Objective: To investigate cognitive impairment in 22 patients with Progressive Supranuclear Palsy with Richardson syndrome (PSP-RS).

Background: PSP is a neurodegenerative disease and common differential diagnosis of idiopathic Parkinson’s disease (IPD). Besides typical motor symptoms, PSP is characterized by a wide range of cognitive and behavioral deficits. Although IPD and PSP share major cognitive similarities, differences in severity of cognitive impairment and performance patterns have been observed. It was described that PSP patients are more severely impaired in executive functioning (EF) like verbal fluency tests and overall attention. Global memory function has been noted to be widely preserved. However, most cognitive studies of PSP have been limited by the use of brief screening instruments, disregarding the necessity of a more specific neuropsychological profile.

Method: We report results of a neuropsychological test battery consisting of EF subscores of the Consortium to Establish a Registry for Alzheimer’s disease (CERAD): the Trail Making Test (TMT) and phonemic verbal fluency, the Frontal Assessment Battery (FAB) and the Mini Mental State Examination (MMSE) as measure of dementia symptomatology.

Results: The patients were at an age of 71.8±4.1 years and had a disease duration of 41.1±7.9 months. Most patients showed no sign of dementia (MMSE cutoff ˂ 24): 2 patients scored below 24. The average MMSE score was at 26±4.2. Results for EF were ambiguous: the average FAB score was at 12.8±4.3 (cutoff ≤ 12). Still, 9 patients presented a FAB score below cutoff. In the TMT, 17 patients showed severe impairment (z < -2.0), 3 patients were moderately impaired (-1.5 < z < -2.0), 2 patients were mildly impaired (-1.5 < z < -1.0). Phonemic fluency was severely impaired in 10 patients, 9 were moderately impaired, 2 showed mild impairment, one was normative. Statistical comparison of patients above and below FAB cutoff showed a significantly stronger impairment in subscores testing for EF in patients below cutoff (p < 0.001). Results were not correlated to age or disease duration.

Conclusion: Our PSP-RS patients showed no signs of dementia, memory was widely normative. EF were more severely impaired in patients with critical FAB score. Since the TMT was pathologic in all observed PSP patients, it might be of use to investigate its diagnostic utility in regards to differential diagnosis of IPD and PSP as well as its variants.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-trail-towards-understanding-cognitive-impairment-in-psp/