Many Believed to Have Alzheimer's May Have Another Form of Dementia

Many people believed to have Alzheimer's disease may actually have another form of dementia, according to an article in the October 16 issue of the New England Journal of Medicine.

Alzheimer's disease affects over four million Americans and is the single most common cause of dementia. But Alzheimer's is difficult to diagnose and can be confirmed only after death.

In his article, Dr. Marsel Mesulam, director of the Cognitive Neurology and Alzheimer's Disease Center at Northwestern University, said diseases other than Alzheimer's may cause about a quarter of all dementias.

One form of dementia that people may confuse with Alzheimer's, according to Mesulam, is primary progressive aphasia, which is characterized by language loss, but not memory problems.

Once considered rare, Mesulam said this condition is now commonly included among dementia syndromes and has been reported in several hundred individuals.

"The daily needs and limitations of Alzheimer's disease differ greatly from those of primary progressive aphasia," Mesulam told Medical Week. "In the past 20 years, the great discovery was that Alzheimer's disease is very common. Today, the new insight is that there are other forms of dementia as well."

In specialized clinics such as those in National Institute of Aging-funded Alzheimer disease centers, Mesulam said the margin of error is small, but still around 10-20percent. However, in general practice, he said a tendency exists to overdiagnose Alzheimer's disease. "So the error rate is probably considerably higher," he added.

Mesulam said such misdiagnoses do not currently have life-or-death implications since none of these conditions is curable.

"When we do come up with more effective and specific treatments, and especially if these have serious side effects, diagnostic accuracy will be much more essential," said Mesulam. "In the meantime, a major advantage of proper diagnosis is to clarify the situation, educate the family and provide the best available genetic and clinical management advice.

Although many Alzheimer's patients tend to lose interest in recreational and social activities, Mesulam said those with primary progressive aphasia maintain and even intensify their involvement in complex hobbies such as gardening, carpentry, sculpting and painting.

In patients with suspected primary progressive aphasia, Mesulam said evaluation by a speech therapist is useful for exploring alternative communication strategies.

Other sources: Northwestern University