Meta-Analysis of Dorsolateral Nigral Hyperintensity on Magnetic Resonance Imaging as a Marker for Parkinson's Disease

Background: Dorsolateral nigral hyperintensity on ironsensitive magnetic resonance imaging (MRI) sequences seems to be a typical finding in Parkinson's disease (PD), but most studies have involved small samples and have had heterogeneous controlpopulations. Objectives: The objective of this study was to perform a meta-analysis on dorsolateral nigral hyperintensity as an imaging marker for PD. Methods: The methods included a systematic literature search and a hierarchical summary receiver operating characteristics curve approach. Results: Of the 16 identified studies, 10 were suitable for analysis, including 364 PD and 231 control cases. The meta-analysis showed an overall sensitivity and specificity of the absence of dorsolateral nigral hyperintensity for PD versus controls of 97.7% and 94.6% (3 and 7 Tesla) and of 94.6% and 94.4% (3 Tesla only). Descriptive analysis among the 4 studies including patients with non-PD parkinsonism showed that dorsolateral nigral hyperintensity was absent in 89.4% of cases with atypical parkinsonian disorders (n = 74), but only in 21.7% of cases with non-neurodegenerative parkinsonism (n = 69). Moreover, in 2 of these studies, the absence of dorsolateral nigral hyperintensity predicted ipsilateral dopamine-transporter deficiency with 87.5% sensitivity and 83.6% specificity. Conclusions: Visual assessment of dorsolateral nigral hyperintensity on iron-sensitive MRI sequences provides excellent diagnostic accuracy for PD versus controls. Moreover, its loss appears to be a marker of nigral pathology and holds the potential for the differentiation of neurodegenerative from non-neurodegenerative parkinsonian disorders. (C) 2017 International Parkinson and Movement Disorder Society