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Predictability of extracranial/intracranial bypass function: a retrospective study of patients with occlusive
T Iwama1, N Hashimoto, Y Takagi
1Department of Neurosurgery, National Cardiovascular Center, Osaka, Japan.
Insights
Extracranial/intracranial bypass surgery efficacy depends on collateral circulation, not just bypass patency. Preoperative studies can predict bypass flow, guiding patient selection for improved hemodynamic status.
Area of Science:
- Neurosurgery
- Vascular Surgery
- Cerebrovascular Disease
Background:
- Efficacy of extracranial/intracranial bypass surgery is debated.
- Bypass function is determined by collateral circulation, not just patency.
Purpose of the Study:
- To determine if preoperative studies can predict bypass flow extent.
- To identify patient groups likely to benefit from bypass surgery.
Main Methods:
- Retrospective analysis of 44 patients (51 hemispheres) undergoing bypass surgery.
- Correlation of bypass flow with preoperative angiographic and cerebral blood flow studies.
Main Results:
- Bypass function is predictable using preoperative studies.
- Good collateral circulation developed in hemispheres with retrograde leptomeningeal anastomoses and decreased acetazolamide reactivity.
- Poor collateral circulation occurred in hemispheres with normal acetazolamide reactivity or antegrade circulation.
Conclusions:
- Bypass surgery benefits are expected in patients with spontaneous leptomeningeal anastomoses and decreased acetazolamide reactivity.
- Preoperative assessment is crucial for predicting bypass efficacy.
Objective:
When the efficacy of extracranial/intracranial bypass surgery is discussed, can we include the patients with extensive collateral circulation through the bypass and those with poor collateral circulation in the same group? The bypass function should be determined not by the patency of the bypass but by the extent of collateral circulation through the bypass. We retrospectively analyzed our patients to determine whether the extent of bypass flow can be predicted from the results of preoperative studies.
Methods:
In 51 hemispheres of 44 consecutive patients who underwent extracranial/intracranial bypass surgery, correlation between the extent of bypass flow and the preoperative results of angiographic and stimulated cerebral blood flow studies were investigated.
Results:
The bypass function is highly predictable with the aid of preoperative studies. In 11 hemispheres that showed both retrograde spontaneous circulation via leptomeningeal anastomoses and decreased reactivity to acetazolamide of cerebral blood flow in an area distal to the arterial lesion, collateral circulation through the bypass developed well and reactivity to acetazolamide improved. In all of 13 hemispheres that showed normal reactivity to acetazolamide, the bypass was patent but the collateral circulation did not develop well. In only 4 of 24 hemispheres with spontaneous antegrade circulation distal to the lesion was there satisfactory collateral circulation through the bypass.
Conclusion:
Our results indicate that improvement of the hemodynamic status by bypass surgery should be expected only in patients with both spontaneously developed leptomeningeal anastomoses and decreased reactivity to acetazolamide.