[Leukodystrophies: clinical aspects and findings with computerized tomography and magnetic resonance imaging]

Leukodystrophies are inherited white matter diseases due to abnormalities occurring in myelin synthesis and/or maintenance. The most common types of these rare childhood conditions are represented by adrenoleukodystrophy, metachromatic leukodystrophy, Canavan's, Alexander's, Krabbe's, and Pelizaeus-Merzbacher's diseases. Most of them are lethal during childhood, with the exception of the adrenoleukodystrophy-adrenomyeloneuropathy complex, which sometimes, during its early phases, may be cured with a dietary therapy. The aims of this paper are: 1) the description of inheritance factors, pathogenesis, pathological and clinical findings of each of the most frequent childhood leukodystrophies; 2) the description of the most common patterns of these conditions on CT and MR imaging; 3) the evaluation of the diagnostic capabilities of these two imaging techniques and the comparison of their results. Finally, some of the therapies suggested for the mild forms of these conditions are discussed. The evaluation of leukodystrophic patients with CT and MR imaging shows both imaging modalities to have high sensitivity, thanks to the detection of abnormally myelinated areas, which appear hypodense on CT and hyperintense on T2-weighted MR images. Frequently, both imaging modalities exhibit high specificity as well: they allow a differential diagnosis between the different types through the demonstration of their location in the early stages and of their mode of spread. The most typical example is represented by adrenoleukodystrophy, which is the most common type of leukodystrophy: the frequent occipito-parietal onset and the anterior and caudal progression allow a correct diagnosis to be made on CT and MR images in most cases. The comparison between CT and MR findings demonstrates a slight superiority of the latter: multiplanarity and high contrast resolution make MR imaging more sensitive than CT in the detection of both caudal spread and involvement of optic and acoustic nervous pathways. Furthermore, MR imaging allows a safe follow-up in children with leukodystrophy.