To help determine what clinical characteristics make this intervention suitable, it is important to consider the National Institutes of Health Stroke Scale (NIHSS) score and the person's overall functional capacity before the stroke. The committee agreed that it was not possible on the basis of the evidence reviewed to specify strict threshold criteria for eligibility based on pre-stroke functional status, clinical severity of stroke or the extent of established infarction on initial brain imaging. This is because there was variation in the trial entry criteria used in the studies and the committee agreed that these factors should be considered as part of the clinical judgement on an individual basis. However, because it was important to make a recommendation that can be implemented in practice, mRS and NIHSS eligibility thresholds were included to be consistent with the NHS England clinical commissioning policy on mechanical thrombectomy for acute ischaemic stroke. Posterior circulation stroke No clinical- or cost-effectiveness evidence was identified for the population with posterior circulation stroke. The committee discussed that prognosis is usually very poor in basilar artery occlusion, with around an 80% mortality. As few as 2% to 5% of people with basilar artery occlusion make a full neurological recovery in the absence of interventions to achieve recanalisation or reperfusion. The committee agreed that the prevalent current practice is to consider intravenous thrombolysis and mechanical thrombectomy. Good outcomes can be achieved even up to 24 hours after stroke onset, which is important because diagnosis can be delayed in this population by a non-focal presentation, a reduced conscious level, or both. The main risk of thrombectomy and thrombolysis in this population is intervening when 2022 there is established disabling ischaemic brain injury. 