Diagnosing dementia in multiple system atrophy by applying Movement Disorder Society diagnostic criteria for Parkinson's disease dementia

Introduction: Dementia is an exclusion criterion in current consensus diagnostic criteria, while growing evidence suggests the occurrence of cognitive dysfunction and even dementia in multiple system atrophy (MSA) patients. The main goal of this study was to determine if Movement Disorder Society (MDS) Parkinson's disease dementia (PDD) LEVEL-1 criteria are useful in screening for dementia in MSA patients compared to full cognitive testing (LEVEL-2 criteria).

Methods: In this retrospective study, MDS diagnostic criteria for PDD were applied in 111 MSA patients from three centres. LEVEL-1 evaluation (short screening test) was compared to LEVEL-2 examination (extensive neuropsychological gold standard assessment). Sensitivity, specificity, positive and negative predictive values were calculated for LEVEL-1 compared to LEVEL-2. Two Mini Mental State Examination (MMSE) cut-off scores were evaluated (<26 according to MDS procedures for the diagnosis of PDD and <27 which has proven more sensitive in a recent study proposing a short procedure for PDD screening).

Results: According to these criteria, 11.7% of MSA patients were demented on LEVEL-2 examination. LEVEL-1 examination showed strong specificity (96.9%) and negative predictive value (94.1%), while sensitivity (53.8%) and positive predictive (70%) value were moderate compared to LEVEL-2 evaluation. Sensitivity increased to 84.6% when using a MMSE threshold <27 for LEVEL-1. Executive dysfunction was the main prevalent finding (52% of all patients), while impairment of memory (15%), language (14%) and visuospatial functions was less frequent (13%).

Conclusion: Our findings suggest that the MDS PDD short screening test may be useful for the diagnosis of MSA dementia.