Objective: To subclassify Progressive supranuclear palsy (PSP) into cortical and subcortical types

To identify the clinical and radiological correlation in PSP

Background: The 2017 International Parkinson and Movement Disorder Society (MDS) PSP study group subclassified PSP into 8 variants: 4 cortical (PSP-F, PSP-CBS, PSP-SL, PSP-RS) and 4 subcortical (PSP-P, PSP-PGF, PSP-PI, PSP-OM).¹ PSP-RS remains the most common subtype.^2,3 Midbrain atrophy, measured by the midbrain-to-pons ratio (M:P) and magnetic resonance parkinsonism index (MRPI), differentiates PSP-RS from Parkinson’s disease.^4-6

Method: This prospective study was conducted at our tertiary care teaching institute, Amrita Institute of Medical Sciences, Faridabad, India, from April 2024 to February 2025. Patients clinically diagnosed with PSP were included after giving informed consent. Age at onset, disease duration, PSP subtype, and MRI findings were recorded, entered into an MS Excel sheet, and statistically analyzed.

Results: 88 patients were included (34.1% females, 65.9% males). The mean age at onset was 65.9±7.4 years (range 50-85), with a symptom duration of 3.8±2.3 years. The most common PSP subtype was PSP-RS (39.8%, n=35), followed by PSP-P (26.1%, n=23), PSP-CBS (23.8%, n=21), PSP-F (n=4), PSP-C (n=2), PSP-PGF (n=2) and PSP-SL (n=1). The most common presentation was akinetic-rigid syndrome (73.8%), while limb/cranio-cervical dystonia occurred in 55.7%. The mean±SD M:P ratio was lowest in PSP-RS (0.17±0.05) compared to PSP-P (0.28±0.08), PSP-CBS (0.26±0.04), and PSP-PGF (0.36±0.02) (p < 0.0001) (Table 1). The mean MRPI was significantly higher in PSP-RS (25.3±21.8) than in PSP-P (10.3±4.2) (p = 0.0035) (Table 2).

Conclusion: In this prospective PSP study, PSP-RS was the most common subtype (39.8%), while other subtypes, including PSP-P and PSP-CBS, accounted for 49.9% of the cases, highlighting their under-recognition. Besides the typical akinetic-rigid presentation, dystonia was also commonly seen (55%). PSP-RS had a lower midbrain-to-pons ratio than other subtypes, suggesting that non-RS variants may be overlooked, especially with subjective visual assessment. Hence, PSP subclassification by clinical and radiological features improves treatment and prognosis.

Table 1

Table 2

References: 1. Höglinger GU, Respondek G, Stamelou M, Kurz C, Josephs KA, Lang AE, Mollenhauer B, Müller U, Nilsson C, Whitwell JL, Arzberger T. Clinical diagnosis of progressive supranuclear palsy: the movement disorder society criteria. Movement disorders. 2017 Jun;32(6):853-64.
2. Guasp M, Molina-Porcel L, Painous C, Caballol N, Camara A, Perez-Soriano A, Sánchez-Gómez A, Garrido A, Muñoz E, Marti MJ, Valldeoriola F. Association of PSP phenotypes with survival: A brain-bank study. Parkinsonism & related disorders. 2021 Mar 1;84:77-81.
3. Chatterjee K, Choudhury S, Kumar H. Relevance of subtype classification of PSP. Annals of Indian Academy of Neurology. 2021 Jan 1;24(1):7.
4. Massey LA, Jäger HR, Paviour DC, O’Sullivan SS, Ling H, Williams DR, Kallis C, Holton J, Revesz T, Burn DJ, Yousry T. The midbrain to pons ratio: a simple and specific MRI sign of progressive supranuclear palsy. Neurology. 2013 May 14;80(20):1856-61.
5. Mahale RR, Krishnan S, Divya KP, Jisha VT, Kishore A. Subtypes of PSP and prognosis: a retrospective analysis. Annals of Indian Academy of Neurology. 2021 Jan 1;24(1):56-62.
6. Pillai KS, Rajeswari P, Kamble RB, Gopalan Nair Santhamma S, Chacko M, Jayakrishnan V, Ramachandran R, Avarachan A, Kishore A. Multimodality Brain Imaging Markers in Progressive Supranuclear Palsy Subtypes and Parkinson’s Disease. Movement Disorders Clinical Practice.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinical-subtypes-and-radiological-patterns-in-progressive-supranuclear-palsy-a-prospective-study/