Teaching NeuroImages: A 48-year-old woman with MELAS

Summary

  • 48 F
  • PMH
    • sensorineural hearing loss
    • DM
  • c/c
    • Sz
    • headache
  • Ex
    • encephalopathy
    • Lt homonymous hemianopia
    • hemineglect
    • MRI
      • diffusion in Rt (NOT follow vascular dist)
    • MR spectroscopy
      • inversion of lipid peak
    • L/D
      • ↑ pyruvate
      • → Lac
    • EMG
      • myopathy
      • w/o denercation
    • genetic
      • m.324A>G (MT-TL1 gene)

Further

Terminology

Original

A 48-year-old woman with sensorineural hearing loss and diabetes presented with seizures and headache. She was thin and short-statured. Examination revealed encephalopathy, left homonymous hemianopia, and hemineglect. MRI showed slowed diffusion in right hemisphere, which did not follow a clear vascular distribution and without apparent diffusion coefficient correlate, inconsistent with infarction (figure 1).1 Magnetic resonance spectroscopy revealed inversion of lipid lactate peak (figure 2). She had elevated pyruvate but normal lactate. EMG demonstrated myopathy without denervation. Genetic testing showed m.3243A>G pathogenic variant of the MT-TL1 gene. This mutation is found in more than 80% of patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes and always coexists with wild-type DNA.2

Figure 1

Figure.1

Brain MRI demonstrates a cortically based region of slow diffusion (A) in the right parietal and right temporal lobes with a small area of darkness on apparent diffusion coefficient (B, arrow), which did not correlate fully with the extent of diffusion restriction
There was corresponding T2 fluid-attenuated inversion recovery (FLAIR) hyperintensity along with mild effacement of the associated sulci (C). In addition, there was abnormal T2 FLAIR signal in the right medial thalamus (C, arrow).

Figure 2

Figure.2

Magnetic resonance spectroscopy (A) within the region of slow diffusion (B) demonstrates an inverted doublet at 1.3 ppm (arrow) consistent with a lactate peak and anaerobic metabolism

References

  1. Ito H, Mori K, Kagami S. Neuroimaging of stroke-like episodes in MELAS. Brain Dev 2011;33:283–288.
  2. Goto Y, Nonaka I, Horai S. A mutation in the tRNA(Leu)(UUR) gene associated with the MELAS subgroup of mitochondrial encephalomyopathies. Nature 1990;348:651–653.