Diagnostic Value of Facial Nerve Antidromic Evoked Potential in Patients With Bell's Palsy: A Preliminary Study

OBJECTIVE To assess the practical diagnostic value of facial nerve antidromic evoked potential (FNAEP), we compared it with the diagnostic value of the electroneurography (ENoG) test in Bell's palsy. METHODS In total, 20 patients with unilateral Bell's palsy were recruited. Between the 1st and 17th days after the onset of facial palsy, FNAEP and ENoG tests were conducted. The degeneration ratio and FNAEP latency difference between the affected and unaffected sides were calculated in all subjects. RESULTS In all patients, FNAEP showed prolonged latencies on the affected side versus the unaffected side. The difference was statistically significant. In contrast, there was no significant difference between sides in the normal control group. In 8 of 20 patients, ENoG revealed a degeneration ratio less than 50%, but FNAEP show a difference of more than 0.295±0.599 ms, the average value of normal control group. This shows FNAEP could be a more sensitive test for Bell's palsy diagnosis than ENoG. In particular, in 10 patients tested within 7 days after onset, an abnormal ENoG finding was noted in only four of them, but FNAEP showed a significant latency difference in all patients at this early stage. Thus, FANEP was more sensitive in detecting facial nerve injury than the ENoG test (p=0.031). CONCLUSION FNAEP has some clinical value in the diagnosis of facial nerve degeneration. It is important that FNAEP be considered in patients with facial palsy at an early stage and integrated with other relevant tests.