Facial electroneurography in Bell's palsy: variability in the early stage and comparison between interpretation methods

To determine the variability of the abnormalities found in the electroneurography (ENG) of the facial nerve in cases of Bell's palsy during the initial two week period was one of the objectives of the authors. A second one was to investigate the value of ENG as a tool to determine an early prognosis of recovery utilizing two different methods. In the first one the amplitude of the compound muscular action potential (CMAP) obtained on the paralyzed side was compared to this potential on the opposite (normal) side. The second method compared the CMAP on the paralyzed side to normal standardized data from normal individuals. A group of 33 patients with Bell's palsy was followed until total recovery of for at least 4 months, if the recovery was not achieved earlier. It was observed that amplitude of the CMAP become stable towards the sixth day of palsy and this is a good time to establish the prognosis. Another conclusion is that both methods were equivalent to determine the prognosis in Bell's palsy.