Quantification of brain damage in cerebrotendinous xanthomatosis with magnetization transfer MR imaging

BACKGROUND AND PURPOSE: Conventional MR imaging for quantification of brain damage in monitoring the evolution of cerebrotendinous xanthomatosis (CTX) has limitations. Magnetization transfer (MT) MR imaging is overcoming these limitations. Using MT MR imaging, we sought to quantify, in vivo, the extent of brain and cerebellar damage in patients with CTX, with the ulimate goal to investigate the magnitude of the correlation between MT MR imaging findings and clinical disability. METHODS: Conventional and MT MR images of the brain were obtained in nine patients with CTX and in 10 sex- and age-matched healthy volunteers. MT ratio histograms were derived of the whole brain, brain normal-appearing white matter (NAWM), brain normal-appearing gray matter (NAGM), cerebellar NAWM, and cerebellar NAGM. Clinical disability was measured by using the Expanded Disability Status Scale (EDSS). RESULTS: Average MT ratio and peak heights of the whole brain, brain NAWM, and brain NAGM histograms in patients with CTX were significantly lower than the corresponding quantities in the control subjects. All cerebellar NAGM MT ratio histogram-derived metrics and average MT ratio of the cerebellar NAWM histogram in patients with CTX were also significantly lower than the corresponding quantities in the control subjects. Strong correlations were found between the EDSS score and a composite whole-brain MT ratio histogram score (r = 0.77, P <.01) and a composite brain white matter MT ratio histogram score (r = 0.71, P <.03). A strong correlation was also found between the cerebellar functional system score and a composite cerebellar NAWM score (r = 0.72, P <.02). CONCLUSION: The quantitative assessment of brain damage in patients with CTX with use of MT MR imaging can provide powerful measures of disease outcome.