If you suspect worrisome cognitive changes in yourself or a loved one, you want answers, and you want them now. But diagnosing cognitive decline or dementia, and then zeroing in on the type of dementia — Alzheimer's, vascular or mixed — can be complicated, even for experienced physicians.
“I often see patients who have been referred to me with a diagnosis of Alzheimer's disease. But when I order imaging to check the brain's blood vessels, I often find signs of disease,” explains Gustavo Roman, M.D., director of the Nantz National Alzheimer Center at Methodist Neurological Institute in Houston. He adds, “That's important information because if we can control cardiovascular risk factors like high blood pressure, we might be able to slow the cognitive decline of vascular dementia.”
Pointing out that people often have both vascular dementia and Alzheimer's, Philip Gorelick, M.D., director of the Center for Stroke Research at the University of Illinois College of Medicine in Chicago, notes, “Once these two disease processes start occurring, they synergize.” When that happens, “we're not always certain which process we're dealing with, which makes diagnosis and treatment challenging.”
That's why doctors rely on a variety of screening tools and diagnostic aids to help them separate the sometimes-subtle differences between Alzheimer's and vascular dementia (also known as “vascular cognitive decline”). Each has strengths and weaknesses, so you'll want to ask the physician why he or she uses a particular test, and what it can and can't tell you.
THE ROMAN CRITERIA
One tool doctors sometimes use for diagnosing probable vascular dementia is commonly called the “Roman Criteria,” which was developed by a task force of neurologists Roman chaired in 1993. Vascular dementia diagnosis may be presumed when:
▪ The patient can no longer function independently due to cognitive decline. This decline should be documented using a physical exam and neuropsychological testing.
▪ Cerebrovascular disease (blood vessel disease in the brain) is present. The patient either shows physical signs of stroke, such as weakness or paralysis, or a CT or MRI brain scan reveals abnormalities, even if there are no obvious symptoms.
▪ There is a relationship between cognitive decline and blood vessel disease. For example, if the patient's mental status declines within about three months of a diagnosed stroke, that's a strong indicator of vascular dementia.
Everyone can have a bad day or a bad week. So how does your doctor distinguish between a case of the mental “blahs” and true cognitive decline? Most doctors rely on one or more in-office screening tests. “The right cognitive screening test is quick and easy to administer in the office as part of the initial workup,” says Gorelick. “We can do it in 10 minutes and get a pretty good idea of what's going on with that patient.”
That's an important point: any cognitive screening tests should be part of a process that also includes a physical exam, medical history and brain imaging, because cognitive tests are not very helpful when used alone.
In general, mental status tests enable the doctor to assess a patient's everyday skills. And once a diagnosis is made, these tests, which typically take 10 minutes to complete, can be given again to track changes in thought processes over time.
Mini Mental State Exam (MMSE): This is the most commonly used test to assess cognitive function. It tests the patient's word recall, language abilities and overall orientation with questions like:
▪ State the day, month and year.
▪ Name familiar objects in the room when the doctor points to them.
▪ Remember and repeat a few minutes later the names of three common objects (like dog, tree, car).
▪ Repeat a common phrase or saying after the doctor.
▪ Copy a picture of two interlocking shapes.
Montreal Cognitive Assessment (MoCA): Though doctors have used the MMSE since 1975, some vascular dementia experts say it has one important failing: it does not pick up or track changes in executive function — cognitive skills like abstract reasoning, goal-setting and carrying out complex tasks. These functions occur in the brain's frontal lobes, the area most likely to be damaged by the cerebrovascular disease that causes vascular dementia.
“When I started my practice, I realized that the MMSE is actually quite insensitive at measuring executive function, which is a huge area of difference we see between patients with vascular dementia and those with Alzheimer's disease,” says neurologist Ziad Nasreddine, M.D., clinical assistant professor at University of Sherbrooke and McGill University in Montreal. “I needed to be able to screen patients in as many types of thinking as possible, so I created the MoCA.”
A study published in the Canadian Journal of Neurosciences in 2009 found that MoCA test results detected cognitive impairment in patients who were at least 65-years-old and had two or more vascular risk factors (high blood pressure, high cholesterol, etc.) that primary care physicians had missed.
These are among the questions from the MoCA test that assess executive function:
Trailmaking: The patient is asked to complete a line connecting letters and numbers in an easily recognized pattern. The correct answer is 1 – A – 2 – B – 3 – C, etc. “If the person connects all the numbers only or all the letters only, that shows a very concrete thought process and that cognitive flexibility is being lost,” says Nasreddine.
Abstract Language: What do a banana and an orange have in common? People who can reason abstractly know they are both fruits. A person with cognitive impairment might not see any similarities, or he might answer that they both have skins, says Nasreddine. Another example: a train and a bicycle. Overly concrete answer: both have wheels. Abstract answer: both are a means of transportation.
Cube Drawing: The patient views a drawing of a cube and is then asked to copy it, with the emphasis on creating the correct three-dimensional effect. But don't worry if this one stumps you and you have no other concerns. “About one third of normal subjects have trouble drawing the cube — if that's our only finding, you don't have to worry,” Nasreddine says. “But seventy percent of people with mild cognitive impairment will fail this one, so it is helpful to us in conjunction with other answers.”
Calculation: The patient is asked to start with 100, then subtract 7, preferably five times (which takes you to 65, by the way). “Some patients with frontal lobe damage can calculate well but cannot keep information in mind, so they forget the instruction while they're doing the subtraction and need guidance,” Nasreddine says. “The Alzheimer's patient can't do either.”
Clock Test: Probably the most well-known question of all is disarmingly simple: Draw a clock with its hands at a specified time. On the MoCA test, that instruction is intentionally abstract: “ten past eleven.” According to Nasreddine, a patient with frontal lobe damage may have lost the ability to think about time abstractly and so may put one hand on the eleven and one hand on the ten (instead of the two). Alzheimer's patients may put all of the numbers on the right side or they may place the hands correctly but not know their meaning. Offering a clue can make a big difference to a patient who has vascular dementia: “If they struggle and then are shown a correct drawing, they will most likely be able to copy the clock fine, whereas the ability to copy is impaired in an Alzheimer's patient,” Nasreddine explains.
While cognitive damage caused by Alzheimer's is typically permanent, vascular dementia may be preventable, or partially reversible, when people keep cardiovascular disease risk factors under control. So it's crucial to get the right diagnosis when there is time to prevent future strokes that will hasten the decline and may even be fatal.
Figure. CLOCK TEST: ...Image Tools
© 2011 American Heart Association, Inc.