Swallow Tail Sign: MRI Test for Parkinson's Disease
Author: University of Nottingham
Published: 30 Apr 2014 - Updated: 13 Nov 2026
Publication Details: Peer-Reviewed | Informative
Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content
Synopsis
This research, a peer-reviewed study published in PLOS ONE by neuroradiologists at the University of Nottingham and Nottingham University Hospitals NHS Trust, describes a simple MRI sign that can help diagnose Parkinson's disease. In healthy brains, a small structure in the substantia nigra called nigrosome 1 appears on high resolution 3T MRI scans in a shape resembling a swallow's tail, and in Parkinson's disease this appearance is lost. Reviewing 114 scans, the team made an accurate diagnosis in 94 percent of cases. Because 3T MRI is standard hospital equipment, uses no ionizing radiation and costs far less than nuclear medicine tests, the finding could make early and uncertain cases of Parkinson's easier and safer to confirm.*
At a Glance
- 1 - The swallow tail sign is absent in Parkinson's disease.
- 2 - The idea came from earlier work using ultra high field 7T MRI scanners.
- 3 - Parkinson's is often diagnosed from symptoms such as stiffness and tremor alone.
- 4 - Before this, imaging to confirm uncertain cases relied on expensive nuclear medicine scans that expose patients to radiation.
Topic Definition
- Swallow Tail Sign
The swallow tail sign is the normal appearance of nigrosome 1, a small cluster of dopamine-producing cells in the substantia nigra of the brain, on susceptibility-weighted MRI scans. In healthy people it looks like the split tail of a swallow, while in Parkinson's disease and related conditions it is usually lost because of iron buildup and cell loss. Its absence is used as a supporting sign in the diagnosis of Parkinson's disease.
Overview
The image, which depicts the healthy state of a group of cells in the sub-region of the human brain, was singled out using 3T MRI scanning technology - standard equipment in clinical settings today.
The research was led by Dr Stefan Schwarz and Professor Dorothee Auer, experts in neuro-radiology in the School of Medicine at The University of Nottingham and was carried out at the Queen's Medical Center in collaboration with Dr Nin Bajaj, an expert in Movement Disorder Diseases at the Nottingham University Hospitals NHS Trust.
The findings have been published in the open access academic journal PLOS ONE.
The work builds on a successful collaboration with Professor Penny Gowland at the Sir Peter Mansfield Magnetic Resonance Center at The University of Nottingham.
'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' - describes how the absence of this imaging sign can help to diagnose Parkinson's disease using standard clinical Magnetic Resonance Scanners.
Parkinson's disease is a progressive neurodegenerative disorder which destroys brain cells that control movement. At the time of the study, around 127,000 people in the UK had the disease. Currently there is no cure but drugs and treatments can be taken to manage the symptoms.
The challenges of diagnosing Parkinson's
Until now diagnosing Parkinson's in clinically uncertain cases has been limited to expensive nuclear medical techniques. The diagnosis can be challenging early in the course of the condition and in tremor dominant cases. Other non-licensed diagnostic techniques offer a varying range of accuracy, repeatability and reliability but none of them have demonstrated the required accuracy and ease of use to allow translation into standard clinical practice.
Using high resolution, ultra high field 7T magnetic resonance imaging the Nottingham research team has already pinpointed the characteristic pathology of Parkinson's with structural change in a small area of the mid brain known as the substantia nigra. The latest study has shown that these changes can also be detected using 3T MRI technology which is accessible in hospitals across the country. They subsequently coined the phrase the 'swallow tail appearance' as an easily recognizable sign of the healthy appearing substantia nigra which is lost in Parkinson's disease. A total of 114 high-resolution scans were reviewed and in 94 percent of cases the diagnosis was accurately made using this technique.
New Findings Give New Hope
Dr Schwarz said:
"This is a breakthrough finding as currently Parkinson's disease is mostly diagnosed by identifying symptoms like stiffness and tremor. Imaging tests to confirm the diagnosis are limited to expensive nuclear medical techniques which are not widely available and associated with potentially harmful ionizing radiation.
"Using Magnetic Resonance Imaging (no ionizing radiation involved and much cheaper than nuclear medical techniques) we identified a specific imaging feature which has great similarity to a tail of a swallow and therefore decided to call it the 'swallow tail sign'. This sign is absent in Parkinson's disease."
The research was funded by The University of Nottingham, the Sarah Matheson Trust, and the Medical Research Council. Dr Schwarz's Academic Clinical Lectureship is funded by the National Institute for Health Research UK. The funders had no role in study design, data collection and analysis.
Image of scan courtesy of Dr Stefan Schwarz - Swallow images courtesy of the RSPB.
Frequently Asked Questions
NOTE: Researched FAQs by Disabled World (DW)
Can an MRI scan diagnose Parkinson's disease on its own?
No. Parkinson's is still diagnosed mainly by a neurologist's examination. MRI signs such as the swallow tail sign support the diagnosis and help rule out other causes.
What is the substantia nigra?
The substantia nigra is a small area in the midbrain that contains dopamine-producing nerve cells. Loss of these cells causes the movement symptoms of Parkinson's disease.
What is a DaTscan?
A DaTscan is a nuclear medicine scan that uses a small amount of radioactive tracer to show dopamine activity in the brain. It is often used when a Parkinson's diagnosis is unclear.
Is the swallow tail sign also lost in other conditions?
Yes. It can also be absent in related disorders such as multiple system atrophy, progressive supranuclear palsy and dementia with Lewy bodies.
What does 3T mean on an MRI scanner?
The T stands for tesla, a measure of magnetic field strength. A 3T scanner is twice as strong as a 1.5T scanner and gives more detailed images.
What are the early signs of Parkinson's disease?
Early signs can include a slight tremor, smaller handwriting, stiffness, slower movement, a softer voice, loss of smell and acting out dreams during sleep.
Is an MRI safe for people with Parkinson's?
MRI uses no ionizing radiation and is safe for most people, but those with some implants, such as older deep brain stimulators or pacemakers, need special checks first.
Can Parkinson's disease be cured?
There is no cure yet, but medications, exercise, therapy and treatments such as deep brain stimulation can control symptoms for many years.
Insights, Analysis, and Developments
Editorial Note: Diagnosing Parkinson's disease early or in unclear cases has long depended on clinical judgment and costly nuclear scans that many hospitals cannot offer. A sign that can be read on a standard MRI scanner could make confirmation faster, cheaper and safer, and could also help separate Parkinson's from conditions that look similar, such as essential tremor. Since this study, other research teams have tested the swallow tail sign, and it is now used as a supporting tool by some neuroradiologists. It does not replace a neurologist's examination, but it gives patients and doctors one more piece of reliable evidence.*
Attribution/Source(s): This peer-reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally issued as a press release by University of Nottingham and published on 30 Apr 2014. Last updated on 13 Nov 2026. This content may have been edited for style, clarity, or brevity.
* Editorial additions by Ian C. Langtree.