Classification of inherited neurometabolic disorders based on radiological aspects: pictorial essay

Inherited neurometabolic disorders represent a diagnostic challenge, and an efficient classification system is needed in order to improve the understanding of these diseases. Although they constitute a group of rare diseases, they have a collective incidence of at least one case per 1,000 live births. Some inherited neurometabolic disorders are treatable. The clinical and radiological presentations are variable and sometimes overlap, depending on the stage of the disease. Therefore, a number of classification systems have been devised, some of which are difficult to apply in practice. The aim of this study was to illustrate a classification system for inherited neurometabolic disorders, based exclusively on radiological findings. This was a retrospective study of imaging examinations of the central nervous system, particularly of children, performed in a network of hospitals. All of the cases were studied by multidetector computed tomography, magnetic resonance imaging, or both, the images having been obtained by two neuroradiologists. We included only cases in which a definitive diagnosis was made. The classification system separates the relevant radiological findings into 10 categories. All of the cases studied presented at least one of those findings. In most of the cases, more than one finding was observed, which increased specificity and narrowed the differential diagnosis. Data from the literature and from this study demonstrate that it is possible to classify inherited neurometabolic disorders by their radiological aspects, which favors a definitive diagnosis.