Altered white and gray matter metabolism in CADASIL -: A proton MR spectroscopy and 1H-MRSI study

Objective: Subcortical white matter hyperintensities (WMH) and small cystic lesions are the radiologic hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary angiopathy causing stroke in young adults. To further characterize the cerebral pathology in vivo we analyzed metabolite concentrations in normal and abnormal appearing brain tissue using single and multiple voxel proton MR spectroscopy (H-1-MRS and H-1-MRSI). Methods: Twenty patients with CADASIL and 21 age-matched controls were studied with H-1-MRSI at the level of the centrum semiovale; short echo time H-1-MRS was performed in six patients (WMH) and 10 controls. LCModel fits were used to estimate absolute and relative concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (Cr) within WMH, normal appearing white matter (NAWM), and cortical gray matter (GM) as well as myo-inositol (mI) and lactate in WMH. Results: H-1-MRSI-Patients with CADASIL showed significantly reduced NAA, Cho, Cr, and total metabolite content (Met(tot)) in WMH and NAWM. Normalization to Met(tot) revealed that NAA/Met(tot) was reduced in all regions, whereas Cho and Cr were relatively elevated in WMH. Short echo time H-1-MRS showed decreased NAA, Cr, Met(tot) and NAA/Met(tot) and elevated mI/Met(tot) and lactate in WMH. Metabolite changes were larger in severely affected subjects. Rankin scores correlated negatively with NAA/ Met(tot) (all regions) and NAA/Cho (WMH), and positively with Cho/Met(tot) (WMH) and Cr/Met(tot) (NAWM). Conclusion: Marked metabolic abnormalities were observed in abnormal and normal appearing white matter in patients with CADASIL. The findings suggest axonal injury, enlarged extracellular spaces, myelin loss, and gliosis. The cortical abnormalities may reflect structural damage or functional neuronal impairment secondary to white matter pathology. NAA reductions were correlated with clinical disability emphasizing the clinicopathologic relevance of axonal injury in CADASIL.