Laryngeal electroglottography as a predictor of laryngeal electromyography

We evaluate a group of patients who have mobile vocal folds, but have flexible laryngeal examinations suspicious for mild vocal fold paresis. The purpose of this retrospective study is to evaluate if electroglottography (EGG) can predict the probability of having an abnormal laryngeal electromyography (LEMG). Charts of patients evaluated and suspected of having mild vocal fold paresis between August 1, 2004 and March 30, 2006 were reviewed. We compared average EGG contact quotients (CQs), average absolute difference of recorded CQ from normal (|CQ-50%|), and EGG waveforms between patients with normal and abnormal LEMG. Waveforms were evaluated in blinded fashion. Statistical analysis was performed using chi square and t test analyses. One hundred and sixteen patients received both flexible laryngoscopy and LEMG as part of their evaluation. Forty-eight patients (41%) had confirmed paresis by LEMG and 68 patients (59%) had normal LEMGs. Only 9.1% of patients with a normal EGG waveform had an abnormal LEMG. In contrast, 40.4% of patients with an abnormal EGG waveform had abnormal LEMGs. The negative predictive value of a normal EGG waveform for an abnormal LEMG was 90.9%. No significant differences were identified between patients with normal versus abnormal LEMG in terms of average CQ (47.8% vs 46.4%) or |CQ-50%| (6.2 vs 5.6). Patients with a normal EGG waveform are unlikely to have an abnormal LEMG.