Localized or diffuse reduction in blood flow through the vertebrobasilar arterial system, which supplies the brain stem; cerebellum; occipital lobe; medial temporal lobe; and thalamus. Characteristic clinical features include syncope; lightheadedness; visual disturbances; and vertigo. brain stem infarctions or other brain infarction may be associated. The disease is MONDO_0001613 (vertebrobasilar insufficiency). Also known as: vertebro-basilar insufficiency, vertebrobasilar arterial insufficiency, vertebrobasilar artery syndrome.