Objective: The goal of the study is to evaluate the reliability of swallow tail sign which claimed to be specific for Parkinson’s disease.

Background: Swallow tail sign (STS), which represents nigrosome-1 in the substantia nigra on 3 Tesla (T), susceptibility weighted, magnetic resonance imaging (MRI), has attracted attention as a promising imaging biomarker for idiopathic Parkinson’s disease (iPD). Some reports have shown high sensitivity and specificity (both above 94%), distinguishing iPD from healthy controls. However, the loss of STS has been observed in many neurodegenerative parkinsonisms and even in multiple sclerosis.

Method: All patients with parkinsonism who had 3T MRI were included from a retrospective chart review from a single movement disorders clinic. All subjects had been evaluated by a single movement disorder specialist, using Movement Disorders Society diagnostic criteria and American Academy of Neurology consensus guidelines for diagnoses. All MRI was performed on a 3T magnet, on SWI, and separately evaluated by a single neuroradiologist who was blinded to the diagnosis.

Results: Twenty patients were included in the study. Twelve had abnormal STS: iPD (n=2), multiple system atrophy (n=3), vascular parkinsonism (n=1), psychogenic gait disorder (n=1), neuroleptic parkinsonism (n=2), cervical dystonia (n=1), static encephalopathy (n=1) and gait disorder of unknown etiology (n=1). Eight had normal STS: iPD (n=1), progressive supranuclear palsy (n=1), vascular parkinsonism (n=2), transient parkinsonism of unknown etiology (n=2), valproic acid induced parkinsonism (n=1), and essential tremor (ET) with parkinsonism (n=1). Dopamine transporter scan results were available on seven subjects; four subjects had incongruency between DaT and MRI.

Conclusion: Our results suggest that the absence of the STS is not, in isolation, a reliable biomarker of neurodegenerative parkinsonism.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-evaluation-of-the-swallow-tail-sign-in-patients-with-parkinsonism-or-gait-disorders/