Spectrum of Dystonia in Progressive Supranuclear Palsy: A Prospective Observational Study and Review of Literature.

BACKGROUND: Dystonia is an under-recognized yet clinically significant feature of Progressive supranuclear palsy (PSP), contributing to disability and impaired motor function. METHOD: In this prospective study, we examined the clinical and neuroimaging details of eighty-eight consecutive PSP patients who visited our movement disorder clinic [2024-2025]. Patients fulfilling the 2017 Movement Disorder Society-PSP criteria for possible or probable PSP were enrolled after ethics approval and informed consent. We aimed to evaluate the prevalence, phenomenology, subtype associations, clinical and neuroimaging correlates of dystonia. Additionally, a literature search was performed and 29 articles were included for detailed review. RESULT: The literature review identified predominantly retrospective studies, reporting dystonia in approximately 30-60% of the patients, with variable patterns of cranio-cervical and limb involvement. In our prospective cohort, dystonia was present in 64.8% (n = 57) cases. PSP-RS was the most frequent subtype (39.8%), followed by PSP-P (26.1%) and PSP-CBS (23.8%). Dystonia was more common in PSP-RS and PSP-CBS, with predominant limb dystonia in PSP-CBS, and cranio-cervical dystonia in PSP-RS. A trend toward earlier dystonia was observed in PSP-CBS. Patients with dystonia demonstrated lower Midbrain to pons ratios and higher Magnetic resonance parkinsonism index, suggesting greater brainstem involvement. Botulinum toxin therapy resulted in clinical improvement in selected dystonia patients. CONCLUSION: Dystonia is a frequent and clinically meaningful feature in PSP. Our prospective study expands upon the existing literature by demonstrating distinct subtype-specific patterns and neuroimaging correlates, supporting the concept of a "dystonia spectrum" in PSP and highlighting its relevance for clinical recognition and management.