Unexplained weight loss is defined as the unintentional loss of at least 10 pounds or 5 percent of body weight over a period of 6 to 12 months. This would be equivalent to a 200-pound man losing 10 pounds or a 130-pound woman losing six to seven pounds.
What It Is. Magnetic resonance imaging (MRI) of the brain is a safe and painless test that uses a magnetic field and radio waves to produce detailed images of the brain and the brain stem. An MRI differs from a CAT scan (also called a CT scan or a computed axial tomography scan) because it does not use radiation.
The Good and Bad of MRI. An MRI provides images of the human body as if it had been sliced like a loaf of bread. The slices can be in any direction and can be as thin as a couple of millimeters. The MRI scan is the best way to look at soft tissues such as the brain and spinal cord.