Objective: To estimate the prevalence and incidence of progressive supranuclear palsy (PSP, ‘Richardson’s syndrome’) and corticobasal syndromes (CBS); in the context of all clinical phenotypes within the spectrum of Frontotemporal Lobar Degeneration (FTLD).

Background: There are limited data on the prevalence and incidence of PSP and CBS, and several factors affect the interpretation of previous data. First, diagnostic criteria for CBS were revised in 2013 to improve sensitivity and specificity for corticobasal degeneration. Second, intermediate phenotypes of uncertain nosological status lie outside former diagnostic categories, e.g. overlap between PSP and CBS. Third, patients may evolve their syndrome, meeting criteria for multiple disorders over time, e.g. PSP may evolve to or from the syndrome of behavioural variant frontotemporal dementia. Finally, previous studies often used widely varying methods, impairing the comparison across reports.

Methods: A prospective study with multiple case referral from specialist and community healthcare services and patient based organisations over 2 years to identify all PSP and CBS, of any age, along with diagnosed or suspected cases of Frontotemporal Dementia, from two UK counties (population 1.7m), adjusting rates to the 2013 European standard population.

Results: We identified 48 people with PSP (29 men, mean age 73, criteria: Litvan et al 1996) and 48 with CBS (17 men, mean age 71, criteria: Armstrong et al 2013). Standardised prevalence was 5.1/100,000 for PSP and CBS combined, with their mortality and incidence matched at 0.8/100,000. Peak prevalence for PSP was 14.5/100,000 at age 70-74, and for CBS 12.5/100,000 at age 75-79 (not including PSP-Parkinsonism or corticobasal degeneration with non-CBS presentations). At assessment, mean 4.6 years from symptom onset, 66% of CBS cases had significant language impairment and 83% of PSP cases had significant behavioural changes.

Conclusions: The prevalences of clinically manifest PSP (Richardson’s syndrome) and CBS are similar, at approximately 2.5 per 100,000 each. Prevalence rises after 65 years. They account for approximately half of the clinical spectrum associated with frontotemporal lobar degeneration. Prevalent cases have frequent language and behavioural change in addition to the core diagnostic features.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/prevalence-and-incidence-of-psp-and-cbs-a-new-prospective-study-in-the-uk/