Vocal Dysfunction in Young-onset Parkinson's Disease
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Vocal dysfunction is well established in persons with older-onset Parkinson's disease (PD), but has not been investigated in the young-onset PD (YOPD) population. Voice deficits associated with older-onset PD mirror the characteristics of vocal aging, suggesting that our current knowledge base of laryngeal dysfunction in the PD population is confounded by aging effects. The purpose of this study was threefold: (a) to examine perceptual voice characteristics and the potential impact of voice symptoms on quality of life; (b) to compare YOPD and healthy control (HC) speakers' performance on two routinely used clinical tasks (sustained vowel phonation and laryngeal diadochokinesis); and (c) to experimentally manipulate and compare speakers' performance in producing phonatory offset-onset gestures as reflected in four phonetic contexts (each eliciting a different mechanism) across three speaking modes. Twelve YOPD speakers and twelve healthy control (HC) speakers participated. YOPD speakers reported voice symptoms of hypophonia, tremor, hoarseness, monotone, and impaired speech intelligibility. They demonstrated a mild to moderate voice handicap. Findings revealed no speaker group differences for speech intensity on sustained vowel phonation and reading tasks. YOPD speakers demonstrated a significantly decreased rate of syllable repetition and used a significantly greater number of pauses during production of one of two laryngeal diadochokinetic tasks. Acoustic measures associated with mechanisms of phonatory offset-onset demonstrated trends of speaker group differences, suggesting that YOPD speakers have impaired voicing control for mechanisms of phonatory offset-onset not associated with oral constriction. Intra-speaker group variability was observed for YOPD speakers. Inspection of speaker groups' performance across speaking modes suggested a disruption in the habitual setting of laryngeal posture in YOPD speakers; namely, they use a laryngeal postural setting that is similar to that observed in HC speakers when speaking in an aspirant or breathy voice mode. Speech masking facilitated a speaking mode change in YOPD speakers and could provide an effective and efficient treatment method for training persons with YOPD to speak in a projected mode. Vocal dysfunction is associated with YOPD and voice symptoms can appear early in the disease process, sometimes preceding onset of limb symptoms. Persons with YOPD should be routinely assessed for vocal dysfunction.