Objective: To assess the utility of susceptibility weighted imaging (SWI) in the diagnosis of idiopathic Parkinson’s Disease (IPD) from the movement disorders clinics at the Walton Centre, UK.

Background: The hallmark pathological manifestation of IPD is the deposition of Lewy bodies and loss of striatal dopaminergic neurons of the substantia nigra (SN). Damier et al described patterns of dopamine-containing neuron loss in 5 compartments within the SN, the main of which is nigrosome-1. Maximal cell loss occurs in nigrosome-1 and has been identified as a potential pathoanatomical correlate of IPD pathology on susceptibility-weighted 3T magnetic resonance imaging. It is proposed that absence of normal nigrosome-1 signal on 3T MR SWI has a high sensitivity and specificity for IPD.

Methods: 21 PD patients who met the UK PDS Brain Bank criteria for IPD were identified who had undergone 3T SWI MRI in our unit. A neuroradiologist, blinded to the clinical details, reviewed the imaging to determine the presence or absence of the nigrosome-1 complex on each side. This data was correlated against the clinical presentation.

Results: 4 scans were excluded due to unacceptable movement artefact, so 17 scans were analysed. The median interval between symptom onset and imaging was 12 months. 88.2% demonstrated abnormal nigrosome-1 complexes on SWI MRI. Of the abnormal scans 52.9% had absent nigrosome-1 complexes bilaterally, whilst the rest demonstrated unilateral changes. There was not a correlation between the clinically most affected side and the absence of the contralateral nigrosome-1 complex.

Conclusions: These findings support those reported in the current literature. SWI MRI has the potential to provide objective imaging support in the diagnosis of IPD. Advantageously this imaging modality does not carry the potential risks associated with DaTScan and is often more readily available.

However, further studies are required to assess the use of this imaging modality in the diagnosis of IPD. We propose a matched case-control study against normal controls and ‘Parkinson-Plus’ disorders to determine the sensitivity and specificity for idiopathic PD. A longitudinal study of serial SWI MRI in an ‘at-risk’ population, such as REM-sleep disorder patients, could help establish whether the imaging changes are present in the pre-motor stages and whether they have value in predicting the development of IPD. 

References: Damier P, Hirsch EC, Agid Y, Graybiel AM. The substantia nigra of the human brain II. Patterns of loss of dopamine-containing neurons in Parkinson’s Disease. Brain. 1999;122(8):1437-48

Goa P, Zhou P-Y, Li G et al. Visualisation of nigrosomes-1 in 3T MR susceptibility weighted imaging and its absence in diagnosing Parkinson’s Disease. Eur Rev Med Pharmacol Sci. 2015;19(23):4603-9

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MDS Abstracts - https://www.mdsabstracts.org/abstract/utility-of-susceptibility-weighted-imaging-in-the-objective-diagnosis-of-idiopathic-parkinsons-disease-is-datscan-necessary/