A narrative review published in Headache found that research into all aspects of trigeminal neuralgia (TN) is needed to streamline accurate diagnosis and treatment success.
TN is a rare condition (70 cases per 100,000) which causes excruciating, short-lasting, and unilateral facial pain. Women are diagnosed more often than men (5.7 vs 2.5, respectively, per 100,000) and peak incidence occurs between 50 to 60 years of age.
Although reports of pain vary in the literature, patients generally report pain in the maxillary/mandibular (33%), mandibular (19%), maxillary (17%), ophthalmic/maxillary/mandibular (13%), or ophthalmic (4%) regions.
Recently, additional subtypes have been linked with TN. The International Classification of Headache Disorders, 3rd edition defined 3 distinct types: classical, secondary, and idiopathic TN.
Classical or idiopathic TN are either purely paroxysmal or with concomitant continuous pain, but classical TN is associated with neurovascular compression and idiopathic TN is not. Secondary TN is attributed to multiple sclerosis (MS), a space-occupying lesion, or other causes.
The diagnostic criterion for TN comprises recurrent unilateral facial pain in more than 1 division of the trigeminal nerve, pain that is severe and lasts up to 2 minutes, pain that feels like a sharp electric shock, and is triggered by innocuous stimuli. Additionally, patient symptoms should not fulfill other headache conditions. To diagnose, patients should undergo clinical examination and magnetic resonance imaging. No TN-specific diagnostic tests have been developed.
Patients consult with primary care physicians (43.1%), dentists (30.4%), headache specialists (14.7%), otorhinolaryngologists (3.9%), and neurosurgeons (3.9%) for their facial pain symptoms. A diagnosis of TN is delayed by an average of 10.8 months after symptom onset.
The first consultation results in a misdiagnosis among 42.1% of patients and common misdiagnoses include migraine, cluster headache, temporomandibular joint dysfunction, tension-type headache, glaucoma, otitis, and tonsillitis.
MS has been associated with a 20-fold increased risk for TN, likely caused by the demyelination of the trigeminal nerve. TN tends to develop 12 years after MS onset and among 1.5% to 7.9% of this patient population. MS-associated TN is more likely to cause bilateral pain (14%) and occur among a younger patient population than classical or idiopathic TN.
For TN caused by space-occupying lesions, varying tumors have been observed as causal. Gamma knife stereotactic radiosurgery has been successfully used to treat benign intracranial tumors, however, associated TN pain does not always resolve.
Carbamazepine is highly efficacious for the management of classical TN and some clinicians have extrapolated its effectiveness as a diagnostic test. Newer drugs, such as antiepileptics or sodium channel blockers have been tested for TN and may improve the treatment landscape.
Some patients may be candidates for surgery depending on age and symptom severity. However, there is a scarcity of data supporting the effectiveness of this therapeutic route.
The review authors concluded, “Research into all aspects of TN — diagnosis, pharmacotherapy, surgery, long-term management prognosis, and natural history — is needed. Research should adhere to the ICHD’s schema for TN. Improved drugs are needed along with rigorous research into surgical options and their efficacy for different subtypes of TN.”
Maarbjerg S, Benoliel R. The changing face of trigeminal neuralgia—A narrative review. Headache. 2021;61(6):817-837. doi:10.1111/head.14144