Morphology of brain stem lesion and bera findings after 60Co irradiation.

Ionizing rays, utilized in radiological diagnostics and oncological therapy affect the central nervous system and may injure auditory pathways and cause hearing disturbances which vary in intensity. On the basis of a stereotactic atlas of the brain of a guinea pig, the trapezoid and geniculate bodies were identified in the skull X-ray pictures. The irradiated region was found to have 10 x 6 x 5 mm in dimensions and to be situated at the depth of 11 mm away from the animals occiput. After introductory recording of the potentials obtained from the brain stems (BERA), the stems of 60 guinea pigs were irradiated in the groups with the doses of 5, 10, 20 Gy. The hearing potentials from the brain stems were recorded on the 1st, 4th, 10th, 21st and 84th day after irradiation. The findings of measurements of hearing potentials were compared with the morphologic picture of the brain stems in the examined animals.