Common causes include inadequate perfusion of the brain causing cerebral hypoxia, acidosis, hypoglycaemia and cerebral oedema leading to raised ICP. Secondary brain injury is indirect damage to brain tissue that that occurs after the primary insult, worsening the original injury. skull fractures, blood vessel injury and haematoma formation) or diffuse (e.g. Primary brain injury is the initial injury caused to brain tissue from the forces of the traumatic event itself. Herniation of the uncus of the temporal lobe through the tentorial notch often leads to compression of cranial nerve three (oculomotor nerve) leading to the classical “blown pupil” that is often assessed for in TBI patients. Herniation of the cerebellar tonsils through the foramen magnum leads to compression of the brainstem and respiratory arrest. Herniation of different brain structures leads to different clinical features. Herniation can be defined as the movement of brain structures from one cranial compartment to another.
If CPP drops too low for a significant amount of time, ischaemia occurs. CPP can be calculated using the equation below:Ī rise in ICP will reduce CPP. Cushing’s triad Cerebral Perfusion Pressure (CPP)Ĭerebral perfusion pressure is the pressure driving blood through the brain tissue, allowing the delivery of oxygen and nutrients. It leads to a triad of hypertension, bradycardia, and an irregular breathing pattern (Figure 3).
The severity of head injuries can vary from minor head injuries to life-threatening traumatic brain injury (TBI) and/or intracranial haemorrhage. You may also be interested in our overview of the ABCDE approach and other emergency management guides.