Supplementary Material for: New-onset progressive ataxia in a 66-year-old woman with longstanding Parkinson’s disease – a case report

Introduction: Parkinson’s disease (PD) is a common neurodegenerative disorder, and its diagnosis remains a clinical one. Hence, the emergence of new symptoms warrants consideration of a new diagnostic work-up even at later disease stages. Important differential diagnoses include atypical or symptomatic parkinsonism, like multiple system atrophy, normal pressure hydrocephalus, or rarely, superficial siderosis (SS). Case Presentation: A 66-year-old woman with longstanding PD presented to our clinic with a four-year history of progressive ataxia and gait impairment. The emergence of a new symptom (ataxia) prompted us to conduct a new, broad diagnostic work-up. Clinical examination revealed both parkinsonian (hypomimia, dyskinesias, right dominant bradykinesia and rigidity, intermittent resting tremor) and cerebellar signs (scanning dysarthria, gaze-evoked nystagmus, severe ataxia of extremities and gait). No signs or symptoms of autonomic dysfunction were present. Magnetic resonance imaging of brain and spine showed extensive hemosiderin depositions and ventral intraspinal fluid collection, establishing a diagnosis of SS. No apparent dural leak was detected in cerebrospinal fluid scintigraphy. The patient was treated with epidural blood patch. Conclusion: The occurrence of new symptoms in PD, especially “red flags” or exclusion criteria, calls for a repeated diagnostic work-up to exclude potentially treatable causes of parkinsonism. While SS has been reported as a cause of symptomatic parkinsonism, we favor a diagnosis of idiopathic PD and comorbid SS in this case. This case report highlights the clinical importance of diagnostic criteria in differentiating PD from atypical parkinsonian disorders or symptomatic parkinsonism as well as signs and symptoms, pathophysiological aspects, and treatment of SS.