Cognitive slowing in multiple sclerosis is strongly associated with brain volume reduction

Area of Science:

• Neuroscience
• Cognitive Psychology
• Radiology

Background:

• Multiple Sclerosis (MS) is associated with cognitive impairment, particularly slowed processing speed.
• Disease pathology, including MRI lesion load and brain volume reduction, may influence cognitive deficits in MS.
• The Amsterdam Neuropsychological Tasks (ANT) are sensitive to cognitive slowing in MS.

Purpose of the Study:

• To investigate the relationship between in vivo disease pathology (MRI lesion load, brain volume reduction) and cognitive functioning in MS patients.
• To specifically examine the influence of pathology on processing speed and accuracy using the ANT.
• To determine if cognitive slowing or impaired accuracy is more strongly associated with MS pathology.

Main Methods:

• Thirty-two MS patients underwent MRI scanning and completed the ANT.
• The ANT assessed attention (focused, divided, sustained), executive function, and psychomotor function.
• Associations between cognitive performance (speed, speed fluctuation, accuracy) and MRI metrics were analyzed.

Main Results:

• Decreased processing speed and stability, and psychomotor accuracy/stability correlated with reduced brain volume and increased lesion load (frontal, occipital).
• Brain volume reduction affected all cognitive domains except visuo-spatial processing.
• Speed and speed fluctuation, not general accuracy, correlated with brain volume reduction; only some speed metrics correlated with lesion load.

Conclusions:

• Cognitive deficits in MS are primarily driven by processing speed and its stability, especially in attention-demanding tasks.
• Accuracy is generally preserved unless high working memory demands are present.
• Brain volume loss is a significant factor in MS neurocognitive impairment, highlighting the importance of diffuse pathology beyond focal lesions.