the earliest descriptions of migraine, is credited with the first indication of TN. He described a headache in which "spasms and distortions of the countenance took place." John Fothergill was the first to give a full and accurate description of TN in a paper titled "On a Painful Affliction of the Face," which he presented to the medical society of London in 1773. Nicholaus Andre coined the term tic douloureux in 1756.

Idiopathic TN is the most common type of facial pain neuralgia. The pain typically occurs in the distribution of one of the branches of the trigeminal nerve, usually on one side. Rarely, it can affect both sides, although simultaneous bilateral trigeminal neuralgia is uncommon. It involves both the mandibular and maxillary divisions of the trigeminal nerve in 35% of affected patients. Isolated involvement of the ophthalmic division is much less common (2.8% of TN cases).

TN reportedly is one of the most excruciating pain syndromes. It has been known to drive patients with TN to the brink of suicide. The name tic douloureux was first used to describe TN and remains synonymous with the classic form of TN. The tic refers mainly to the visible effects of the brief and paroxysmal pain that, in classic TN, lasts only a few seconds. The pain is so severe that it often causes the patient to wince or make an aversive head movement, as if trying to escape the pain, thus producing an obvious movement, or tic.

An interactive Web site now allows patients to self-diagnose facial pain based on a brief series of questions. An artificial intelligence method (neural network modeling) provides immediate feedback to the patient regarding the diagnosis and patient education resources.¹

For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education articles Trigeminal Neuralgia (Facial Nerve Pain), Tic Douloureux, and Pain Medications.

Problem

A lack of clear definitions for facial pain has hampered the understanding of trigeminal neuralgia. The condition has no clear natural history, and no long-term follow-up study of the progression of the disorder has ever been published. In an attempt to rationalize the language of facial pain, recently, a new classification scheme that divides facial pain into several distinct categories was introduced:²

• Trigeminal neuralgia type 1 (TN1): This is the classic form of trigeminal neuralgia in which episodic lancinating pain predominates.
• Trigeminal neuralgia type 2 (TN2): This is the atypical form of trigeminal neuralgia in which more constant pains (aching, throbbing, burning) predominate.
• Trigeminal neuropathic pain (TNP): This is pain that results from incidental or accidental injury to the trigeminal nerve or the brain pathways of the trigeminal system.
• Trigeminal deafferentation pain (TDP): This is pain that results from intentional injury to the system in an attempt to treat trigeminal neuralgia. Numbness of the face is a constant part of this syndrome, which has also been referred to as anesthesia dolorosa or one of its variants.
• Symptomatic trigeminal neuralgia (STN): This is trigeminal neuralgia associated with multiple sclerosis (MS).
• Postherpetic neuralgia (PHN): This is chronic facial pain that results from an outbreak of herpes zoster (shingles), usually in the ophthalmic division (V1) of the trigeminal nerve on the face and usually in elderly patients.
• Geniculate neuralgia (GeN): This is typified by episodic lancinating pain felt deep in the ear.
• Glossopharyngeal neuralgia (GPN): This is typified by pain in the tonsillar area or throat, usually triggered by talking or swallowing.

Frequency

The disease begins after age 40 in 90% of patients and is slightly more common in women. The incidence is said to be approximately 4-5 per 100,000 persons, although this is likely an underestimate. TN is observed with increased frequency in one disease category, ie, multiple sclerosis (MS). TN occurs in up 4% of these patients, in whom it is often bilateral. About 2% of patients with TN have MS.

Etiology

The etiology of most cases of TN is chronic vascular compression and injury to the trigeminal nerve at its entrance into the brainstem (pons). In one study, 64% of the compressing vessels were identified as an artery, most commonly the superior cerebellar (81%). Venous compression was identified in 36% of cases.³

Pathophysiology

Vascular compression of the trigeminal nerve appears to cause demyelination and remyelination of the nerve with persisting abnormalities of myelination (dysmyelination).

The most common theoretical explanation for TN proposes that high-frequency ectopic impulses are either generated from or augmented by areas of dysmyelination.⁴ These abnormal discharges may ignite a chain reaction of neuronal depolarization in the trigeminal ganglion.⁵ The subsequent cascade of neuronal activity is progated centrally into the trigeminal nucleus and is then perceived by the patient as an overwhelming burst of pain.

