To evaluate the utility of diagnostic studies in identifying treatable etiologies of trigeminal neuropathy (TNP).

We performed a review of consecutive patients with nontraumatic, noniatrogenic TNP seen at Mayo Clinic between January 1, 2000, and August 31, 2019. Patients were excluded if they had trigeminal neuralgia without neuropathy or if their diagnostic work-up had been completed elsewhere. Data were analyzed to determine which diagnostic studies were most useful in identifying treatable etiologies.

In total, 439 patients were included. The mean ± SD age was 56.3±13.6 years and 285 (64.9%) were female. Among the 180 cases in which an etiology was identified (41.0%), neoplasms were causative in 76 (42.2%), while specific connective tissue diseases were implicated in 71 (39.4%). Bilateral TNP (n=83) was associated with the presence of underlying connective tissue disease (P<.01). Identification of etiology was made by magnetic resonance imaging in 88 cases (48.8%), by abnormal connective tissue disease cascades combined with rheumatology consultation in 42 (23.3%), by a previously known connective tissue disorder in 30 (16.7%), and by abnormal connective tissue disease cascades alone in 8 (4.4%). Among the 439 study patients, electromyography was performed in 211 (48.1%) and lumbar puncture in 139 (31.7%), but their diagnostic utility was low.

Underlying causes of nontraumatic, noniatrogenic TNP can be identified in approximately 40% of cases. Bilateral TNP is strongly associated with underlying connective tissue disease. Careful history taking, dedicated magnetic resonance imaging, and connective tissue panels have the greatest diagnostic utility. Electromyography and cerebrospinal fluid analysis are unlikely to elucidate treatable etiologies of TNP.