Artificial manipulation of voice in the human by an implanted stimulator.

Abstract

Traditional approaches influencing voice quality (e.g., anatomical and chemical denervation for spasmodic dysphonia, surgical medialization for paralysis) have ignored the dynamic nature of the larynx. We report here the first attempt to manipulate voice using an implanted stimulator to systematically control vocal fold adduction. Devices placed for aspiration in three subjects retaining speech after stroke, cerebral palsy, and multiple sclerosis were used to stimulate recurrent laryngeal nerves with 42 Hz, 52 to 200 microsecond pulses of incremental amplitudes during phonation with the tracheostomy tube occluded. Vocal fold adduction increased with stimulation strength (P < .05). Speech was analyzed with the Vox Metria program. We found highly significant differences for fundamental frequency (P < .007), jitter (P < .004), and shimmer (P < .005), between natural and stimulated voice (aah and eeh) when using higher charges. Dynamic vocal fold manipulation seems promising in terms of versatility lacking with static approaches to voice control.