Mapping cortical degeneration in ALS with magnetization transfer ratio and voxel-based morphometry

Area of Science:

• Neuroimaging
• Neurology
• Biomedical Engineering

Background:

• Amyotrophic lateral sclerosis (ALS) is increasingly recognized as a multisystem disorder affecting multiple brain regions.
• Conventional pathological and imaging data suggest cerebral cortical involvement in ALS.
• Quantitative magnetic resonance imaging (MRI) offers in vivo insights into cerebral cortex volume and microstructure in ALS.

Purpose of the Study:

• To evaluate the capability of advanced MRI techniques, specifically voxel-based morphometry (VBM) and magnetization transfer (MT) imaging, to detect neurodegeneration in the cerebral cortex of ALS patients.
• To investigate whether MT imaging changes are independent of local gray matter atrophy.

Main Methods:

• Eighteen ALS patients and 18 age-matched healthy controls underwent 1.5T MRI scans.
• A high-resolution 3D T1 weighted spoiled gradient recalled sequence with and without MT saturation pulse was used.
• Voxel-based analysis (VBA) computed regional gray matter (GM) atrophy and MT ratio (MTr) changes.
• Multimodal image analysis adjusted MTr for local GM atrophy.

Main Results:

• Voxel-based analysis identified clusters of combined GM atrophy and MTr decrease in motor and extra-motor frontotemporal cortical areas.
• Multimodal analysis revealed isolated MTr decreases in premotor and extra-motor frontotemporal regions, independent of atrophy.
• These findings support the hypothesis of widespread, multisystemic neurodegeneration in ALS.

Conclusions:

• VBM and MT imaging are effective in detecting the distribution of neurodegenerative alterations in the ALS cortical gray matter.
• MT imaging detects pathological changes in frontotemporal cortices that extend beyond simple volume loss.
• The study reinforces the understanding of ALS as a multisystem disease affecting various cortical areas.