14800-DvRappard

107 Quantitative MR spectroscopic imaging in metachromatic leukodystrophy 7 INTRODUCTION Metachromatic leukodystrophy (MLD, Online Mendilian Inheritance in Man (OMIM) 250100) is an autosomal recessive lysosomal disorder with deficient activity of arylsulfatase A (ASA), essential for sulfatide degradation. 1 Sulfatides are major myelin components; their accumulation in MLD results in demyelination and neurological decline. 2 MLD has 3 clinical subtypes, based on age of onset. The late-infantile form starts < 30 months of age, the juvenile form between 2.5 and 16 years and the adult form thereafter. 1 Hematopoietic cell transplantation (HCT) shows promising results, especially for patients with juvenile and adult MLD in early disease stages. 3-5 Eligibility for HCT is currently based on neurological examination and cognitive function; the degree of MRI abnormalities 6 is also prognostic. 7,8 Proton magnetic resonance spectroscopy ( 1 H-MRS) providesadditionalmetabolicinformation,aseithersinglevoxelMRSorMRspectroscopic imaging (MRSI). 9 MLD spectra are characterized by decreased N-acetylaspartate (NAA), elevated myo-inositol (Ins) and choline-containing compounds (Cho) in abnormal white matter (WM). 10,11 This study investigates the relationship between clinical outcome in patients with juvenile or adult MLD and WM metabolite concentrations at baseline. All examinations at diagnosis at the same scanner using two-dimensional (2D) MRSI, for simultaneous acquisition of spectra in multiple regions of a single slab 9 were defined as baseline scans. For patients with follow-up examinations, we additionally studied longitudinal evolution of metabolites. METHODS Patients and control subjects In this retrospective study, approved by the institutional review board, we included 21 MLD patients (12 juvenile, 9 adult) and 16 subjects who served as controls (same age range; median 10.6 y, range 4.2-29.6 y; undergoing MRI for reasons like mild developmental delay, tics, headache; theyhadnormalMRI andneurological examination) who underwent quantitative MR imaging including MRSI between January 2007 and April 2013. One patient was described before. 12 MLD was diagnosed by brain MRI, ASA activity and ARSA mutation analysis. Patient characteristics and number of examinations at the same scanner are summarized in Table 1.