JADA Continuing Education
Trigeminal neuralgia and glossopharyngeal neuralgia
Two orofacial pain syndromes encountered by dentists
MICHAEL HOROWITZ, M.D.,
MARTIN HOROWITZ, D.D.S.,
MARK OCHS, D.M.D., M.D.,
RICARDO CARRAU, M.D. and
AMIN KASSAM, M.D.
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ABSTRACT
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Background. Dentists frequently evaluate patients for oropharyngeal pain that may or may not eventually be related to oral pathology. Two rare neurological disorders that present with severe orofacial pain are trigeminal neuralgia, or TN, and glossopharyngeal neuralgia, or GPN. Both are secondary to cranial nerve compression by arteries and veins at the point at which the nerves exit the pons and brainstem.
Results. The authors present the results for two series of patients treated for TN and GPN. Significant success can be seen after intracranial microvascular decompression for both disorders, with low complication rates. Short- and long-term outcomes depend on proper patient selection.
Clinical Implications. It is important for practitioners to recognize these syndromes and properly refer patients to a neurosurgeon experienced in treating such disorders. This can help the dentist and patient avoid oral procedures that will not alleviate the painful symptoms.
All pain syndromes are in some way related to the central nervous system, the peripheral nervous system, or both. Successful treatment requires identification of the central or peripheral irritants and etiologies. Two orofacial pain syndromes that dentists may encounter early in their presentation include trigeminal neuralgia, or TN, and glossopharyngeal neuralgia, or GPN. It is important for clinicians to recognize these two syndromes so that unsuccessful interventions such as extractions, endodontic treatment and temporomandibular joint repairs are avoided, and patients can be referred early on for definitive therapy. We discuss the clinical presentations, treatment options and outcomes for these two debilitating conditions.
Significant success can be seen after intracranial microvascular decompression for trigeminal neuralgia and glossopharyngeal neuralgia.
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GENERAL DENTAL EVALUATION FOR ORAL PAIN AND DIFFERENTIAL DIAGNOSIS
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Patients often visit a dentist with oral pain, extraoral pain, or both along one side of the head, cheek, maxilla or mandible. To ascertain the source of the discomfort, the dentist needs to obtain a detailed medical history and radiographs, as well as perform a clinical examination.
History.
The dentist needs to ask pertinent questions regarding the patient’s pain, including the quality, duration, time of initial onset and triggers of the discomfort, as well as the factors that elicit comfort. More specifically, the dentist needs to know if the patient has a history of facial or oral trauma, facial swelling, pain during mastication, pain when eating or drinking hot or cold foods and liquids, pain from interdental food impaction, a history of chipped or fractured teeth, or a history of temporomandibular joint pain.
Oral examination.
The clinician needs to carefully examine the patient’s mucosa, gingivae, tongue and palate for oral abrasions, infections, cancerous growths, bleeding and ulcerations. He or she also should rule out malocclusion as a cause of pain.
Radiographs.
Dentists need to examine intraoral radiographs for tooth caries; carious nerve (pulp) exposures; periodontal involvement of dentition, alveolar bone and gingival tissue; apical root infection; retained subgingival root fractures; and impacted or unerupted teeth.
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TRIGEMINAL NEURALGIA
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Syndromes.
Fehr first described TN in the late 17th century,1 and later Locke noted that this ailment affected the Countess of Northumberland.2 According to Brown and colleagues,3 Andre termed the syndrome "tic douloureux" in 1756, noting that this was a "cruel and obscure illness, which causes ... in the face some violent motions, hideous grimaces, which are an insurmountable obstacle to the reception of food, which put off sleep."
Classic or typical TN has been described as the most painful condition known to humans. It consists of unilateral, lancinating, electrical pain in one or more of the trigeminal nerve distributions (V1, V2, V3). Patients usually describe typical trigger points on the face and triggering stimuli or activities that can elicit pain. These may include touching the trigger point, cool wind on the face such as that from air conditioning or a breeze, chewing, talking and subtle mouth movements. Almost all affected people can relate a memorable first onset of the pain syndrome. They may report certain head positions being more painful than others. Most patients will describe some modicum of pain relief from medications such as carbamazepine, phenytoin, baclofen or neurontin.
