Endovascular revascularization of symptomatic chronic middle cerebral artery occlusions: Two case reports

Abstract

For patients with chronic middle cerebral artery occlusions who have recurrent ischemic symptoms despite antiplatelet therapy and vascular risk factor control, treatment options are limited. Because of concerns about the safety of endovascular revascularization of these occlusions and the technical skills required, these procedures have not been widely performed. We report on two patients with successful endovascular revascularization of the chronic middle cerebral artery occlusion with impaired cerebral hemodynamics, with vessel patency maintained on follow-up imaging and no recurrence of stroke. A literature review of treatment options for such patients was performed. Revascularization is technically feasible and can be considered an option for carefully selected chronic middle cerebral artery occlusion patients with recurrent ischemic symptoms despite medical therapy.

Introduction

For many patients with symptomatic chronic middle cerebral artery (MCA) occlusion, only medical therapy was offered because of the risk of intervention. However, a small proportion of these patients had poor collaterals and had recurrent symptoms despite medical treatment.¹ Treatment options for this subgroup of patients have not been well established. Extracranial-intracranial arterial bypass is one option, but its efficacy has yet to be conclusively demonstrated in large studies even for patients with hemodynamic compromise.² With the advent of improved endovascular devices and operators’ experience, angioplasty and stenting can be considered as a treatment alternative. We hereby report on two cases of symptomatic chronic MCA occlusion treated successfully by endovascular means.

Case report

Patient 1

A 54-year-old male patient with a history of hypertension and smoking presented with a three-month history of recurrent dysarthria and right-side weakness. He first presented in March 2013 with 10 minutes of dysarthria. Magnetic resonance imaging (MRI) showed no ischemic changes. Magnetic resonance angiography (MRA) showed severe stenosis of the left MCA M1 segment. Two months later, he developed another episode of dysarthria with right-side weakness. MRI fluid-attenuated inversion recovery (FLAIR) imaging showed T2 hyperintensity over the left basal ganglia and corona radiata. Computer tomography angiography (CTA) showed severe left MCA M1 stenosis. The patient was put on dual aspirin and clopidogrel therapy and statins, and his blood pressure was kept below 140/90 mmHg. He had complete motor recovery with mild residual dysarthria. In June 2013, he developed another episode of transient ischemic attack (TIA) of right-side weakness lasting for minutes and was admitted to our hospital. MRI FLAIR did not show any new lesion. Computed tomography perfusion (CTP) showed hypoperfusion over the left fronto-temporo-parietal region. Digital subtraction angiogram (DSA) showed left MCA M1 occlusion, with partial collateral flow from the left anterior cerebral artery and left posterior cerebral artery leptomeningeal branches (Figure 1(a)). The patient refused open bypass surgery and opted for endovascular therapy, which was performed in July 2013. Under general anesthesia and systemic heparinization, with activated clotting time (ACT) aiming for a range of 250–300 seconds, the left MCA occlusion was crossed by a 205 cm 0.014-inch Transend microwire (Stryker, USA) and an Excelsior SL-10 microcatheter (Stryker, USA). Selective injection via the microcatheter showed satisfactory opacification of distal vessels (Figure 1(b)). An exchange length 0.014-inch Transend microwire was advanced to the left M3 segment under a superselective roadmap, and the microcatheter was withdrawn. The diameter of the vessel at the proximal end of the occlusion measured 2.0 mm, and the occlusion measured 7 mm in length. A 2.0 mm × 10 mm Gateway balloon (Stryker, USA) was inflated with 8 atmospheric pressure (atm) at the site of occlusion. Post-angioplasty angiogram showed flow restoration past the occluded segment and good perfusion of the left MCA territory (Thrombolysis in Cerebral Infarction (TICI) grade 3), so stenting was not performed (Figure 1(c)). Postoperatively, blood pressure was maintained at 100–120/60–80 mmHg. Subcutaneous low-molecular-weight-heparin was given for three days, clopidogrel continued for three months and aspirin was given long term. The patient did not have any recurrence of TIAs or stroke during a 24-month follow-up period. Follow-up CTA showed good left MCA opacification.

Figure 1.

(a) Angiography showed left M1 occlusion; (b) Selective injection via the microcatheter showed satisfactory distal vessels opacification; (c) post-angioplasty angiogram showed a patent left middle cerebral artery (MCA) with good distal perfusion.

Patient 2

A 58-year-old male patient with a history of hypertension and smoking presented with dysarthria and right-side weakness in July 2013. Diffusion weighted imaging (DWI) showed left fronto-parieto-temporal hyperintensities. MRA showed severe stenosis of the left MCA M1 segment. The patient was put on aspirin, clopidogrel, atorvastatin and antihypertensives, with full recovery of neurological function. One month later, the patient developed another episode of dysarthria and right-side weakness with recovery. DSA showed left M1 total occlusion. In October 2013, the patient developed a TIA attack of right-side weakness lasting 10 minutes and was admitted to our hospital. CTP showed left fronto-temporo-parietal region hypoperfusion. DSA showed left M1 total occlusion (Figure 2(a)), with partial collateral supply from the left posterior cerebral artery leptomeningeal branches. Patient refused open surgery and opted for endovascular treatment. Under general anesthesia and systemic heparinization, an exchange length 0.014-inch Transend microwire and a Prowler-14 microcatheter (Codman, USA) was navigated past the occlusion under roadmap guidance. Selective injection via the microcatheter showed opacification of distal vessels (Figure 2(b)). The microwire was then advanced to the left M3 segment and the microcatheter was withdrawn. The diameter of the vessel at the proximal end of the occlusion measured 2.1 mm, and the length of the occlusion was 6 mm. Angioplasty was performed with a 2.0 mm × 10 mm Gateway balloon. Post-angioplasty angiogram showed restoration of flow across the previously occluded segment with a residual stenosis of 50%. A 4.0 mm × 20 mm Solitaire stent (EV3, USA) was deployed over the stenotic region. Angiography confirmed satisfactory stent placement and distal perfusion (TICI 3) (Figure 2(c) and (d)). Immediate postoperative CT showed no bleed. Postoperatively, blood pressure was maintained at 90–110/60–70 mmHg, subcutaneous low-molecular weight heparin given for three days, clopidogrel was continued for three months and aspirin was given long term. Follow-up at 18 months showed no recurrence of ischemic symptoms. CTA showed normal left MCA opacification.

