Comparison of nerve conduction study and transcranial magnetic stimulation for early diagnosis and prognosis prediction of idiopathic facial palsy.

Objective: Multiple electrophysiologic studies have been conducted in the evaluation of facial neuropathy. In our study, the diagnostic and prognostic values of nerve conduction studies (NCSs) and transcranial magnetic stimulation (TMS) were compared for idiopathic unilateral facial neuropathy.

Method: We recruited patients with newly diagnosed idiopathic unilateral facial neuropathy and performed a blink reflex test, facial NCSs, and TMS. The amplitude of facial compound muscle action potential (CMAP) and motor evoked potential (MEP) between the affected and unaffected sides of the face was compared.

Result: A total of 30 patients were enrolled in the final analysis. TMS yielded a better detection rate, and MEP reduction rate was significantly higher than CMAP reduction rate, early in the course of the disease. Poor prognosis was positively associated with the CMAP reduction rate. The cutoff value of the CMAP reduction rate in the prediction of poor prognosis was established as 0.42.

Conclusion: Facial TMS could detect idiopathic unilateral facial neuropathy with a high sensitivity when used as an early diagnostic tool. Facial NCS could predict prognosis, and the CMAP reduction rate was significantly associated with poor short-term prognosis.