神经损伤与修复
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Figure 1｜Factors of radiation impact in cosmos and psycho-physiological effects on CNS.
Radiation dose and age dependence have to be also taken into consideration in the evolution of neuro-cognitive impairments, that can manifest even from young age (Figure 1) (Newton et al., 2020). Early insults can cause lifelong problems, both physical and mental. The brain that is not mature enough, is highly susceptible to negative impacts on its circuit formation. Radiotherapy causes adverse neurocognitive outcome in young age survivors. They may develop motor, intellectual, visual, and psychological dysfunctions, with moderate to severe disabilities. The younger the age, higher cranial irradiation dose, larger brain volume irradiated, and prolonged time predict worse neurocognitive outcomes (Chu et al., 2020). In clinical research, it is difficult to gather much data about the group of older patients, since they are often excluded from clinical trials. Also, radiation therapy in this case requires special considerations, concerning also other comorbidities and chronic conditions they may have. Nevertheless, higher age is one of the significant predictors of cognitive decline after whole brain radiotherapy. In the recent study by Chan et al. (2020) was seen that after WBRT there is diminished cognitive function in older patients, and also that every patient over 70 years experienced cognitive decline after WBRT.
Figure 2｜Schematic illustration of the use and effects of active agents in the radiation research and therapy.
In radiation medicine, there are agents used in protection against ionizing radiation. Radioprotectors are used before radiation to protect cells and tissues from the damage. Other group of agents, radiomitigators are used early after the exposure to help in repairing and recovering of the tissues even before the presence of symptoms. And finally, there are therapeutics that are utilized after radiation to enhance healing of injuries and regeneration (Obrador et al., 2020). Various radioprotectants have different effect on tissues and organs. Not each one has effect in neural cells, however, there are some used in a therapy of CNS radiation damage (Figure 2).