Maple syrup urine disease (MSUD) is an autosomal recessive disorder with dys- functional branched-chain a-keto acid dehydrogenase complex, leading to accu- mulation of branched-chain amino acids in all organs. Clinical symptoms were first described 1954. Several variants, have been identified. Decreased cognitive ability, hyperactivity, hallucinations, dys- tonia, ataxia, and altered consciousness have been described during acute meta- bolic intoxication. Cerebral edema and intracranial hypertension (IH) are fre- quent complications. We present an adult MSUD-patient with cerebral edema and IH with a favorable course after metabolic control and optic nerve sheath fenestration.