Brain radiation induces neurological deterioration that is progressive and often irreversible.
Results from direct injury to brain tissue and blood vessels and therisk increases with higher total dose, higher dose per fraction and with concomitant use of neurotoxic chemotherapeutic agents.
Clinical manifestations range from mild cognitive neurological impairment to dementia and death.
Occurs more commonly after radiosurgery but can occur after conventional whole brain radiation therapy as well.
Radiation causes vascular abnormalities in the brain reducing blood vessel density, restricting blood supply to brain tissue, causing chronic ischemic changes with infiltrative tumor cells and adjacent astrocytes producing cytokines such as VEGF.
A radiation produces damage to the myelin sheath and impairs oligodendrocytes from repairing this sheath.
Radiation necrosis is difficult to diagnose because it appears similar to progressive tumor on diagnostic imaging.
Radiation necrosis usually occurs at the treatment site, but it also can be distant, usually near a cerebral ventricle, and may also be diffuse, multifocal, and resemble tumor metastases
It is the the major complication of radiosurgery.
Potentially fatal complication.
May develop months or even years after irradiation.
Most cases occurs at random, without known genetic or other predisposing risk factors.
Treatment options presently is surgery to remove dead tissue and use of the steroids to provide symptom control.
Radiation necrosis of the brain can be managed and possibly prevented by the use of bevacizumab, suggesting that VEGF has a role in the etiology of the problem.
May result in headaches, seizures, impaired concentration, personality changes, focal weakness, and speech problems.
In a retrospective study from M.D. Anderson Cancer Center CNS radiation necrosis developed and 24% of patients treated with radiation and chemotherapy after resection of brain glial tumors: in those patients 44% had both had necrotic lesions and recurrent residual tumor.
CNS radiation necrosis is associated with increased cytokine production.
Brain radiation can induce destruction of hippocampal neural stem cell components (NCD) which can involve symptoms of memory, speech, executive function and processing speed impairments.