Spinal cord atrophy as a measure of severity of myelopathy in adrenoleukodystrophy

Abstract

Background All men and most women with X‐linked adrenoleukodystrophy (ALD) develop myelopathy in adulthood. As clinical trials with new potential disease modifying therapies are emerging, sensitive outcome measures for quantifying myelopathy are needed. This prospective cohort study evaluated spinal cord size (cross‐sectional area ‐ CSA) and shape (eccentricity) as potential new quantitative outcome measures for myelopathy in ALD. Methods Seventy‐four baseline MRI scans, acquired in 42 male ALD patients and 32 age‐ matched healthy controls, and 26 follow‐up scans of ALD patients were included in the study. We used routine T₁‐weighted MRI sequences to measure mean CSA, eccentricity, right‐left and anteroposterior diameters in the cervical spinal cord. We compared MRI measurements between groups and correlated CSA with clinical outcome measures of disease severity. Longitudinally, we compared MRI measurements between baseline and one year follow‐up. Results CSA was significantly smaller in patients compared to controls on all measured spinal cord levels (p<0.001). The difference was completely explained by the effect of the symptomatic subgroup. Furthermore, the spinal cord showed flattening (higher eccentricity and smaller anteroposterior diameters) in patients. CSA correlated strongly with all clinical measures of severity of myelopathy. There was no detectable change in CSA after one year follow‐up. Conclusions The cervical spinal cord in symptomatic ALD patients is smaller and flattened compared to controls, possibly due to atrophy of the dorsal columns. CSA is a reliable marker of disease severity and can be a valuable outcome measure in long term follow‐up studies in ALD.