Original Article: Dizziness: Approach to Evaluation and Management

Issue Date: February 1, 2017

See additional reader comments at: https://www.aafp.org/afp/2017/0201/p154.html

To the Editor: I appreciated the thorough discussion of dizziness. In discussing cerebrovascular disease as a cause, the authors did not include subclavian steal. In our rural tribal health center, we have had a handful of cases that presented as vertigo and intermittent disequilibrium. In most cases, the diagnosis was suggested by carotid and vertebral artery Doppler ultrasonography showing reversal of flow and retrograde flow in the vertebral arteries. Follow-up magnetic resonance or computed tomography angiography showed subclavian stenosis. The patients were successfully treated with percutaneous stenting. One patient needed to be stented multiple times and still has difficulty. Furthermore, the cardiologist consulting on the case was falsely reassured by similar blood pressures in both arms, not realizing that the patient had subclavian stenosis bilaterally.

A recent study that followed 232 patients over a decade showed that 16% of patients restenosed and required rest-enting.¹ Symptoms included dizziness, imbalance, visual disturbance, syncope, and upper extremity exertional ischemia.

In Reply: We appreciate Dr. Renwick bringing attention to another central cause of dizziness. In our article, we wanted family physicians to think about more serious causes of dizziness, especially vertebrobasilar ischemia, if a patient had any brainstem symptoms such as diplopia, dysarthria, weakness, or clumsiness. As Dr. Renwick noted, subclavian artery stenosis could be considered in patients with dizziness and symptoms of upper extremity exertional ischemia.

In the study Dr. Renwick cited, the patient's blood pressure was taken in both arms if subclavian artery stenosis was suspected.¹ An interarm difference of 15 mm or greater strongly suggests subclavian artery stenosis. The next diagnostic step would be an imaging study of the subclavian and vertebrobasilar arteries. Significant obstruction can be treated with percutaneous transluminal angioplasty, which may relieve the dizziness.¹