MR diffusion tensor imaging, fiber tracking, and single-voxel spectroscopy findings in an unusual MELAS case

Abstract

A 23-year-old man was admitted to the intensive care unit for respiratory failure, global lower and upper limb palsy, and higher cognitive function deterioration. Imaging, performed with a combination of the MR diffusion tensor imaging, fiber tracking, and MR spectroscopy, suggested the diagnosis of an acute severe unusual mitochondrial encephalopathy, lactic acidosis, and strokelike event, which was confirmed by muscle biopsy, but fiber tracking showed unexpected unaltered white matter tracts.

Fig 1.

Axial fluid-attenuated inversion recovery MR (A) and diffusion-weighted b0 (B) images show an abnormal area in the right mesencephalon (arrows). Apparent diffusion coefficient (C) and fractional anisotropy (D) color-scale parametric maps show an increased apparent diffusion coefficient and decreased fractional anisotropy values (green) in the same abnormal area (B) (arrowheads).

Fig 2.

Spinal cord sagittal T2-weighted MR (A) and diffusion-weighted b0 (B) images show wide intraspinal abnormal areas (arrows). Apparent diffusion coefficient (C) and fractional anisotropy (D) color-scale parametric maps show increased apparent diffusion coefficient and decreased fractional anisotropy values (green) in the same abnormal area (arrowheads).

Fig 3.

Spinal cord sagittal T2-weighted MR (A) and diffusion-weighted b0 (B) images show wide intraspinal abnormal areas (arrows). Fiber tracking (C), coregistered and projected on a T2-weighted image, shows an unexpected unaltered shape of the white matter tracts, with visualization (D) of corticospinal tracts and nerve roots (arrowhead).

Fig 4.

Sagittal T2-weighted MR image (A) shows extensive abnormal areas involving the brain stem and the cervical spinal cord (arrow). A long TE MR spectroscopy voxel was located on fluid-attenuated inversion recovery abnormal areas in the medulla oblongata (B, arrow) and showed a spectrum with increased Cho peak, decreased NAA peak, and an inverted 1.3-ppm lactate peak (Lac, arrow box). Cr indicates creatine.