How Common is the Diagnosis of Alzheimer's Wrong?

Alzheimer's disease appears slowly and insidiously. The symptoms may be barely noticeable at first - minor forgetfulness and difficulty concentrating and thinking abstractly. Slowly the disease progresses to more severe symptoms with loss of memory and language skills. Even though the symptoms of Alzheimer's dementia are well described, a new study shows that the diagnosis of Alzheimer's disease isn't always an accurate one. It's a condition that can be frequently misdiagnosed.

Diagnosis of Alzheimer's Disease: It May Be Overdiagnosed in the Elderly

When researchers did a post-mortem exam of the brains of 426 Japanese-American residents of Hawaii almost half of whom had been diagnosed with Alzheimer's disease while still alive they made a surprising discovery. Many didn't have enough evidence on autopsy to confirm the diagnosis of Alzheimer's disease.

People with Alzheimer's disease usually have three characteristic brain lesions: plaques, neurofibrillary tangles and granulovascular degeneration - and their brains are usually smaller than normal due to atrophy.

More specifically, these people lacked enough of these characteristic brain lesions to make the diagnosis. Many had brain abnormalities that suggested another form of dementia, not Alzheimer's disease. In fact, half of the people they autopsied didn't have enough evidence to say they had Alzheimer's disease while alive.

Alzheimer's Dementia: It's Not the Only Cause of Memory Problems

Alzheimer's disease is a diagnosis of exclusion, which means other causes of dementia are excluded first. The only way to definitely diagnose Alzheimer's is by looking for the characteristic brain changes on autopsy. Imaging studies such as CT and MRI may help, but they're best for excluding other causes of dementia.

Most tragic are cases where Alzheimer's disease is misdiagnosed and a treatable cause of dementia goes untreated. Some treatable causes that mimic Alzheimer's disease are B12 deficiency, thyroid disease, syphilis and normal pressure hydrocephalus, a condition where there's too much fluid pressing on the brain. Plus, there are other untreatable causes of dementia. This is why doctors do so many lab and imaging studies before making the diagnosis - to exclude these diseases.

Diagnosis of Alzheimer's Dementia: The Bottom Line?

The diagnosis of Alzheimer's is a tricky one to make - and the misdiagnosis rate is high. If someone you know is being evaluated for Alzheimer's disease be sure they get a thorough work-up. And remember - Alzheimer's disease is not the only cause of dementia.

References:

Eurekalert.org. "Alzheimer's Disease May Be Easily Misdiagnosed"