Diagnosing dementia, Part I

Navigate the pitfalls of this elusive disease

By Gloria Gaspard

Dr David Conn says the case is typical. A retired university professor comes in to see him, afraid she's developing symptoms of Alzheimer's disease (AD). But every test he throws at her comes back negative. Still, she just can't be reassured that everything's all right. "It's a very common fear," says Dr Conn, chief psychiatrist at Baycrest in Toronto. And one that's not entirely unfounded. According to conservative estimates, 10% of people over age 65 and up to 50% of those over 85 have some form of dementia.

Without hard evidence to rely on — no test has yet made it into clinical practice — you can never diagnose dementia with absolute certainty. Yet the best way to put your patients' minds at ease is to give them as much information as possible, with as much confidence as you can.

TIMES A-CHANGIN'
The four most common types of dementia — AD, vascular dementia (VD), dementia with Lewy bodies (DLB) and the frontotemporal dementias (FTDs) — are not always easy to tell apart. And to complicate matters further, so-called mixed dementia — a combination of AD and VD — is increasingly being recognized as a primary form of the disease. "We have to appreciate that the brain is commonly host to multiple pathologies with aging and that will change the natural history of any one particular disease state," explains Dr Howard Feldman, director of the UBC Clinic for AD and related disorders.

As we get better at recognizing its different forms, physicians are also becoming more and more aware that memory loss — the hallmark of dementia according to the DSM IV — may need to take a back seat. "To say that a person with no memory impairment doesn't have dementia misses the boat," explains Dr Lonn Myronuk, president of GeriPsych Medical Services in Parksville, BC.

A SECOND OPINION
Most physicians will forego formal cognitive tests like the mini-mental state exam and take an informal history, asking about cognition (memory, language, orientation), function (finances, housekeeping, bathing), mood (depression, fatigue), behaviour (aggression, wandering) and drives (appetite, sleep). But Dr Myronuk says that while speaking to the patient is obviously important, there's nothing quite like hearsay to help you paint an accurate picture of what's going on inside their head. "A reliable informant's description of behaviour and functioning in and around the home is gold," he says.

BEFORE YOU LEAP
Dr Myronuk explains that one of the major pitfalls to diagnosing dementia in primary care is overlooking a correctible disorder — most often depression or side effects of medications. "I'm seeing fewer and fewer cases of depression masquerading as dementia because FPs are so good at identifying and treating it," he says, "but the effects of medications on cognitive function are much harder to keep on top of." While drugs with known psychotropic effects, like antidepressants, readily come to mind, there are others — like some for acid reflux or incontinence — that can be easily overlooked. "If you begin to see cognitive decline soon after starting a new treatment, that's obviously very suggestive," he says.

CLOSE BUT NO CIGAR
Patients who fall short of the diagnostic criteria for dementia should be assessed for mild cognitive impairment (MCI). "With MCI, patients have impaired memory function for their age and education, but the activities of daily living are still intact," explains Dr Conn. He says the outcome is variable: some will stay stable for years, while others progress to dementia, at a rate of about 10-15% per year. "MCI — like dementia — is a heterogeneous group," says Dr Myronuk. "As we get better at understanding the pathophysiology of dementia, we'll be able to distinguish this preclinical MCI cloud into distinct groups." No scientific evidence supports the use of medication for these patients, but they should be monitored regularly so that treatment can be initiated at the first sign of decline.

For some patients, the fear of a positive diagnosis can be so consuming that they won't even tell you there's a problem to begin with. And that, according to Dr Myronuk, may be your biggest barrier of all. "Patients need to understand that while dementia is increasingly common with advancing age, it's not necessary," he says. "There are people in their 90s who are as sharp as a tack — it's not just about the mileage on the odometer."

Next issue: Part II will focus on recognizing and treating the four most common types of dementia