THE EFFECT OF LARYNGEAL IRRADIATION ON PHARYNGOESOPHAGEAL MOTILITY

The upper esophageal sphincter (UES) receives the full radiation dose during external beam radiotherapy to the adjacent larynx. The aim of the study was to assess the effects, if any, of radical laryngeal radiotherapy on motility patterns in the pharyngoesophageal segment. A strain gauge assembly and a digital manometric recorder were used to assess 19 patients 13 to 71 months after irradiation of T1 to T3 glottic cancer to a central dose of 52.5 to 55.7 Gy in 20 daily fractions. Results were compared with those of 23 healthy controls. Tonic lower esophageal sphincter (LES) pressure, distal peristaltic contraction, tonic UES pressure, and eight parameters of pharyngoesophageal dynamics during water and bread swallows were studied. No difference was found between the two groups in tonic LES pressure, peristaltic amplitude, or tonic UES pressure. Water swallow pharyngoesophageal wave velocity was significantly lower in patients than in controls, and the irradiated group also showed a trend toward increased duration of the distal esophageal peristaltic wave. The reduction in upper esophageal wave velocity was associated with the interval following irradiation. The post-treatment interval was also inversely related to the amplitude of UES after-contraction, and associated with an increase in wave duration throughout the pharyngoesophageal segment. A study of 23 laryngectomy specimens, 5 of which had been removed following radiotherapy, failed to identify pathological features in nerves or muscle which characterised previous laryngopharyngeal irradiation. We conclude that laryngeal irradiation has no effect on upper or lower esophageal sphincter tone but causes an increase in wave duration and a reduction in wave velocity in the pharyngoesophageal segment. These changes are independent of age and sex and are not associated with pathological features like the neural degeneration described in the myenteric plexus of irradiated rectum.