Explaining Executive Deficits in Multiple Sclerosis Patients

Research supports the slowed processing speed in the executive deficits found in individuals with multiple sclerosis (MS), according to a paper from the Kessler Foundation.

The investigators wanted to further explore cognitive deficits, since they affect nearly half the population of MS patients. These disabling symptoms can adversely affect patients' quality of life. Data was collected from 50 MS patients and 28 healthy controls and all patients were evaluated through executive functioning tasks both with and without a processing speed element. The tasks included the Trail Making and Wisconsin Card Sorting tests.

The researchers found the MS patients performed on tasks related to executive function compared to their healthy counterparts. While analyzing the data for speed control, the scientists discovered the differences between the healthy and MS group disappeared. The data also revealed no difference on executive tasks with non-processing speed demands.

Disease progression was also something the researchers investigated throughout this study in the MS group. For MS patients, higher atrophy was associated with greater deficits on speeded executive tasks. However, the relationship vanished when the researchers controlled for processing speed. The researchers noted there was no association between atrophy and performance when analyzing non-processing speed executive tasks.

“Our results point to slowed processing speed as the mechanism underlying deficits in executive function,” Nancy Chiaravalloti, PhD, said in a press release. “Understanding this association is an important step toward the development of effective cognitive rehabilitation strategies for individuals with MS. We should focus our efforts on 2 key domains - processing speed and memory.”

Executive deficits in MS may be explained by slow processing speed, the researchers concluded in their paper. Slowed processing speed may be a primary impairment which underlies other cognitive functions. They believe it is important to unwrap processing speed contributions to executive function, which would be an important step toward the development of appropriate treatment and rehabilitation techniques for MS patients.

"Additional neuropsychological measures should be included in future studies,” Chiaravalloti added. “We also need to focus on the contribution of specific brain pathology, such as frontal atrophy and lesion load, to executive deficits.”

The paper was published online ahead of print August 18, 2014 in Rehabilitation Psychology.