Spontaneous brain fluctuation abnormalities in retired football players

Abstract

Abstract BACKGROUND New measures of the spontaneity of signal amplitudes of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF) present in resting state functional MRI (rsfMRI) may provide useful objective information when applied to concussion. These metrics provide a spatial map of where signal spontaneity departs from normal values to indicate areas of impairment or over-compensation. Former professional American-style football players would show diffusely decreased ALFF and fALFF. METHODS: This was a prospective cohort study of 18 retired Canadian Football League (rCFL) players (male, aged 58.78 ± 6.10) recruited and 62 healthy age and sex-matched controls (male, aged 58.81 ± 5.69) downloaded from OASIS-3. High resolution 3D T1-weighted and rsfMRI data was collected on a 3T GE MRI. CONN was used to preprocess the rsfMRI data and compute ALFF/fALFF metrics, while voxel-wise and brain region-of-interest (ROI) Z-scoring analyses were computed in MATLAB. The rCFL participants also completed self-reporting clinical behavioural tests. Significant ALFF and fALFF differences were calculated as clusters (Threshold Free Cluster Enhancement, FWE-corrected p < 0.05) and ROI Z-scoring (Abnormal ROI, +3≤Z-score≤-3). Correlations and multiple linear regression analyses between participant demographics, clinical test data, and total number of abnormal brain ROIs were also computed. RESULTS: Two large clusters of decreased signal spontaneity and one large cluster of increased signal spontaneity were found in retired athletes compared to controls. The Z-scoring analysis found consistently abnormal ROIs from ALFF and fALFF data from the right amygdala, right thalamus, bilateral occipital pole, and bilateral cerebellum crus II. The total number of positive fALFF Z-score outliers correlated with a longer career length. CONCLUSIONS: Our analyses showed that cerebellar and central sub-cortical brain regions were most frequently and seriously abnormal. Spontaneous brain activity, a measure of brain health, was compromised in retired athletes years after competitive sport.