The Effect of Radiation Dose on Swallowing: Evaluation of Aspiration and Kinematics.

Radiation oncologists have focused on the pharyngeal constrictors as the primary muscles of concern for dysphagia. However, our prior investigations have demonstrated that radiation dose to the geniohyoid rather than the constrictor muscles was more closely related to penetration aspiration scores (PAS). We examined the relationship between (1) radiation dose and swallowing temporal kinematics, and (2) between PAS and swallowing kinematics in these patients. Videofluoroscopic swallowing studies of 41 patients following radiation therapy for oropharyngeal cancer were analyzed for thin liquid boluses. Timing measures included duration of laryngeal vestibule closure (DLVC), duration to maximum hyoid elevation (DTMHE), duration to cricopharyngeal opening (DTCPO), and pharyngeal transit time (PTT). PAS was extracted for each swallow and considered normal if ≤ 2. As minimum and mean dose to the geniohyoid increased, DTMHE, DTCPO, and PTT increased. Worse PA scores were most strongly correlated with radiation dose received by geniohyoid (r = 0.445, p < 0.0001). Mean DLVC varied according to PAS group (normal PAS mean = 0.67 s, abnormal PAS mean = 0.13 s; p < 0.001). Similarly, DTCPO was significantly different based upon PAS (normal PAS mean = 0.22 s, abnormal PAS mean = 0.37 s, p = 0.016). As PAS increased, DTPCO and PTT increased (r = 0.208, p = 0.04; r = 0.204, p = 0.043). A negative correlation was noted between PAS and DLVC (r = -0.375, p = 0.001). Higher doses of radiation to the geniohyoid muscles are associated with increased severity of dysphagia as measured through both kinematics and PAS. Consideration of dose to the geniohyoid should be considered when planning radiation.