Red flags to spot the parkinsonian variant of multiple system atrophy

The parkinsonian variant of multiple system atrophy (MSA-P) can be difficult to differentiate from Parkinson's disease (PD). This Practice Point commentary discusses a multicenter study performed by the European MSA Study Group that sought to determine whether certain clinical features could serve as 'red flags', or warning signs, to assist in the early diagnosis of MSA-P. The study included 57 patients with probable MSA-P and 116 patients with probable PD. The presence of two out of six red-flag categories yielded 98.3% specificity and 84.2% sensitivity for a diagnosis of MSA-P as opposed to PD. In 13 of 17 patients with possible MSA-P who later progressed to probable MSA-P, use of the red-flag categories would have accelerated the diagnosis of probable MSA-P by an average of 15.9 months. Although this study has several limitations, the identified red-flag categories may be useful as supportive criteria in diagnosing probable MSA-P.