Deconstructive and Reconstructive Techniques in Treatment of Vertebrobasilar Dissecting Aneurysms: A Systematic Review and Meta-Analysis

Discussion

This systematic review and meta-analysis demonstrated that both deconstructive (parent artery occlusion, aneurysm trapping) and reconstructive (stent placement/stent-assisted coiling) techniques are effective in the treatment of ruptured and unruptured VBDA. Deconstructive techniques achieved higher rates of complete angiographic occlusion compared with reconstructive techniques; however, periprocedural morbidity rates were lower for reconstructive techniques. Both techniques resulted in high rates of good long-term neurologic outcome and similar low rates of recurrence and retreatment. Overall, these findings suggest that reconstructive techniques may be as effective as and possibly safer than deconstructive techniques; especially in cases in which patients lack sufficient collateral circulation.

Comparisons of clinical and angiographic outcomes between reconstructive and deconstructive techniques in the literature are limited, largely due to the small sizes of most case series. The largest study to date comparing deconstructive and reconstructive techniques was that of Kim et al,⁷ which compared 62 VBDA treated with reconstructive techniques and 57 treated with deconstructive techniques This study demonstrated no difference in recurrence and rebleeding rates between reconstructive and deconstructive techniques. Recurrence rates were 10.2% for patients treated with reconstructive techniques versus 17.1% for those treated with deconstructive techniques. Although our study found that deconstructive techniques result in higher angiographic occlusion rates, we found no difference in recurrence, retreatment, and rebleeding rates when comparing reconstructive and deconstructive techniques. These findings are important because they run contrary to the expectation that reconstructive techniques result in higher recanalization and rebleeding rates. With the advent of flow diverters and increased use of multiple overlapping stents in the treatment of dissecting VBDA, it is likely that angiographic outcomes of patients treated with reconstructive techniques will improve with time.^7⇓–9 Higher rates of long-term angiographic occlusion with multiple overlapping stents compared with single-stent treatment have been demonstrated in multiple series.^10⇓–12

Our study found similar rates of good long-term neurologic outcome between patients treated with reconstructive and deconstructive techniques but higher rates of perioperative morbidity among patients treated with deconstructive techniques. Patients treated with deconstructive techniques are at a higher risk of neurologic complications secondary to ischemia resulting from sacrifice of the parent vessel. Most ischemic complications are the result of occlusion and ischemia of perforating arteries and the anterior spinal artery.¹³ In a series of 72 patients treated with deconstructive techniques, Kashiwazaki et al¹³ reported 2 cases of spinal cord infarction and 7 cases of partial Wallenberg syndrome secondary to occlusion of vertebrobasilar dissecting aneurysms involving the PICA. Despite these perforator complications, only 1 patient died and the remaining patients had mRS ≤2. Perforator infarctions are rare with stent and flow-diverter reconstruction for treatment of vertebrobasilar aneurysms.¹⁴ Large-vessel infarcts resulting from thrombotic complications or hemodynamic alterations in the setting of deconstructive techniques are rare as well.^15⇓–17

Despite their overall lower rate of perioperative morbidity, reconstructive techniques are far from a panacea in the treatment of VBDA. One major limitation of treatment of VBDA with stents is in the treatment of PICA-origin VBDA. Especially in the setting of ruptured VBDA, complete obliteration of the aneurysm should be the primary goal because recanalization is associated with a high rate of rupture. Deconstructive techniques could be considered in this setting; however, in the absence of adequate cerebellar circulation, these are associated with a high risk of stroke and associated mass effect.¹² Reconstruction of PICA-involving lesions often requires the aneurysm sac to be left partially open to ensure adequate PICA flow.¹⁸ This places the patient at a high risk of recanalization, which, in the setting of ruptured VBDA, can result in hemorrhage. Thus, for these types of lesions, bypass surgery should be considered.¹⁹ Reconstructive treatments are also associated with a host of other complications, including stent migration, in-stent thrombosis leading to stroke, and dissection. However, these complications are rare.^7,10,12

The most important consideration in the treatment of VBDA is weighing the risks of treatment with the risks of the natural history of these lesions. Ruptured VBDA are known to have a poor natural history with high rates of rebleeding and mortality.¹ Rabinov et al¹⁶ compared mortality rates among patients with ruptured VBDA treated with deconstructive techniques and surgical clipping with a small group of patients managed conservatively and found that mortality rates in the conservative group were 50% compared with 20% in the treatment group. Kobayashi et al³ followed 113 patients with unruptured VBDA without ischemic symptoms at presentation for a mean of 3 years and found a 3% morbidity at follow-up, with 2 patients having clinical deterioration due to mass effect and 1 patient having ischemic stroke and hemorrhage. Five patients had enlargement of the aneurysm in this series.³