| Trigeminal Neuralgia | | Counselor, Trigeminal neuralgia (TN), also known as tic douloureux, is a disabling pain syndrome recognizable by patient history alone. The condition is characterized by pain often accompanied by a brief facial spasm or tic. Pain distribution is unilateral and follows the sensory distribution of cranial nerve V, typically radiating to the maxillary (V2) or mandibular (V3) area. At times, both distributions are affected. Physical examination eliminates alternative diagnoses. The pain is initiated by almost any form of external stimulus, for example by a draught of air; movement of the facial muscles or tongue while speaking; touching the skin, particularly over those points from which the pain seems to take its origin; and the act of swallowing, especially when the pain involves the mucous membrane field of distribution of the nerve. It is not a self-limited disease. In some instances the neuralgia reaches such a frightful intensity that it renders the patient's life unbearable. In earlier times suicide was not an uncommon consequence. We value all your comments, so, if you have a suggestion for a newsletter subject but haven't submitted it yet, or if you have already submitted one but think of another, please take a minute to let us know by clicking on your "Reply" button and dropping us a note. To learn more about AMFS, Inc., the organization run by Physicians and Attorneys that provides medical experts and case review services nationwide, and has produced the following informational newsletter to aid you in understanding complex medical issues, please click here - www.medicalexperts.com. |
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| Pathophysiology: The mechanism of pain production remains controversial. Usually no structural lesion is present, although many investigators agree that vascular compression, typically venous or arterial loops at the trigeminal nerve entry into the pons, is critical to the pathogenesis of the disease. This compression results in focal trigeminal nerve demyelination. Since the exact pathophysiology remains controversial, TN may have either a central and/or peripheral etiology. |
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| Frequency: The prevalence of TN is approximately 107 men and 200 women per 1 million people. Approximately 40,000 patients in the US suffer from this condition at any particular time. Therefore, the incidence is 4-5/100,000. There is a relationship between multiple sclerosis and the condition. Approximately 1% of patients with multiple sclerosis (MS) develop TN, whereas 2% of patients with TN have MS. |
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| | Mortality/Morbidity: TN is not associated with a shortened life. However, the morbidity associated with the chronic and recurrent facial pain can be considerable if the condition is not controlled adequately. Individuals may choose to limit activities that precipitate pain, such as chewing, possibly losing weight in extreme circumstances. TN may evolve into a chronic pain syndrome, and patients may suffer from depression and related loss of daily functioning. Age of onset typically is 60-70 years; thus, advanced age is a major risk factor. Patients who present with the disease when aged 20-40 years are more likely to suffer from a demyelinating lesion in the pons secondary to MS. |
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| | History: TN presents as a stabbing unilateral facial pain that is triggered by chewing or similar activities or by touching affected areas on the face. Patients can localize their pain precisely. Of patients, 60% complain of lancinating pain shooting from the corner of the mouth to the angle of the jaw. Strictly unilateral, the disorder affects the right side of the face 5 times more frequently than the left. It commences with a sensation of electrical shocks in an affected area, then quickly crescendos in less than 20 seconds to an excruciating discomfort felt deep in the face, often contorting the patient's expression. The pain then begins to fade within seconds, only to give way to a burning ache lasting seconds to minutes. The number of attacks may vary from less than one per day, to a dozen or more per hour, up to hundreds per day. Outbursts fully abate between attacks, even when they are severe and frequent. In contrast to migrainous pain, persons with TN rarely suffer attacks during sleep, which is a key point in the history. The natural history and prognosis of the condition is such that after an initial attack, the disorder may remit for months or even years. Thereafter the attacks may become more frequent, more easily triggered, more disabling, and may require long-term medication. Patients may find immediate and satisfying relief with one medication, typically carbamazepine. However, over the years, they may require a second or third drug to control breakthrough episodes and finally may need surgical intervention. |
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| | Physical: Physical examination findings are normal; in fact, a normal neurologic examination is part of the definition of idiopathic TN. Any abnormality on physical exam suggests that the pain syndrome is secondary to another process. Patients report pain following stimulation of a trigger point; thus, some patients may limit their examination for fear of stimulating these points. |
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| | Causes: Most patients' conditions are idiopathic, but compression of the trigeminal roots by tumors or vascular anomalies may cause similar pain. Other diagnostic considerations are relevant with TN. These include other syndromes with paroxysmal lancinating head pain including the less common glossopharyngeal neuralgia (GN) and occipital neuralgia (ON) syndromes. Acoustic neuromas, cerebral aneurysms, trigeminal neuromas, and meningiomas can produce syndromes similar to idiopathic TN. These conditions should be considered in patients with onset of pain when younger than 40 years, those with predominant forehead and/or orbit pain (ie, first division of the trigeminal nerve), or those with bilateral facial pain. |
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| | Lab/Imaging Studies: No laboratory, electrophysiologic, or radiologic testing routinely is indicated for diagnosis. Brain MRI with and without contrast helps to distinguish secondary causes of TN from the idiopathic form. Rarely, MS presents with TN. Consider MS in the diagnostic evaluation of individuals who display other features of this demyelinating disorder. |