Atypical TN denotes a syndrome in which patients describe unilateral pain of longer duration than that with typical TN. In addition, the pain, while in a trigeminal distribution, is more often burning or aching in nature. If the pain is electrical (that is, shocklike), it lasts for a longer duration than it does in typical TN and patients may describe their discomfort as continuous. Trigger points may or may not exist. Atypical TN rarely responds to medications that control typical TN. Some patients describe a history of typical TN that has evolved over the years into their current atypical condition. These patients may have traveled through a stage termed "transitional TN," which has characteristics of both typical and atypical TN.
Neurophysiological mechanism.
TN is believed to be a consequence of abnormal neural impulse transmission within the intracranial pre-ganglionic portion of the trigeminal nerve. Ephaptic or nonsynaptic transmission of neural signals in areas of myelin damage has been proposed as one mechanism for pain generation. Such abnormal impulse transmission may allow afferent volleys in large-diameter tactile fibers to inappropriately activate small-diameter nociceptive afferents, thus generating a sensation of pain from nonpainful stimulations such as touching and chewing. Another hypothesis suggests that abnormal impulses may be generated spontaneously within areas of focal demyelination.4 Excessive depolarization may lead to the perception of pain when small-diameter nociceptive fibers are activated.4
Neurosurgeons have noted that patients with TN who do not have multiple sclerosis, or MS, and a demyelination MS plaque involving the trigeminal nerve have blood vessels (arteries, veins or both) compressing the trigeminal nerve as it enters the pons (Figure 1
). Elevation of these vessels from the nerve and placement of a padded material between the vessel and the nerve have been shown to be an effective means of relieving pain. Whether the vessel is responsible for myelin destruction and subsequent pain generation, or the vessel irritates a nerve that has pre-existing myelin damage remains to be demonstrated.
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Figure 1. Top: Artery compressing cranial nerve V (trigeminal nerve) at the brainstem. Bottom: Padded material (Teflon, DuPont, Wilmington, Del.) is applied to decompress the artery.
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TREATMENT
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Medications.
The first line of therapy for patients with TN is medical. The most commonly used medications are the anticonvulsants carbamezapine, phenytoin and neurontin and the 
-aminobutyric acid agonist baclofen. These medications may inhibit pain by increasing the threshold for cross-stimulation between large-diameter propriceptive fibers and small-diameter nociceptive fibers, thus reducing ephaptic transmission (that is, they act as a chemical neural insulator). They also may enhance the activity of feedback mechanisms that dampen the response of the trigeminal nucleus to abnormally increased firing of the trigeminal nerve.4 Eighty percent of patients with TN initially experience pain relief after receiving carbamezapine therapy. Up to 20 percent of patients, however, become intolerant of the drug and develop cognitive slowing, liver dysfunction, decreased blood cell counts, rash and/or diplopia, which necessitates termination of therapy.
Baclofen has been shown to help up to 74 percent of patients who were not helped by, or are intolerant of, carbamezapine.4 Approximately 10 percent of patients treated with this medication, however, find the side effects (drowsiness, dizziness and gastrointestinal discomfort) intolerable.4 Dilantin has been reported to help 60 percent of patients.4 Side effects, such as liver dysfunction, nystagmus, rash, ataxia, dysarthria, gingival hyperplasia, osteomalacia and anemia, may make prolonged use impossible.
Surgical intervention.
Ninety-two percent of patients with typical TN who visited the University of Pittsburgh Medical Center for surgical intervention had not responded to medical therapy, while 96 percent of patients with atypical TN had not responded to medical therapy before seeking surgical intervention.5 When medical therapy fails, surgery involves a retromastoid craniectomy, exposure of the trigeminal nerve where it exits the pons and microvascular decompression, or MVD. MVD consists of separating from the nerve arteries and veins that are compressing the nerve, especially at the point at which the nerve enters the brainstem (root entry zone), and placing padding between the vessels and the nerve so that pulsations are dampened.
In 2002, Tyler-Kabara and col-leagues5 reviewed our institutional experience with 2003 MVD procedures for typical TN and 672 MVD procedures for atypical TN. The goal was to help determine patient characteristics that would predict the outcome after MVD, and also to assess surgical complication rates in these two populations. The authors divided the outcomes into three categories:
- – "excellent" denoted patients who were pain-free and not receiving any medications after surgery;
- – "good" denoted patients with infrequent pain that was controlled with low-dose medications;
- – "poor" described patients with no postsurgical pain relief with or without medications.
Table 1 summarizes the immediate and long-term results for this series of patients.
The mean and median long-term follow-up for 974 patients with typical TN was 11.3 and 10.5 years, respectively, and for 220 patients with atypical TN, 9.8 and 7.9 years, respectively.
