What is Thoracic Outlet Syndrome?

The Thoracic Outlet Syndrome test (TOS) is an examination performed primarily to discriminate between the causes of patient symptoms due to compression at the thoracic outlet. The compression can affect the blood vessels or nerves, and the TOS test is conducted to determine whether the patient symptoms originate from vascular or neurogenic causes.


How to Perform Thoracic Outlet Syndrome Test

This diagnostic vascular TOS procedure tests for intermittent perfusion loss, particularly in the arms and hands. Either Doppler, PVR, or PPG sensors can detect normal resting waveforms in the digits or hands. Then, the patient is instructed through a sequence of positional maneuvers, which include the symptomatic position.


The examination tries to identify a position that significantly reduces perfusion to determine whether the symptoms originate from a vascular disorder. The examination is typically performed in parallel on both the right and left sides.


PPG Sensors
Secondary Method of ABI Assessment


Doppler Probes
Gold Standard ABI Measurement Method

Inflatable Cuffs High quality available in a variety of sizes

Inflatable Cuffs
High quality available in a variety of sizes

Using the Falcon for TOS Assessment

The Falcon is designed with a dedicated TOS protocol to allow a complete and effective diagnosis. The protocol guides both the examiner and the patient through a series of positional maneuvers that are visually presented with schematic pictures for clarity and to avoid mistakes. The range of positions includes maneuvers such as:


  • Hands-up Test,
  • Adson or Scalene Maneuver,
  • Costoclavicular Maneuver,
  • Allen Test,
  • Provocative Elevation Test,
  • And more.

However, additional maneuvers can be added, and the protocol can be easily configured accordingly. The symptomatic position, which is probably the most important maneuver, is also included in the protocol. The examiner can use the Falcon camera to take a picture of the symptomatic position and document it in the protocol and subsequent report.


While standard TOS requires the use of PPG sensors (photoplethysmography sensors), the Falcon also supports a complete range of TOS testing capabilities, including Doppler and PVR measurements. All sensors can be placed for maximal efficiency, for example, on both the right and left digits, and these sites will be measured simultaneously. For even more effective evaluation, up to 5 PPG sensors and 10 PVR waveforms (for each finger) can be measured simultaneously.


The diagnosis of the TOS test is primarily visual. Still, the Falcon also provides a range of quantitative parameters, including PPG and PVR waveform amplitudes and the Doppler parameters range. These quantitative measurements help to support the qualitative findings.

Expected Results

The diagnosis of the TOS test is primarily qualitative in nature. The focus is on viewing the measured waveforms on both the right and left sides for each positional maneuver and determining whether a specific position resulted in an abnormal decrease in amplitude or resulted in signal flattening. Such a case is indicative of a potential decrease in perfusion, suggesting a vascular source of TOS.

An example of a Thoracic Outlet Syndrome examination taken using Viasonix Falcon/PRO system.


Selected Literature


Reporting standards of the Society for Vascular Surgery for thoracic outlet syndromeKarl A. Illig et al.J Vasc Surg 2016;64:e23-e35.


Diagnosis and Treatment of Thoracic Outlet SyndromeEditors Julie Ann Freischlag and Natalia O. Glebova2018 MDPI, Basel, Switzerland


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