The concept of vertebrobasilar insufficiency was introduced by Silversides in 1954. Milliken and Siekert coined the term in 1955 when describing eight patients with symptoms suggesting episodic ‘insufficiency’ of blood flow in the vertebrobasilar arterial territory supplying the brainstem with—in four cases—basilar artery thrombosis found at postmortem. This followed Denny-Brown’s descriptions of ‘cerebrovascular insufficiency’—referring to focal cerebral ischaemia in any of the cerebral arterial territories—and Miller Fisher’s use of ‘carotid insufficiency’ to describe transient ischaemic attacks (TIA) in the carotid artery territory.

Vertebrobasilar insufficiency remains a controversial clinical entity lacking clear diagnostic criteria. The term is used to describe transient neurological deficits in the vertebrobasilar territory and thus denotes hypoperfusion of the cerebral tissue within the posterior circulation. Vertebrobasilar insufficiency therefore is no different from what is more commonly described as posterior circulation TIA—usually caused by athero-thromboembolism related to vertebrobasilar stenosis (figure 1A), cardiac embolism, or small vessel occlusion—and we therefore argue that the term vertebrobasilar insufficiency is redundant.