CC BY-NC-ND 4.0 · J Neurosci Rural Pract 2022; 13(02): 181-185
DOI: 10.1055/s-0041-1740578
Original Article

The Swallow Tail Sign of Substantia Nigra: A Case–Control Study to Establish Its Role in Diagnosis of Parkinson Disease on 3T MRI

Ruchi Gupta
1   Department of Radiodiagnosis, Indira Gandhi Institute of Medical Sciences, Patna, Bihar, India
Gunjan Kumar
2   Department of Neuromedicine, Patna Medical College and Hospital, Patna, Bihar, India
Subhash Kumar
3   Department of Radiodiagnosis, All India Institute of Medical Sciences, Patna, Bihar, India
Bhaskar Thakur
4   Division of Biostatistics and Epidemiology, Texas Tech Health Science Center, El Paso, Texas, United States
Richa Tiwari
5   Department of Radiodiagnosis, Shaikh-Ul-Hind Maulana Mahmood Hasan Medical College, Saharanpur, Uttar Pradesh, India
Amit Kumar Verma
6   Department of Radiodiagnosis, King George's Medical University, Lucknow, Uttar Pradesh, India
› Author Affiliations
Funding None.


Background and Objectives The loss of swallow tail sign (STS) has been studied for the diagnosis of Parkinson's disease (PD). The study aims to establish the role of STS on high-resolution 3D susceptibility-weighted images (SWI) on 3T MRI in clinically diagnosed cases of PD and compare with control population.

Methods and Materials Forty-five patients with clinically diagnosed PD and Parkinson plus syndrome (PPS) formed the study group and were compared with 45 controls without any neurological disease and normal brain magnetic resonance imaging (MRI). Presence or absence of STS was studied on 1-mm thick axial 3D SWI images in bilateral substantia nigra by two radiologists independently, followed by consensus reading. Bilateral absent, unilateral absent, and faintly present STS were considered as absent STS and predicted PD or PPS, and bilateral presence was considered as a positive STS, and was assessed keeping the clinical diagnosis as the gold standard.

Results The sensitivity of the absent STS was 75.55%, specificity 97.77%, positive predictive value 97.14%, negative predictive value 80% and accuracy 86.66%, in the diagnosis of PD or PPS, with odd ratio of 132 (confidence interval 15.97–1098.75). Kappa coefficient was 0.80 (p < 0.001) for both inter- and intrarater agreement, suggesting high reproducibility for the detection of STS.

Conclusions Absence of the STS is a good predictor of degeneration of the nigrosome 1 in the substantia nigra in the PD or PPS patients; hence, it can act as a useful marker of these diseases.

Publication History

Article published online:
09 February 2022

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