When a dementia diagnosis isn't Alzheimer's diease, the neurologist's job becomes much trickier.
“I think most doctors are trained in how to diagnose Alzheimer’s disease,” says Michael Geschwind, MD, PhD, associate professor of neurology, University of California, San Francisco, “We kind of recognize it when we see it. It’s when it’s not Alzheimer’s disease that our job becomes much, much trickier.”
Part of the reason, he notes, is that the other forms of dementia are less common and therefore not as well known. “If you read the textbooks that most neurologists were trained with, they talk about Alzheimer’s dementia and barely mention the other dementias; in fact, they describe frontotemporal dementia (FTD) as a rare dementia, and now we know that it’s the third most common,” he continues.
Distinguishing the non-Alzheimer’s dementias from one another, and from Alzheimer’s disease, is important because the management and treatment are often very different. Geschwind points to the example of acetylcholinesterase inhibitors, which “can make a patient with FTD worse, both cognitively and behaviorally.” He says that the symptoms of FTD “often respond very well to SSRIs, while patients with Lewy body dementia can respond very well to the acetylcholinesterase inhibitors,” much more so than Alzheimer’s disease, who “often respond to much higher dosesthan the typical Alzheimer’s patient.”
A close look at early behavioral features is often very helpful, says Geschwind. “Alzheimer’s is usually a deficit of memory; there can also be a lot of visual-spatial problems,” he explains. “Episodic memory is often one of the earlier symptoms, and people usually maintain their personalities but experience apathy, depression, and mild irritability, whereas a disease like Lewy body dementia might have those symptoms but also early on might cause some delusions or hallucinations.” Patients with frontotemporal dementia “might have some more agitation, irritability; these patients’ personalities take a 180 degree turn,” says Geschwind.
He admits that white matter diseases can be difficult to recognize because they can mimic other diseases or be a combination of other diseases. “Most often, patients will have more frontal executive deficits, something that you will see more commonly in Lewy body dementia and in FTD, less commonly in Alzheimer’s disease,” he adds. Distinguishing the rapidly progressive dementias from other forms is important because some are entirely treatable, if not curable.
While treatment might be based on addressing symptoms, Geshwind thinks it is important to know what you are treating first, particularly because some treatments for one dementia might actually worsen the condition of a patient with a different form of dementia. “For a patient with Lewy body disease, if you think it is Alzheimer’s disease and they have episodes of decreasing level of consciousness, you might think they are having a seizure or stroke, when in fact it’s just the fluctuation of Lewy body disease, where patients sometimes can become unresponsive for hours at a time,” he adds. “Knowing that a patient has frontotemporal dementia can help prepare the family for the course. Plus, we don’t want to put a person into the wrong treatment trial. Nowadays, we are in the era of actually trying to treat the underlying disease and not just the symptoms.”
That’s certainly easier said than done, especially when dealing with co-morbid dementias. “It’s very common to have Lewy body dementia mixed with Alzheimer’s disease, Alzheimer’s with progressive supranuclear palsy, and of course vascular disease mixed with Alzheimer’s disease,” says Geschwind. “Being able to differentiate those mixed dementias can really take clinical acumen and experience.”
And making that distinction—whether Alzhiemer’s dementia, non-Alzheimer’s dementia, or mixed dementia—will mostly come from obtaining “a really good history from the patient,” Geschwind states. By the time a neurologist is done taking the history, “they should have a really good idea of what the diagnosis is, not that the exam isn’t important to help fortify that,” he says.
Knowing the right questions to ask is very important. For example, patients with Lewy body disease often have a REM sleep behavior disorder that can manifest years before onset. Geschwind says that knowing to ask the spouse, “Does your husband or wife kick a lot in their sleep? Do they act out their dreams? Did you have to move to a different bed because they were so violent at night?” can be the key to making the right diagnosis. Another example would be asking them about visual spatial symptoms, which Geschwind says is something that “a lot of patients don’t want to talk about, but they often have both frank hallucinations, as well as extracampine hallucination.” He says that it’s common for people with Lewy body not to mention that they’ve “been seeing little people or little creatures or figures in the dark.” But if you don’t ask about these symptoms, you won’t elicit that they are occurring.
Knowing the course or major symptoms of these dementias can help clinicians ask the right questions and establish a diagnosis, just by the history alone. For frontotemporal dementia, knowing more about the patient’s eating behaviors is helpful—Has the person changed the way they eat or the types of foods they eat? Have they developed or acquired a new taste for sweets? Have they done things that are socially inappropriate? Have they become uninhibited or done something sexually inappropriate? Geschwind says that although the family “often doesn’t want to talk about such things, they are really important for making a diagnosis.”