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

Abstract

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.

Treatment of late sequelae after radiotherapy for head and neck cancer

“…Pharyngeal constrictors and the larynx were first identified by multiple investigators as primary dysphagia-aspiration-related organs (DARS) [95]. Beyond the classic DARS, emerging work suggests relevance of dose/volume distributions to submental musculature (i.e., geniohyoid, mylohyoid) that are critical to elevate the hyolaryngeal complex and assist with cervical esophageal opening [96,97]. Reporting normal tissue complications probabilities as a function of DARS, Eisbruch et al gave solid ground for efforts to reduce dysphagia in the IMRT era [95,98,99].…”

Pathophysiology of Radiation-Induced Dysphagia in Head and Neck Cancer

“…As such, external radiation may be partially absorbed by soft tissue within the submandibular space (i.e., submandibular glands and lymph nodes), lessening the radiation dose to the suprahyoid muscles. Two dosimetry studies were recently conducted correlating dysphagia with radiation dose to the genioglossus and submental complex [52,50]. Kumar et al [52] measured dosimetric characteristics in genioglossus, and found that a minimum dose (30 Gy) strongly correlated with abnormal (≥3) penetration-aspiration scores.…”

Examination of swallowing maneuver training and transfer of practiced behaviors to laryngeal vestibule kinematics in functional swallowing of healthy adults

“…Starmer et al (2015) reported that patients with post-radiated submental muscles who penetrated and aspirated also had decreased dLVC (Starmer et al, 2015). These, and many other studies that link disordered LVC to aspiration, highlight the complexity of LVC mechanics and its pathophysiology (Lee et al, 2016; Power et al, 2009; Power et al, 2007).…”