General Description

Although strokes to the posterior circulation territory are less frequent than those to the anterior circulation, they represent an important opportunity for intervention that can be complex because of anatomical limitations as well as a lack of devices designed specifically with these limitations in mind. Often treatment of these lesions requires flexibility and creativity to achieve adequate revascularization.

Indications

Despite that posterior circulation strokes have limited clinical trials data, compared to those of the anterior circulation, many feel that thrombectomy, in particular, for basilar occlusion, is strongly indicated because of the catastrophic consequences of untreated basilar artery strokes. We routinely treat posterior circulation strokes with mechanical thrombectomy in patients who present with clinical and imaging evidence of large vessel occlusion (vertebral, basilar, CSAs, or PCAs), a National Institutes of Health Stroke Scale (NIHSS) > 5, and lack clear evidence of brainstem infarction.

Neuroendovascular Anatomy and Imaging Evaluation

The paired vertebral arteries arise from the bilateral subclavian arteries. Obtaining adequate computed tomography angiogram imaging from the arch to the vertex is important in patients with potential for posterior circulation strokes for two reasons. First, one of the most common sources of emboli to the posterior circulation is vertebral origin stenosis, so it is useful to understand whether stenting or angioplasty might be needed en route to thrombectomy. Second, anatomy is variable in several domains, including dominance of the vertebral arteries and the location and angularity of the vertebral artery origin, all of which should be considered when evaluating whether to proceed with a transfemoral or transradial approach for access to the target vessel. The vertebral arteries join after entering the intracranial space to form the basilar artery that runs anterior to the brainstem. The basilar artery gives rise to several arteries, but for the purposes of thrombectomy, the important arteries to evaluate are the superior cerebellar arteries (SCAs) and posterior cerebral arteries (PCAs). Importantly, one must evaluate patency and relative contributions through the posterior communicating arteries to understand which vessels one expects to be patent, atretic, or occluded by thrombus. One final anatomical consideration is that in many patients, the vertebral artery is not large enough to safely accommodate a triaxial system, so measuring vessels and planning the treatment approach accordingly is vital.

Specific Technique and Key Steps

1. 
   

   Review the noninvasive imaging studies to identify the best access route and laterality of approach.

   
   
2. 
   

   Usually, a biaxial system is all that can be accommodated by the vertebral arteries. In this case, the femoral or radial artery access is obtained that allows the most direct access to the vertebral artery of interest.

   
   
3. 
   

   A Benchmark (Penumbra) or similar 6 French (F) distal access catheter is advanced over a Berenstein (Cook Medical) or Simmons select (Cordis) catheter and 0.035-inch angled Glidewire (Terumo) to access the origin of the vertebral artery ( Fig. 19.1–19.3, Video 19.1–19.3 ).

   
   
4. 
   

   Distal wire access is obtained, often extending to the level of the C1 vertebra; and the guide catheter is advanced as far as can easily be performed, after which the wire is withdrawn.

   
   
5. 
   

   The microsystem, consisting of the microcatheter (either for stent delivery or distal aspiration) and 0.014-inch J-shaped microwire, is advanced into the basilar artery ( Video 19.1–19.3 ).

   
   
6. 
   

   If possible, the guide catheter may be advanced over the microsystem to improve distal support and provide the possibility of aspiration through the guide catheter.

   
   
7. 
   

   The microwire is advanced to the clot face (for a direct aspiration first pass technique, ADAPT) or crosses the clot in a J fashion (for use of a stent retriever) and the microcatheter is advanced into position ( Video 19.1–19.3 ).

   
   
8. 
   

   For a stent retriever procedure, the wire is withdrawn and 3 cc of 100% contrast material is used to obtain an angiographic run documenting that the clot is completely crossed, and that the catheter is within the vessel lumen ( Fig. 19.1–19.3, Video 19.1–19.3 ). The stentriever is then deployed using standard techniques (see Chapter 17).

   
   
9. 
   

   For aspiration alone, the microcatheter is advanced to the clot face, engaged in the clot, and withdrawn using standard techniques (see Chapter 16).

   
   
10. 
    

    Standard thrombectomy techniques apply (see Chapters 16 and 17), with the main difference being that intermediate catheters are rarely used, so it is crucial to ensure back bleeding from the guide catheter after removal of the retrieval device because, in this case, the likelihood of clot fragments lodging in the guide is higher ( Fig. 19.1–19.3, Video 19.1–19.3 ).

    
    
11. 
    

    Follow-up runs are obtained through the guide catheter.

    
    
12. 
    

    Once adequate revascularization has been obtained, the guide is withdrawn into the cervical vertebral artery and completion runs are obtained.

    
    
13. 
    

    The guide is withdrawn, and the access point is closed.

Device Selection

• 
  

  6F short femoral or radial sheath.

  
  
• 
  

  Benchmark or similar 6F distal access system with Berenstein select catheter.

  
  
• 
  

  0.035-inch angled Glidewire.

  
  
• 
  

  3MAX (Penumbra) or similar aspiration catheter.

  
  
• 
  

  Velocity (Penumbra) or similar microcatheter for stent retriever.

  
  
• 
  

  0.014-inch microwire (Synchro 2, Stryker).

Pearls

• 
  

  For difficult clots within large vertebral arteries, the use of triaxial systems may be an option. In such cases, the guide catheter is placed within the distal cervical vertebral artery and the aspiration microcatheter is advanced from that position, as is typically done for anterior circulation stroke interventions.

  
  
• 
  

  Radial access with triaxial systems is most safely achieved using sheathless guide catheter placement ( Fig. 19.3, Video 19.3 ). The 6F sheath is placed, after which an exchange length wire is advanced into the arch; the sheath is exchanged out; and a guide catheter, such as the Neuron MAX (Penumbra) or Infinity (Medtronic), without a sheath, is advanced with the introducer into the arch.

  
  
• 
  

  Aspirating from the guide catheter helps to reduce the risk of distal emboli, even if the guide catheter cannot be engaged directly in the clot face.

Case Overview: CASE 19.1 Acute Basilar Artery Occlusion: Solumbra Technique

• 
  

  A 82-year-old female was brought to the emergency department after sudden lost of consciousness. On arrival, she was unresponsive, eyes closed, pupils 3 mm symmetric but sluggishly reactive to light, with sixth cranial nerve palsy and localizing to pain stimulation bilaterally. Her initial National Institutes of Health Stroke Scale score (NIHSS) was 21. She has a past medical history of hypertension, diabetes, and atrial fibrillation. She recently stopped coumadin because of hip fracture that required surgery. Patient received tissue plasminogen activator (tPA) with no improvement.

  
  
• 
  

  Computed tomography (CT) was normal. CT angiography demonstrated basilar artery (BA) occlusion. CT perfusion showed increased time-to-peak with preserved volume on posterior circulation territory.

Related posts:

17 Anterior Circulation Aspiration-Only Mechanical Thrombectomy (ADAPT) 20 Mechanical Thrombectomy with Intracranial Stenting/Angioplasty 21 Anterior Circulation Mechanical Thrombectomy with Extracranial Stenting/Angioplasty 22 Intracranial Atherosclerotic Disease—Intracranial Angioplasty 18 Anterior Circulation Mechanical Thrombectomy with a Stent Retriever 38 Embolization of Carotid Body Tumors

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