Traumatic Brain Injury (TBI) - Symptoms, Causes & Mechanisms PDF

**1 Traumatic Brain Injury** **Explain the pathophysiology of focal and diffuse traumatic brain injuries.** **Focal Traumatic Brain Injury** Focal TBIs refer to injuries localized to a specific area of the brain. They often involve direct mechanical forces leading to contusions (brain bruises), l...

**1 Traumatic Brain Injury** **Explain the pathophysiology of focal and diffuse traumatic brain injuries.** **Focal Traumatic Brain Injury** Focal TBIs refer to injuries localized to a specific area of the brain. They often involve direct mechanical forces leading to contusions (brain bruises), lacerations, or hematomas. Common causes of focal injuries include blunt trauma or penetrating injuries. 1. **Mechanism of Injury:** - Focal injuries result from direct impact, leading to localized compression, deformation, and mechanical stress on neural tissue. - Typical injuries include contrecoup (opposite site of impact) lesions or epidural/subdural hematomas. 2. **Pathophysiological Processes:** - Initial damage to blood vessels can cause hemorrhage, leading to local ischemia and cell death. - Swelling and increased intracranial pressure can compress adjacent areas, further exacerbating damage. - Inflammation and excitotoxicity (excess glutamate release leading to calcium influx and neuronal damage) are prominent secondary responses. **Diffuse Traumatic Brain Injury** Diffuse TBIs are characterized by widespread damage to neurons and axons throughout the brain, commonly caused by rotational or shearing forces, such as those seen in motor vehicle accidents. 1. **Diffuse Axonal Injury (DAI):** - The most common type of diffuse injury is DAI, which involves the tearing or stretching of axons due to rapid acceleration-deceleration forces. - Axonal shearing disrupts communication between neurons, often leading to loss of consciousness and long-term neurological impairments. 2. **Pathophysiological Mechanisms:** - **Shearing Forces:** Differences in brain tissue densities lead to varying acceleration rates, causing axonal damage. - **Excitotoxicity:** Similar to focal injuries, there is excess glutamate release, leading to calcium-mediated damage to neurons. - **Secondary Injury:** This includes blood-brain barrier disruption, neuroinflammation, oxidative stress, and apoptotic pathways. 3. **Role of Microhemorrhages:** - Diffuse brain injuries may also involve microhemorrhages (small areas of bleeding), typically seen in the subarachnoid space due to vessel rupture. 4. **Long-Term Outcomes:** - Damage to axons can sometimes be reversible with repair, but in severe cases, long-term deficits and disabilities occur. In summary, focal injuries are more localized and primarily involve tissue deformation and hematomas, while diffuse injuries involve shearing forces causing widespread axonal damage and functional impairments. **Describe the clinical manifestations of traumatic brain injuries.** **1. General Symptoms Across TBIs:** - **Physical manifestations**: Headache, dizziness, fatigue, nausea, vomiting, and motor dysfunction. - **Cognitive changes**: Memory issues, confusion, difficulty concentrating, and altered mental status. - **Emotional/psychological disturbances**: Mood changes, irritability, and anxiety. **2. Mild TBI (e.g., Concussion):** - Glasgow Coma Scale (GCS): 13 to 15 - May or may not lose consciousness (\