Subject-specific anatomical assessment of the human tongue in amyotrophic lateral sclerosis (ALS) by high-resolution MRI and diffusion tensor imaging

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a progressive and irreversible neurological disorder, which affects upper and lower motor neurons in the motor cortex that control voluntary movements including speech and swallowing. High-resolution MRI (hMRI) and Diffusion Tensor Imaging (DTI) can provide non-invasive imaging of three-dimensional muscle anatomy and fiber myoarchitecture such as fiber orientation within the human tongue, respectively. In this work, we aim to assess anatomical differences of the tongue using both imaging methods by demonstrating the differences in quantities related to fiber connectivity for both normal and ALS subjects. We first manually delineate the genioglossus and superior longitudinal muscles on hMRI, which are aligned to each b0 image of DTI using deformable registration to provide regions of interest. We then compute fractional anisotropy and statistics about fibers connecting each pair of muscles. We apply our framework on five datasets including both normal and ALS subjects, revealing obvious quantitative degradation of muscle fibers in ALS patients compared to that in controls within and between muscles. Our framework has the potential to provide insight regarding the detrimental effects of ALS on speech and swallowing when combined with tongue motion data.