Objective: Our goal was to evaluate the concordance between asymmetry in nigral hyperintensity detected with 3T MRI and clinical symptomatology.

Background: A promising MRI marker for Parkinson’s disease is the swallow tail sign (STS), which was found to partially overlap with nigrosome 1, the dopaminergic region that is most affected during the initial stages of the disease [1]. Segmental echo-planar imaging (EPISEG) is a useful sequence for evaluating STS as its brief acquisition time makes it less susceptible to motion artefacts [2]. Although the agreement between the loss of hyperintensity and contralateral clinical symptoms may improve diagnostic confidence, as of now there is limited data available regarding the comparison of imaging asymmetry and clinical laterality.

Method: Anonymized EPISEG MR scans of PD subjects, acquired between 2019 and February 2023, during their diagnostic workup, were retrospectively evaluated in consensus by two experienced raters blinded to patients’ clinical data. Nigral hyperintensity was rated for each hemi-mesencephalon on a 3-point ordinal scale (0 = not visible, 1 = probably present, 2 = clearly present). If there was any difference in the nigral hyperintensity between the right and left sides, the scans were categorized as asymmetric. We examined the concordance between the detected asymmetry in hyperintensity and clinical symptoms using Cohen’s κ test.

Results: Imaging asymmetry was found in the case of 20 patients (11 male, mean age 65.25 ± 13.94 years). Of these 20 patients, 1 showed no clinical asymmetry, 4 had left-, while 15 had right-sided dominant symptoms. Evaluating the data of 19 patients with clinical laterality, the level of agreement between MRI and contralateral clinical findings was substantial (κ = 0.826, p = 0.004).

Conclusion: Our results suggest that imaging asymmetry, even without the complete loss of hyperintensity on one side, has a high concordance with clinical laterality, thus it may assist clinicians in establishing a diagnosis of Parkinson’s disease with more confidence.

References: [1] Brammerloh M, Kirilina E, Alkemade A, et al. Swallow Tail Sign: Revisited. Radiology. 2022;305(3):674-677. doi:10.1148/radiol.212696

[2] Hernadi G, Pinter D, Nagy SA, et al. Fast 3 T nigral hyperintensity magnetic resonance imaging in Parkinson’s disease. Sci Rep. 2021;11(1):1179. Published 2021 Jan 13. doi:10.1038/s41598-020-80836-7

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MDS Abstracts - https://www.mdsabstracts.org/abstract/agreement-between-swallow-tail-sign-asymmetry-and-clinical-laterality-in-parkinsons-disease/