Diagnosis can be particularly challenging due to the anatomic variations of posterior arterial circulation, as well as the fluctuating nonfocal or multifocal symptoms.2 Specific symptoms include vertigo, ataxia, unilateral motor weakness, dysarthria, and oculomotor dysfunction. However, nonspecific symptoms such as headache, nausea, dizziness, hoarseness, falls, and Horner syndrome may be the only presenting signs of a posterior circulation stroke—as was the case with our patient.2 Her radiating neck pain could have been interpreted as a pointer to vertebral artery dissection within the context of severe hypertension.4 Unfortunately, the diagnosis was delayed and head imaging was obtained only after her mental status deteriorated.
Immediate neuroimaging is necessary to guide treatment in patients with suspected acute posterior circulation stroke,1,5,6 although it is not always definitive. While CT is pivotal in stroke work-up and may reliably exclude intracranial hemorrhage, its ability to detect acute posterior circulation ischemic strokes is limited given its poor visualization of the posterior fossa (as low as 16% sensitivity).5 Fortunately, CT angiography has a high sensitivity (nearing 100%) for large-vessel occlusion and high predictive values for dissection (65%-100% positive predictive value and 70%-98% negative predictive value).5,7 Diffusion-weighted MRI (when available in the emergency setting) has the highest sensitivity for detecting acute infarcts, although posterior circulation infarcts still can be missed (19% false-negative rate).5,8 Thus, correlative vessel imaging with magnetic resonance or CT angiography is very important, along with a high index of suspicion. In some instances, repeat MRI may be necessary to detect small strokes.
A patient-specific approach to management is key for individuals with suspected posterior circulation stroke.5 Because specific data for the appropriate management of posterior circulation ischemic stroke are lacking, current American Heart Association/American Stroke Association (AHA/ASA) guidelines apply to anterior and posterior circulation strokes.6 For eligible patients without multifocal disease, intravenous tPA is the first-line therapy and should be initiated according to guidelines within 4.5 hours of stroke onset9; it is important to note that these guidelines are based on studies that focused more on anterior circulation strokes than posterior circulation strokes.6,9-13 This can be done in combination with endovascular therapy, which consists of mechanical thrombectomy, intra-arterial thrombolysis, or a combination of revascularization techniques.3,5,6
Mechanical thrombectomy specifically has high proven recanalization rates for all target vessels.3-6 The latest AHA/ASA guidelines recommend mechanical thrombectomy be performed within 6 hours of stroke onset.6 However, there is emerging evidence that suggests this timeframe should be extended—even beyond 24 hours—given the poor prognosis of posterior circulation strokes.5,6,14 More data on the management of posterior circulation strokes are urgently needed to better understand which therapeutic approach is most efficient.
In patients such as ours, who have evidence of multifocal disease, treatment may be limited to endovascular therapy. Intracranial stenting of symptomatic lesions in particular has been controversial since the publication of the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis trial, which found that aggressive medical management was superior to stenting in patients who recently had a transient ischemic attack or stroke attributed to stenosis.15 Although additional studies have been performed, there are no definitive data on the topic—and certainly no data in the emergency setting.16 Further challenges are raised in patients with bilateral disease, as was the case with this patient.
When our patient was admitted to the rehabilitation clinic, she had a GCS score of 10 to 11/15. After 9 months of rehabilitation, she was discharged home with a GCS score of 15/15 and persistent left-side hemiparesis.
THE TAKEAWAY
Posterior circulation stroke is a life-threatening disease that may manifest with a variety of symptoms and be difficult to identify on emergent imaging. Thus, a high degree of clinical suspicion and additional follow-up are paramount to ensure prompt diagnosis and a patient-tailored treatment strategy.
CORRESPONDENCE
Kristine A. Blackham, MD, Associate Professor, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland; kristine.blackham@gmail.com Orcid no: 0000-0002-1620-1144 (Dr. Blackham); 0000-0002- 5225-5414 (Dr. Saleh)