Induced unilateral vocal fold paralysis and recovery rapidly modulate brain areas related to phonatory behavior: A case study

Background: Peripheral and behavioral effects of voice disorders are well documented in the literature; yet, there is little information regarding the central neural biomarkers and mechanisms underlying these disorders. Understanding the details of brain function changes in disordered voice production is a critical factor for developing better treatment strategies that result in more robust patient outcomes. Objective: To examine a model of induced unilateral vocal fold paralysis (iUVFP) to demonstrate and characterize the form of activity changes within central mappings of the larynx to the induced paralysis. The induced paralysis model allowed the participant to serve as his or her own control when comparing baseline results of normal voice with results during the paralysis and subsequent recovery. Study Design: Prospective, case-study design. Methods: Functional magnetic resonance imaging was used to examine central laryngeal representations during three time points: pre-iUVFP, during iUVFP, and postrecovery from iUVFP. iUVFP was induced using a lidocaine with epinephrine nerve block unilaterally. Percent changes in blood oxygenation level-dependent (BOLD) activity served as the dependent variable. Results: Results indicated an overall reduced activity level in sensorimotor, subcortical, and cerebellar regions during paralysis. Recovery from paralysis led to augmented responses, particularly in sensory, association, and cerebellar zones. Conclusions: The decrease in activity during iUVFP and the significantly increased activity during the recovery phase likely represent immediate neuroplastic events occurring within minutes of nerve blockade. Recovery-related changes in the BOLD response are hypothesized to be associated with a recalibration of the system after return of normal laryngeal function.