# Predictive clinical factors for the progression from idiopathic late-onset cerebellar ataxia to multiple system atrophy cerebellar type

## TL;DR

This study identifies clinical factors like orthostatic dizziness and RBD that predict progression from idiopathic late-onset cerebellar ataxia to multiple system atrophy cerebellar type.

## Contribution

The study introduces new predictive factors and explores the potential of neurofilament light chain as a biomarker for conversion from ILOCA to MSA-C.

## Key findings

- Orthostatic dizziness and RBD at baseline are associated with conversion from ILOCA to MSA-C.
- The median time to conversion from ILOCA to MSA-C is 5.0 years.
- Neurofilament light chain (NFL) shows moderate predictive ability when combined with clinical factors.

## Abstract

Patients initially diagnosed with idiopathic late-onset cerebellar ataxia (ILOCA) may develop multiple system atrophy cerebellar type (MSA-C). However, data on conversion time, associated clinical factors, and the role of the neurofilament light chain (NFL) in this process remain limited. This study aims to investigate the conversion from ILOCA to MSA-C and examine the associated factors and the predictive value of NFL.

This retrospective study included patients with ILOCA at the initial visit, recording the conversion to MSA-C and its duration. The median time to conversion was estimated using the Kaplan–Meier analysis. The roles of baseline orthostatic dizziness, rapid eye movement sleep behavior disorder (RBD), hot cross-bun sign, and urinary symptoms in conversion were analyzed. In a subset of patients, NFL levels in plasma collected before conversion were measured to examine their ability to predict conversion.

Seventy-two patients with ILOCA at the initial visit were included, of whom 32 experienced conversion to MSA-C. The median time-to-conversion was 5.0 years. RBD or orthostatic dizziness at baseline was associated with conversion, whereas hot cross-bun sign and urinary symptoms demonstrated no significant effect. Receiver operating characteristic analysis revealed moderate discriminative ability (area under the curve: 0.69) when NFL, orthostatic dizziness, and age at blood collection were included.

This study identified that orthostatic dizziness and RBD, assessable in outpatient settings, correlated with ILOCA-to-MSA-C progression. Additionally, the NFL may play an auxiliary role in estimating the conversion time. Therefore, further studies incorporating diverse clinical and serological markers are required.

The online version contains supplementary material available at 10.1007/s00415-025-13292-w.