A recent research publication in PLoS ONE has described a new 3T MRI sign of Parkinson disease known as the 'absent swallow tail sign'. The discovery, which has the potential to revolutionise the diagnosis of this important disease, uses axial high resolution susceptibility weighted imaging (SWI) to assess the structure of the substantia nigra within the midbrain. 

In healthy individuals, a linear or comma shaped region within the substantia nigra known as nigrosome-1 returns high SWI signal. This nigrosome is bordered anteriorly, laterally and medially by low signal structures which produce a distinct likeness to the split tail of a swallow (Figure 1, Figure 1A - healthy subject).  

In Parkinson disease, the high SWI signal within nigrosome-1 is lost and the normal 'swallow tail sign' cannot be identified (Figure 1B - Parkinson disease). The researchers found that absence of the swallow tail sign had a diagnostic accuracy of greater than 90% for Parkinson disease.

You can read more in the original publication here. As always, please let us know your thoughts in the comments section. Do you think this diagnostic sign is going to translate into clinical practice? Should high resolution SWI imaging of the midbrain be standard in the MRI assessment of Parkinson disease? 

Dr Andrew Dixon is a Radiologist at the Alfred Hospital in Melbourne, Australia. He is a managing editor for Radiopaedia.org and has interests in neuroradiology and the use of technology and social media to disseminate medical knowledge. 

Reference: Schwarz ST, Afzal M, Morgan PS et-al. The 'swallow tail' appearance of the healthy nigrosome - a new accurate test of Parkinson's disease: a case-control and retrospective cross-sectional MRI study at 3T. PLoS ONE. 2014;9 (4): e93814. Image adapted under creative commons license 3.0.

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  • No photo
    pirouz pirouzi22nd Oct 2014 07:34 UTC

    This is great, thanks for sharing.
    and absolutely yes, high resolution images such this one should be included in standard brain MRI studies.

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    Ashley30th Oct 2014 18:29 UTC

    #MRI is poised to reach approximately $5.24 billion by 2018 at a #CAGR of 4.56%, Get more details at http://bit.ly/1oQMN5V

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    Maureen stewart19th Sep 2018 13:21 UTC

    I was diagnosed 2 years ago at age 63. Symptoms were tremor in right leg, loss of handwriting ability, and soft voice. I also have difficulty rising from a seated position and have balance issues. I started out taking only Azilect, then Mirapex, and 6 months ago Sinemet. Several months ago I started falling frequently, hence the reason for Sinemet. I tried every shots available but nothing worked. In June 2018, my neurologist and I decided to go with natural treatment and was introduced to Natural Herbal Gardens natural organic Parkinson’s Herbal formula, i had a total decline of symptoms with this treatment, the Tremor, falling frequently, stiffness, body weakness, balance issues, depression and others has subsided. Visit Natural Herbal Gardens official website ww w. naturalherbalgardens. com. This treatment is a breakthrough for all suffering from Parkinson’s, don’t give up Hope. Keep Sharing the Awareness, herbs are truly gift from God.

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