4.1
A systematic review of 2,591 patients (2 randomised controlled trials [RCTs] with follow-up intervals of 56 and 25 months, and 19 non-randomised studies with follow-up not stated) reported no difference in stroke rates (any type) between patients having extracranial to intracranial (EC‑IC) bypass (plus best medical treatment) and those having medical treatment only (in the RCTs n=1,691; odds ratio [OR] 0.99, 95% confidence interval [CI] 0.79 to 1.23, p=0.91 and in the non-randomised studies [18 studies], n=881; OR 0.80, 95% CI 0.54 to1.18, p=0.25). In the same systematic review, ischaemic stroke rate was not statistically significantly different between patients having EC‑IC bypass and those having medical treatment only (in the RCTs n=1,573; OR 0.69, 95% CI 0.44 to 1.08, p=0.11 and in the non-randomised studies [13 studies], n=640; OR 0.72, 95% CI 0.44 to 1.18, p=0.19). Two RCTs reported a statistically significantly smaller probability of stroke, vascular event or vascular death among the patients having EC‑IC bypass when compared with patients having medical treatment only (n=1,573; OR 0.68, 95% CI 0.51 to 0.91, p=0.009). No statistically significant difference in ischaemic stroke rate was seen in the systematic review of 2,591 patients (13 non-randomised studies; n=673; OR 0.69, 95% CI 0.45 to 1.04, p=0.079). Two non-randomised studies (n=361) reported no statistically significant difference in intracranial haemorrhage rates between patients having EC‑IC bypass when compared with patients having medical treatment only (OR 1.14, 95% CI 0.44 to 2.93, p=0.79) in the same systematic review. A systematic review of 506 patients reported a statistically significantly lower rate of stroke 12 months after surgery in patients with severe stage I failure (loss of autoregulatory vasodilation) who had EC‑IC bypass (1%) than in patients having medical treatment only (19%, 95% CI 1.17 to 4.08, p=0.015). In the same systematic review, stroke rate was not statistically significantly different in patients with stage II failure (autoregulatory failure characterised by decreases of cerebral blood flow and increases of oxygen extraction fraction) who had EC‑IC bypass (0%) when compared with patients having medical treatment only (13%, 95% CI 0.89 to 3.63, p=0.10). In an RCT of 1,377 patients, EC‑IC bypass surgery was associated with a 14% (90% CI 3 to 34) increased relative risk of fatal and non-fatal stroke (Mantel-Haenszel chi-squared =1.72) at a mean follow-up of 56 months (p value not reported). In an RCT (n=195) comparing 97 patients having EC‑IC bypass with 98 patients who had medical treatment only, ipsilateral ischaemic stroke rate was not statistically significantly different between groups (rate difference 2%, 95% CI −10 to 14, p=0.81) at 2‑year follow-up. A case series of 204 patients who had EC‑IC bypass reported the rate of patients free of stroke or fatal stroke to be 92% (138/150) at 1‑year follow-up and 87% (86/99) at 5‑year follow-up.