You are in: eMedicine Specialties > Neurosurgery > MEDICAL TOPICS Trigeminal NeuralgiaArticle Last Updated: Oct 6, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Kim J Burchiel, MD, FACS, John Raaf Professor and Chairman, Department of Neurological Surgery, Professor, Department of Neurological Surgery, and Department of Anesthesiology and, Oregon Health and Science University 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 Editors: Paul L Penar, MD, Professor, Department of Surgery, Division of Neurosurgery, University of Vermont School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Allen R Wyler, MD, Former Medical Director, Northstar Neuroscience, Inc; Herbert H Engelhard III, MD, PhD, Director, UIC Neuro-Oncology Program, Chief, Division of Neuro-Oncology, Associate Professor, Department of Neurosurgery, University of Illinois at Chicago; Allen R Wyler, MD, Former Medical Director, Northstar Neuroscience, Inc Author and Editor Disclosure Synonyms and related keywords: trigeminal neuralgia, tic douloureux INTRODUCTIONSection 2 of 10
  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 (Limonadi, 2006). 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. ProblemA 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 (Burchiel, 2003):
FrequencyThe 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. EtiologyThe 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 (Anderson, 2006). PathophysiologyVascular 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 (Burchiel, 1980). These abnormal discharges may ignite a chain reaction of neuronal depolarization in the trigeminal ganglion (Devor, 2002). 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. However, the success of MVD in some patients with TN and MS suggests that other combined mechanisms play a role in the generation of pain. ClinicalTN 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. Differentials: Most of the following conditions are not easily confused with TN:
INDICATIONSSection 3 of 10
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 ANATOMYSection 4 of 10
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. WORKUPSection 5 of 10
Lab Studies
Imaging Studies
TREATMENTSection 6 of 10
Medical therapyThe most effective medication for the treatment of trigeminal neuralgia (TN) is carbamazepine. It acts by inhibiting the neuronal sodium channel activity, thereby reducing the excitability of neurons. The effective dose ranges from 600-1200 mg/d, with serum concentrations between 40-100 mcg/mL. However, many adverse CNS effects (eg, vertigo, sedation, ataxia, diplopia) are associated with carbamazepine, which may make it difficult to use in elderly patients. The dose may be tapered once pain is controlled, since remission may occur. Obtain a blood count during the first few weeks of therapy and yearly thereafter. Agranulocytosis and aplastic anemia are extremely rare adverse effects, but suppression of the WBC count in the range of 200-3000 103/µL is not uncommon. This mild suppression of the WBC count does not warrant discontinuation of carbamazepine therapy. Hepatic function should also be monitored. Up to 70% of patients receive complete or acceptable partial relief, at least temporarily. Oxycarbazine is a newer agent that may have fewer side effects, but it can cause hyponatremia, which should be monitored with serial serum sodium measurements in the first few weeks of therapy. Gabapentin, lamotrigine topiramate, and several other newer anticonvulsants are being used to treat trigeminal neuralgia. Further outcome studies on their use in the treatment of trigeminal neuralgia are needed. Surgical therapyIn some studies, more than 50% of patients with TN eventually had some kind of surgical procedure. Experience would indicate that medical management eventually fails in most patients with TN, and those patients undergo surgery. Microvascular decompression (MVD) is the classic and most effective surgical procedure. It involves a posterior fossa craniotomy and dissection of vascular elements that compress the trigeminal nerve in the subarachnoid space. Teflon felt is used to pad the nerve away from the offending artery or vein. The effectiveness of MVD is based on the hypothesis that compression from vessels in the vicinity of the trigeminal nerve leads to abnormal nerve activity. Percutaneous approaches
COMPLICATIONSSection 7 of 10
Morbidity associated with trigeminal nerve decompression stems from hemorrhage, infection, and possible damage to the brainstem around the area of decompression. In centers where MVD is frequently performed, complications include facial dysesthesia (0.3%), facial numbness (0.15%), cerebellar injuries and hearing loss ( <1%), and CSF leakage (<2%). With thermocoagulation, dysesthesia can occur in 5-25% of patients, although this complication is uncommon when the degree of facial numbness is controlled. Corneal numbness can occur in up to 15% of patients, and masseter weakness can occur in about 4%. Many of these complications are reversible over time. OUTCOME AND PROGNOSISSection 8 of 10
Accurate data on surgical outcome are still difficult to obtain. Most surgical series do no meet modern criteria for evidence-based medicine. Recently, an evidence-based approach has been applied to all of the surgical procedures for trigeminal neuralgia (TN), including microvascular decompression (MVD). The results of this analysis are still unpublished and will be available in the next update of this article. The challenges of the field are exemplified by a paper published by Zakrzewska and Lopez (Zakrzewska, 2004). They assessed the quality of 222 reports of surgical management of trigeminal neuralgia and found only 3 randomized controlled trials (RCTs) on peripheral techniques. The vast majority of the evidence was of case series reports (class 3 evidence), and a very high proportion was of poor quality. The difficulties center around the following important issues:
Certain principles seem to transcend even the relatively poor outcomes studies performed thus far on procedures for trigeminal neuralgia. The chance of success is seemingly less likely the longer the duration of symptoms. Of all the procedures, MVD carries the lowest rate of facial dysesthesia at 0.3%. Facial numbness caused by MVD is not common (0.15%) compared with that caused by the percutaneous procedures; in addition, MVD is the procedure of choice in younger patients who desire no sensory deficit. MVD is also the most likely treatment to provide sustained postoperative pain relief. One study found that 70% of patients had excellent results (defined as a cure or significant pain relief) 10 years after the procedure, with a recurrence rate of less than 1% (Barker, 1996). Possible reasons for failure include new vascular compression from scarred implants or other sources, but these are rarely identified during posterior fossa re-exploration for failed MVD. After an initial 10% risk of recurrence of TN within one year after MVD, the risk of pain recurrence is about 3.5% every succeeding year (Burchiel, 1988). The reasons for this recurrence are not clear. In a 1999 study, cerebellar injuries and hearing loss occurred in less than 1% of the patients, and CSF leakage occurred in 1.85% (McLaughlin, 1999). As expected, these complication rates were inversely proportional to the total number of procedures performed. FUTURE AND CONTROVERSIESSection 9 of 10
Once developed, trigeminal neuralgia (TN) is likely to have an exacerbating and remitting course. Over time, the pain-free intervals appear to diminish, and the pain becomes progressively more medically intractable. Temporary spontaneous remission may occur at any time, but permanent remission never occurs. Without treatment, typical TN (TN1) may transform over time to become atypical TN (TN2), with a change in the character of the pain to more constant and background pain and the development of sensory impairment. Therefore, some authorities recommend early intervention to give the opportunity of pain relief without sensory deficits. REFERENCESSection 10 of 10
Article Last Updated: Oct 6, 2006 |
