with Mild Clinical Course Validated by Diffusion Tensor Imaging and MR Spectroscopy

boy that was diagnosed when the patient was 34 months old. The patient presented clinically with megalencephaly and delayed onset of slowly progressive neurologic dysfunc-tion. Serial MR imaging and biochemical analysis were performed to differentiate VML from other disease entities with megalencephaly and leukoencephalopathy of infantile onset. Information obtained with diffusion tensor MR im-aging revealed nearly intact white matter anisotropy and vectors in parietal and posterior temporal lobes in which hyperintense abnormality was shown on conventional T2-weighted images, and proton MR spectra showed a signif-icant decrease in N-acetylaspartate-creatine phosphocre-atine ratio. Vacuolating megalencephalic leukoencephalopa-thy (VML) (leukoencephalopathy, megalencephaly, and mild clinical course; van der Knaap disease) is a new entity of neurodegenerative disorders character-ized by infantile-onset megalencephaly, cerebral leu-koencephalopathy, and a delayed onset of slowly pro-gressive neurologic dysfunction (1–8). In contrast to the relentlessly progressive infantile-onset leukoen-cephalopathy that is frequently fatal within the first decade of life, such as with Canavan disease, Alex-ander disease, and GM1 gangliosidosis, VML has the distinguishing feature of a remarkably slow course of deterioration in neurologic function. Neuropatho-logic appearance of VML is that of a spongioform leukoencephalopathy (3), although the cause of this leukoencephalopathy is still unknown. In light of the potential sensitivity of diffusion tensor (DT) MR im-aging in the assessment of white matter diseases, as proposed by recent studies (9–11), we present the serial DT imaging and proton (1H) MR spectroscopy findings in a 5-year-old boy with VML. Case Repor