Retrospective medical record study: timing & order of anatomical structural movement within hyolaryngeal elevation in stroke patients - a continuation of the two-sling model

Thesis (M.A.)--Boston UniversityEffective pharyngeal swallowing requires the neuromuscular coordination of several important events. Swallowing is a complex neuromuscular activity that consists of three phases; oral, pharyngeal and esophageal phase. This thesis proposes and investigates that timing and order of the anatomical structures due to the movement of the “two-sling model” musculature in hyolaryngeal elevation during the pharyngeal swallow and activation of such during a swallow are crucial to the difficulties faced post-stroke. It focuses on the question: does the timing and order of anatomical structural movement within the complex of movements causing hyolaryngeal elevation in stroke patients affect the efficiency of the overall swallow? Test and control groups were created, by age and gender matching the 20 subjects in each group (40 subjects total). The data was collected from patient records, using the Boston Medical Center – Medical Record Database, and video fluoroscopic swallowing studies. A total of 4 swallows were analyzed per subject (160 total swallows analyzed), one for each of the four bolus types used in the recorded modified barium swallows: thin barium, nectar thick barium, pudding barium, and cracker with barium. Points of interest within the video swallows were located on the anterior hyoid, and the anterior and posterior vocal fold edges (above the air column); all measured at both minimum and maximum values to obtain time and distance calculations. Those results were then averaged for each subject before analyzed against the rest of the subject set (a total of 40 averaged data sets). Coordinates were recorded from two time points using the ImageJ program: minimum and maximum hyolaryngeal excursion and then mathematically converted into multiple kinematic measurements of hyolaryngeal movement. Linear regressions analyzed to evaluate the strength of relationship to hyoid-laryngeal order did not reveal strong statistical correlations of how well the produced regression lines approximated the real data points. Using two-tailed paired t-test analysis, we failed to reject Ho since the t-values were greater than -1.729 and less than 1.729. We did not have statistically significant evidence at α = 0.05 to show that there is a difference between the experimental and control groups for all three of the analyzed variables. Even though the t-test data showed no difference between the three tested variables within the experimental and control groups, we did see 40% of the experimental group show an abnormal anatomical initiation of movement during the swallow, showing the larynx moving prior to the hyoid. Pearson coefficient calculations analyzed the relationships between (1) hyoid excursion (cm), (2) laryngeal elevation (cm), and (3) timing (ms) to hyoid-laryngeal latency (ms) and revealed the strongest positive association of predictability, r = 0.993, to be found in the experimental group within the timing to hyoid-laryngeal latency comparison; predicting timing duration from the hyoid-laryngeal latency. The experimental group relationship of laryngeal elevation to hyoid-laryngeal latency produced the weakest association of predictability of r = 0.056. [TRUNCATED