Traumatic brain injury: Pathology review

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Traumatic brain injury: Pathology review


Autonomic nervous system disorders

Horner syndrome

Orthostatic hypotension


Traumatic brain injury: Pathology review

USMLE® Step 1 questions

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A 30-year-old woman is brought to the emergency department following a fall during a climbing trip. Her partner, who accompanied her, reports that the patient fell from a 4-meter height and hit her head. En route to the hospital, the patient is comatose and unresponsive. Glasgow Coma Score is 3. She is sedated and intubated. On arrival, her temperature is 36.0°C (96.8°F), pulse is 43/min, respirations are 7/min and irregular, and blood pressure is 200/70 mmHg. On physical examination, her arms are stiff and bent, with clenched fists and outstretched legs. Both pupils are fixed and dilated. A non-contrast CT is obtained and shows a large biconvex-shaped lesion. Which of the following additional findings is most likely to be present?  


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.


Traumatic brain injury (TBI) is a type of injury that occurs when an external force blows or jolts the head, resulting in temporary or permanent brain dysfunction. Sometimes, TBI can lead to increased intracranial pressure, which can have various consequences, like brain herniations that are life-threatening.

TBI can range from mild to severe and can result in a wide range of physical, cognitive, and emotional symptoms. Symptoms can include headaches, confusion, memory loss, difficulty concentrating, mood changes, and more.

Diagnosis can be made based on clinical presentation, imaging tests of the brain, like CT or MRI, or other techniques such as a lumbar puncture. TBIs usually require surgery. Treatment for TBI typically involves drugs such as mannitol to control intracranial pressure, antiseizure medications like phenobarbital to control seizures, and neurosurgical interventions like when there is a need for hematoma evacuation.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Brain Injury" Springer Science & Business Media (2001)
  4. "Adams and Victor's Principles of Neurology, Ninth Edition" McGraw Hill Professional (2009)
  5. "Neuropsychiatric Sequelae of Traumatic Brain Injury" Psychosomatics (2000)
  6. "Classification of Traumatic Brain Injury for Targeted Therapies" Journal of Neurotrauma (2008)
  7. "Communication Disorders Following Traumatic Brain Injury" NA (1999)
  8. "Pathophysiology of traumatic brain injury" British Journal of Anaesthesia (2007)
  9. "Pioglitazone Therapy and Fractures: Systematic Review and Meta- Analysis" Endocrine, Metabolic & Immune Disorders - Drug Targets (2018)
  10. "Brain Herniation and Intracranial Hypertension" Neurologic Clinics (2021)

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