Correlation of the nerve excitability test and electroneurography in acute facial paralysis

In a retrospective study of 77 patients with acute facial palsy, the results of the nerve excitability test (NET) and electroneurography (ENoG) were analyzed in order to establish a mathematic correlation and to relate the prognostic NET values to quantitative ENoG results. The two tests are related by exponential functions. Coefficients of correlation were higher for the results between NET and the optimized lead placement (OLP) ENoG compared to NET and standardized lead placement (SLP) ENoG. The highest correlation coefficients were demonstrated when NET was performed over the marginal and zygomatic branches of the facial nerve and OLP ENoG recorded in the nasolabial region. Good prognostic NET threshold differences in patients with a small percentage of intact motor axons, calculated by ENoG, may represent segmental demyelination or the deblocking phase of neuropraxia. The tests are complimentary in establishing the integrity of the facial nerve in acute paralysis.