Thin and Plain Supplementary Motor Area in Chronic Ankle Instability: A Volume- and Surface-Based Morphometric Study

Area of Science:

• Neuroscience
• Orthopedics
• Radiology

Background:

• Chronic ankle instability (CAI) is associated with functional deficits, potentially involving the supplementary motor area (SMA).
• The precise structural alterations in the SMA in individuals with CAI remain largely uncharacterized.

Purpose of the Study:

• To investigate volumetric and surface-based morphologic differences in SMA subregions between CAI patients and healthy controls.
• To explore the correlation between SMA morphologic features and clinical indicators of CAI severity.

Main Methods:

• A cross-sectional study involving 32 CAI patients and 31 healthy controls.
• T1-weighted structural MRI was used to assess morphologic features of SMA subregions, including Brodmann area 6 subdivisions (6 ma, 6 mp).
• Statistical analyses included between-group comparisons and correlation with clinical CAI measures.

Main Results:

• Individuals with CAI exhibited a moderately thinner posterior subdivision of the medial portion of Brodmann area 6 (6 mp), a motor-output site.
• A moderately plainer anterior subdivision of the medial portion of Brodmann area 6 (6 ma), a motor-planning site, was also observed in the CAI group.
• Reduced thickness in the 6 mp region correlated significantly with lower functional ankle scores.

Conclusions:

• Patients with CAI demonstrate distinct structural changes in the SMA, specifically a thinner 6 mp and plainer 6 ma.
• The observed morphologic alterations, particularly in the motor-output area, are associated with ankle dysfunction.
• These findings suggest maladaptive neuroplasticity within the SMA in CAI, potentially informing targeted rehabilitation strategies.