Objective: To describe the diagnostic challenges, and management of a patient with overlapping features of corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP)

Background: CBS and PSP are both 4R-tauopathies with overlapping motor and cognitive features. CBS is characterized by asymmetric parkinsonism, dystonia, myoclonus, and apraxia, while PSP presents with vertical gaze palsy, axial rigidity, and early postural instability. Vertical gaze palsy is rarely an early feature in CBS and is more suggestive of PSP. Distinguishing between these syndromes can be challenging, particularly in cases with atypical progression and mixed features.

Method: We reviewed the clinical presentation, imaging findings, treatment response, and disease progression of a 65-year-old woman over nine months.

Results: The patient, with a history of hypertension, rheumatoid arthritis, and alcohol use disorder, presented with six months of progressive cognitive decline, right arm hemiparesis, tremor, imbalance, and episodic dystonic movements. Initial MRI was unremarkable. Examination revealed cognitive impairment, hypophonia, right arm dystonia, rigidity, and tremor, raising suspicion for CBS. Carbidopa-levodopa provided partial dystonia relief but induced severe dyskinesia, leading to discontinuation. Quetiapine was introduced for agitation and resulted in temporary improvement of dystonia and cognition.

Over the next nine months, symptoms worsened, with increasing motor dysfunction and cognitive decline. Notably, downward vertical gaze palsy developed within nine months—earlier than expected in CBS. She exhibited a forward-leaning posture to maintain balance, unlike the characteristic backward posture of PSP. Her dystonia progressed to the right leg, accompanied by choreiform movements and myoclonic wrist-flapping. Despite clinical deterioration, repeat MRI remained unremarkable for known neurodegenerative findings.

Conclusion: This case highlights the diagnostic complexity of CBS when symptoms overlap with PSP. The early onset of vertical gaze palsy is unusual in CBS. Symptomatic improvement with antipsychotics is also atypical. This patient’s progression suggests a complex interplay between CBS and PSP-like features, emphasizing the need to consider a broad spectrum of neurodegenerative disorders in atypical presentations. We plan to conduct CSF studies for Tau and Phosphorylated Tau to aid in diagnosis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-of-mixed-presentation-of-4r-tauopathies/