Late effects on hearing and balance after treatment for childhood cancer

Abstract: During the last several decades, improvements in diagnostic skills and in the treatment of children with cancer have substantially increased the number of long term survivors of childhood cancer. Treatment of children with cytostatic drugs is known to create a range of late adverse effects. Among these are damage to certain structures of the inner ear and hearing impairment. In children, a hearing loss can delay speech and language development, as well as influence educational achievements and social and emotional development. Chemotherapy in childhood may also cause other significant functional disturbances, such as postural instability, impaired motor control of the eyes and difficulties in processing visual information. The overall objective of this thesis is to increase the knowledge of the late effects on hearing and balance in individuals who have received chemotherapy during childhood. The results show a continuous impairment of hearing in subjects with deficiencies related to chemotherapy. The treated subjects had severe difficulties with word recognition in noise, compared to subjects with the same degree of hearing impairment from other causes. With proper hearing aids, their ability for word recognition in noise improved up to 46%. The subjects had poorer postural stability and postural adaption during balance perturbation than healthy subjects. They also had a reduced accuracy in smooth pursuit gain and velocity accuracy, a faster saccade velocity, as well as shorter smooth pursuit and saccade latencies. The subjects were more visually dependent in orientation than healthy controls. There was a high incidence of symptoms related to hearing disabilities: poor concentration, visual disturbances, headaches and unsteadiness, light-headedness or the feeling that things around them were spinning or moving. Age at time of treatment and the time elapsed since the end of treatment seem to be critical factors. Those treated at a younger age had poorer postural stability, more oculomotor deficits and subjective disabilities, which tended to worsen with increased time since the treatment. This study further emphasises the need of regular follow-up of patients treated with chemotherapy for cancer during childhood, and the inclusion of assessment of hearing and balance function, as such dysfunctions may advance, or not be evident until several years after treatment.