Proton MR spectroscopic and diffusion tensor brain MR imaging in X-linked adrenoleukodystrophy: initial experience.

PURPOSE

To compare conventional magnetic resonance (MR) imaging, proton MR spectroscopic imaging, and diffusion tensor (DT) MR imaging findings in patients with X chromosome-linked adrenoleukodystrophy (X-ALD).

MATERIALS AND METHODS

Multisection proton MR spectroscopy and DT imaging were performed in 11 patients with X-ALD and in 11 healthy control subjects. Quantitative measures of N-acetylaspartate (NAA), choline, and creatine values and of isotropic apparent diffusion coefficient (IADC) and fractional anisotropy (FA) were obtained from coregistered regions of interest. DT imaging and metabolic parameters were compared by using regression analysis. In addition, differences in DT imaging and metabolite measurements between normal- and abnormal-appearing white matter on conventional MR images were evaluated by using a nonparametric (Mann-Whitney) test.

RESULTS

A strong logarithmic relationship between NAA value and FA (r = 0.64, P <.001) and an inverse logarithmic relationship were found between NAA value and IADC (r = -0.69, P <.001). Creatine and choline values correlated poorly with IADC and FA. In the normal-appearing white matter of asymptomatic patients, the NAA value was 17% lower than that in the healthy control subjects (P =.016), whereas no significant difference in DT imaging measures was seen in these regions.

CONCLUSION

In patients with X-ALD, MR spectroscopic imaging can depict abnormalities in white matter that have a normal appearance on both conventional MR and DT images; this finding suggests that it may be the most sensitive technique for detecting early abnormalities of demyelination or axonal loss in patients with X-ALD.