647 EFFECTS OF MASTOID RADIATION ON THE HEARING FUNCTION OF CHILDREN WITH ACUTE LYMPHOCYTIC LEUKEMIA (ALL)

Abstract

Co 60 cranial radiation, 1500 to 2400 rads plus intrathecal methotrexate for childhood ALL became an integral part of our “Total Therapy” program. Radiation is delivered to the mid-plane of the skull in 14 to 15 sections in 18 days. The ports include the temporal bone with all structures of the auditory system. This study was designed to detect any immediate or long-term ionizing effect on the hearing function. Pure tone audiograms were obtained before radiation and at 6 and 12 months. The following frequencies were tested: 500, 1000, 2000, 4000, 6000 and 8000 Hz. For younger children unable to respond to pure tone testing, stapedial reflexes were obtained for 500, 1000, 2000 and 4000 Hz. Testing was done using a Beltone 200 C audiometer and an American Electromedics Impedance Bridge Model 81 and test scores were obtained for ears free of outer or middle ear disease. One hundred children registered into the current “Total Therapy” from January ′76 to July ′77 were studied. Audiograms were obtained for 180 ears pre-treatment, 132 ears at 6 and 102 ears at 12 months post-radiation. A sign test for statistical significance was run to compare combined test scores for each frequency at 6 and 12 months after radiation to combined test scores for each frequency before radiation. No statistically significant reduction in hearing levels was noted for any test frequency at either 6 or 12 months post-radiation. Individual audiograms indicated essentially normal hearing levels for all patients at 6 and 12 months.In summary, at 1 year post-radiation, 1500 to 2400 rads of cranial radiation resulted in no statistically significant reduction in hearing levels.