When reviewing factors that were predictive of outcome, the authors5 found that the presence of trigger points and memorable onset of pain were predictors of excellent outcomes. However, preoperative sensory loss, previous MVD procedures, bilateral pain and previous destructive trigeminal nerve procedures were predictors of negative outcomes. Patients who underwent surgery for typical TN had better long-term outcomes than did those who underwent surgery for atypical TN. Table 2 summarizes the surgical complications for 2,003 typical and 672 atypical TN surgical cases.
Percutaneous glycerol rhizotomy, or PRGR.
At our institution, we use PRGR to treat patients with MS-related TN or patients who do not respond to medical therapy for typical TN and who cannot receive general anesthetic safely because of comorbid conditions. Although PRGR is associated with a slightly higher rate of pain recurrence and trigeminal sensory loss than is MVD, it has a lower incidence of trigeminal sensory loss than do other destructive percutaneous procedures, such as radiofrequency rhizotomy and balloon compression rhizotomy.6
PRGR involves the passage of a spinal needle under fluoroscopic guidance through the cheek and foramen ovale and into the trigeminal cistern. Once the needle is in position, the surgeon instills glycerol around the trigeminal roots. The surgeon adjusts the amount of glycerol and the patient’s head position to treat V3, V2 or V1 pain. Since 1981, we have used PRGR to treat more than 800 patients.
Seventy-seven percent of patients at our institution achieved long-lasting pain control, with 55 percent of all patients pain-free with no drug therapy. Within two to five days after the procedure, 37 percent of patients experienced one or more of the following complications: headache, nausea, emesis and herpes simplex oralis eruption (due to activation of the herpes simplex virus that resides in the trigeminal ganglion). Postoperative sensory loss was mild in 32 percent, moderate in 13 percent and dense in 6 percent of patients. Two percent of patients developed facial paresthesias or dysesthesias. Only one death was recorded secondary to a postprocedural myocardial infarction.6
Stereotactic Gamma Knife radiosurgery.
Stereotactic radiosurgery for typical TN involves the application of a single dose of radiation using a Gamma Knife (Elekta, Stockholm, Sweden) stereotactic radiosurgery unit. The neurosurgeon applies approximately 60 to 90 gray of radiation in a single fraction with a 4-millimeter isocenter to the trigeminal nerve at the root exit zone. This procedure is entirely noninvasive. Although not as effective as MVD, it is useful for treating patients with contraindications for general anesthesia and for patients who have undergone invasive procedures without long-term success.
In 2001, Maesawa and colleagues7 conducted a review of 220 patients at our institution who underwent radiosurgery for primarily typical TN. The authors followed up the patients for a median of two years and reported complete or partial pain relief in 85.6 percent of the patients. At six months, 65 percent of the patients experienced complete pain relief, and 75 percent experienced complete pain relief at 33 months. Only 17 percent of patients developed new or increased subjective facial paresthesias or numbness.
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GLOSSOPHARYNGEAL NEURALGIA
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Syndrome.
GPN is a rare condition that often presents with deep throat pain, particularly during swallowing. In 1927, Dandy8 described it as paroxysmal pain frequently brought on by eating and swallowing. The posterior tongue and pharynx are involved, with pain radiating to the throat, deep ear structures, or both. Researchers and clinicians believe that GPN is secondary to vascular compression of the glossopharyngeal nerve (cranial nerve, or CN, IX) and the upper fascicles of the vagus nerve (CN X) (Figure 2, page 1430).
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Figure 2. A: Vagus nerve (cranial nerve, or CN, X). B: Glossopharyngeal nerve (CN IX). C: Large blood vessel (posterior inferior artery) causing compression.
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Treatment.
Surgeons have treated GPN with surgical sectioning of CN IX and the upper fascicles of CN X, as described by Sicard and Robineau9; multiple variations of intracranial, cervical and pharyngeal approaches for nerve destruction; and MVD of the nerves via a retromastoid craniotomy and brainstem exposure of the nerves and vessels at the pontomedullary junction. We prefer to use the decompression procedure because it preserves all neural tissue.
In 2002, Patel and colleagues10 reviewed 217 cases of patients with GPN treated with MVD at our institution between 1973 and 2000. The authors defined complete relief as no residual pain after surgery. Partial relief was defined as a minimum four-point improvement compared with preoperative pain on a pain scale of 1 to 10 (for example, pain rated as a 6 before surgery needed to be reduced to a 2 after surgery). The authors considered improvement of fewer than four points to be a therapeutic failure.
