Morphological study of the stylopharyngeus in elderly group

<p>【Objective】Dysfunction of pharyngeal clearance increases with age, so aspiration in elderly people shows higher development. The stylopharyngeus（SP）has been regarded as the main pharyngeal shortening muscle because of its longitudinal direction, and it is also suggested that the muscle serves to clear pharyngeal retention. In the present study, SP was examined to clarify the morphological characters of aspiration in the elderly.</p><p>【Materials and Methods】 169 left and right specimens obtained from 89 formalin-treated room cadavers were used. The dimensions of SP were measured and its cross sectional area was calculated. The insenion angle of SP to the pharyngeal wall and insenion frequency of SP to piriform recess was also measured. The cadavers were sorted by age：55 to 74（young-old）and 75 or older (old-old). Age, sex and right-and-left differences were found using the Bonferroni test and paired t-test.</p><p>【Results】SP was separated into three parts：upper, middle and lower bundle immediately after penetrating the pharyngeal wall. The upper muscle bundle was in a fundus of the palatine tonsil bed. The middle bundle accompanied the pharyngoepiglottic fold to the epiglottis. The lower bundle（91% in male and 88% in female）reached the base of piriform recess and was inserted into the lateral wall of thyroid cartilage.</p><p> In the insertion angle of SP, the right angle was significantly larger than that of left, and among females of the old‐old group it was significantly larger than among males. The cross sectional area of SP was significantly larger in the old-old group than in the young-old group.</p><p>【Discussion】It is widely known that the larynx descends after 70 years old, therefore, it is expected that during swallowing a larger load is added for laryngeal elevation than before swallowing. Our results showed that the insertion angle of SP of the male old-old group was significantly smaller than that of the female group, and the SP cross sectional area of the old-old group was significantly larger than that of the young-old group. It is suggested that, compared with females, the larynx descent width of males is larger, thus the enlargement of SP cross sectional area was due to work hypertrophy in the old-old group and SP contributed to pharyngeal clearance.</p>