Myelin measurement in amyotrophic lateral sclerosis with synthetic MRI: A potential diagnostic and predictive method

Background: Myelin damage has recently been highlighted as a major causative factor of amyotrophic lateral sclerosis (ALS). Although myelin damage has been pathologically identified in ALS, it has not been clinically evaluated. This study aimed to quantify myelin volume using synthetic MRI to evaluate myelin damage in patients with ALS, and determine its association with clinical parameters.

Methods: We evaluated patients with ALS (n = 35) and individuals (n = 16) without intracranial disease using synthetic magnetic resonance imaging (MRI) and measured total myelin volume (TMV), myelin fraction (MYF), and myelin partial volume (V_MY) in the cerebral peduncle and the posterior limb of the internal capsule (PLIC). We also investigated factors associated with acquired quantitative values.

Results: The TMV was significantly lower in the patients with ALS than in the control group (P = 0.045). The TMV (r = 0.42, P = 0.013) and MYF (r = 0.34, P = 0.047) significantly correlated with Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) scores in the patients, and MYF was independent of the traditional white matter lesion grading score. The V_MY of the PLIC was significantly lower in the ALS than the control group (P = 0.018), and the ALS group significantly correlated with ALSFRS-R scores (r = 0.36, P = 0.033).

Conclusions: Myelin damage can be quantified by synthetic MRI as reduced myelin volume, with the possibility of predicting prognoses in patients with ALS. Furthermore, myelin measurements in the PLIC might be a novel diagnostic marker for ALS.