Lacerations, when the pia is torn These lesions are the hallmark of head injury, are most severe at the crest of gyri and are caused by the movement of the brain within the skull. Most common in temporal regions. Brain damage due to raised intracranial pressure. Usually produced by swelling from haematomas and contusions. Morphological markers are flattening of gyri, shift of midline structures, reduction in size of ventricles, herniation of the cingular gyrus, uncal herniation and brain stem compression.
Terminal event is midline haemorrhage and infarction of midbrain and pons.
It is the commonest cause of post-traumatic coma and disability in the absence of expanding lesion. It is widely distributed and multifocal. It MUST be found independent of other lesions. It involves one or both cerebral hemispheres. Close association between diffuse swelling and ipsilateral subdural haematoma.