Management of tandem occlusions in acute ischaemic stroke

Intra- and extracranial tandem occlusions (TOCs) in acute ischaemic stroke (AIS) are defined by the coexistence of an intracranial anterior or posterior circulation large vessel occlusion together with an ipsilateral extracranial occlusion or significant stenosis in the corresponding proximal vascular axis. They represent a distinct subgroup of AIS requiring tailored diagnostic and therapeutic strategies and are commonly divided into anterior (ATOCs) and posterior (PTOCs) forms. This narrative review synthesises the current evidence base regarding diagnosis, management (medical and interventional) and prognosis of TOCs. ATOCs account for around 20% of anterior circulation large-vessel occlusions, while PTOCs appear proportionally more frequent in posterior circulation stroke. Atherosclerosis is the predominant mechanism (around 70%), followed by arterial dissection (around 20%-25%), with cardioembolism and rarer causes playing a smaller role. Diagnosis can be challenging, particularly due to pitfalls such as carotid pseudo-occlusion. Endovascular thrombectomy (EVT) is the cornerstone of treatment for TOCs. In ATOCs, emerging evidence suggests that emergent carotid artery stenting improves outcomes in selected patients, with large observational cohorts such as CERES-TANDEM reporting higher functional independence without increased bleeding risk. In PTOCs, EVT is feasible and technically effective, but evidence remains limited. Vertebral stenting may be beneficial in selected cases, though morbidity and mortality remain high. Periprocedural antithrombotic therapy varies widely between centres, and high-quality data are lacking. Bridging therapy with intravenous thrombolysis appears safe and should be performed in eligible patients with tandem lesions. Prognosis has improved substantially for patients with ATOCs in the EVT era, whereas outcomes in PTOCs are less well defined. Continued efforts to generate higher-quality evidence, particularly for PTOCs, will be essential to guide treatment strategies and improve patient outcomes.