Strict dietary control was initiated, plasma amino acid levels decreased and the papilloedema improved. The optic chiasm and optic radiations were also involved. Imaging features of papilloedema included dilated optic nerve sheaths and bulging optic nerve heads (Figure 1D, E). Signs of raised intracranial pressure included reduced cerebral sulcal spaces and papilloedema, cerebral tonsils lying just below the foramen magnum and intrasellar arachnoid herniation (Figure 1E, F). This showed bilateral symmetrical striking white matter T2 hyperintense signal and restricted diffusion in the U fibres, corona radiata, posterior limbs of the internal capsules, thalami, lentiform nuclei, corticospinal tracts, brainstem and cerebellum (Figure 1A-C). MRI brain imaging showed the typical intramyelinic pattern of MSUD oedema caused by a metabolic decompensation. Plasma amino acid levels of leucine and isoleucine levels were elevated. On admission, an ophthalmology assessment revealed bilateral papilloedema, reduced visual fields and acuity with preserved colour vision. The most recent neuroimaging, an MRI brain, had been normal 2 years prior. MSUD was diagnosed at birth with no prior complications or imaging abnormalities. We report a rather late presentation of a 17-year-old female who presented with a gradual reduction in vision over a 1-month period and a new worsening generalised headache. Reference Riviello, Rezvani, DiGeorge and Foley 3 Reference Reddy, Calloni, Vernon, Boltshauser, Huisman and Soares 2 Cerebral oedema can be reversible but in severe cases may lead to death. Cerebral oedema is a serious complication of MSUD precipitated by worsening biochemical control during intercurrent illness Reference Ha, Kim and Eun 1 or from high protein intake from poor dietary compliance. Reference Ha, Kim and Eun 1 Much of the literature and experience with MSUD metabolic decompensations to date has been with neonates. Maple syrup urine disease (MSUD) is due to an autosomal recessive genetic defect in the mitochondrial branched-chain a-ketoacid dehydrogenase complex, causing accumulation of branched-chain amino acids (BCAA) leucine, isoleucine and their alpha-ketoacids.

Maple syrup urine disease presentation