A 52-Year-Old Woman With Episodes of Severe Jaw and Cheek Pain

Correct Answer: D. Initiate a course of anticonvulsant (oxcarbazepine)

You will have to forgive the author’s immersion into deep neurology/neurosurgery therapeutics in the question and answer. But the vignette and question serve as a good, basic segue into reviewing an old and classic syndrome: tic douloureux (“painful tic”). In the less semantic and more sterile nomenclature required in our times, it is called trigeminal neuralgia. This topic takes us back in time to our earliest freshman medical school days when we were introduced to the dreaded 12 cranial nerves, their numbers, their names, origins, where they emerged from the skull, and what they do. Indeed, this topic was one of the earliest shocks that portended we were not in sophomore college philosophy or sociology class anymore but, rather, the big leagues now!

So, yes, the case presented manifests one of the more dramatic diseases effecting one of those cranial nerves, specifically nerve V. The trigeminal nerve whose 3 branches—mandibular, maxillary, and ophthalmic—provide sensory innervation to the face. In synopsis, which will be expanded below, trigeminal neuralgia is a condition wherein abnormal anatomy where the nerve exits the pons and brain case results in pathophysiology of the nerve roots with hyperexcitability and seizure-like activity that cause the nerve to abnormally fire neuropathic pain. And despite the romantic (and actually descriptively quite accurate) “tic douloureux” name, this is a clinically extremely painful disease.

Trigeminal neuralgia is uncommon to rare, with an incidence of 3 to 4 cases per 100,000 population.¹ The incidence increases with age and is more common in women.¹ The classical presentation is unilateral severe pain in the distribution of 1 of the 3 branches of nerve V, usually mandibular or maxillary. The pain most often comes in paroxysms with variable durations and, as is the case in many neuropathies, has a shock-like sensation to it.² Taking a detailed history will detect a triggering stimulus or stimuli. These range from specific movements such as shaving or tooth brushing to even more commonly innocuous everyday incidental situations such as gentle touching of the face, talking, or chewing.² Although initial thoughts such as dental or temporomandibular joint problems are considered, as was the case with the presented patient, eventually the neuropathic nature is considered and a diagnosis follows. And the diagnosis remains, certainly initially, a clinical one and has 3 main criteria: (1) paroxysms of sudden, intense, short “electric” like pain; (2) innervation of division(s) of the trigeminal nerve; and (3) the pain syndrome has a triggering behavior or finding associated with it. The latter criteria is found in 91% to 99% of cases and may be the most pathognomonic of the 3 criteria.^2,3 Reviews have listed common triggers such as talking, face washing and drying, chewing, tooth brushing, and gentle facial touching/stimulation as with wind or air flow.² Historically, if strictly and timely observed, a subtle movement or “tic” is seen with the response to a trigger and initiation of the episode.

In recent decades, the pathophysiology of the syndrome has been elucidated, and as will be discussed below, this has resulted in much-improved therapeutics. Anatomically, the advent of accurate magnetic resonance imaging (MRI) radiologic techniques has demonstrated that, in most cases of trigeminal neuralgia, there is abnormal compression of the trigeminal nerve root where it leaves the pons and exits the cranium. The specific neuroanatomy is a tortuosity or loop of the superior cerebellum artery, causing pressure on the nerve root at that site, which is demonstrable as demyelination in the affected area.^1,4 The physiology then shows such demyelination causes hyperexitability at the nerve root and axon with ectopic discharging. So, if you will allow a simple internist’s overly simplified characterization of the process, the result is a “seizure” of the trigeminal nerve root or a supraventricular tachycardia arrhythmia-like, overfiring process of the trigeminal nerve.

These detailed MRI findings are not a requirement for diagnosis initially. As mentioned above, the diagnosis remains a clinical one. But if medical maneuvers are not effective and surgery is considered, these refined MRI techniques to define the anatomy in the area need to be performed. The MRI scan will also demonstrate or exclude the “differentials” in trigeminal neuralgia cases, which are quite limited to other causes of tic douloureux, specifically multiple sclerosis and benign cerebellopontine tumors, which compromise about 15% of cases.^2,4

This brings us to therapy, which is now so much better since it is based on the abnormal anatomy and physiology findings described above. Essentially all patients diagnosed with tic douloureux, regardless of cause, should receive a trial of antiseizure medications, specifically carbamazepine or oxcarbazepine. These agents stabilize the nerve membrane and inhibit abnormal firings. They have excellent efficacy, ranging from 94% to 98%, but an unfortunate 20% or higher adverse effect profile as well.⁵ Gabapentin and antidepressants have been used alone or in combination with carbamazepine agents. They are less effective but also have fewer adverse effects. Digesting this data makes Answer D the best option for the presented patient at this time.

When medical therapy does not provide adequate benefit or is too toxic, neurosurgical maneuvers are the next level of treatment. Prior to the detailed MRI mapping described above, ablative techniques of percutaneously damaging the trigeminal ganglion as it exits the base of the skull are able to provide relative long-term (3 years or more) benefits. Modalities and response rates of balloon compression (68%), radiofrequency thermocoagulation (58%), and glycerol lysis (38%) are outlined in the literature.^6,7 Finally, a newer technique takes advantage of the now-known abnormal anatomy at the nerve root seen with most cases. This is microvascular decompression wherein the abnormal vessel is identified, moved from under to over the nerve V root, and separated from the nerve by a decompressive sponge. A meta-analysis of case collections demonstrated 60% to 80% efficacy at 4 to 5 years, such that this procedure is now the optimal surgical one for classical primary cases.⁸

What’s the Take Home? Trigeminal neuralgia is an uncommon disease but a morbid one to patients who have it. It causes severe pain, stabbing, paroxysmal, and electric-like sensations in the distribution of one of the branches of the trigeminal nerve, usually either the maxillary or mandibular branch. Episodes are usually related to a variety of common and innocuous stimuli and triggers, such as face touching. The initial diagnosis is clinical based on the patient’s history. The pathology and pathophysiology relate to abnormal compression to the nerve root where it meets the pons, which results in damage and demyelination in the area. The damaged nerve then exhibits hyperexitability and discharges the effected nerve root with the subsequent clinical findings. MRI techniques can define the anatomy and exclude secondary causes. Initial therapy should be medical, with an attempt to control episodes using antiseizure agents such as oxcarbazepine and gabapentin, which can be 90% effective but carry a 20% adverse effect profile. If medical therapy fails, surgical techniques, specifically microvascular decompression, are available to provide relief in roughly 70% of cases with an acceptable surgery-related morbidity rate.

Patient Follow-Up. A clinical diagnosis of trigeminal neuralgia was made. An MRI scan was scheduled, and oxcarbazepine, 300 mg/d, was prescribed for 1 month. There was a marked decrease in number and intensity of episodes during that time, at the cost of minimal episodes of dizziness with certain rapid head movements. The MRI results were negative for multiple sclerosis and cerebellopontine tumors and confirmed the typical loop artery at the root of the trigeminal nerve. The patient will continue the correct dosage of oxcarbazepine for now. The patient and her care team believe there is likely room for some dose escalation if needed. Neurosurgery is being consulted, as her findings seem to make her a good candidate for microvascular decompression if needed in the future.