Defining and categorizing leukoencephalopathies of unknown origin: MR imaging approach

PURPOSE: To categorize leukoencephalopathies of unknown origin into a few major groups by using magnetic resonance (MR) imaging criteria to facilitate further studies, and to assess the possibility of defining "new" (ie, until now unknown) disease entities within these major groups. MATERIALS AND METHODS: MR images of 92 patients (55 male, 37 female; mean age, 9.3 years) with a leukoencephalopathy were examined by using a scoring list of 68 items. Seven major categories were defined according to the predominant location of the white matter abnormalities. Statistical analysis was used to assess the validity of these seven categories. RESULTS: Statistical analysis results showed that the seven categories could be well distinguished by either using the defining variables initially accepted as inclusion criteria or selecting a few other variables found to have discriminating value. The additional variables confirmed that the categories are essentially distinct and vary systematically with regard to items other than the inclusion criteria. The existence of two recently defined leukoencephalopathies was confirmed, but no consistent evidence of other new disease entities could be provided. CONCLUSION: Establishing these seven categories helps in the interpretation of individual studies by demonstrating features that the patient has in common with other patients, and it may facilitate further research on homogeneous subgroups of patients and allow pooling of data across multiple centers.