Quantitative Brain MRI Analysis in Neurodegenerative Langerhans Cell Histiocytosis.

Background: Neurodegenerative Langerhans Cell Histiocytosis (ND-LCH) is a severe central nervous system involvement complicating LCH. ND-LCH is characterized by a cerebellar ataxia, pyramidal signs, pseudobulbar palsy, cognitive impairment, and behavioral disturbances. Cerebellar atrophy, the most common MRI finding, has been widely described in the literature. However, the natural history of volumetric changes in the cerebellum has never been examined. In this study, we aim to perform a quantitative analysis of cerebellar atrophy in ND-LCH patients compared to a control cohort.

Methods: MRI of patients with ND-LCH was compared to those of controls. An automated cerebellum analysis was performed using the Volbrain software (CERES) and a linear regression analysis was used to score the severity of cerebellar atrophy over time.

Results: We retrospectively analyzed the follow-up MRI of 16 adult patients with ND-LCH compared to those of 22 control patients. We examined an average of four MRIs per patient over a median follow-up period of six years. All patients with ND-LCH exhibit global and cortical cerebellar atrophy over time. The average atrophy rate is -1.86 cm3/year (range - 5.90 to 0.34) and is heterogeneous between patients. All cerebellar lobules are affected by atrophy.

Conclusions: Longitudinal quantitative MRI analysis of the cerebellum in ND-LCH: (i) is feasible, (ii) confirms significant global and cortical cerebellar atrophy in patients with ND-LCH over time, (iii) estimates the rate of cerebellar atrophy, and (iv) could be useful as a therapeutic endpoint in a clinically slow-progressing disease. Further studies are needed to validate our findings.