Review Neonatal Neuroimaging Findings in Inborn Errors of Metabolism Andrea Poretti, MD, 1–3 Susan I. Blaser, MD, 4 Maarten H. Lequin, MD, 5 Ali Fatemi, MD, 3,6 Avner Meoded, MD, 1,3 Frances J. Northington, MD, 3,7 Eugen Boltshauser, MD, 2 and Thierry A.G.M. Huisman, MD 1,3 * Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomy- opathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limit- ing the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic labora- tory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the avail- ability of the newborn screening results. It is therefore im- portant that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroi- maging findings of metabolic disorders presenting in the neonatal time period. Key Words: inborn errors of metabolism; neonates; neu- roimaging; brain; MRI J. Magn. Reson. Imaging 2013;37:294–312. V C 2012 Wiley Periodicals, Inc. INBORN ERRORS OF METABOLISM INDIVIDUALLY, inborn errors of metabolism (IEMs) are very rare, but overall they account for a remarkable number of disorders of the pediatric central nervous system (CNS) (1). About 25% present in the neonatal pe- riod (2,3). Early diagnosis and institution of the appro- priate therapy is mandatory in IEM to prevent death or ameliorate long-term neurological sequelae (3,4). The incidence, variability, complexity, and nonspecific clini- cal presentation of IEMs, however, present a diagnostic challenge for the neonatologists and neonatal neurolo- gists. Neuroimaging plays a key role in the investigation of neonates with IEM. Therefore it is important to be fa- miliar with the neuroimaging findings of IEM. After a general introduction summarizing the classi- fication, presentation, and common diagnostic work- up of IEM in neonates, we review the neuroimaging findings of the most common IEMs that may present in the neonatal period. Classification of IEM IEMs may be defined as a group of conditions in which there is a deficiency in production, synthesis, metabolism, storage, or transport of biochemical com- pounds. They can be classified into four major groups depending on the mechanism leading to the clinical presentation: 1) intoxication disorders, 2) energy pro- duction disorders, 3) disorders of the biosynthesis and breakdown of complex molecules, and 4) neuro- transmitter defects (2). Intoxication disorders are typically characterized by a variable symptom-free interval, which is followed by symptoms of acute and/or chronic intoxication of the CNS. In these disorders, the metabolic error leads to accumulation of toxic metabolites proximal to the metabolic block. Because these metabolites cross the placenta in utero and are metabolized by the mother, affected newborns are typically asymptomatic at birth. Subsequent deterioration occurs due to 1 Division of Pediatric Radiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. 2 Department of Pediatric Neurology, University Children’s Hospital of Zurich, Switzerland. 3 Neuro Intensive Care Nursery Group, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. 4 Division of Neuroradiology, Department of Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada. 5 Department of Radiology, Sophia Children’s Hospital, Erasmus University Medical Center, Rotterdam, The Netherlands. 6 Kennedy Krieger Institute, Department of Neurology, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA. 7 Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. *Address reprint requests to: T.A.G.M.H., Medical Director, Division of Pediatric Radiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medi- cine, Baltimore, MD 21287. E-mail: [email protected] Received January 11, 2012; Accepted April 3, 2012. DOI 10.1002/jmri.23693 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 37:294–312 (2013) CME V C 2012 Wiley Periodicals, Inc. 294
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