Hearing morbidity post head and neck radiotherapy

Abstract

Radiation therapy carries an important role in the treatment of head and neck (H&N) cancers. Exposure of cells to ionizing radiation produces a variety of biological and molecular changes that may manifest clinically as tumor killing or normal tissue toxicity,the type and severity of these effects depend on variables such as the energy and type of radiation,the composition of target biologic tissue,the cellular and molecular response,duration of exposure,and cellular microenvironment.A sound signal in the environment is collected by the pinna,passes through external auditory canal and strikes the tympanic membrane_ Vibrations of the tympanic membrane are transmitted to stapes footplate through a chain of ossicles coupled to the tympanic membrane Movements of stapes footplate cause pressure changes in the labyrinthine flu ids which move the basilar membrane. This stimulates the hair cells of the organ of Corti. It is these hair cells which act as transducers and convert the mechanical energy into electrical impulses which travel along the auditory nerve.to determine the effect of radiotherapy on hearing process.Prospective case control study on 45 patients (90 ears) in Al diwaniyah teaching hospital from January 2013 to October 2016 with head and neck malignant tumors diagnosed by histopathological specimens,of both sexes and treated with radiotherapy are included in the study. Patient with history of hearing impairment (disabling or documented sever to profound hearing loss),chronic otitis media and those who receive chemotherapy previously are excluded from study. Pre radiotherapy pure tone audiogram and 6 month after when the patient come back to oncology unit for fellow up their condition those patients allocated in group A while group B (control) 45 healthy person (90 ears) are chosen from staff of hospital and college of medicine after announcement for volunteers in study pure tone audiogram done for them as in case group.Regarding the mean of age for group A was 53 years with range from 30-70 years, with male: female ratio 4:1while for control group (B) was 49 years with range 25-60 yearsand male to female ratio 2:1. Most common neoplasia was carcinoma of larynx followed by nasopharyngeal, oropharyngeal and hypo pharyngeal carcinoma,oral cavity and paranasal sinuses Regarding hearing about 38 (42.18%) of patients (group A) not affected by radiotherapy while 43 patients (47.75%) got worse hearing after radiotherapy,only 9 patients (9.99%) had hearing improvement. While in control group 73 (81.11%) not changed,6 (6.66%) deteriorate and 11 (12.22%) had improved hearing.Radiotherapy induced hearing problems occur in significant number in patient with head and neck tumors.Hearing morbidity post radiotherapy mainly sensory neural.  Patient counselling before radiotherapy about hearing disabilities should be regarded. Further long term studies and larger sample are needed.