Noninvasive clinical tools to aid in early detection and monitoring of dysphagia in ALS: translating findings from mice to humans
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Previous work in our lab identified lingual dysfunction (i.e., slow lick rate) as the earliest clinical sign of dysphagia in SOD1-G93A transgenic mice, a mouse model of amyotrophic lateral sclerosis (ALS). The goal of this study was to identify a human correlate for lick rate that could be used to detect early lingual dysfunction in humans with ALS. Healthy adults (n = 133) ranging from 20-89 years old were recruited for a 30 minute test battery consisting of 5 noninvasive tasks: tongue tick rate (to mimic lick rate), diadochokinetic speech rate (DDK), mastication rate, water swallow rate, and tongue strength. Subjects were divided into two age groups: young (20-59 years, n=88) and old (>60 years, n=45). We found that a significant difference exists between young and old adults for tongue tick rate, DDK, mastication rate, chew/swallow ratio, and tongue strength. Specifically, older participants produced significantly reduced tongue strength and slower tongue tick and diadochokinetic speech rates, experienced a greater level of fatigue during the tick rate task compared to the speech rate task, and required greater oral preparation time before swallowing a pretzel bolus. These data suggest deterioration in lingual function and the oral stage of swallowing for adults >60. This novel task holds promise in detecting subtle lingual dysfunction that may be contributing to dysphagia in primary aging and neurological disease conditions.