When compared to anterior circulation ischemic stroke, the presentation of posterior circulation ischemic stroke (PCIS) is often less obvious, owing to the anatomical and functional complexity of the posterior circulation brain territory. Patients with PCIS may present with vague dizziness, difficulty walking, nausea, or headache without any lateralizing symptoms.¹ This may lead to delays in time-sensitive treatment. Even though PCIS accounts for 15 to 20 percent of all stroke events, it is three times more commonly missed in emergency departments (EDs) compared to anterior strokes with up to 10 percent being missed on the first ED visit.^2,3 Yet, systematic reviews suggest that outcomes with intravenous thrombolysis are at least as good as with anterior circulation strokes with a lower risk of intracranial hemorrhage, while comparable.^4–6 It is therefore incumbent upon the EM physician to make their best effort to identify patients with posterior circulation stroke in a timely manner so that those who fulfill criteria for emergency treatment such as endovascular therapy or intravenous thrombolysis can be optimized to improve outcomes. I outline some key clinical clues to help identify patients with posterior circulation stroke.

Understanding the Anatomy

An understanding of the vascular anatomy can help recall the symptoms of posterior circulation stroke. The vertebral arteries, cerebellar arteries, and posterior cerebral arteries supply the brainstem, cerebellum, and occipital lobes. Brainstem deficits include unilateral limb weakness, sensory loss, cranial nerve palsies, and altered level of awareness (including locked-in syndrome. Cerebellar features include vertigo, truncal, limb ataxia, and nystagmus. Occipital lobe features include visual field deficits.

The most common symptoms of PCIS based on registry data are dizziness (47 percent), unilateral weakness (41 percent) dysarthria (31 percent), gait ataxia (31 percent), headache (28 percent), nausea and vomiting (27 percent), and nystagmus (24 percent).¹ One easy way to remember the clinical features of PCIS is the “Dangerous Ds” memory aid: diplopia, dysarthria, dysphagia, dysdiadochokinesia, dysmetria, dystaxia, and dysphonia. While observational data suggest that isolated vertigo is rare in patients with PCIS, it may be that clinical assessment is simply not thorough enough to detect additional clinical findings.⁷ A detailed history and physical are imperative, paying close attention to three things: risk factors, cranial nerve dysfunction, and gait.

First, risk factor assessment: A key risk factor for PCIS is atrial fibrillation, especially in patients who are not anticoagulated for stroke prevention. In fact, a cardioembolic cause (predominantly as a result of atrial fibrillation) is the most common etiology of PCIS, ahead of atherosclerosis and arterial dissection.⁸ Traditional cardiovascular risk factors should also be taken into account. Unusual neck pain that lacks features of musculoskeletal injury, especially if it presents after recent head or neck trauma, should raise the suspicion for a vertebral artery dissection, especially in young adults with any PCIS symptoms.