Dysmyelination in the brain of adolescents and young adults with maple syrup urine disease

Maple syrup urine disease (MSUD) is associated with increased branched-chain amino acids (BCAA), their keto acids (BCKA), and acute or chronic encephalopathy. Aim of treatment is to reduce BCAA and BCKA to prevent or minimize brain dysfunction. We investigated 14 juvenile and adult patients with MSUD by means of cerebral magnetic resonance imaging (MRI) and correlated MRI changes to biochemical control measured as median plasma BCAA concentrations over 6-36 months prior to investigation. Abnormalities consisted of an increased signal in the white matter on T2-weighted images which is compatible with a disturbed water content of the white matter and dysmyelination. Areas affected most commonly were mesencephalon, brain stem, thalamus and globus pallidus; supratentorial lesions seem to be restricted to severe cases. No patient with white matter changes had acute neurological/encephalopathic symptoms indicating that the severity of dysmyelination does not correlate to acute neurotoxicity.