Neuroradiological patterns and prognostic implications in type I Alexander disease

Introduction: Type I Alexander Disease (AxD) is a rare leukodystrophy that can be subclassified into subtypes (Ia, Ib, Ic, and Id), in order of decreasing severity. To date, no study has correlated MRI findings with AxD type I clinical evolution. This study aims to identify MRI features that may predict disease progression. Methods: Patients with genetically confirmed type I AxD were recruited from multiple Leukodystrophy Centers worldwide. Clinical data were collected via RedCap, and patients were retrospectively classified by disease subtype. Leukodystrophy experts analyzed the first available MRI scans using an adapted AxD MRI scoring protocol, and imaging findings were correlated with disease subtypes. Results: 47 subjects with type I AxD were enrolled. Subtype distribution included 3 Ia, 12 Ib, 8 Ic, 10 Id, 10 Ic/Id, and 4 undetermined. Risk of belonging to type Ib compared to other subtypes was significantly increased in case of involvement of parietal subcortical WM (OR = 16.1, p = 0.003), occipital deep WM (p = 0.008), temporal deep (p = 0.018), and periventricular WM (p = 0.013), body of corpus callosum (p = 0.018), genu of corpus callosum (p = 0.047) and hilar region of cerebellum (p = 0.008). Involvement of occipital periventricular WM was associated to a higher risk of being type Ic compared to type Id (p = 0.010). Conclusions: Some distinct MRI patterns on initial MRI scans may predict disease outcomes in type I AxD. These findings may help clinicians in early prognostic stratification, with key brain regions needing careful evaluation. Further studies are required to validate these findings and improve prognostic accuracy in type I AxD.