Computed Tomography Angiography in the Diagnosis of Subclavian-Vertebral Artery Steal

Purpose: Computed tomography angiography (CTA) is commonly used in the diagnosis and evaluation of subclavian steal (SS). However, the abnormal manifestations of vertebral artery (VA) in SS on CTA are vastly under-recognized and prone to misdiagnosis. We reported for the first time the abnormal CTA manifestations of VA in SS, and evaluated the value and pitfalls of CTA in the diagnosis of SS, aiming to avoid misdiagnosis and facilitate correct diagnosis of SS using CTA.

Patients and methods: This study retrospectively included 19 patients diagnosed with SS using carotid duplex sonography (CDS) and digital subtraction angiography (DSA) between 2018 and 2022 at a tertiary neurology clinic in Chongqing, China. Their CDS, DSA and CTA results were collected and analyzed. The diagnostic consistency between CTA and DSA in grading subclavian artery stenosis was evaluated, and the CTA manifestations of VA were summarized.

Results: All patients presented subclavian steno-occlusion on the affected side, without steno-occlusion of the contralateral subclavian artery or bilateral VA on DSA. A high concordance was observed between CTA and DSA in grading subclavian artery stenosis (Kappa = 0.825, P = 0.000). However, only 26.3% of patients presented normal VA on CTA, whereas 73.7% of patients presented shallow VA ipsilateral to subclavian steno-occlusion. A 28.6% of patients with shallow VA were misdiagnosed as having vertebral arteriopathy. The presence of shallow VA had no significant correlation with age, gender, severity of subclavian artery stenosis, diameter of VA or model of CT scanner (all P>0.05). Although not statistically significant, the incidence of shallow VA increased with higher SS grade.

Conclusion: Carotid CTA is highly accurate for diagnosing subclavian steno-occlusion, whereas shallow VA is the pitfall of CTA in diagnosing SS. It is important to improve the recognition of shallow VA to avoid misdiagnosis.