Extracranial-intracranial bypass surgery to reduce the risk of haemodynamic stroke in cerebroocclusive atherosclerotic disease of the anterior cerebral circulation - a systematic review

BACKGROUND AND PURPOSE: Selected patients with acute or continual ischaemic symptoms from occlusions or inaccessible stenotic lesions of the internal carotid artery or middle cerebral artery have been considered candidates for an extracranial-intracranial (EC-IC) bypass procedure. Hitherto, no effectiveness of this surgical therapeutic option for various patient subgroups could be found in a large international randomized trial, and therefore various guidelines give negative recommendations for its usefulness. The aim of the present report was to analyze clinical effectiveness of EC-IC bypass for cerebral revascularization in haemodynamic subgroups of patients with advanced occlusive cerebrovascular disease in the anterior cerebral circulation. MATERIAL AND METHODS: A computerized database search from November 1985 to November 2001 was performed. Language restriction was done for English, French and German. Reports dealing with EC-IC bypass surgery for cerebral revascularization in case of advanced cerebrovascular disease in the anterior cerebral circulation were reviewed when appropriate. Studies were included if they contained valuable data on clinical state, pre- and postoperative haemodynamic state, surgical outcome and follow-up. RESULTS: The postoperative outcome related to death or stroke depended mainly on preoperative haemodynamic subgroups (CBF/CBV; OEF). The final functional status was worse the more the CBF/CBV ratio and OEF increased. Perioperative risk for death (0.6%) or stroke (2%) during the first month after surgery was similar to the death or stroke rate during the following 2 to 12 months after surgery. The overall risk profile for subsequent death or stroke of surgically treated patients is significantly better within the first 12 months than that of conservatively treated patients (1.3% vs. 3.6% per year). Neurological function was improved over the preoperative state in 84% of the patients and was unchanged in 6%. Postoperatively, modified Rankin scale score was 0-1 in 90% of patients and 2 in 1% of patients. Long-term patency was excellent, with 1% failure rate per year following the first year after surgery. CONCLUSION: Neurological function and subsequent stroke attributable to haemodynamic insufficiency in patients with symptomatic carotid occlusion or severe stenosis are improved significantly by EC-IC bypass surgery if the brain area corresponding to the impaired neurological function remains viable. The haemodynamic parameters observed for patients who experience improved neurological function or diminished stroke risk profile after EC-IC-bypass surgery contain both significantly elevated OEF and CBF/CBV. Therefore haemodynamic profile represents an important indicator for EC-IC bypass surgery and gives a good rationale for new trials conducted in a subgroup of patients selected on the basis of their haemodynamic profile.