White matter disorders.

Magnetic resonance imaging (MRI) has a leading role in the diagnosis of white matter disorders because of its superior sensitivity. It also allows a detailed analysis of white matter disorders, improving the specificity of the diagnoses. There is an increasing knowledge about MRI patterns, in particular in hereditary metabolic disorders. Although these patterns are not always pathognomonic, they often serve as a guide for further diagnostic steps. In the non-hereditary white matter disorders, MRI has an increasing role in the diagnoses, follow-up, and monitoring of clinical trials. In inflammatory disorders, gadolinium-diethylenetriamine-penta-acetic acid (Gd-DTPA) appears to be helpful in analyzing the 'natural' course of the disease. Magnetic resonance spectroscopy (MRS) is gradually also finding a niche in the diagnosis of white matter disorders, both as a marker of neuronal loss and as an indicator of the age and activity of a lesion. New magnetic resonance techniques, such as diffusion and magnetic transfer imaging, will probably provide more information about the involvement of myelin sheaths.