Featuring Dr. Glenn Clark, Professor and Director of the Online Master of Science in Orofacial Pain and Oral Medicine Program, Herman Ostrow School of Dentistry of USC
Multiple sclerosis is a great mimic. That is how Dr. Glenn Clark—a 50-year veteran of academic dentistry, lifetime achievement award recipient from the American Academy of Orofacial Pain, and director of USC Ostrow’s online Orofacial Pain and Oral Medicine program—opened his contribution to our podcast series on MS and orofacial pain. His message to dental clinicians was direct: when something does not feel right about a trigeminal neuralgia presentation, it usually is not.
A Patient Who Stays With You
Dr. Clark recounted a colleague whose first symptoms were vocal—she came to work saying her voice was off and she could not speak normally. He assumed a viral upper respiratory infection. Then she developed pain in teeth with no caries, no apical lucency, and no findings to support pulpal disease. A colleague performed root canals on those teeth. The pain came and went—which, as Dr. Clark pointed out, is not how a true odontogenic pain behaves. Years later, she was diagnosed with MS. That kind of case, he said, burns itself into a clinician’s memory. The lesson is preventive: learn from the cases others have missed.
Why MS-Related Trigeminal Neuralgia Does Not Fit the Classic Pattern
Classic trigeminal neuralgia is unilateral, confined to a single division, brief and stabbing, and typically appears in patients in their 50s, 60s, or 70s. MS-related trigeminal neuralgia breaks every one of those rules. Because demyelination can occur at multiple sites in the central nervous system simultaneously, the pain can be bilateral, can involve multiple divisions, and frequently appears in patients in their 20s to 50s—the typical MS age range. Dr. Clark’s clinical rule of thumb: bilateral pain is weird, multiple divisions is weird, a young patient is weird. Any one of those features should raise the red flag.
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The Real Risk: Right Drug, Wrong Diagnosis
Carbamazepine—the standard first-line medication for trigeminal neuralgia—can calm an angry nerve. But, as Dr. Clark emphasized, it does not regenerate myelin or stop demyelination. In an MS patient, treating the pain without treating the underlying disease means the demyelinating process continues unchecked, and damage accumulates. “It’s not that the treatment is wrong,” he noted. “It’s just not the right treatment.” The primary diagnosis must be made first, and the patient must be started on appropriate immunosuppressive therapy by a neurologist. Even an experienced orofacial pain specialist should refer MS suspects to neurology rather than co-managing the underlying disease.
Prescribing Carbamazepine: What Has to Be in Place
When carbamazepine is the right choice, three things have to be confirmed first. Liver function must be documented through baseline testing—a standard CBC with liver function panel covers anemia screening and hepatic enzymes in a single bundled order. A drug-drug interaction analysis must be performed, since carbamazepine shares metabolic enzymes with many other medications and patients on polypharmacy can move into toxic ranges quickly. And patients must be counseled on what to watch for and when to call.
Dosing should also be validated by response. Carbamazepine works fast: when the right dose is reached, symptoms typically resolve within three or four days. If they do not, the working hypothesis should shift—either the dose is too low, the drug is wrong, or the diagnosis is wrong.
Stevens-Johnson Syndrome and Genetic Screening
Most carbamazepine hypersensitivity reactions present as hives and itchy skin rather than full Stevens-Johnson syndrome, but true Stevens-Johnson is life-threatening and demands awareness. The HLA-B*1502 allele substantially increases risk and is most prevalent in Han Chinese and other Southeast Asian populations, which is why Singapore and Thailand require genetic screening before carbamazepine can be prescribed. In North American practice, Dr. Clark noted, most observed reactions are seen in Hispanic patients and typically present as hives. Either way, patients must be told to call immediately about any unusual skin sensation, and the drug must be tapered or stopped promptly if a reaction occurs.
The Underlying Discipline
Dr. Clark’s contribution to the series reinforces a theme that ran through every guest conversation: in orofacial pain, the cost of a missed diagnosis is rarely a single failed treatment—it is years of unnecessary procedures performed while the real disease progresses. The discipline he advocates is not flashy. Take a careful history. Notice when the presentation does not fit. Trust the red flags. Refer when neurology is the appropriate next step. As he put it, you learn this by seeing the cases you missed—so let the missed cases of clinicians who came before you save your patients from the same trajectory.
Are you interested in a variety of issues focused on orofacial pain, medicine and sleep disorders? Consider enrolling in the Herman Ostrow School of Dentistry of USC’s online, competency-based certificate or master’s program in Orofacial Pain and Oral Medicine.
