Editors' Note: The inability to visualize nigrosome 1 on a 7T brain MRI is suggestive of Parkinson disease, as described by Blazejewska et al. Mueller et al. report that similar sensitive and specific findings can be obtained with the more widely available 3T MRI. Replication of this finding on a larger cohort is warranted. In response to Liguori et al., Friedman et al. caution against diagnosing idiopathic intracranial hypertension syndrome on the basis of elevated opening pressure alone without other objective findings.—Chafic Karam, MD, and Robert C. Griggs, MD
Blazejewska et al.1 identified a hyperintense ovoid area within the dorsolateral border of the otherwise hypointense pars compacta of the substantia nigra (SNc) in healthy controls (HC) and the absence of this MRI feature2 in patients with Parkinson disease (PD) using T2*-weighted 7T MRI. Moreover, the postmortem 7T MRI with histopathologic correlations suggested that this MRI feature corresponded to nigrosome 1. We studied this MRI feature in consecutively recruited HC and patients with PD3 (16 HC, 53 PD; mean ± SD age, y: HC 54 ± 10, PD 67 ± 8; proportion female: HC 68%, PD 28%; mean ± SD disease duration, y: 8 ± 4) using susceptibility-weighted imaging (SWI) at 3T (Siemens Verio MRI scanner, Munich, Germany). Datasets of 2 HC and 18 patients with PD were not of diagnostic quality due to patient motion. In the remaining patients, presence of dorsolateral hyperintensity within the otherwise hypointense SNc was identified in 14/14 HC and 5/35 patients with PD. Absence of this MRI feature resulted in 85.7% sensitivity and 100% specificity to detect PD. We suggest that this MRI feature reported at 7T MRI using T2*-weighted sequences1 can also be detected at 3T using SWI sequences and that absence of this MRI feature might have potential for diagnosing PD.
Author Response
Following our article on the application of 7T T2* MRI for PD diagnostics,1 we were delighted to read about the successful use of 3T SWI for detection of nigrosome 1 absence in the substantia nigra in patients with PD by Mueller et al. We also studied the application of 3T SWI in PD cohorts as a fast and easily applicable diagnostic tool. Early findings indicated a sensitivity of 89%–95% and a specificity of 91% of nigrosome 1 detection using 3T MRI,4 which are similar to the results from the 7T MRI study.
Of interest, our rate of nondiagnostic scans was lower than that of Mueller et al. (29%). Their study in 14 controls and 35 patients with PD needs replication with a more robust protocol and in a larger cohort including atypical parkinsonism. Translation of the discovery made at 7T to 3T is particularly promising due to the general availability of 3T scanners. In addition, the lack of postprocessing required for nigrosome detection indicates a potential viable alternative to the more expensive nuclear medical techniques currently licensed.
- © 2014 American Academy of Neurology
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