A CT scan is the test of choice to be performed when a patient is presenting with stroke-like symptoms. Its purpose is to look for signs of brain ischemia (lack of oxygen) secondary to an ischemic stroke, i.e., a stroke caused by a blocked brain artery, resulting in lack of blood flow and therefore lack of oxygen to the part of the brain supplied by the blocked artery. CT scan will also show if there is a hemorrhagic stroke, one caused by a blood vessel bleeding in the brain. The most common cause of a hemorrhagic stroke is hypertension (high blood pressure). If the bleeding is significant enough it will create mass effect, shifting of the brain from one side of the skull to the other, and will increase intracranial pressure. If the increased pressure is not treated, it can result in additional brain damage beyond what was already caused by the bleeding within the brain or even death.
Acute or recent bleeding in the brain appears bright or hyperdense on a CT scan. Over days to weeks, as the brain breaks down the blood and begins to resorb it, the blood becomes less bright and the blood is replaced by edema (swelling) in the brain. Edema appears dark on a CT scan. This edema can create additional mass effect and shift in the brain exacerbating the issues that the original hemorrhage caused.
Strokes can present with numerous types of symptoms depending on the location of the brain that is affected. A stroke on the right side of the brain will affect the left side of the body and, correspondingly, a stroke on the left side of the brain will affect the right side of the body. In most people, the left side of the brain is the “dominant side” where the center for speech and language is located. Therefore, a left-sided stroke, especially one in the left temporal lobe (the specific location of the brain where speech and language are centered), could cause speech difficulties ranging from mild difficulty with pronouncing words to complete aphasia.
An expanding mass in the temporal lobe, whether due to a stroke, tumor, or trauma, can be particularly concerning because it has the potential create a life-threatening herniation syndrome. A mass within the temporal lobe will push the medial portion of the temporal lobe against the midbrain, i.e., the beginning of the brain stem and spinal cord. The midbrain is the part of the brain where basic functions of the brain occur automatically. For example, it tells the body to breathe without us having to consciously think about breathing. Pressure on the midbrain for too long will cause it to shut down, therefore causing the automatic functions of the brain to shut down resulting in complete brain dysfunction, i.e., brain death.