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Imaging Studies

Skull x-rays: are used occasionally in the evaluation of penetrating head trauma to provide a rapid assessment of the degree of foreign body penetration in nonmissile penetrating head injuries (eg, stab wounds) or in gunshot wounds to screen for retained intracranial bullet fragments.


CT scan

  1. A CT scan is the diagnostic study of choice in the evaluation of TBI.
  2. The standard CT scan for the evaluation of acute head injury is a noncontrast scan, from the base of the occiput to the top of the vertex in 5-mm increments.
  3. Each intracranial structure has a characteristic density, which is expressed in Hounsfield units. On this scale, CSF has a density of (+) 4 to (+) 10 units, white matter has a density of (+) 22 to (+) 36 units, and gray matter has a density of (+) 32 to (+) 46 units. Extravascular blood has a density of (+) 50 to (+) 90 units, and calcified tissue and bone have a density of (+) 800 to (+) 1000 units.
  4. Extra-axial hematomas include epidural (extradural) and subdural hematomas. Epidural hematomas are located between the inner table of the skull and the dura.
  5. They typically are biconvex in shape.
  6. Epidural hematomas usually are caused by injury to an artery, although 10% of epidural hematomas may be venous in origin. Q
  7. Subdural hematomas are located between the dura and the brain.
  8. Their outer edge is convex, while their inner border is usually irregularly concave. Q
  9. Subdural hematomas usually are venous in origin, Q although some subdural hematomas are caused by arterial injuries.
  10. The classic cause of a posttraumatic subdural hematoma is an injury to one of the bridging veins that travel from the cerebral cortex to the dura.
  11. Intra-axial hematomas are defined as hemorrhages within the brain parenchyma.
  12. These hematomas include intraparenchymal hematomas, intraventricular hemorrhages, and subarachnoid hemorrhages. Q
  13. Subarachnoid hemorrhages that occur because of trauma typically are located over gyri on the convexity of the brain.
  14. The subarachnoid hemorrhages that occur as the result of a ruptured cerebral aneurysm usually are located in the subarachnoid cisterns at the base of the brain.

Frontal contusions on head CT scan (arrow)

There is a focal area of haemorrhagic contusion in the right frontal lobe, with surrounding low density due to infarction or oedema. This is a frequent location for a contre-coup injury following a blow to the back of the head.


MRI: Although MRI provides extraordinary anatomic detail, it is not commonly used to evaluate acute head injuries because of its long acquisition times and the difficulty in obtaining MRIs in persons who are critically ill. MRI is superior to CT scan in identifying diffuse axonal injury (DAI) and small intraparenchymal contusions. Q
Treatment Q
Medical therapy: The treatment of head injury may be divided into the treatment of closed head injury and penetrating head injury.

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