Neurogenic diplophonia: a high-speed digital image analysis

Abstract

AbstractHigh-speed digital image analysis was made on five cases with diplophonia. All cases had developed diplophonia associated with unilateral recurrent or superior laryngeal nerve paralysis, the definite diagnosis of which was made electromyographically. It was found that there was a difference in vibratory frequency between the left and right vocal folds in all cases. It appeared that the phase difference between the two folds showed a quasiperiodic variation and, as a result, corresponding quasiperiodic perturbation in voice waveform was induced. Coexistence of the frequency of quasiperiodic perturbation in voice waveform and mean voice frequency appeared to give a perceptual impression of diplophonia. It was considered that mass/tension difference between the left and right vocal folds due to neurogenic laryngeal disorders should be the cause of the phase difference between the two folds.