Highlights
- Intravenous thrombolysis (IVT) remains a safe and effective first-line approach for isolated vertebral artery occlusion (iVAO), associated with superior early neurological recovery and recanalization compared to conservative care.
- The BRAVO study reveals a paradoxical outcome for endovascular treatment (EVT) in iVAO: despite significantly higher recanalization rates, EVT was associated with worse 3-month functional outcomes and higher rates of early neurological deterioration.
- Safety concerns regarding EVT in this population include a six-fold increase in symptomatic intracerebral hemorrhage (sICH) compared to medical management.
- Patient selection is paramount; subgroup analysis suggests that patients with moderate-to-severe deficits (NIHSS ≥10) may still derive benefit from EVT, whereas those with milder symptoms do not.
Background
Acute ischemic stroke (AIS) involving the posterior circulation accounts for approximately 20% of all ischemic strokes. While basilar artery occlusion (BAO) has been extensively studied—culminating in randomized controlled trials such as ATTENTION and BAOCHE which support endovascular treatment—the optimal management of isolated vertebral artery occlusion (iVAO) has remained a subject of clinical debate. iVAO can present with a wide spectrum of severity, from minor dizziness and ataxia to life-threatening brainstem infarction, depending on collateral flow through the contralateral vertebral artery and the Circle of Willis.
The clinical dilemma centers on whether the high technical success of mechanical thrombectomy in large vessel occlusions translates to clinical benefit in the vertebral artery, or whether the risks of the procedure—including perforator injury and distal embolization—outweigh the potential gains. Until the publication of the BRAVO (Outcomes and Safety of Revascularization Approaches for Stroke Related to Isolated Vertebral Artery Occlusions) study, clinicians relied on retrospective data often confounded by small sample sizes and selection bias.
Key Content
Study Overview and Methodology
The BRAVO study represents a landmark international, multicenter retrospective cohort investigation. Spanning 30 comprehensive stroke centers across Europe, North America, and Asia, the study analyzed 494 patients treated between 2016 and 2022. All patients presented within 24 hours of symptom onset with imaging-confirmed iVAO. To address the inherent biases of a non-randomized study, the investigators utilized Inverse Probability of Treatment Weighting (IPTW) to balance baseline characteristics between treatment groups.
Intravenous Thrombolysis (IVT) vs. Conservative Treatment
Of the total cohort, 218 patients (44%) received IVT-only, while 143 (29%) received conservative treatment (Cx). The analysis of this subgroup provided robust evidence for the safety of thrombolysis in the posterior circulation.
- Early Neurological Improvement: Patients receiving IVT showed significantly greater improvement in NIHSS scores within the first 24 hours compared to those treated conservatively (IPTW-adjusted-β -1, 95% CI -2.05 to 0.05).
- Recanalization: IVT was associated with a more than four-fold increase in the odds of successful recanalization (aOR 4.33, 95% CI 1.36–13.78).
- Long-term Outcomes: While the 3-month mRS shift favored IVT numerically (aOR 1.32), it did not reach statistical significance in the adjusted model, likely due to the generally favorable prognosis of iVAO when collateral circulation is robust.
Endovascular Treatment (EVT) vs. Medical Management (MM)
The most striking findings of the BRAVO study concerned the 133 patients (27%) who underwent EVT (with or without bridge IVT). When compared to medical management (the combined Cx and IVT groups), the results for EVT were unexpectedly unfavorable across several metrics.
- Functional Shift: EVT was associated with an unfavorable shift in the 3-month mRS (aOR 0.51, 95% CI 0.35–0.74). This suggests that for the “average” iVAO patient in this cohort, EVT actually decreased the likelihood of a good functional outcome.
- The Recanalization Paradox: Despite the poor clinical outcomes, EVT was highly effective at opening the vessel, with an odds ratio of 4.64 for recanalization. This dissociation between technical success and clinical benefit is rare in modern stroke trials.
- Safety Signals: The study identified significant safety risks. The rate of early neurological deterioration of ischemic origin was nine times higher in the EVT group (aOR 9.06). Furthermore, the risk of symptomatic intracerebral hemorrhage (sICH) was six times higher (aOR 6.05).
Subgroup Analysis: The NIHSS Threshold
Crucially, the BRAVO investigators performed a subgroup analysis based on stroke severity. A significant interaction (P=0.025) was found between the baseline NIHSS score and the effect of EVT. In patients with an NIHSS score ≥10, the point estimates shifted to favor EVT. This suggests that the risks of EVT may be justifiable in more severe presentations where the natural history of the occlusion is likely to be devastating, whereas in milder cases (NIHSS <10), the procedural risks predominate.
Expert Commentary
The results of the BRAVO study require careful interpretation within the context of posterior circulation anatomy. The vertebral artery is characterized by numerous small, critical perforators supplying the medulla and lower cerebellum. The high rate of early neurological deterioration in the EVT group (9.06 aOR) suggests that mechanical manipulation within the vertebral artery may cause “snow-plowing” of plaque into these perforators or trigger distal embolization into the basilar artery—transforming a relatively stable iVAO into a more severe basilar territory stroke.
Furthermore, the high rate of sICH in the EVT group (6.05 aOR) is a sobering reminder of the fragility of the posterior circulation. Unlike the middle cerebral artery, where large-bore aspiration or stent-retrievers are standardized, the vertebral artery’s tortuosity (particularly the V3 segment) and the potential for underlying intracranial atherosclerotic disease (ICAD) may complicate thrombectomy. In cases of ICAD-related occlusion, standard thrombectomy may cause vessel dissection or require emergent stenting, necessitating potent antiplatelet therapy which further increases hemorrhage risk.
From a guideline perspective, BRAVO reinforces that IVT should be the standard of care for eligible iVAO patients. For EVT, the study suggests a more cautious, individualized approach. Surgeons should perhaps reserve EVT for patients who fail to improve with IVT or those presenting with significant neurological deficits (NIHSS ≥10) where the risk of brainstem infarction is imminent.
Conclusion
The BRAVO study provides a much-needed evidence base for the management of isolated vertebral artery occlusion. It validates the safety and efficacy of intravenous thrombolysis in achieving early recovery. Conversely, it serves as a cautionary tale for endovascular intervention, demonstrating that recanalization does not always equate to clinical success. The high rates of neurological deterioration and sICH following EVT suggest that the procedure should be approached with selective clinical judgment. Future prospective randomized trials are warranted, specifically focusing on the moderate-to-severe stroke population (NIHSS ≥10) to determine if refined techniques or better patient selection can mitigate the risks observed in this retrospective analysis.
References
- Salerno A, et al. Outcomes and Safety of Revascularization Approaches for Stroke Related to Isolated Vertebral Artery Occlusions (BRAVO). Stroke. 2026-03-10. PMID: 41804648.
- Jovin TG, et al. Trial of Thrombectomy 6 to 24 Hours after Stroke. N Engl J Med. 2017;377(23):2211-2221. PMID: 29129157.
- Nogueira RG, et al. Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct. N Engl J Med. 2018;378(1):11-21. PMID: 29129157.