Posterior circulation ischaemic stroke.

There are important differences between posterior and anterior circulation stroke. The differences include the value of screening instruments, optimum diagnos‐ tic modalities, and clinical features (table). The face arm speech test (FAST), a widely used prehospital stroke recognition screening instrument, is less sensitive for detecting posterior circulation stroke than for anterior cir‐ culation stroke (the carotid territory, including the ante‐ rior and middle cerebral arteries and their branches). It can be difficult to determine the vascular territory of an acute ischaemic clinical syndrome on purely clinical grounds, but this knowledge may be needed to deter‐ mine the most appropriate acute treatment and preven‐ tion strategy. However, computed tomography (CT), the standard brain imaging modality in hyperacute stroke, has limited sensitivity in posterior circulation stroke. About 20‐25% (range 17‐40%) of the 150 000 ischaemic strokes in the United Kingdom each year affect posterior circulation brain structures (including the brainstem, cerebellum, midbrain, thalamuses, and areas of tempo‐ ral and occipital cortex), which are supplied by the verte‐ brobasilar arterial system. Early recognition of posterior circulation stroke or transient ischaemic attack (TIA) may prevent disability and save lives, but it remains more dif‐ ficult to recognise and treat effectively than other stroke types. Delayed or incorrect diagnosis may have devas‐ tating consequences, including potentially preventable death or severe disability, if acute treatment or second‐ ary prevention is delayed. The annual adjusted inci‐ dence of posterior circulation infarction was estimated at 18 per 100 000 person years (95% confidence interval 10/100 000 to 26/100 000) in an Australian study. Pre‐ ceding posterior circulation TIA or other transient brain‐ stem symptoms, particularly if recurrent, signal a high risk of impending ischaemic stroke and should prompt specialist urgent referral for further management. New acute treatment options and stroke prevention strategies specific to the posterior circulation are important areas of active research. This review aims to demonstrate the importance and challenges of recognising and treating posterior circula‐ tion stroke, including the key differences between poste‐ rior and anterior circulation stroke.