Neurophysiological tests for facial-trigeminal pain

Abstract

Comprehensive neurophysiological and psychophysical examination provides unique, sensitive and specific information about possible underlying neuropathy in patients with orofacial pain. Special ENMG techniques, brainstem reflex examinations, sensory and motor evoked potential recordings as well as quantitative sensory tests provide diagnostic biomarkers for large and small nerve fiber systems, and confirm definite diagnosis of neuropathic pain within the trigeminal distribution with up to 95–100% accuracy. They enable precise differential diagnosis between neuropathic and musculoskeletal pain within the orofacial area. Neurophysiological tests also allow accurate topographic level diagnosis from peripheral nerves to the cortex, helping to guide further imaging studies to the most likely region of underlying neuropathology, significantly increasing the overall diagnostic yield. Systematic application of neurophysiological testing has elucidated neural mechanisms of various orofacial pain conditions including trigeminal neuropathic pain, trigeminal neuralgia, persistent idiopathic orofacial pain, and burning mouth syndrome. Neurophysiological and psychophysical testing can also provide invaluable prognostic information regarding risk of persistent pain and recovery after nerve injury. Furthermore, clinical neurophysiology can measure and confirm phenomena associated with neuropathic pain, caused by deficient endogenous inhibitory systems or neuroplastic alterations. Neurophysiological tools enable more efficient treatment based on accurate diagnosis and individual profiling of the underlying pathophysiology.