DEAR DOCTOR K:
My father’s memory has worsened lately, and we suspect he may have Alzheimer’s disease. Can you tell us what is involved in making a diagnosis?
There is no single test for Alzheimer’s disease. Diagnosing it begins with identifying symptoms associated with Alzheimer’s and ruling out other possible causes of memory loss.
Your father should begin with his primary care physician. This doctor can combine his knowledge of your father and his medical history with results from a physical exam and blood tests. He may discover that your father’s symptoms are related to medications he’s taking or perhaps a medical condition.
There are many causes of forgetfulness, confusion and inattentiveness besides Alzheimer’s disease. Most of the patients I have seen who start to worry that they may be developing Alzheimer’s never actually develop the disease.
Your father should expect a lot of questions about his memory. And since answering questions about memory and thinking requires memory and thinking, the doctor might want a family member who knows your father well in the room. The questions the doctor is likely to ask include:
- How long have you been having problems?
- Did the trouble come on gradually or suddenly?
- What sorts of things have become hard to remember?
- Are your difficulties preventing you from doing ordinary things like cooking or paying the bills?
Your father (or his spouse/caretaker) may need to track his symptoms for several months. This will show if his symptoms are improving, staying the same or getting worse.
The physician may refer your father to a neuropsychologist. Neuropsychologists typically use a battery of paper-and-pencil tests, or computer-administered tests, to evaluate cognitive function. The tests assess attention, memory, executive function, language, spatial ability and even mood.
A brain scan — usually either computed tomography (CT) or magnetic resonance imaging (MRI) — may also be done. These scans can help rule out other conditions that could contribute to memory loss. They also can show shrinkage of the brain in areas that tend to shrink with Alzheimer’s disease, but they cannot identify Alzheimer’s with certainty.
However, the ability of other types of brain scans to diagnose Alzheimer’s has improved greatly in recent years. Especially promising is a positron emission tomography (PET) scan that uses a chemical tracer known as PiB.
In Alzheimer’s disease, a substance called amyloid-beta slowly gets deposited in the brain. It is invisible on most types of brain scans. However, when PiB is injected into a person’s blood, it binds to amyloid deposits in the brain. When the PET scan is done, it can see all the places where there are amyloid deposits.
Tests of chemicals in the spinal fluid, the liquid that surrounds the brain and spinal cord, also show promise in diagnosing Alzheimer’s. Most of these new technologies are still used largely for research. I predict they are going to become important in regular clinical medicine very soon.