Abstract 107: Endovascular Therapy for Tandem Vertebral and Basilar Artery Occlusion in a Patient with Low NIHSS
Authors: Dammavalam Vikalpa , Nessa Sayedatun , Guido Michael , Wang Jingxin , Fiorella David 
Published: March 2024

Introduction
Basilar artery occlusion (BAO) is a devastating minority stroke subtype with variable clinical presentations and high mortality.1,2 The National Institute of Health Stroke Scale (NIHSS) cutoff for poor outcomes is lower in BAO compared to anterior circulation large vessel occlusions (LVO) due to the scale’s weighted scoring towards cortical signs.3,4 To bridge this gap, Alemseged et.al created the underutilized posterior circulation (PC) NIHSS as an improved stroke assessment tool in PC LVO to better identify endovascular therapy (EVT) candidates. 5 Current randomized trials point to mixed evidence regarding EVT for BAO; although recent studies such as Endovascular Treatment for Acute Basilar Artery Occlusion (ATTENTION)6 and Basilar Artery Occlusion Chinese Endovascular Trial (BAOCHE)7 suggest positive results of EVT within 24hrs. Smaller retrospective subgroup analyses demonstrated EVT for BAO with low NIHSS has good clinical outcome of modified Rankin Scale (mRS) 0‐2 at 3 months in 60‐70% of patients4,8. We present a case of tandem vertebrobasilar artery occlusion in a patient with subacute symptoms and low NIHSS treated with mechanical thrombectomy.

Methods
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Results
41‐year‐old male with past medical history of hypertension, insulin dependent diabetes and active smoking presented with worsening vertigo, nausea and vomiting for 3 weeks with progression to right sided headache and syncope. EMS noted right facial weakness prompting transport to nearest primary stroke center where CT head non‐contrast showed right cerebellar infarct and CT angiogram (CTA) head and neck showed right vertebral artery occlusion with basilar extension. Intravenous thrombolytic (IVT) was deferred due to unclear last known well. He was treated with aspirin 324mg and transferred to our tertiary stroke center. Arrival NIHSS was 1 for right upper extremity ataxia. Premorbid mRS was 0. Repeat CTA redemonstrated right vertebrobasilar artery tandem occlusion. CT perfusion was without mismatch. Patient underwent emergent mechanical thrombectomy with ADAPT to TICI3 revascularization with future plan for possible angioplasty and stenting of R vertebral stenosis. Subsequently admitted to neurocritical care unit and treated with dual antiplatelet therapy. Initially maintained on aspirin and Cangrelor infusion, then transitioned to aspirin and Plavix without hemorrhagic conversion. Diffusion weighted MRI brain showed right cerebellar and right pontine infarcts. Hospital course was complicated by severe intractable hiccups due to area postrema syndrome; ultimately resolved with baclofen and gabapentin after extensive unsuccessful medication trails. NIHSS remained 1 for ataxia throughout admission, although exam also revealed mild unsteady gait requiring home physical therapy and a walker on discharge. Post‐stroke mRS was 1 on discharge; 3‐month mRS is pending.

Conclusion
Evidence regarding EVT for low NIHSS BAO remains varied with some studies showing superior benefit with IVT alone9 while others suggest improved outcomes with EVT in mild to moderate deficits.4,8 One prospective study particularly revealed better outcomes in EVT for BAO due to tandem occlusions similar to this case.10 Given the potential devastating sequalae of BAO and limited overall treatment options, EVT should remain a strong contender for treatment of PC LVO, especially in patients with milder neurologic deficits or tandem occlusions. Additionally, heightened use of PC‐NIHSS may better prognosticate candidates for EVT.