Posterior circulation stroke

Goldmakher GV, Camargo EC, Furie KL et al (2009) Hyperdense basilar artery sign on unenhanced CT predicts thrombus and outcome in acute posterior circulation stroke. Stroke 40 134-139. 

Schaefer PW, Yoo AJ, Bell D et al (2008) CT angiography-source image hypoattenuation predicts clinical outcome in posterior circulation strokes treated with intra-arterial therapy. Stroke 39 3107-3109. 

Airway. Airway protection in stroke patients may require immediate intervention. An impaired level of consciousness combined with emesis can occur in patients with increased intracranial pressure (ICP) and posterior circulation stroke. Vertebrobasilar ischemia may affect medullary respiratory centers and cause apnea, or more commonly, paralysis of pharyngeal and tongue musculature leading to obstruction of the airway. The patient may require gastric suction and intubation to protect the airway from aspiration of gastric contents. An oral airway or nasal trumpet can be helpful if the patient has an upper airway obstruction. 

Acute ischemic stroke s3miptoms with onset or last known well, clearly defined. Treatment within 6 h of established, nonfluctuating deficits due to Anterior Circulation (carotid/MCA) stroke, between 6 and 8 h mechanical treatment (e.g.. Concentric Retriever) should be considered. The window of opportunity for treatment is less well defined in posterior circulation (vertebral/basilar) ischemia, and patients may have fluctuating, reversible ischemic symptoms over many hours or even days and stiU be appropriate candidates for therapy. 

Patients usually have multiple signs of neurologic dysfunction on physical examination. The specific deficits observed depend upon the area of the brain involved. Hemi- or monoparesis and hemisensory deficits are common. Patients with posterior circulation involvement may present with vertigo and diplopia. Anterior circulation strokes commonly result in aphasia. Patients may also experience dysarthria, visual field defects, and altered levels of consciousness. 

As shown above, MRA techniques are susceptible to artificial effects. High resolution time consuming measurements such as TOF-MRA are usually not suitable for the agitated patient suffering from acute stroke. Very fast and robust measurements, on the other hand, might be less detailed. In acute stroke with suspected arterial occlusion, the question of localization in the anterior or posterior circulation is of particular significance. 

Using only a few neurological findings the Oxfordshire Community Stroke Project (OCSP) classification allocates strokes to four subgroups, locating them either in the territory of the anterior (total anterior circulation infarct, TACI partial anterior circulation infarct, PACI lacunar infarct, LACI) and the posterior circulation, (posterior circulation infarct, POCI) (Bamford et al. 1991). The OCSP is a clinical syndromic classification, which... 

Simultaneous or sequential strokes in different arterial territories, multi-level posterior circulation infarcts, simultaneous infarcts in the three subterritories (superficial anterior, superficial posterior and deep) of the MCA, and hemorrhagic transformation of an ischemic infarct also point to a cardiac origin of the stroke (Arquizan et al. 1997 Ay et al. 1999 Ferro 2003a,b). Occlusion of the carotid artery by a mobile thrombus, early recanalization of an occluded vessel and the identification of microembolism in both MCAs are all highly indicative of a cardiac source of emboli. 

Kumral E, Afsar N, Kirbas D et al (2002a) Spectrum of medial medullary infarction clinical and magnetic resonance imaging findings. J Neurol 249 85-93 Kumral E, Bayulkem G, Akyol A et al (2002b) Mesencephalic and associated posterior circulation infarcts. Stroke 33 2224-2231... 

Giant cell arteritis is the most common vascuUtic cause of stroke and is associated particularly with posterior circulation ischemia (Nesher 2000 Ronthal et al. 2003 Eberhardt and Dhadly 2007). Medium and large arteries are affected, especially branches of the external carotid artery, the ophthalmic artery and the vertebral artery. The patients are elderly, with the diagnosis being rare under age 60 years. Malaise, polymyalgia and other systemic symptoms are frequently present. The erythrocyte sedimentation rate is usually raised, often to over 100 mm/h in the first hour. 

Neurological involvement in Behcet s disease may be subclassified into two major forms a vascular-inflammatory process with focal or multifocal parenchymal involvement and a cerebral venous sinus thrombosis with intracranial hypertension. The vasculitis and meningitis may affect cerebral arteries, particularly in the posterior circulation, to cause ischemic stroke and possibly intracranial hemorrhage (Farah et al. 1998 Krespi et al 2001 Siva et al. 2004 Borhani Haghighi et al. 2005). 

Headache is not uncommon around the time of stroke onset. It is more often severe in primary intracerebral hemorrhage than ischemic stroke, and more often severe with posterior than anterior circulation strokes. If the headache is localized at all, it tends to be over the site of the lesion. Headache is more common in cortical and posterior circulation than lacunar infarcts (Kumral et al. 1995). Severe unilateral neck, orbital or scalp pain suggests internal carotid artery dissection, particularly if there is an ipsilateral Horner s syndrome. Severe occipital headache can occur with vertebral artery dissection. Headache is also a particular feature of venous infarcts. Unusual headache in the days before stroke would suggest giant cell arteritis or perhaps a mass lesion rather than a stroke. 

The early risk of stroke after TIA also depends on the vascular territory of the event. Monocular events are associated with a low risk of subsequent cerebral stroke (Hankey et al. 1991, Benavente et al. 2001). Posterior circulation TIAs, which make up approximately 25% of all attacks, were thought for many years to be associated with a lower risk of stroke than carotid territory TIAs (Sivenius et al. 1991 Mohr et al. 1992 Caplan 1996). Correspondingly, they were often managed less aggressively. 

Fig. 15.2. Stroke-free survival curves for consecutive patients with transient ischemic attacks (TIAs) and anterior (—) versus posterior (—) circulation events in the Oxford Vascular Study (OXVASQ (log rank p = 0.04) (Flossman et al. 2006).

Few trials of antiplatelet agents have distinguished between different vascular territories or mechanisms of stroke, but there are some data on antiplatelet agents in posterior circulation disease. The Canadian Cooperative Study Group (1978) showed that aspirin reduced recurrent episodes of cerebral ischemia and death in patients with vertebrobasilar events. The European Stroke Prevention Study (ESPS Sivenius et al. 1991) of aspirin and immediate-release dipyridamole versus placebo appeared to show that patients with posterior circulation TIA benefited more than those with carotid disease, but the numbers of events were too small to be certain. 

There are no randomized trials of surgical procedures for posterior circulation disease and, therefore, data are only available from case series. For proximal vertebral reconstruction, perioperative mortaUty in pubUshed case series is 0-4%, with rates of stroke and death... 

Malek AM, Higashida RT, Phatouros CC et al. (1999). Treatment of posterior circulation ischaemia with extracranial percutaneous balloon angioplasty and stent placement. Stroke 30 2073-2085... 

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