[Progressive mental deterioration after radiotherapy in adult patients with brain tumors].

We report a study on changes of mental function in twenty five adult patients with cerebral low-grade gliomas after radiotherapy. None of them had shown mental deterioration before radiotherapy nor tumor recurrence after radiotherapy. Radiation was given at a dose of 48 to 78 Gy (mean: 54.2 Gy). Patients were assigned for mental functional levels according to Karnofsky performance scale (KPS) after radiotherapy. Ten patients (40%) were normal. Seven patients (28%) showed moderate disabilities and 8 (32%) severe disabilities. The median interval time from radiotherapy to the onset of mental deterioration was 2.5 years in the moderate group and 1.6 years in the severe group. CT findings in severe group demonstrated severe brain atrophy and diffuse low density in the white matter after radiotherapy. The risk factors responsible for progressive mental deterioration after radiotherapy may be radiation site and size (whole frontal lobe), total dose (over 60 Gy) and patients age at the time of radiotherapy (over 60 yrs).