Evaluation of Brain Functional Changes With 18F-FDG PET and Cognitive Processes After Brain Radiotherapy for Cavernous Sinus Meningiomas and Non-secreting ACTH Adenomas

The use of radiotherapy for irradiation of all or part of the brain, in the treatment of extracerebral intracranial neoplasms, is growing rapidly, both due to the increase in diagnoses of primary tumors thanks to new imaging methods, and for the increase in the number of new cases of cancer.

Cerebral neurotoxicity linked to radiation treatment is an adverse effect that is not always accurately evaluated based on the prognosis of some brain pathologies. The progression of diagnostic and therapeutic methods has recently generated a modification of therapeutic protocols and some categories of radiotreated patients may incur acute, subacute and late effects. These include manifestations of acute neurological deterioration, more frequently effects classified as sub-acute such as "somnolence syndrome" (from 2 to 6 weeks after the end of treatment) and finally late effects, which manifest themselves as a variety of neurological deficits in particular a decline in cognitive brain functions, probably linked to a direct effect on neurons or the result of an imbalance in the connections between white matter and cerebral gray matter. In relation to the myelin function of conduction of axonal transmission, the result of radio-induced damage in this site would manifest itself with a significant reduction in the speed of transmission of the impulse and consequently with a dramatic worsening of cognitive processes. In particular, clinically, radiologically and in some cases also from a pathological point of view, the damage from rays on the brain parenchyma would have aspects similar to those of a degenerative pathology such as Alzheimer's disease. These effects are usually measured on the patient by subjective assessments or using neuropsychological tests. The use, not only experimental, of neurophysiological methods for the study of cognitive processes in neurology and in degenerative disorders such as dementia is increasingly frequent. These methods are based on the study of specific neuronal circuits involved in the cognitive functions of the human brain in normal conditions and in the presence of pathology. Among the techniques that allow an analysis of molecular alterations in vivo there are scintigraphic ones, i.e. nuclear medicine ones, including single photon emission tomography (SPET) and positron emission tomography (PET).