Dorsolateral Nigral Hyperintensity on 1.5 T Versus 3 T Susceptibility-Weighted Magnetic Resonance Imaging in Neurodegenerative Parkinsonism.

Background: An absent dorsolateral nigral hyperintensity (DNH) is a common finding in patients with neurodegenerative parkinsonism at high or ultra-high field susceptibility-weighted magnetic resonance imaging (SWI). Objective: Despite increasing use of high field magnetic resonance imaging (MRI) in specialized centers, these scanners are still frequently unavailable in primary care or outpatient facilities and underdeveloped or emerging countries. Therefore, the aim of the present study was to evaluate the diagnostic utility of DNH assessment at 1.5 versus 3 T MRI to distinguish patients with neurodegenerative parkinsonism, including Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP), from healthy controls (HC). Methods: Absence of DNH was assessed on visual inspection of anonymized 1.5 T and 3.0 T SWI scans in a case-control study including 86 patients with neurodegenerative parkinsonism and 33 healthy controls (HC). All study participants were consecutively recruited to undergo 1.5 and 3 T MRI. Results: Overall correct classification was 81.7% (95% CI, 72.6-88.4%) for 1.5 T and 95.7% (95% CI, 89.1-98.7%) for 3 T MRI in discriminating neurodegenerative parkinsonism from controls. However, while DNH was bilaterally present in all but one of the HC at 3 T MRI, it was rated as abnormal (at least unilateral absence) in 15 of 22 HC at 1.5 T MRI, resulting in a specificity of 31.8%. Conclusions: The results of the present study demonstrate an insufficient specificity of visual assessment of DNH at 1.5 T MRI for the diagnosis of neurodegenerative parkinsonism.