How to distinguish spinocerebellar ataxia 27B from late onset cerebellar ataxia: insights from a case-control study.

BACKGROUND

Spinocerebellar ataxia 27B is the most common genetic late onset cerebellar ataxia (LOCA). However, it commonly overlaps with other genetic LOCA as with the cerebellar form of multiple system atrophy (MSA-C).

OBJECTIVES

To pinpoint which clinical signs and symptoms best discriminate between FGF14 + from FGF14 - patients at symptoms' onset.

METHODS

Twenty SCA27B (≥ 250 GAA repeat expansion) patients were retrospectively matched by gender and age at disease onset with 20 negative FGF14 (-) LOCA patients and with 20 MSA-C patients. Clinical features were ranked based on their contribution towards distinguishing between the groups (feature importance ranking).

RESULTS

SCA27B patients had significantly higher rates of episodic symptoms, cerebellar oculomotor signs, dysdiadochokinesia, and alcohol intolerance than LOCA-FGF14 - ataxia patients. The lack of autonomic symptoms and MRI signs in SCA27B patients were the most discriminating features from MSA-C. An AUC of 0.87 was obtained if using the "top 3 clinical features model" (episodic symptoms, cerebellar oculomotor signs and dysdiadochokinesia) to distinguish SCAB27 from LCOA FGF14 - . Regarding MRI findings, no significant differences were found between SCA27B and FGF14 - patients, while a positive hot cross buns sign and the presence of brainstem atrophy were key distinguishing features between SCA27B from MSA-C patients (p < 0.005).

CONCLUSION

Our pilot case-control study contributes to the identification of early clinical symptoms to differentiate SCA27B to LOCA patients including FGF14- and MSA-C ones. From a feature perspective, while clinical features are crucial, identifying surrogate biomarkers-such as ocular or gait parameters-could aid in the early diagnosis and follow-up of SCA27B patients.