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Head and Neck, MRI, Ultrasound, Unknown Cases, Vascular

Solution to Unknown Case # 6 – Subclavian Steal Syndrome

History: 60 year old female with arm pain. 

Subclavian Steal Syndrome: Doppler ultrasound of the right vertebral artery with spectral waveform shows that flow is in the proper direction away from the transducer (orange color) and towards the patients head ("P" indicator at the top left of the grayscale image)

Subclavian Steal Syndrome: Doppler ultrasound of the right vertebral artery with spectral waveform shows that flow is in the proper direction away from the transducer (orange color) and towards the patients head (“P” indicator at the top left of the grayscale image). Note the elevated velocity in the right vertebral artery.

Subclavian Steal Syndrome: Doppler ultrasound of the left vertebral artery with spectral waveform and velocities shows flow abnormally going away from the transducer (blue color) and the patients head ("P" indicator at the top left of the image). This is a complete subclavian steal.

Subclavian Steal Syndrome: Doppler ultrasound of the left vertebral artery with spectral waveform shows flow abnormally going away from the transducer (blue color) and the patients head (“P” indicator at the top left of the image). This is a complete subclavian steal.

Oblique MR angiogram of the neck vessels shows no flow through the proximal left subclavian artery (between the red arrows). Flow is maintained in distal portions of the left subclavian artery, likely from reversal of flow through the left vertebral artery.

Subclavian Steal Syndrome: Oblique MR angiogram of the neck vessels shows no flow through the proximal left subclavian artery (between the red arrows). Flow is maintained in distal portions of the left subclavian artery, likely from reversal of flow through the left vertebral artery.

This is a case of subclavian steal syndrome. Subclavian steal syndrome occurs when there is an occluded subclavian artery and collateral blood flow to the distal subclavian artery and arm is provided by reversed flow in the ipsilateral vertebral artery. As seen in the MR angiogram image above, this was due to occlusion of the proximal left subclavian artery. Usually subcalvian steal is asymptomatic, however, when symptoms do occur they usually manifest as exertional arm pain.

Subclavian steal syndrome is diagnosed on ultrasound by documenting reversal of flow in the vertebral artery, and sometimes with elevated velocity (about >60 cm/sec) in the contralateral vertebral artery. Subclavian steal syndrome can be classified on spectral Doppler ultrasound as mild (slight decreased peak systolic velocity), moderate (alternating biphasic flow, in which provocative maneuvers can cause complete reversal), and complete (no forward systolic velocity towards the head).

It is essential to know the positioning of the transducer and the color scheme chosen by the sonographer, as this can be variable. Traditionally orange/red is towards the transducer and blue is away from the transducer, however as you can see in the images above this can be changed by the sonographer. This is why it is important to look at the directional velocity (the “+” and “-” signs on the scale in the top right of the ultrasound images) and the orientation of the transducer. In the first image above, the transducer is oriented pointing towards the patient’s head, thus flow away from the transducer (in the negative “-” direction) is normal (also note, the spectral waveform can be flipped). In the second ultrasound image above, the transducer is oriented towards the patients feet, and flow is going away from the transducer (in the negative “-” direction again), and this is abnormal. It can get confusing at times!

See an article here about internal thoracic artery doppler in patients with subclavian steal syndrome.

Read about an occluded internal carotid artery here and understand the “string sign” for diagnosing near complete occlusions.

Thanks to Paul Murphy, M.D., Ph.D. for these beautiful images!

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About radiologypics

I am a radiology physician from California, USA.

Discussion

One thought on “Solution to Unknown Case # 6 – Subclavian Steal Syndrome

  1. could you simply explain this to me that I can understand.Cerebrovascular Accident Posterior circulation CVA. Thank You!

    Posted by julie caissie | May 4, 2016, 4:44 pm

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