Intraparenchymal hemorrhage

Overview
Intraparenchymal hemorrhage, or intracerebral hemorrhage, a type of intra-axial bleeding, can be caused by brain trauma, or it can occur spontaneously in hemorrhagic stroke. As with other types of hemorrhages within the skull, intraparenchymal bleeds are a serious medical emergency because they can increase intracranial pressure. The mortality rate for intraparenchymal bleeds is over 40%.

Causes
More common in adults than in children, intraparenchymal bleeds are usually due to penetrating trauma, but can also be due to depressed skull fractures, acceleration-deceleration trauma,  rupture of an aneurysm or arteriovenous malformation (AVM), and bleeding within a tumor.

Prognosis
The risk of death from an intraparenchymal bleed is especially high when the injury occurs in the brain stem. Intraparenchymal bleeds within the medulla are almost always fatal, because they cause damage to cranial nerve X, the vagus nerve, which plays an important role in blood circulation and breathing. This kind of hemorrhage can also occur in the cortex or subcortical areas, usually in the frontal or temporal lobes when due to head injury, and sometimes in the cerebellum.

Symptoms
Patients with intraparenchymal bleeds have symptoms that correspond to the functions controlled by the area of the brain that is damaged by the bleed. Other symptoms include those that indicate a rise in intracranial pressure due to a large mass putting pressure on the brain.

Diagnosis
Intraparenchymal hemorrhage can be recognized on CT scans because blood appears brighter than other tissue and is separated from the inner table of the skull by brain tissue. The tissue surrounding a bleed is often less dense than the rest of the brain due to edema, and therefore shows up lighter on the CT scan.