Brain Response Characteristics Associated with Subclavian Steal Phenomenon

BackgroundChronic, repetitive, and sublethal hypoperfusion by intra- or extracranial artery stenosis promotes collateral development and conditions the brain toward preventing subsequent lethal ischemia, although these latent properties have rarely been demonstrated in the clinical setting. This study assessed the previously unexplored role of subclavian steal syndrome (SSS) on inciting and protecting brain damage.MethodsWe enrolled patients diagnosed with SSS associated with subclavian artery stenosis. Subclavian steal was determined by transcranial Doppler and/or digital subtraction angiography. We analyzed the prevalences and predictors of posterior ischemic symptoms and infarcts in SSS patients and also investigated individual cases to demonstrate a clinical evidence of brain conditioning, focusing on cytotoxic and vasogenic edema.ResultsOf 54 SSS patients, 36 (66.7%) had been asymptomatic and incidentally diagnosed with SSS, whereas 18 (33.3%) patients had presented with posterior ischemic symptoms. Symptoms and infarcts including old silent lesions occurred more frequently as unstable hemodynamics of the anterior circulation were combined. Of 18 symptomatic patients, 13 patients (72.2%) had transient ischemic attack and 5 (27.8%) patients had an infarct in the posterior circulation territory. Four patients with cytotoxic edema had mild neurologic deficits and rapid and complete recovery, whereas 1 patient had prolonged, severe vasogenic edema after acute hypertension.ConclusionsAlthough we noted low rates of disabling or fatal strokes in patients with SSS, a variety of vascular and neural factors beyond severity of subclavian steal could influence the likelihood of brain damage.