HEMORRHAGE. Hemorrhage is due to the rupture of a blood vessel which in turn may be due to a head injury, the rupture of an aneurysm or venous malformation, or weakening and death of the vessels due to occlusion by a thrombus. Bleeding may be minute and then cease altogether, or the bleeding may continue slowly such that a pool of blood begins to build up over hours, days, or even weeks. If a major artery ruptures. or if the vessel is severed, bleeding may be profuse such that blood rushes out of the broken artery and begins to pool, which in turn puts pressure on adjoining brain tissues. Hemorrhage can induce coma and then death if the build up blood compresses the brain which is squeezed down into the foramen magnum such that the brainstem becomes compressed--also referred to as herniation.

STROKE. The middle cerebral artery perfuses the lateral surface and deep structures of the temporal lobe as well as the adjoining frontal, parietal, and occipial tissues. Occlusion of this artery induces massive cognitive impairments, including (with left hemisphere stroke), loss of the ability to comprehend language or written words (receptive aphasia and alexia) or to speak intelligibly or to write (expressive aphasia and agraphia). With right hemisphere stroke, the capacity to perceive or appreciate music and the emotional aspects of speech may be lost, including the ability to sing or to vocally convey emotion.