Laryngeal contraction normally entails activation of mutually cooperative intrinsic laryngeal muscles (ILMs). Unfortunately, standard stimulating methods do not completely mimic the normal ongoing synchrony between the muscles. We submit that this problem can be addressed by modifying the stimulating waveform.
This study extends prior canine research to the human using quasitrapezoidal (QT) currents instead of standard square waves, which while valuable incompletely express normal ILM interactions.
In two patients undergoing laryngectomy for cancer, the recurrent laryngeal nerve on the uninvolved side received QT pulses (4 Hz, 60–2,000 μA, 100–500 μs width, 0–500-μs decay) via a bipolar cuff electrode. Pairs of needle electrodes placed into the posterior cricoarytenoideus (PCA), lateral cricoarytenoideus (LCA), and thyroarytenoideus (TA) were used to record electromyography amplitudes, and waveforms were analyzed by a specially designed computer program.
With activity from square waves serving as control, we observed statistically significant (P < .05) shifts in mutual relationships among PCA, LCA, and TA for an array of specific QT configurations.
Our preliminary data on selective ILM manipulation offer promise for improved dynamic control of faulty laryngeal contraction patterns.