Context:

The supplementary motor area (SMA) is involved in the functional deficits of chronic ankle instability (CAI), but the structural basis of its abnormalities remains unclear.

Objective:

To determine the differences in volume and surface-based morphological features of SMA between patients with CAI and healthy controls, and their relationship with the clinical features of CAI.

Design:

Cross-sectional study.

Setting:

Sports medicine laboratory.

Patients or Other Participants:

A total of 32 CAI patients (10 females; age: 32.46 ± 7.51 years) and 31 healthy controls (12 females; age: 29.70 ± 8.07 years) participated in this study.

Main Outcome Measure(s):

Participants perform T1 structural magnetic resonance imaging and calculate volume and surface-based morphological features of SMA subregions. These included anterior and posterior subdivisions of Brodmann’s area 6 m (6 ma/6 mp), and supplementary and cingulate eye fields. Between-group comparisons and correlation analysis with clinical features of CAI were performed.

Results:

Moderately thinner 6 mp (Cohen’s d = −0.61) and moderately plainer 6 ma (Cohen’s d = −0.70) were observed in patients compared with controls. Before and after regressing out the covariates, the thinner 6 mp was correlated with the lower foot and ankle ability measure scores of daily activities (r-before=0.400, r-after = 0.449).

Conclusions:

Patients with CAI had a thinner posterior subdivision (motor-output site) and a plainer anterior subdivision (motor-planning site) of SMA than that of controls. The thin motor-output site of the SMA is associated with ankle dysfunction in patients. These morphologic evidence of maladaptive neuroplasticity in SMA might promote more targeted rehabilitation of CAI.

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