At the emergency department, 65-year-old Christian came in complaining of headaches, vision problems, and memory loss. These symptoms have gradually progressed over the past couple of weeks. On examination, there’s slurred speech, and his gait is unsteady. He has a history of chronic alcohol abuse. Head CT shows a “crescent-shaped” hyperdense mass that crosses the suture lines. Later that day, 33-year-old Max is brought in after a fight. They reported being knocked unconscious, but regained consciousness after an unknown period of time. Head CT is ordered and shows a “lens-shaped” hyperdense mass that doesn’t cross the suture lines. Max was very agitated and said they felt fine. They then left the hospital against medical advice. Later that day, Max lost consciousness again and died at home.
Okay, so Christian and Max had some form of traumatic brain injury. When an external force damages the head resulting in temporary or permanent brain dysfunction, we call it a traumatic brain injury, or TBI. Now, as a direct result of the external force, TBIs can cause extra-axial and intra-axial injuries. Extra-axial injuries are within the skull but don’t involve the brain parenchyma. The most high yield ones are epidural and subdural hematomas, as well as a subarachnoid hemorrhage. Intra-axial injuries - on the other hand - do involve the brain parenchyma, and the most high yield one for your exams is diffuse axonal injury. Now, the initial brain injury can impair the normal functioning of the cerebral metabolism and result in complications, such as tissue hypoxia, cognitive impairment, and seizures. Additionally, if the brain injury is associated with intracranial bleeding or severe inflammation followed by edema, the pressure within the skull may rise and result in severe complications. For your exams, it’s important to note that the most important complication of increased intracranial pressure is brain herniation. Trauma initiates a series of molecular events along with the primary brain injury, which can persist for hours, or even days. These are referred to as “secondary brain injury”, and eventually can result in increased intracranial pressure, which in turn, has numerous consequences, and for the exams, the most important is brain herniation.