<P> In addition to the above, if mass effect is present with resulting displacement of brain tissue, additional signs may include pupillary dilatation, abducens palsies, and the Cushing's triad . Cushing's triad involves an increased systolic blood pressure, a widened pulse pressure, bradycardia, and an abnormal respiratory pattern . In children, a low heart rate is especially suggestive of high ICP . </P> <P> Irregular respirations occur when injury to parts of the brain interfere with the respiratory drive . Biot's respiration, in which breathing is rapid for a period and then absent for a period, occurs because of injury to the cerebral hemispheres or diencephalon . Hyperventilation can occur when the brain stem or tegmentum is damaged . </P> <P> As a rule, patients with normal blood pressure retain normal alertness with ICP of 25--40 mmHg (unless tissue shifts at the same time). Only when ICP exceeds 40--50 mmHg do CPP and cerebral perfusion decrease to a level that results in loss of consciousness . Any further elevations will lead to brain infarction and brain death . </P> <P> In infants and small children, the effects of ICP differ because their cranial sutures have not closed . In infants, the fontanels, or soft spots on the head where the skull bones have not yet fused, bulge when ICP gets too high . ICP correlates with intraocular pressure (IOP) but seems to lack the accuracy necessary for close management of intracranial pressure in the acute posttraumatic period . </P>

Causes of increased intracranial pressure in head injury