EEG Pattern in Neonatal Maple Syrup Urine Disease: Description and Clinical Significance

Maple Syrup Urine Disease (MSUD) is a rare autosomal recessive disorder characterized by deficiency of branched-chain keto acid dehydrogenase complex, which is required to metabolize the three branched chain amino acids (BCAAs), leucine, isoleucine and valine. This metabolic dysfunction results in progressive encephalopathy manifesting with lethargy, vomiting, posturing and abnormal movements during the neonatal period in the classic form of the disease. If untreated, progressive brain damage causes coma, seizures and death usually within a few weeks. EEG is an essential investigation in a neonate with progressive encephalopathy and seizures. EEG abnormalities in neonatal encephalopathies due to inborn error of metabolism (IEM) are widely variable depending on the severity. Central comb-like rhythm is an EEG marker of neonatal MSUD in appropriate clinical context. This pattern should not be mistaken for epileptic abnormalities, sleep spindles or other similar nonspecific activities. We describe a patient with classic MSUD who presented with an EEG pattern of comb-like rhythm. Background abnormalities and epileptic discharges are common along comb-like rhythm in MSUD patients. EEG technologists and interpreters should be able to identify this pattern to support the early diagnosis and treatment of MSUD.