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| | Medical Care: Since most patients incur TN when older than 60 years, medical management is the logical initial therapy. Medical therapy often is sufficient and effective, allowing surgical consideration only if pharmacologic treatment fails. Because this disorder may remit spontaneously after 6-12 months, patients may elect to discontinue their medication in the first year following the diagnosis. Most must restart medication in the future. Serum levels of carbamazepine in ranges appropriate for epilepsy may be necessary, at least to control initial symptoms, although a much smaller maintenance dosage may be adequate thereafter. Once a patient experiences breakthrough pain on a single agent, a second and even third additional medication may be required to restore relief. Carbamazepine is the drug of choice for TN. A 100-mg tablet may produce significant and complete relief within 2 hours, and for this reason it is a suitable agent for initial trial. So predictable and powerful is the relief that if the patient does not respond at least partially to carbamazepine, reconsider the diagnosis of idiopathic TN. If this dosage does not relieve the discomfort adequately, then a higher dose should be administered. Other anticonvulsant agents possibly useful in the treatment of this disorder include sodium valproate and clonazepam. Their therapeutic efficacy has not been confirmed by formal studies. Commonly, Baclofen is added to anticonvulsants when breakthrough symptoms occur. |
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| |  Surgical Care: Over time, the drugs used for the treatment of TN often lose effectiveness, and patients experience breakthrough pain. For patients in whom medical therapy has failed, surgery is a viable and effective option. 25-50% of patients eventually stop responding to drug therapy and require some form of alternative treatment. The clinician then may consider referral to a surgeon for one of the 3 procedures discussed below. Among patients who develop TN when younger than 60 years, surgery is the definitive treatment. However, surgery exposes the patient to operative risks and the risk of permanent, residual facial numbness and dysesthesias. Moreover, the various operations often fail after 1 or several years of initial relief. This requires a repeat procedure, often with improved but still incomplete results. And, many patients require pain medication even after surgery. Two operative strategies now prevail: percutaneous procedures and microvascular decompression. Percutaneous procedures usually can be performed on an outpatient basis under local or brief general anesthesia at acceptable or minimal risk of morbidity. For these reasons, they commonly are performed in debilitated persons or those older than 65 years. Three types of procedures are commonly performed: percutaneous radiofrequency trigeminal gangliolysis (PRTG), percutaneous retrogasserian glycerol rhizotomy (PRGR), and percutaneous balloon microcompression (PBM). PRGR may be the favored procedure, as it includes only a minimal risk of disturbed facial sensitivity postoperatively. However, some investigators argue that PRGR has the highest rate of pain recurrence. Discussion of each of these is beyond the scope of this review. Microvascular decompression commonly is performed in younger, healthier patients, especially those with pain isolated to the ophthalmic division or in all 3 divisions of the trigeminal nerve and in those with secondary TN. The procedure is performed under general anesthesia, incising the skin behind the ear and performing a 3-cm craniectomy. After retracting the dura to expose the trigeminal nerve, the surgeon identifies an arterial loop compressing the nerve as it enters the pons. The vascular structure is then padded with Teflon felt. Patients spend 4-10 days in the hospital and another week convalescing at home, and thus recovery is more prolonged compared with percutaneous procedures. Mortality for this more invasive procedure approaches 0.5%. Serious morbidity includes dizziness, cerebrospinal fluid leaks, meningitis, cerebellar stroke, and hearing loss, which may occur in 1-5% of cases. 90% of patients are pain free after any of the operations mentioned above. Those in whom the first percutaneous procedure fails may undergo a repeat procedure, which usually provides relief. |
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| | Complications: The chief complication is the adverse effects and toxicity experienced routinely with long-term use of anticonvulsants. Another complication is the waning efficacy over several years of these anticonvulsants in controlling neuralgia, necessitating the addition of a second anticonvulsant, which may cause more drug-related adverse reactions. Some patients permanently lose sensation over a portion of the face or mouth. Occasionally, patients may suffer jaw weakness and/or corneal anesthesia. The worst complication is anesthesia dolorosa, an intractable facial dysesthesia, which may be more disabling than the original TN. |
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| | Prognosis: After an initial attack, the disorder may remit for months or even years. Thereafter the attacks may become more frequent, more easily triggered, disabling, and may require long-term medication. Although patients may find immediate and satisfying relief with one medication, typically carbamazepine, over the years they may require a second or third drug to control breakthrough episodes, finally necessitating surgical intervention. The simpler, less invasive surgical procedures are well tolerated but provide relief only for a couple of years. At that point, further and perhaps more invasive operations may be required, which increases the risk of the disabling adverse effect of anesthesia dolorosa. Therefore, the prognosis of this disorder is unpredictable. |
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| | Medical/Legal Pitfalls: Failure to properly assess for secondary TN is a major potential pitfall. A careful examination of the cranial nerves and an MRI of the brain, especially in an individual who develops the disorder when younger than 60 years, should protect against missing structural lesions (eg, tumor, cerebral aneurysm, acoustic neuroma). Anticonvulsant medications pose risks of sedation and ataxia, particularly in elderly patients, which may make driving or operating machinery hazardous. They also may pose risks to the liver and the hematologic system. Thus documentation of patient education about these potential risks is important. Patients also need to understand that medications for TN are only palliative and often are of limited and temporary value. They also must be informed thoroughly of the risks involved with neurosurgical interventions, including anesthesia dolorosa. |
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