Transverse diffusivity of cerebral parenchyma predicts visual tracking performance in relapsing-remitting multiple sclerosis
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Published on: April 14, 2014
Nele P Warlop1, Eric Achten, Els Fieremans
1Laboratory for Neuropsychology, Department of Neurology, Ghent University, De Pintelaan 185-4K3, B-9000 Ghent, Belgium. nele.warlop@ugent.be
Abstract:
This study investigated the relation between cerebral damage related to multiple sclerosis (MS) and cognitive decline as determined by two classical mental tracking tests. Cerebral damage in 15 relapsing-remitting MS patients was measured by diffusion tensor imaging (DTI). Fractional anisotropy, longitudinal and transverse diffusivity were defined in the cerebral parenchyma. Cognitive performance of the MS patients was assessed with the oral response format of the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT). A significant correlation was found between performance on the SDMT and the fractional anisotropy in the brain. This correlation was predominantly induced by transverse diffusivity. Transverse diffusivity refers to the diffusion across fibers rather than along the fibers and is believed to be a specific marker for axonal loss and demyelination associated with MS. No significant association between DTI-measures and PASAT performance was found and this negative finding was mainly attributed to psychometric qualities. These results indicate that diffusivity along the non-principal diffusion direction, a possible signature of MS-related white matter pathology, contributes to information processing speed as measured with the SDMT, a task that requires close visual tracking and a widely used clinical marker for cognitive decline in MS.
Insights
This study links brain white matter damage in multiple sclerosis (MS) to cognitive decline. Specifically, altered diffusivity in the brain correlates with slower information processing speed on the Symbol Digit Modalities Test (SDMT).
Area of Science:
- Neuroscience
- Medical Imaging
- Neurology
Background:
- Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
- Cognitive decline is a common symptom in MS patients, impacting daily functioning.
- Diffusion Tensor Imaging (DTI) is a neuroimaging technique used to assess white matter integrity.
Purpose of the Study:
- To investigate the relationship between cerebral white matter damage in MS patients and cognitive performance.
- To determine if DTI-derived measures of brain microstructure correlate with cognitive decline.
Main Methods:
- 15 relapsing-remitting MS patients underwent DTI scans to measure fractional anisotropy and diffusivity in the cerebral parenchyma.
- Cognitive function was assessed using the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT).
- Statistical analysis was performed to correlate DTI metrics with cognitive test scores.
Main Results:
- A significant positive correlation was observed between fractional anisotropy in the brain and SDMT performance.
- This correlation was primarily driven by transverse diffusivity, a marker of axonal loss and demyelination.
- No significant association was found between DTI measures and PASAT performance, potentially due to psychometric limitations.
Conclusions:
- Altered white matter microstructure, specifically transverse diffusivity, is associated with impaired information processing speed in MS patients.
- DTI measures, particularly those reflecting non-principal diffusion directions, may serve as sensitive markers for MS-related cognitive deficits.
- The SDMT appears to be a more sensitive cognitive measure than the PASAT for detecting MS-related white matter pathology.
