Presentation
Tingling and numbness of the right arm with motor weakness of the hand muscles.
Patient Data
Bulky brachial plexus trunks showing interstitial edema of the surrounding fat. The middle scalene muscle shows a tapering posteroinferior end denoting medialized insertion into the 1st rib. The subclavian artery shows a normal wave pattern in the neutral position.
However, on raising the patient's arm above the head with the face to the contralateral side, the waveform displays a sharp systolic upstroke (staccato wave) with increased peak systolic velocity (nearly doubled) denoting significant stenosis. The left side shows a normal caliber of the brachial plexus trunks compared to the affected right side.
Annotated figure of the anatomy of the right scalene triangle:
middle scalene muscle (note the tapering posteroinferior end denoting medialized insertion of the muscle)
Case Discussion
Thoracic outlet syndrome occurs due to the compression of the nerves or vascular structures of the thoracic outlet. Neurogenic thoracic outlet syndrome accounts for the majority of the cases. This is a case of a patient diagnosed with brachial plexopathy. Thoracic outlet syndrome was suspected clinically and based on the nerve conduction study. Ultrasound showed signs of both neurogenic and vascular compression.
This case also highlights the importance of sonography as a readily available non-invasive tool in the diagnosis. Sonographic signs of neurogenic thoracic outlet syndrome include the bulky size of the brachial plexus trunks compared to the contralateral side and the wedge-sickle sign (medialized insertion of the middle scalene muscle).
In the vascular thoracic outlet syndrome, the subclavian artery may show Doppler signs of turbulence at the site of compression and tardus parvus flow distal to it during stress test.
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