Although most cases of TN are caused by vascular compression, other structural disease is present in secondary TN, which can produce either typical or atypical pain. For example, a mass may displace and damage the nerve, resulting in pain. Alternatively, inflammation secondary to multiple processes may be due to the underlying lesion. (See Differentials).

In MS, lesions in the pons at the root entry zone (REZ) of the trigeminal fibers have been demonstrated. This is one form of "symptomatic" trigeminal neuralgia related to visible pathology. 

Presentation

TN presents with multiple episodes of severe and spontaneous pain that usually lasts seconds to minutes. The pain is often described as shooting, lancinating, shocklike, or stabbing. The episodes frequently are triggered by painless sensory stimulation to perioral trigger zones, eg, a patch of facial skin, mucosa, or teeth innervated by the ipsilateral trigeminal nerve. Triggers include touch, certain head movements, talking, chewing, swallowing, shaving, brushing teeth, or even a cold draft. The most commonly affected dermatomal zones are innervated by the second and third branches of the trigeminal nerve.

The episodes may be repetitive, recurring, and remitting randomly. Pain-free intervals, which might last for years early in the course of TN, typically grow shorter as the disease progresses. During episodes of pain, some patients have difficulty talking, eating, and maintaining facial hygiene out of fear of triggering the pain.

Physical: Standard bedside neurological examination findings are normal in TN. Patients may refuse examinations of the face, fearing the triggering of pain. Male patients may present with an area of the face, the trigger zone, that is unshaven and unkempt. The finding of numbness in the trigeminal distribution of TN suggests secondary TN and more extensive damage to the trigeminal nerve.

• Trigeminal neuropathy: Sensory loss is usually prominent; pain is slight.
• Herpetic and postherpetic neuralgia (PHN): This condition usually affects the first branch of the trigeminal nerve. The diagnosis of PHN usually requires the outbreak of shingles (herpes zoster) in the forehead or eye. Acute herpetic neuralgia is the norm in shingles, but pain that persists after the lesions have healed is PHN. The risk of PHN development is directly related to patient age.
• Neoplasms: These may present as a compressing mass or neoplastic cell infiltration of the trigeminal nerve. Pain is usually more constant than in TN1, and facial numbness is more common.
• Granulomatous inflammation (eg, tuberculosis, sarcoidosis, Behçet syndrome, collagen vascular diseases): These and other vasculitides may affect the trigeminal nerve and simulate TN.
• Other conditions that may mimic TN include odontogenic pain, geniculate neuralgia, glossopharyngeal neuralgia, temporomandibular disorders, cluster headache, hemicrania, and SUNCT (short-lasting, unilateral neuralgia from headache attacks with conjunctival injection and tearing) syndrome.

Indications

Surgical treatment is indicated for patients whose trigeminal neuralgia (TN) is intractable despite medical therapy, in those who are intolerant to the adverse effects of the medications, and in those in whom previous procedures failed.

Microvascular decompression (MVD) is usually indicated for patients younger than 70 years who are at lower risk for complications during general anesthesia, although healthy older patients can tolerate it well. Percutaneous approaches (eg, radiofrequency ablation, glycerol injection, balloon compression, radiosurgery) are more frequently offered to elderly patients, those in poor medical condition, those with MS, and those in whom previous MVD has failed.

Relevant Anatomy

The trigeminal nerve is the largest of all the cranial nerves. It exits laterally at the mid-pons level and has 2 divisions—a smaller motor root (portion minor) and a larger sensory root (portion major). The motor root supplies the temporalis, pterygoid, tensor tympani, tensor palati, mylohyoid, and anterior belly of the digastric. The motor root also contains sensory nerve fibers that particularly mediate pain sensation.

The gasserian ganglion is located in the trigeminal fossa (Meckel cave) of the petrous bone in the middle cranial fossa. It contains the first-order general somatic sensory fibers that carry pain, temperature, and touch. The peripheral processes of neurons in the ganglion form the 3 divisions of the trigeminal nerve, ie, ophthalmic, maxillary, and mandibular. The ophthalmic division exits the cranium via the superior orbital fissure; the maxillary and mandibular divisions exit via the foramen rotundum and foramen ovale, respectively.

The proprioceptive afferent fibers travel with the efferent and afferent roots. They are peripheral processes of unipolar neurons located centrally in the mesencephalic nucleus of the trigeminal nerve.

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