Abstract 1122‐000027: Bilateral Vertebral Artery Occlusion and Involvement of the Posterior Circulation
Authors: Tong Brian A , Giurgiutiu Dan‐Victor 
Published: December 2021

Introduction
: Rationale: Bilateral vertebral artery occlusion with collateral reconstitution is a rare finding. Compared to patients with acute occlusion, symptom progression may be much slower [1]. Atherosclerotic risk factors lead to occlusion, including hypertension and hyperlipidemia, but it is unclear what leads to collateral reconstitution [2]. These patients may have collateral circulation from anterior and posterior circulation sources that are well developed [1] [2]. Sufficient collateral flow correlates with lower rates of hemorrhagic transformation following recanalization [3] [4]. However, given the risk of spontaneous hemorrhage from microvascular collaterals, the hemorrhagic risk associated with thrombolytic therapy in patients with moyamoya collaterals, due to the fragility of these vessels [5], must be balanced with the benefit of therapy in the presence of severe neurologic deficits along with the mortality and morbidity that may stem from the occlusion.

Patient concerns: 67 year old Caucasian male with past medical history of coronary artery disease, abdominal aortic aneurysm, hypertension, history of tobacco use and type 2 diabetes mellitus presents with acute right‐sided weakness.

Methods
: Diagnoses: On admission, CTA Head and Neck suggested chronic total occlusion of bilateral V4 segments from their origin to the midportion with tandem bilateral high‐grade stenoses throughout the imaged distal V2 and V3 segments bilaterally. MRI could not be obtained because of old lumbar fusion spinal hardware. Cerebral angiography showed microvascular reconstitution, analogous to moyamoya, with slow mid basilar flow, which could be either due to occlusion or competitive flow from top of the basilar collaterals.

Interventions: Patient received intra‐arterial integrilin and tPA thrombolysis with TICI 1 reperfusion.

Results
: Outcomes: Patient presented with NIHSS 18 notable for right sided weakness (2/5 strength in his right upper extremity and 1/5 strength in RLE), bilateral hemianopia, severe dysarthria and right gaze preference. Patient had significant improvement in his exam the next day following thrombolysis. Notably, patient had 5/5 strength in his right upper and right lower extremities compared to his strength on presentation. Repeat head CT on the following day after thrombolysis showed left pontine infarct. Repeat NIHSS was 3 at 24 hours for partial hemianopia, minor nasolabial flattening and mild dysarthria.

Conclusions
: Conclusion: Bilateral intracranial vertebral artery stenosis and occlusion commonly occurs distal to PICA and near the vertebrobasilar junction [2]. Proximal (specifically areas supplied by PICA) and distal territories within the posterior circulation are often infarcted [2], which can yield a unique exam upon presentation that can help accurately guide diagnosis and treatment when appropriately recognized. The involvement of collateral circulation can play a crucial role in patients undergoing endovascular revascularization therapy [6]. In the setting of bilateral vertebral occlusion with microvascular reconstitution, patients can still undergo catheter based thrombolysis, but not thrombectomy.