Brain Cortical Complexity Alteration in Amyotrophic Lateral Sclerosis: A Preliminary Fractal Dimensionality Study

Abstract

Objective . Fractal dimensionality (FD) analysis provides a quantitative description of brain structural complexity. The application of FD analysis has provided evidence of amyotrophic lateral sclerosis‐ (ALS‐) related white matter degeneration. This study is aimed at evaluating, for the first time, FD alterations in a gray matter in ALS and determining its association with clinical parameters. Materials and Methods . This study included 22 patients diagnosed with ALS and 20 healthy subjects who underwent high‐resolution T1‐weighted imaging scanning. Disease severity was assessed using the revised ALS Functional Rating Scale (ALSFRS‐R). The duration of symptoms and rate of disease progression were also assessed. The regional FD value was calculated by a computational anatomy toolbox and compared among groups. The relationship between cortical FD values and clinical parameters was evaluated by Spearman correlation analysis. Results . ALS patients showed decreased FD values in the left precentral gyrus and central sulcus, left circular sulcus of insula (superior segment), left cingulate gyrus and sulcus (middle‐posterior part), right precentral gyrus, and right postcentral gyrus. The FD values in the right precentral gyrus were positively correlated to ALSFRS‐R scores ( r = 0.44 and P = 0.023), whereas negatively correlated to the rate of disease progression ( r = −0.41 and P = 0.039). Meanwhile, the FD value in the left circular sulcus of the insula (superior segment) was negatively correlated to disease duration ( r = −0.51 and P = 0.010). Conclusions . Our results suggest an ALS‐related reduction in structural complexity involving the gray matter. FD analysis may shed more light on the pathophysiology of ALS.

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