Cerebral haemodynamic changes after extracranial-intracranial bypass surgery.

Abstract

SUMMARY Regional cerebral blood flow, oxygen utilisation, fractional oxygen extraction, and cerebral blood volume were measured by positron emission tomography in twelve patients with carotid artery occlusion. Follow-up studies were carried out at a mean interval of eleven weeks after extracranial-intracranial bypass surgery. Clinical improvement was observed in three patients who had presented with frequent transient ischaemic attacks. One patient with multiple vascular occlusions suffered a stroke at the time of surgery. Follow-up studies showed an increase of regional cerebral blood flow in only two of the twelve patients. In the group as a whole, there was no significant change of cerebral blood flow, oxygen consumption or fractional oxygen extraction after bypass surgery. The most consistent post-operative change, observed in eleven of the twelve patients, was a fall of cerebral blood volume in the cortical territory of the bypassed carotid artery (p < 0-01). This effect was most marked in patients with bilateral carotid occlusion, in whom there was often an accompanying fall of blood volume in the contralateral hemisphere. The post-operative findings were consistent with an increase of regional cerebral perfusion pressure as a result of the bypass procedure. Although this effect is potentially of value, those patients with most to gain from bypass surgery may also run the highest risk of peri-operative cerebral ischaemia.

Measurement of cerebral perfusion with arterial spin labeling: Part 2. Applications

“…Three patients were treated for giant aneurysms, and four were treated for symptoms related to internal carotid occlusion. A turbo transfer insensitive labeling method was used to acquire flow images at inversion times ranging from 200 ms to 2600 ms. ASL CBF measured within the operated and contralateral hemispheres and within the basilar circulation was within the normal range, supporting PET studies that found flow normalization following ECIC arterial bypass (Gibbs et al, 1987;Marshall et al, 2002). …”

Extracranial-intracranial bypass for ischemic cerebrovascular disease: what have we learned from the Carotid Occlusion Surgery Study?

“…12 This criticism was likely invalid given that multiple groups have reported that STA-MCA cortical branch anastomosis can reverse an abnormally elevated oxygen extraction fraction (OEF). 6,17,33,39 Second, many of the highest-risk patients may have been operated on outside of the trial and, therefore, not included in the study results, leading to a selection bias. 3,42 This claim was conclusively refuted by further data provided by the EC-IC Bypass Trial Investigators.…”

“…Importantly, previous studies had established that EC-IC bypass surgery could improve hemispheric OEF ratios in Stage II patients back toward normal levels. 6,17,33,39 Therefore, despite the negative results of the EC-IC Bypass Trial, the STLCOS set the stage for a randomized controlled trial with a reliable method for identifying patients in whom cerebral hemodynamic factors were of primary pathophysiological importance.…”

Progressive Cortical Neuronal Damage and Extracranial-Intracranial Bypass Surgery in Patients with Misery Perfusion

“…In patients with MP, the risk for perioperative ischemic events is reported to be high. 28,29 Patients with MP have a marginally adequate blood supply relative to metabolic demand, which increases the risk of cerebral ischemia. 1,3,4 Therefore, it is reasonable to hypothesize that fluctuations of cerebral hemodynamics during perioperative periods might have caused ischemic neuronal damage in surgically treated patients with MP.…”