van der Knaap's leukoencephalopathy: report of five new cases with emphasis on diffusion-weighted MRI findings.

We present five new cases of van der Knaap's leukoencephalopathy, which is a rare abnormality characterized by infantile-onset white matter disease with swelling and mild clinical course. Based on the very rare histopathological data, this disease is considered a vacuolating myelinopathy with peripherally located intralamellar vacuoli. Although approximately 70 cases have so far been published, there are very limited data in the literature regarding diffusion-weighted imaging (DWI) findings of this recently discovered entity. In this paper, in addition to MRI, MRS and DWI findings in three patients are shown, apparent diffusion coefficient (ADC) maps are calculated, and ADC measurements made from various regions of interest are documented. MRI showed diffuse swelling and areas of T2 high signal in supratentorial white matter, sparing the cortex and central gray matter structures. MRS findings indicated some degree of neuronal loss. DWI and ADC maps showed increased diffusion rates, suggesting a different type of tissue damage than that would be expected in vacuolating myelinopathies. We believe that DWI and ADC mapping would be of help in providing a baseline for monitoring the progression of the disease.