Cognitive Deficits in ALS Are Usually Subtle

by Margaret Wahl on Sat, 2003-03-01 09:08
Dr. Benjamin Brooks
Benjamin Brooks says it’s important to distinguish between cognitive changes brought about by respiratory abnormalities and those attributable to direct effects of ALS on the brain.

A number of reports in the medical literature, some of which have found their way onto the Internet and into the general press, have suggested that ALS does affect cognitive functioning (thinking) after all. This comes despite more than a century of observation that thinking is well preserved in this disease.

But these findings may have little meaning for people with ALS at this point, says neurologist Hiroshi Mitsumoto, director of the Eleanor and Lou Gehrig MDA/ALS Center at Columbia Presbyterian Medical Center in New York.

"The disease we knew and the disease we know have not changed," Mitsumoto says. "We simply have a greater research armamentarium to detect subtle changes.

"In a strict sense, ALS affects broad areas of the nervous system," he explains. "However, clinically (with respect to experienced symptoms), it is [usually] a pure motor neuron disease."

Mitsumoto says only about 5 percent of people with ALS have significant cognitive difficulties. But when investigators employ highly sophisticated techniques to investigate cognitive and other nervous system functions, they "always find dysfunction in those systems."

And the cognitive deficits in ALS are generally subtle — "not the usual memory deficit that we see in Alzheimer’s disease," he adds.

Minor changes

Maura Del Bene, an advanced practice nurse and clinical administrator of the Gehrig MDA/ALS Center, agrees with the 5 percent figure for serious thinking impairment in ALS. Most people with ALS who have problems, she says, "have a minor processing change. It’s not an overall memory or decision-making problem."

Following complex, multistep instructions can sometimes pose a challenge, she says. Instructions may have to be broken down into smaller bits.

Jackie Boswell
The vast majority of people with ALS continue to think and communicate well and often learn to use complex electronic devices if speech muscles weaken.

Neurologist Benjamin Brooks, who directs the MDA/ALS Center at the University of Wisconsin Hospital & Clinics in Madison, says that low blood oxygen levels, especially during sleep, may contribute to the apparent cognitive decline that sometimes occurs in ALS.

He says recent studies show that low blood oxygen levels that occur during the night don’t necessarily show up with standard, daytime respiratory testing. Research is needed to discern the difference between cognitive changes due to the disease itself and the "physical changes brought about by the process of ALS," he says.

Because of the recent reports, investigators at Columbia will be among those examining cognitive involvement in ALS. The group will use "a different approach, namely a more physiological, chemical and biological analysis."

In the long run, such studies may lead to better treatment or preventive strategies, Mitsumoto says. In the short run, they may lead to a better appreciation of what families and patients are going through and what, if anything, needs to be altered when professionals and caregivers impart information to patients.

Margaret Wahl
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