Cortical microstructure in primary progressive aphasia: a multicenter study

Area of Science:

• Neuroimaging
• Neurodegenerative Diseases
• Neurology

Background:

• Cortical mean diffusivity (CMD) is a novel imaging metric sensitive to early neurodegenerative changes.
• Elevated CMD values indicate microstructural disorganization and may precede macroscopic cortical alterations.
• This study investigates CMD's sensitivity in detecting cortical changes in primary progressive aphasia (PPA).

Purpose of the Study:

• To test if cortical mean diffusivity is more sensitive than cortical thickness in detecting cortical changes in PPA.
• To evaluate CMD as a potential biomarker for early neurodegeneration in PPA variants.
• To correlate CMD changes with disease severity in PPA.

Main Methods:

• A multicenter, case-control study involving 120 PPA patients and 89 controls.
• 3-Tesla MRI with structural and diffusion-weighted sequences was utilized.
• Cortical thickness and cortical mean diffusivity were computed using a surface-based approach.

Main Results:

• Cortical mean diffusivity increases and cortical thinning were observed in PPA variants, overlapping with canonical neurodegeneration loci.
• CMD increases extended to additional PPA-related areas and correlated with disease severity across all PPA groups.
• Elevated CMD was detected in very mild PPA cases with minimal cortical thinning, correlating well with disease severity.

Conclusions:

• Cortical mean diffusivity demonstrates potential as a sensitive biomarker for neurodegeneration-related microstructural changes in PPA.
• CMD may offer earlier detection of pathological changes compared to cortical thickness.
• This metric aids in understanding and monitoring the progression of PPA.