Neurocognitive effects of therapeutic irradiation for base of skull tumors

Abstract

Purpose: To determine whether radiation therapy delivered to the paranasal sinuses causes any long-term impairment in neurocognitive function as a result of incidental brain irradiation. Methods and Materials: Nineteen patients who received paranasal sinus irradiation at least 20 months and up to 20 years before assessment were given a battery of neuropsychologic tests of cognitive function. Radiation was delivered by a three-field (one anteroposterior and two lateral) technique. The median radiation dose was 60 Gy (range 50–68 Gy) in fractions of 1.8 to 2 Gy. The volume of irradiated brain was calculated from planning computed tomography slices or simulation films. The results of the neuropsychologic tests were compared to normative control values. Results: Memory impairment was found in 80% of the patients, and one-third manifested difficulty with visual-motor speed, frontal lobe executive functions, and fine motor coordination. Two of the patients had frank brain necrosis with resultant dementia and blindness, and three had evidence of brain atrophy. Three of the fourteen patients without documented cerebral atrophy or necrosis were disabled from their normal activities. Three patients also developed pituitary dysfunction. Neurocognitive symptoms were related to the total dose of radiation delivered but not to the volume of brain irradiated, side of radiation boost, or chemotherapy treatment. The pattern of test findings was consistent with radiation injury to subcortical white matter. Conclusions: Radiation therapy for paranasal sinus cancer may cause delayed neurocognitive side effects. Currently, however, the development of severe adverse effects appears to be decreasing because of improvements in the techniques used to deliver radiation. Lowering the total dose and improving dose distributions should further decrease the incidence of delayed brain injury due to radiation.