Fatal course of maple syrup urine disease (MSUD) encephalopathy in a 6 year old boy with characteristic MRI-changes

Aims: Metabolic decompensation in maple syrup urine disease (MSUD) can lead to toxic cerebral edema. MR imaging, especially MR diffusion imaging (DWI), shows characteristic cerebral changes.

Case report: 6,5year old boy with MSUD, postnatally diagnosed because of severe metabolic decompensation Development with global retardation. At present a gastroenteritis induced another severe metabolic decompensation with progressive cerebral impairment. Excessive elevation of branched chain amino acids (BCAA) (e.g. leucine 1470µmol/l (normal 100–250)). Despite dialysis with declining BCAA he developed progressive decerebration. MR imaging with DWI showed diffuse cerebral edema with more intense localized edema in cerebellar white matter, dorsal brainstem, cerebral peduncals, globi palladi and thalami. The boy died of cerebral impairment.

Discussion: Metabolic decompensation in MSUD leads to a toxic elevation of BCAA and metabolites (alpha-keto-acids BCKA) which affects the brain tissue resulting in brain impairment. MR imaging shows a diffuse cerebral edema and characteristic accentuated edema as described in our patient (described as MSUD encephalopathy). In the neonate these changes correspond to the myelinated regions. Spectroscopy and MR diffusion images give evidence of accumulation of BCAA/BCKA in these areas leading to cytotoxic intramyelinic edema.

Conclusion: MRI in MSUD encephalopathy shows characteristic findings which are caused by a cytotoxic intramyelinic edema that can lead to cerebral impairment and death.