Cerebellar ataxias and functional movement disorders: navigating clinical overlap

Functional movement disorders (FMDs) are commonly classified along canonical non-ataxic movement disorder patterns, creating a potential blind spot for frequently observed ataxia-like presentations. At the same time, normal diagnostic findings and episodic symptom variability in some cerebellar ataxias predispose to an incorrect FMD diagnosis.

We present three cases that illustrate pitfalls in the differential diagnosis of ataxia. First, a patient treated for presumed immune-mediated cerebellar ataxia was diagnosed with FMD based on clinical signs. Next, a patient with intermittent and inconsistent symptoms was diagnosed with FMD after extensive exclusionary workup, but was then found to have a novel type of spinocerebellar ataxia. The third patient had a genetically confirmed spinocerebellar ataxia but developed additional functional motor symptoms.

Differentiating cerebellar ataxias from FMDs and recognising mixed presentations is essential. Enhanced clinical awareness and systematic diagnostic evaluation are crucial to avoid misdiagnosis and ensure optimal treatment.