What is brain injury?

Brain injury refers to any injury or damage to the brain that disrupts its normal function. Brain injuries can range from mild, such as a concussion, to severe, such as traumatic brain injury (TBI). They can result from various causes, including trauma, infection, stroke, lack of oxygen (hypoxia), tumors, or degenerative diseases.


The effects of brain injury can vary widely depending on the type, location, and severity of the injury. Common symptoms of brain injury may include headache, confusion, memory problems, difficulty concentrating, mood changes, changes in sleep patterns, sensory disturbances, weakness or paralysis, and difficulties with speech or language.


What is the relationship between brain injury and oxidative stress?

Oxidative stress plays a crucial role in the pathophysiology of various types of brain injury. Oxidative stress refers to an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defenses, leading to cellular damage and dysfunction. Here’s how oxidative stress is related to different types of brain injury:


  • Traumatic Brain Injury (TBI): Following a traumatic brain injury, such as a concussion or more severe TBI, there is an acute increase in oxidative stress in the brain. The mechanical forces of the injury can lead to the production of ROS, which can cause damage to cell membranes, proteins, and DNA within brain cells. This oxidative damage contributes to secondary injury processes, including inflammation, excitotoxicity, and apoptosis (cell death), which can worsen brain damage and impair recovery.


  • Ischemic Stroke: In ischemic stroke, the brain is deprived of oxygen and nutrients due to a blockage in the blood vessels supplying the brain. This lack of oxygen leads to an increase in ROS production, particularly during reperfusion (restoration of blood flow) following treatment. The production of ROS contributes to oxidative damage to brain cells, exacerbating tissue injury and neuronal death in the affected area.


  • Hemorrhagic Stroke: In hemorrhagic stroke, bleeding within the brain tissue leads to inflammation and oxidative stress. Blood breakdown products, such as hemoglobin and iron, can generate ROS and promote oxidative damage to surrounding brain cells. This oxidative stress further contributes to tissue injury and neurological deficits following hemorrhagic stroke.


  • Hypoxic-Ischemic Brain Injury: In hypoxic-ischemic brain injury, such as occurs in cases of cardiac arrest or near drowning, the brain is deprived of oxygen and blood flow. The reperfusion of blood flow following hypoxia-ischemia leads to the production of ROS and oxidative stress, which exacerbates neuronal injury and cell death. Oxidative stress plays a critical role in the pathogenesis of hypoxic-ischemic brain injury and contributes to long-term neurological deficits in survivors.


  • Neurodegenerative Diseases: Oxidative stress is also implicated in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS). In these conditions, the accumulation of abnormal proteins, mitochondrial dysfunction, and inflammation contribute to increased ROS production and oxidative damage in the brain, leading to progressive neuronal loss and cognitive decline.


Overall, oxidative stress is a common feature of various types of brain injury and neurodegenerative diseases.