Correspondence between MMSE and detailed neuropsychological testing in Parkinson’s disease

Although the Mini-Mental Status Examination (MMSE) has long been criticised as being insufficiently sensitive to cognitive decline, it is still considered fundamental for the diagnosis of cognitive impairment in Parkinson’s disease, with many papers continuing to use this tool to characterise cognition. This study investigates how intact performance on the MMSE in Parkinson’s disease relates to performance on detailed neuropsychological testing, and how intact performance on individual MMSE subtests corresponds to performance on cognate neuropsychological tests. We examined the wider neuropsychological performance of 264 PD patients screened using the MMSE. 85.7 per cent of PD patients passing the MMSE demonstrated impairment upon detailed neuropsychological assessment, more frequently on non-MMSE domains (76.1 per cent) than MMSE domains (40.8 per cent). Furthermore, despite performing flawlessly on individual MMSE domains, up to 22.6 per cent failed cognate tests upon detailed neuropsychological testing. We conclude that the MMSE is inadequate for the accurate detection or characterisation of cognitive impairment in PD.