Vertebrobasilar Insufficiency

Excerpt

Vertebrobasilar insufficiency (VBI) is defined by inadequate blood flow through the posterior circulation of the brain, supplied by the 2 vertebral arteries that merge to form the basilar artery. The vertebrobasilar arteries supply the cerebellum, medulla, midbrain, and occipital cortex. When the blood supply to these areas is compromised, it can lead to severe disability and/or death. Because the cerebellum is involved, survivors are often left with dysfunction of many organs including ataxia, hemiplegia, gaze abnormalities, dysarthria, dysphagia and cranial nerve palsies. Fortunarely, many patients have small vessel involvement and thus the neurological deficits are mild and localized.

The term, VBI, was coined in the 1950s after C. Miller Fisher used carotid insufficiency to describe transient ischemic attacks (TIA) in the carotid supplied territories and is therefore often used to describe brief episodes of transient ischemic attacks in the vertebrobasilar territory. Also known as the posterior circulation, the vertebrobasilar vasculature supplies areas such as the brainstem, thalamus, hippocampus, cerebellum, occipital and medial temporal lobes. Although patients may initially be asymptomatic, the significant build-up of atherosclerotic plaques over time may lead to ischemic events. Stroke may occur either due to an occlusion of the vertebral or basilar artery or an embolus that that may lodge more proximal to the brain. In the emergency setting, VBI is an important diagnosis to consider as many symptoms can appear like other benign etiologies such as labyrinthitis, vestibular neuritis, and benign paroxysmal positional vertigo (BPPV).

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