Inborn Errors of Metabolism Presenting in Childhood

Neurodegenerative and neurometabolic disorders may cause significant morbidity and mortality in children. Imaging is important in early diagnosis of metabolic disorders and in determining the extent of brain injury. Especially after the development of new techniques such as diffusion-weighted magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), neuroimaging plays more important role in the diagnosis and management of these disorders. In these disorders, usually a mutation causes a clinically significant block in one or more metabolic pathways. This blockage usually results in either a deficiency of the product or in an accumulation of substrate with damage induced by either storage or toxicity. The presenting symptoms are usually nonspecific. In some of the metabolic disorders, long-term dietary or medical treatment options are available, and to make an early diagnosis in these disorders is important before the brain damage occurs. Prompt diagnosis, particularly in treatable disorders, is crucial to prevent neurological sequelae or death. If treatment is indeed available, neuroimaging also provides a baseline in evaluation of the efficacy of treatment. Therefore, the neuroradiologist should be aware of these disorders to prevent devastating results of delayed diagnosis. Metabolic disorders affecting the central nervous system, both gray and white matter can be classified by involvement of the primary cellular organelle as lysosomal, peroxisomal, mitochondrial disorders, or biochemical classification can be made as amino acid and organic acid metabolism defects or primary white matter disorders. This article presents the neuroimaging features of relatively more common metabolic disorders.