Brain Scans That Help Identify Dementia
Brain Scan Tests for DementiaDoctors may use brain scans to identify strokes, tumors, or other problems that can cause dementia. A brain scan may also show cortical atrophy, which is the degeneration of the brain's cortex (outer layer) and is common in many forms of dementia.
The brain's cortex normally appears very wrinkled, with ridges of tissue (called gyri) separated by "valleys" called sulci. In individuals with cortical atrophy, the progressive loss of neurons causes the ridges to become thinner and the sulci to grow wider. As brain cells die, the ventricles (or fluid-filled cavities in the middle of the brain) expand to fill the available space, becoming much larger than normal. Brain scans can also identify changes in the brain's structure and function that would suggest Alzheimer's disease.
Computed Tomography Scan or Magnetic Resonance Imaging
The most common types of brain scans are computed tomography (CT) scans and magnetic resonance imaging (MRI). Doctors frequently request a CT scan of the brain when they are examining a patient with suspected dementia. These scans, which use x-rays to detect brain structures, can show evidence of:
MRI scans use magnetic fields and focused radio waves to detect hydrogen atoms in tissues within the body. They can detect the same problems as CT scans but they are better for identifying certain conditions, such as brain atrophy and damage from small TIAs.
Doctors also may use electroencephalograms (EEGs) to help examine people with suspected dementia. In an EEG, electrodes are placed on the scalp over several parts of the brain in order to detect and record patterns of electrical activity and to check for abnormalities. This electrical activity can indicate cognitive dysfunction in part or all of the brain. Many patients with moderately severe to severe Alzheimer's disease have abnormal EEGs. An EEG may also be used to detect seizures, which occur in about 10 percent of people with Alzheimer's disease. EEGs can also help diagnose Creutzfeldt-Jakob disease.