Trigeminal reflex testing abnormalities as a predictive model for distinguishing classical and idiopathic trigeminal neuralgia

•Trigeminal reflex latency asymmetry longer than 0.5 ms between the affected and unaffected sides is predictive of classical TN.•The latency asymmetry in trigeminal reflexes probably reflects the association of classical TN with neurovascular compression.•In idiopathic TN the impairment in large-myelinated fibers is undetectable. Primary trigeminal neuralgia (TN) is a representative neuropathic facial pain condition classified into classical (associated with neurovascular compression), and idiopathic (unknown etiology). Differentiating between classical and idiopathic TN based on clinical and neurophysiological findings remains challenging. In this clinical and neurophysiological study, we aimed to identify predictive clinical and neurophysiological variables that may distinguish between the two types of TN. We retrospectively analyzed clinical records and neurophysiological data from 114 patients with primary TN (84 classical TN, 30 idiopathic TN). We implemented a logistic regression model to identify predictive variables for classical and idiopathic TN. The logistic regression model showed that a trigeminal reflex latency asymmetry longer than 0.5 ms between the affected and unaffected sides was predictive of classical TN (p