Table 3 shows the overall outcomes. Table 4 shows the outcomes in relation to the presenting symptoms (patients may have had more than one pain complaint). Table 5 shows the outcomes in patients with isolated pain locations. Table 6 summarizes the surgical complications. The mean patient follow-up period was four years.
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TABLE 4 OUTCOMES OF MVD* FOR 217 PATIENTS WITH GLOSSOPHARYNGEAL NEURALGIA ACCORDING TO PRESENCE OF AT LEAST ONE SYMPTOM.
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TABLE 5 OUTCOMES OF MVD* FOR 217 PATIENTS WITH GLOSSOPHARYNGEAL NEURALGIA WHEN ONLY ONE PAIN SYMPTOM WAS PRESENT BEFORE SURGERY.
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This analysis has shown that in patients undergoing MVD for GPN, 90 percent experience complete or significant pain relief immediately after surgery, and 75 percent experience long-term pain relief. When patients with throat pain only are analyzed, 98 percent experience long-term pain relief. In our experience, clinically significant complication rates have been less than 3 percent.
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CONCLUSION
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TN and GPN are extremely painful orofacial syndromes that may be encountered first by dentists because oral causes are considered. Their classic presentations and the availability of effective medical and surgical therapies make referral to a neurosurgeon experienced in treating these rare disorders rewarding for the patient.
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FOOTNOTES
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Dr. Michael Horowitz is an associate professor, Departments of Neurosurgery and Radiology, University of Pittsburgh Medical Center, Presbyterian University Hospital. Address reprint requests to Dr. Horowitz, Center for Cranial Nerve Disorders, Department of Neurosurgery, 200 Lothrop St., Suite B400, Presbyterian University Hospital, Pittsburgh, Pa. 15213-2582, e-mail "horowitzmb{at}upmc.edu".
The late Dr. Martin Horowitz had a private dental practice in Ozone Park, N.Y.
Dr. Ochs is a professor and chairman, Oral-Maxillofacial Surgery, University of Pittsburgh Medical Center, Presbyterian University Hospital.
Dr. Carrau is an associate professor, Department of Otolaryngology, University of Pittsburgh Medical Center, Presbyterian University Hospital.
Dr. Kassam is an associate professor, Departments of Neurosurgery and Otolaryngology, University of Pittsburgh Medical Center, Presbyterian University Hospital.
Drs. Michael Horowitz, Carrau and Kassam are founding partners of the Surgical Technology Assessment Group and the Center for Assessment Surgical Technology, Pittsburgh.
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REFERENCES
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- Schmidt JE. Medical discoveries. Springfield, Ill.: Charles C. Thomas; 1959.
- Stookey B, Ransohoff J. Trigeminal neuralgia: Its history and treatment. Springfield, Ill.: Charles C. Thomas; 1959.
- Brown JA, Coursaget C, Preul MC, Sangvai D. Mercury water and cauterizing stones: Nicolas Andre and tic douloureux. J Neurosurg 1999;90:977–81.[Medline]
- Rovit RL, Murali R, Jannetta PJ, eds. Trigeminal neuralgia. Baltimore: Williams and Wilkins; 1990.
- Tyler-Kabara EC, Kassam AB, Horowitz MH, et al. Predictors of outcome in surgically managed patients with typical and atypical trigeminal neuralgia: comparison of results following microvascular decompression. J Neurosurg 2002;96:527–31.[Medline]
- Jho HD, Lunsford LD. Percutaneous retrogasserian glycerol rhizotomy: current technique and results. Neurosurg Clin North Am 1997;8:63–74.[Medline]
- Maesawa S, Salame C, Flickinger JC, Pirris S, Kondziolka D, Lunsford LD. Clinical outcomes after stereotactic radiosurgery for idiopathic trigeminal neuralgia. J Neurosurg 2001;94:14–20.[Medline]
- Dandy WE. Glossopharyngeal neuralgia: its diagnosis and treatment. Arch Surg 1927;15:198–214.
- Sicard R, Robineau J. Communications et presentations: part I-Algie velopharyngee essentielle—traitment chirugical. Rev Neurol (Paris) 1920;36:256–7.
- Patel A, Kassam A, Horowitz M, Chang YF. Microvascular decompression in the management of glossopharyngeal neuralgia: analysis of 217 cases. Neurosurgery 2002;50:705–11.[Medline]
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ABSTRACT
GENERAL DENTAL EVALUATION FOR...
