MR imaging of Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease (PMD) is a rare, slowly progressive, sex-linked demyelinating disorder generally classified with the sudanophilic leukodystrophies. The onset is most often in the pediatric age group and may be diagnosed as cerebral palsy because of the subtle onset. Cranial magnetic resonance (MR) imaging of two patients with PMD showed reversal of the normal gray/white matter signal relationships, consistent with dysmyelination, as well as low intensity lentiform nuclei and thalami possibly suggesting pathologic iron deposition. Magnetic resonance also better demonstrated low volume brain without the beam hardening limitations of X-ray CT. Although our MR findings correlate well with the pathophysiology of PMD, the MR characteristics are not specific. The diagnosis of PMD remains one of clinical and laboratory exclusion.