Impact of radionecrosis on cognitive performance and possible intervention: An analysis of the correlation between lesion sites, lesion volume and severity of cognitive deficits

Radionecrosis is observed in about 1–3% of patients after radiotherapy for nasopharyngeal carcinoma. Previous studies indicated that patients with radiation-induced brain lesion manifested impairment on memory and language. However, little is known about whether these deficits are related to location and volume of the lesion. In addition, effective intervention to improve their cognitive function is not available at present. A series of experiments were conducted to explore these issues. In Experiment One, the memory performance of a group of patients with bilateral lesions over the lateral temporal lobe sparing the hippocampus was assessed and compared with that of patients with relatively spared cortex and patients with bilateral damage to the lateral temporal lobe and the hippocampus. The results demonstrated that bilateral damage to the lateral temporal lobe resulted in memory impairment across verbal and visual modalities. This finding provided valuable implication to the well-established model of memory that suggested the specific role of the medial temporal lobe on memory processing. Experiment Two investigated the relationship between the volume of radiation-induced lesion and the severity of cognitive impairments. Fifty patients treated with radiotherapy for nasopharyngeal carcinoma were evaluated by a battery of neuropsychological tests of cognitive functions. Cognitive impairment in patients with radiation-induced brain lesion was found to be correlated with the volume and location of the radiation-induced brain lesion, while the volume of the lesion was affected by the age at the completion of radiotherapy. Specifically, larger left-sided lesions were correlated with lower verbal memory and language while larger right-sided lesions were associated with lower visual memory. In addition, the younger the patients were when they received radiotherapy, the smaller the lesion volume would be. In Experiment Three, mega doses of vitamin E were delivered to patients with radiation-induced brain lesion for one year. As compared with patients without receiving the medication, global cognitive functioning and memory were significantly improved after taking vitamin E for one year. Therefore, vitamin E might be considered a possible intervention for patients with radiation-induced brain lesion.