Abstract
Background: Exposure to radiation from natural and human-made sources became ubiquitous. This review aims to highlight the main reported radiation-induced neurological clinical manifestations. Although neurological injury inflicted by exposure to ionizing radiation is well established, its molecular mechanisms are still not fully understood. Moreover, adverse health effects of non-ionizing radiation are still an unresolved controversy.
Methods: This narrative review was conducted by synthesizing the evidence gathered through literature database search. Radiation induced brain injury, neuroinflammation after radiation, radiation neurological outcomes and electromagnetic radiofrequency radiation brain were the main search terms used to identify human studies published in English within the last 5 years. After implementing the eligibility criteria, 59 references were included.
Results: radiation-induced brain injury is a constellation of symptoms that could be categorized as: acute (days to 1 month), subacute (1–6 months) and late (>6 months). While acute and subacute manifestations are milder and reversible, late manifestations are more severe and irreversible. Fatigue, headache, and cognitive impairment are the most consistent manifestations in all phases. Other forms of delayed manifestations are central neurological deficits consistent with cerebrovascular ischemic or hemorrhagic insults with higher risk in younger populations. Endocrinopathies and metabolic dysfunctions were also described as manifestations of hypothalamic-pituitary injury. Manifestations of leukoencephalopathy are not uncommon after radiation exposure, such as dementia, gait apraxia and urinary incontinence. Limb sensorimotor deficits are commonly due to radiation-induced peripheral neuropathy, and occasionally due to a more serious myelopathy or plexopathies. Regarding the health effects of non-ionizing radiation, an unsettled controversy is still growing. Despite the controversy, the concerns for adverse health effects of non-ionizing radiation should not be disregarded. Many mitigation strategies are being investigated and established with varying levels of evidence. However, those strategies fall under three main categories: radiotherapy precision protocols, neuroprotective agents, and neuroinflammatory modulators.
Conclusions: Radiation-induced brain injury is diagnostically and therapeutically challenging. A careful exposure history taking and structured diagnostic tools are critical for the development of preventive and therapeutic measures. Scientific conventions with collaborative frameworks are needed to move past the current point of conflict regarding health effects of non-ionizing radiation.