A Rare Vascular Cause of Left Arm Pain and Numbness In A 30 Year-Old

A 30 year-old woman with three weeks of numbness and tingling in her left arm underwent an arterial ultrasound that showed recent thrombosis/occlusion of the radial and ulnar arteries. She described blanching of her raised hand, which occurred while washing her hair. Interestingly, she also had a longer-standing history of several years of neck pain and left arm pain, numbness and tingling.

A vascular surgeon then performed surgery (open embolectomy) to remove the blood clots in her arteries and restore blood flow to her hand. A CT scan of the neck and upper chest was also obtained which showed a cervical rib, an aneurysm of the left subclavian artery, and a false joint (or pseudarthrosis) of the C7 rib where it meets with the 1st thoracic rib.

The course of events and clinical and anatomic findings may seem straightforward as I’ve described them. But the long-standing symptoms may have contributed to the length of time that the underlying anatomic abnormalities went undiagnosed by creating a difficulty for the physicians who had previously seen her. They had evaluated her for musculoskeletal or nerve-related abnormalities. Those diagnostic evaluations were unsuccessful in yielding the true nature of her ailment until the arterial ultrasound was performed and interpreted by this vascular radiologist. She will still need definitive therapy, constituting surgical resection of the abnormal rib to remove the extrinsic compression on the subclavian artery and eliminate the potential for further vascular problems.

3-D CT rendering of a left C7 cervical rib

3-D CT rendering of a left C7 cervical rib

Cervical rib depicted as anatomical cartoons, also demonstrating the relationships to adjacent nerves and the subclavian artery, which are displaced anteriorly.

Cervical rib depicted as anatomical cartoons, also demonstrating the relationships to adjacent nerves and the subclavian artery, which are displaced anteriorly.

From Wikipedia:

“A cervical rib is a rare congenital abnormality where a rib arises from the seventh cervical vertebra. A cervical rib is estimated to occur in 0.5% of the population, 66% are bilateral, and are twice as common in females as in males.

Most cases of cervical ribs are not clinically relevant and do not have symptoms; cervical ribs are generally discovered incidentally. However, they may cause problems such as brachial plexopathy or thoracic outlet syndrome, because of pressure on the nerves or subclavian artery, respectively.

A cervical rib represents a persistent ossification of the C7 lateral costal element. During early development, this ossified costal element typically becomes re-absorbed. Failure of this process results in a variably elongated transverse process or complete rib that can be anteriorly fused with the T1 first rib below.

The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the lower trunk of the subclavian artery. These structures become encroached upon by the cervical rib and scalene muscles. Aneurysm formation can occur, followed by distal embolization if not earlier identified and treated.

Compression of the brachial plexus may be identified by weakness of the muscles around the muscles in the hand, near the base of the thumb. Compression of the subclavian artery is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder. A positive Adson's sign is non-specific for the presence of a cervical rib, however, as many individuals without a cervical rib will have a positive test.”

The importance of the above vignette and discussion is that some abnormalities are difficult to identify. Often, the appropriate specialists, in this case a vascular/interventional radiologist, are needed to identify the underlying abnormalities, and a vascular surgeon and a cardiothoracic surgeon are needed to treat them. With a coordinated team approach to health care, the highest quality of care can be delivered and patients will have the best chance at prompt diagnoses and treatments.