Neuropsychological evaluation of late-onset post-radiotherapy encephalopathy: a comparison with vascular dementia.

It is known that radiotherapy (RT) may cause cerebral injury. The most frequent neurotoxic effect of RT at any age is diffuse cerebral injury. Brain injury by therapeutic irradiation has traditionally been classified according to its time of onset into acute, early delayed, and late forms. The latter is not reversible. The neurocognitive sequelae of cranial irradiation can be mediated through vascular injury. Because the pathologic changes are most profound in the white matter, we compared a group of patients treated by RT (n=34) with a group of patients affected by subcortical vascular dementia (sVaD, n=34). Patients with a total radiation does <35 cGy did not show any sign of cognitive impairment. All the patients with a total irradiation dose >45 cGy did show profound cognitive and behavioural alteration. The patients who received a total dose of brain radiation comprised between 35 and 45 cGy did show slowness of executive function, and profound alterations of frontal functions, such as attention focusing, mentation control, analogical judgement and insight. The patients who suffered from the consequences of RT had slowness of executive functions, and profound alterations of frontal functions, such as attention focusing, mentation control, analogical judgement and insight, similar to those obtained by the patients suffering from subcortical vascular dementia. High dose RT might result in a severely demented, bedridden patient, who "has been cured" from his primary disease, the brain tumour. This constellation demands serious consideration before RT is given.