Endovascular Therapy for Acute Basilar Artery Occlusion
Endovascular Therapy for Acute Basilar Artery Occlusion
The majority of patients presenting with basilar artery occlusion are aged 50–80 years, although women tend to present at an older age than men. Significant risk factors for basilar occlusion include hypertension, diabetes mellitus, smoking, hyperlipidemia, coronary and peripheral vascular disease and previous stroke. The majority of patients have transient ischemic attacks preceding the onset of stroke. It is difficult to obtain a universal view from the literature regarding the prognosis of this population when managed conservatively. Comparisons across observational studies are difficult because of differences in eligibility criteria and in classifications of favorable outcome. Bearing this in mind, some studies have reported favorable outcomes in 44–77% of patients while others have described poor outcome rates in 54–95% of patients (Table 1). The results highlight the fact that prognosis is diverse, and that this condition should be considered as a disease spectrum with various factors influencing the prognosis (see below). Indeed, as the natural history of basilar occlusion is so varied, there is considerable difficulty in assessing the positive and negative impact of treatment; this is probably the source of much of the controversy pertaining to treatment of this condition. What is certain is that the outcome can be very poor and that strategies to select those who will respond to treatment are warranted.
Voetsch et al assessed outcome relative to etiology of occlusion and presentation in the New England Medical Center Posterior Circulation Registry. This prospectively-collected series of 407 consecutive patients with posterior circulation ischemia identified 55 patients with moderate (50–70%) or severe (>70%) basilar stenosis and 32 patients with basilar occlusion as documented by MR angiography, conventional angiography or transcranial Doppler sonography. Factors that were significantly associated with more severe outcomes by univariate analysis were distal territory involvement, embolic etiology and basilar artery occlusion. One explanation for a poorer outcome in embolic occlusions is that emboli most often lodge in the rostral basilar artery and that these patients have less time to develop collateral circulation to maintain perfusion. Likewise, patients with basilar stenoses who have residual flow are at lower risk of severe outcomes than those with basilar occlusion.
As well as pathological predictors of poor outcome, clinical predictors include decreased level of consciousness, tetraparesis and abnormal pupils. In the New England Medical Center Posterior Circulation Registry these clinical signs increased the probability of major disability or death 3–4-fold. Devuyst et al found that decreased consciousness was the single most powerful prognostic factor in basilar disease, followed by pupillary disorders, bulbar signs and dysarthria.
Natural History
The majority of patients presenting with basilar artery occlusion are aged 50–80 years, although women tend to present at an older age than men. Significant risk factors for basilar occlusion include hypertension, diabetes mellitus, smoking, hyperlipidemia, coronary and peripheral vascular disease and previous stroke. The majority of patients have transient ischemic attacks preceding the onset of stroke. It is difficult to obtain a universal view from the literature regarding the prognosis of this population when managed conservatively. Comparisons across observational studies are difficult because of differences in eligibility criteria and in classifications of favorable outcome. Bearing this in mind, some studies have reported favorable outcomes in 44–77% of patients while others have described poor outcome rates in 54–95% of patients (Table 1). The results highlight the fact that prognosis is diverse, and that this condition should be considered as a disease spectrum with various factors influencing the prognosis (see below). Indeed, as the natural history of basilar occlusion is so varied, there is considerable difficulty in assessing the positive and negative impact of treatment; this is probably the source of much of the controversy pertaining to treatment of this condition. What is certain is that the outcome can be very poor and that strategies to select those who will respond to treatment are warranted.
Voetsch et al assessed outcome relative to etiology of occlusion and presentation in the New England Medical Center Posterior Circulation Registry. This prospectively-collected series of 407 consecutive patients with posterior circulation ischemia identified 55 patients with moderate (50–70%) or severe (>70%) basilar stenosis and 32 patients with basilar occlusion as documented by MR angiography, conventional angiography or transcranial Doppler sonography. Factors that were significantly associated with more severe outcomes by univariate analysis were distal territory involvement, embolic etiology and basilar artery occlusion. One explanation for a poorer outcome in embolic occlusions is that emboli most often lodge in the rostral basilar artery and that these patients have less time to develop collateral circulation to maintain perfusion. Likewise, patients with basilar stenoses who have residual flow are at lower risk of severe outcomes than those with basilar occlusion.
As well as pathological predictors of poor outcome, clinical predictors include decreased level of consciousness, tetraparesis and abnormal pupils. In the New England Medical Center Posterior Circulation Registry these clinical signs increased the probability of major disability or death 3–4-fold. Devuyst et al found that decreased consciousness was the single most powerful prognostic factor in basilar disease, followed by pupillary disorders, bulbar signs and dysarthria.
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