Brain magnetic resonance imaging findings and radiologic review of maple syrup urine disease: Report of three cases.

BACKGROUND: Maple syrup urine disease (MSUD) is a rare autosomal-recessive disorder that affects branched-chain amino acid (BCAA) metabolism and is named after the distinctive sweet odor of affected infants' urine. This disease is characterized by the accumulation of BCAAs and corresponding branched-chain ketoacids of leucine, isoleucine, and valine in the plasma, urine, and cerebrospinal fluid. However, the mechanisms of MSUD-induced brain damage remain poorly defined. The accumulation of BCAAs in the brain inhibits the activity of pyruvate dehydrogenase and α-ketoglutarate, disrupting the citric acid cycle and consequently impacting the synthesis of amino acids, causing cerebral edema and abnormal myelination.

CASE SUMMARY: We report three neonates admitted to our hospital with the classic subtype of MSUD. All three patients, with a transient normal period, presented with poor feeding, vomiting, poor weight gain, and increasing lethargy after birth. Laboratory testing revealed metabolic acidosis. The serum tandem mass spectrometry amino acid profile showed elevated plasma levels of BCAAs (leucine, isoleucine, and valine). Brain magnetic resonance imaging (MRI) presented abnormal signals mainly involving the globus pallidus, thalamus, internal capsule, brainstem, and cerebellar white matter, which represent the typical myelinated areas in normal full-term neonates.

CONCLUSION: In our patients, MRI showed typical features, in concordance with the available literature. Early detection and timely treatment are very helpful for the prognosis of MSUD patients. Therefore, we discuss the neuroimaging features of MSUD to enhance the knowledge of pediatricians about this disease.