Objective: To explore accuracy of DaTscan^TM Ioflupane I123 Injection (DaTscan) in a multiple system atrophy (MSA) cohort 

Background: There are isolated cases of normal DaTscan in neuropathologically confirmed MSA-cerebellar subtype (MSA-C) contrasting with cases which have shown a high diagnostic accuracy in clinically confirmed MSA-C. We reviewed the DaTscans of MSA subjects, who are part of a longitudinal study at our multidisicplinary MSA clinic, with the aim of correlating clinical diagnosis of MSA with radiographic results.

Methods: DaTscans  in the MSA database had been ordered by four experienced movement disorders specialists based on the clinical course and presentation at the time of the test. Clinical diagnosis was established using the 2008 consensus criteria for all patients in the database including those that had recieved a DaTscan (2008). Patients were divided into 6 clinical subgroups: probable MSA-P (PR MSA-P), possible MSA-P (PO MSA-P), probable MSA-C (PR MSA-C), possible (MSA-C), probable MSA-Mixed (PR MSA-Mix), and possible MSA-mixed (PO MSA-Mix) and DaTscan data for each subgroup was reviewed by the author. 

Results: A total of 19 subjects had recieved a DaT scan as part of their clinical evaluation. Eleven out of the twelve patients (92%) in the PR MSA-C group had a normal DaT scan; all five patients (100%) in the PR MSA-P group had an abnormal scan; one patient with PR MSA-Mix had normal DaTscan while the PO MSA-Mix subject’s DaTscan was abnormal.

Conclusions: This study sheds light on the limited utility of qualitative DaTscan in the diagnosis of MSA-C. Early and accurate diagnosis of MSA-C without parkinsonian features is critical to avoid unnecessary and expensive testing in singletons with ataxia and for ensuring appropriate outcomes in disease modifying treatment trials which mandate a high degree of diagnostic accuracy. Our study results are at odds with previously pubslished reports of high accuracy DaTscan in MSA-C, likely due to methodological differences (qualitative v quantitative analysis). However, the most commonly available DaTscan in clinical practice utilizes a qualitative, visual review of  dopamine transporter uptake in the striatum with binary outcomes of either normal or abnormal. It is apparent that more accurate radiographic tools need to be developed for incorporation into clinical practice to facilitate the early diagnosis of MSA , especially its cerebellar phenotype. 

References: 1. Munoz, et. al. Subclinical nigrostriatal dopaminergic denervation in the cerebellar subtype of multiple system atrophy (MSA-C). J. Neurol (2011) 258:22-2253

2. McKinley, et al. Normal dopamine transporter imaging does not exclude multiple system atrophy. Parkinsonism and Related Disorders (2014): 933-934

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MDS Abstracts - https://www.mdsabstracts.org/abstract/datscan-in-clinical-evaluation-of-multiple-system-atrophy/