Neurologic complications of radiation therapy and chemotherapy

Radiation induced toxicities are due to the effect of irradiation of normal surrounding tissue which is included in the radiation port. The mechanisms of radiation induced damage have not been completely elucidated. Hypotheses include direct damage to neural cells versusdamage to the vascular endothelium with secondary effeas on nervous system structures. Another hypothesis is that radiation damaged glial cells release antigens that are able to evoke an autoimmune response against the nervous system resulting in both cellular necrosis and vascular damage. The clinical diagnosis of radiation induced neurotoxicity may be difficult especially in patients who had neurologie signs prior to treatment. It is helpfúl to determine if the clinical signs correlate with the irradiated site and to know the total dose received and the dose per fraction. Prior or concomitant chemotherapy may act to increase the toxicity produced by radiation. The age of the patient at the time of radiation is important as the very young and the elderly are more likely to develop, toxicities. Finally, concurrent neurologic diseases such as dernyelinating disorders appear to sensitize neural tissue to radiation damage.