Figure 2.

(a) Angiography showed a left M1 occlusion; (b) selective injection via the microcatheter showed satisfactory opacification of the distal vessels; (c), (d) angioplasty with a Gateway balloon and stenting with a Solitaire stent was performed. Post-stenting angiography confirmed satisfactory stent placement and distal perfusion.

Discussion

Atherosclerotic intracranial stenosis is known to be more prevalent in Asians;³ however, the incidence of chronic MCA occlusions is unknown, and there are few studies on the natural history of these occlusions to guide treatment. Most chronic MCA occlusions do not have significant hemodynamic compromise on perfusion imaging studies and some are discovered incidentally.¹ Leptomeningeal anastomoses are the principal pathways of blood supply for the territory distal to the occlusion, but if the recruitment of these collaterals is insufficient or if there are coexisting stenoses, hemodynamic stroke may occur. Impaired cerebral hemodynamics is a strong risk factor for stroke recurrence for carotid occlusions.⁴

For patients who failed aggressive medical treatment because of impaired cerebral hemodynamic reserve, treatment options include surgical bypass or endovascular therapy. The Extracranial/Intracranial Bypass Trial had not demonstrated benefit of surgical bypass for MCA occlusions.⁵ In Chou’s retrospective review of 23 patients with bypass surgery performed for symptomatic MCA occlusions with impaired hemodynamics on acetalozamide challenge, there was one perioperative stroke. No recurrent stroke events were reported during a mean follow-up of 26.5 months.⁶ For endovascular revascularization of chronic MCA occlusions, there were two prior reports. Mori et al. reported a 100% revascularization rate for angioplasty for three patients with Mori type B lesions (total occlusions less than or equal to three months old), and 33% for three patients with type C lesions (total occlusions more than three months old, more than 10 mm long or with extreme angulation),⁷ while Ma et al. reported two successful stentings.⁸ The reason why there were only a few reports on revascularization for MCA occlusion was probably because of the technical difficulty in performing the procedure, with risks of vessel perforation, dissection, hyperperfusion, acute thromboembolic occlusion or restenosis.

Patients for whom our center would consider neurointervention were those with recurrent symptoms attributed to the MCA occlusion despite being on aggressive medical treatment for more than one month, and major hemodynamic insufficiency demonstrated on perfusion imaging. Other modalities such as positron emission tomography (PET) or acetazolamide challenge may provide more information about the hemodynamic reserve, but these are not yet available in our center. For patients with stroke, the intracranial intervention was done at least four weeks afterwards due to the hemorrhagic risk of the infarct, and only if the patients did not have a large (>1/3) territory infarct or a significant residual neurological deficit. Both of our patients had refused open surgical bypass. For endovascular treatment, assessment of the feasibility and risks of the operation was performed by analyzing the patients’ previous vascular imaging and the retrograde flow from collaterals to study the length of the occlusion and the vasculature morphology distal to the occlusion. For patient one, his CTA allowed us to deduce that the occlusion had been present for about one month, the length of the occlusion was less than 1 cm, with good patency of distal vasculature, and therefore revascularization was considered feasible. During the operation, we used the late phase of the angiogram to study the distal vessel characteristics, and used roadmap injections though the microcatheter to guide microwire crossing of the occlusion to decrease the risk of complications. After angioplasty, the residual stenosis was less than 10%, and there was no recoil during an observation period of 10 minutes, hence stenting was not performed. Stenting was considered when there was significant residual stenosis as in our patient two, or if intracranial dissection occurred. For the second patient, the diseased segment had an acute bend and the distal end was near the M2 segment. We chose the Solitaire stent as it is more easily navigable than the available balloon-mounted stent in our center, and it is easier to deploy, and does not have the firmer distal tip of the Wingspan delivery system (Boston Scientific, USA), which may pose risk of injury to the distal vasculature. A recent case series suggested that the Solitaire stent was safe and effective for selected patients with complex severe intracranial stenosis. The recurrence rate using the Solitaire stent was lower than the Wingspan stent in their center.⁹ Further studies with more patients and longer follow-up data would be needed to guide the method of intervention for these lesions. Postoperatively, meticulous monitoring and control of blood pressure was implemented for at least one week, being vigilant to the possibility of hyperperfusion syndrome. Both of these patients had technical success, with satisfactory restoration of perfusion on postoperative CTP, MCA patency maintained on follow-up CTA and no more recurrence of symptoms. No perioperative complications occurred.

Conclusion

Revascularization of chronic MCA occlusion is technically feasible and can be considered a treatment option for selected patients with recurrent stroke attributed to impaired cerebral hemodynamics who have failed medical treatment. But full preoperative evaluation, meticulous manipulation of the devices during the operation and close monitoring after the procedure are required to minimize the risks of the operation.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.