To explore the incidence and trends of Progressive Supranuclear Palsy (PSP) and Corticobasal Syndrome (CBS) in a population-based incident cohort study in Olmsted County, MN.

Only few studies have investigated the incidence of PSP and CBS in the population due to their rarity.

We used the 1991-2005 population-based incident cohort study of parkinsonisms in Olmsted County, MN defined via the Rochester Epidemiology Project. A movement disorder specialist reviewed all the medical records to confirm the diagnoses.

We identified 21 patients in our cohort; 18/21 (85.7%) were diagnosed with PSP, whereas 3/21 (14.3%) had a clinical diagnosis of CBS. The median age at diagnosis was 78 years (range: 66-88). 13/21 (62.0%) were male. A MRI was performed before the diagnosis in 10 patients (7 PSP and 3 CBD) and all but one showed cortical atrophy consistent with the clinical diagnoses. Two PSP patients underwent autopsy and showed concordance between the clinical and the pathological diagnoses. The combined incidence for PSP and CBS in Olmsted County, MN was 3.1/100,000 (95% CI 1.7, 4.4, P< 0.001); the incidence was higher in men (4.5, 95% CI, 2.0-7.0, P< 0.001) than women (1.8, 95% CI, 0.5-2.9, P< 0.001). CBS incidence was 0.4/100,000 (95% CI 0.0, 0.9, P<0.001); PSP incidence was 2.6/100,000 (95% CI 1.4, 3.8, P<0.001). When combined a significant trend of increasing incidence was observed between 1991-2005 (B=0.69, 95% CI 0.42, 0.96, p<0.001).

The combined incidence for PSP and CBS was 3.1/100,000 in our cohort and was higher in men than women. We observed a relevant increase in the trend of the incidence of both PSP and CBS, which is likely due to advancing imaging technology and improved diagnostic ability among physicians.