Background: Progressive myelopathy is the main cause of disability in adrenoleukodystrophy (ALD). Development of therapies is hampered by a lack of quantitative outcome measures. In this study, we investigated whether myelopathy in ALD is associated with retinal neurodegeneration on optical coherence tomography (OCT), which could serve as a surrogate outcome measure.
Methods: Sixty-two patients (29 men and 33 women) and 70 age-matched and sex-matched controls (33 men and 37 women) were included in this cross-sectional study. We compared retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) and peripapillary retinal nerve fiber layer (pRNFL) thickness between ALD patients and controls. In addition, we correlated these OCT measurements with clinical parameters of severity of myelopathy.
Results: Patients had significantly thinner RNFL (male group, p < 0.05) and pRNFL superior and temporal quadrant [both male (p < 0.005) and female (p < 0.05) groups] compared to controls. Comparing three groups (symptomatic patients, asymptomatic patients and controls), there were significant differences in RNFL thickness (total grid and peripheral ring) in the male group (p ≤ 0.002) and in pRNFL thickness (superior and temporal quadrant) in both male (p ≤ 0.02) and the female (p ≤ 0.02) groups. Neuroretinal layer thickness correlated moderately with severity of myelopathy in men (correlation coefficients between 0.29-0.55, p < 0.02), but not in women.
Conclusions: These results suggest that neurodegeneration of the spinal cord in ALD is reflected in the retina of patients with ALD. Therefore, OCT could be valuable as an outcome measure for the myelopathy of ALD. Additional longitudinal studies are ongoing.
Keywords: Myelopathy; Neurodegeneration; Optical coherence tomography; Retinal nerve fiber layer; Spinal cord; X-linked adrenoleukodystrophy.