Objective: Recurrent laryngeal nerve damage is a rare complication after receiving conventional radiotherapy for treatment of head and neck cancers and will always be underestimated. The purpose of the present study was to focus on the prevalence of vocal cord paralysis after irradiation and the natural history in those patients.
Material and Method: All patients who received more than 60 Gy radiation dose of convention radiotherapy for treatment of head and neck carcinoma from Phramongkutklao Hospital and Nation Cancer Institute of Thailand were recruited in the present study during follow-up period between May 2006-December 2007. The subjects had to have good mobility of bilateral vocal cords with no recurrence or persistent tumor before the enrollment. Baseline characteristic and the associated symptoms of the recurrent laryngeal nerve paralysis were recorded. Laryngeal examinations were done by fiberoptic laryngoscope and in suspicious cases; stroboscope and/or laryngeal electromyography were also performed. The vocal fold paralysis was diagnosed by reviewing recorded VDO by 2 laryngologist who were not involved in the present study.
Results: 70 patients; 51 male and 19 female were recruited. 5 patients (7.14%) were diagnosed to have vocal cord paralysis and 2 patients (2.86%) were found to have vocal cord paresis confirmed by electromyography. Most of them were the patients with nasopharyngeal cancers (6/7) with the only one had oropharyngeal cancer (1/7). All of the paralysis/paresis was unilateral lesion; 4 on the left and 3 on the right side. The duration from the patients completed radiotherapy to the time of the diagnosis of vocal cord palsy was 14-35 months. The measure of agreement or Kappa value with 95% CI was 0.818 + 0.245. Associated symptoms of vocal cord palsy are hoarseness (100%), dysphagia (28.6%) and aspiration (28.6%).
Conclusion: A significant number of vocal fold palsy may occur in patients with head and  carcinoma after receiving  radiotherapy. Subcutaneous fibrosis or compromised blood vessels at the skull base or the neck area may be important risk factors for development of the complications and further studies are need to solve the pathogenesis.

Keywords: Vocal fold palsy, Radiation, Head and neck carcinoma