Changes in intracranial stenotic lesions after extracranial-intracranial bypass surgery

Abstract

The natural history of intracranial arterial stenosis is not well understood. The lesions are pathologically quite diverse, and are subject to resolution, progression, or occlusion. The authors undertook an investigation to examine what effects, if any, extracranial-intracranial (EC-IC) bypass surgery had on the evolution of intracranial arterial stenosis in 18 patients undergoing EC-IC bypass procedures for ipsilateral hemispheric ischemia. There was inaccessible internal carotid artery stenosis in 14 patients, and middle cerebral artery stenosis in four patients. Early (within 2 weeks) and late (at 6 months) postoperative angiography was performed in all patients. During the period of the study, there was a significant change in the arterial stenosis in 50% of the patients (nine of 18). The stenotic artery became occluded in four patients while the grafts were widely patent. The occlusion occurred within a few days after the operation in three of the four cases, and was accompanied by an ischemic stroke in these patients. There was improvement or resolution of the stenotic lesion in five patients; the graft became occluded in two of these cases and was patent but showed poor cortical artery filling in the other three. All these patients remained asymptomatic and the change was detected on routine late postoperative angiograms. It is concluded that arterial stenoses should not be viewed as static or inflexible lesions, and that EC-IC bypass procedures can modify the hemodynamic parameters across stenotic lesions, predisposing them to improvement or worsening. This, in turn, may affect bypass patency. Such hemodynamic interactions are accompanied by ischemic symptoms in some patients, and contribute to the relatively higher morbidity associated with EC-IC bypass surgery in the setting of arterial stenosis.

Encephaloduroarteriosynangiosis for adult intracranial arterial steno-occlusive disease: long-term single-center experience with 107 operations

“…Patients with ICASD represent a more challenging group than those with MMD, as they are typically older, have higher cardiac risk, and have been shown to be more resistant to other forms of treatment, such as direct bypass and angioplasty and stenting, with high recurrent stroke rates reported in the literature despite intensive medical management. [1][2][3]11,13,19,23 Observations in clinical trials have confirmed an important role for collateral circulation in averting stroke in ICASD, providing pathophysiological support for the hypothesis that collateral enhancement by EDAS could improve outcome. Evaluation of the WASID (WarfarinAspirin for Symptomatic Intracranial Disease) population demonstrated that when the degree of arterial luminal stenosis was severe (≥ 70%), the presence of good collaterals had a dramatic role in averting stroke.…”

“…8,14 In addition, in the EC-IC bypass trial, patients with intracranial stenotic lesions consistently fared worse following bypass because the sudden change in flow dynamics across the stenotic segment may produce stasis of flow and thrombosis, which can embolize and/or propagate to occlude lenticulostriate arteries. 1,13 However, direct bypass has the potential advantage that it may provide immediate protection from ischemia. Our findings support the concept that strict medical management protects patients from ischemia in the initial period.…”

“…23,24 Interventions such as angioplasty and stenting or bypass surgery have failed to improve outcomes in ICASD 1,2,19 and have not been tested in pivotal clinical trials for MMD. Although the short-term (30-day) stroke and death rates with angioplasty alone have been shown to be low (3.3%) in one study subgroup, the longer-term (2-year) outcomes of these techniques have been disappointing (18% 2-year stroke rate in the SAMMPRIS [Stenting and Aggressive Medical Management for Preventing Recurrent stroke in Intracranial Stenosis] trial) and no better than medical management alone.…”

Natural History of Stenosis From Intracranial Atherosclerosis by Serial Angiography

“…2,21,22 Progression of stenoses has also been reported with use of serial transcranial Doppler measurements. 23 We offer several possible explanations for the relative stability of the intracranial ICA lesions compared with those in other intracranial sites.…”

“…In the setting of EC/IC bypass, 9 of 18 stenoses showed significant angiographic changes on follow-up studies: 4 sites occluded and 5 sites improved. 22 For example, an 80% stenosis of the carotid siphon completely resolved, but the bypass occluded. We conducted a retrospective study of patients with intracranial atherosclerotic stenoses who had undergone repeat angiography at our institution to learn more about the natural history of these lesions.…”