Vertebrobasilar Insufficiency

Temporary symptoms from decreased blood flow/ischaemia to the posterior circulation — supplying the medulla, pons, midbrain, cerebellum, and (via the posterior cerebral artery) the thalamus and occipital cortex (70–80% of strokes affecting this territory).

Mechanism

Transient events share the pathophysiology of TIAs — an acute thrombotic event. Artery stenosis is the most common cause, often combined with vasospasm from BP change or head positioning (rotational vertebral artery syndrome). Subclavian steal syndrome can also contribute.

Presentation

Similar to posterior circulation stroke but briefer:

• Cranial nerve palsy with contralateral motor/sensory deficit
• Bilateral motor or sensory deficit
• Eye movement abnormalities (e.g. nystagmus)
• Cerebellar dysfunction
• Isolated homonymous hemianopia
• Vertigo — often triggered by head motion, especially looking upward
• Dysarthria, facial numbness, hemiparesis, headache, diplopia
• Drop attacks may occur with brainstem/cerebellar ischaemia
• Vertigo/disequilibrium can occur without other neurological signs

Other contributing causes of the vertigo/disequilibrium presentation: cervical spondylosis, postural hypotension, subclavian steal syndrome.

Diagnosis

History plus a normal neurological exam outside of events. CT brain excludes an intracranial bleed; MRI is better for detecting ischaemia; CT angiogram or MRA identifies structural stenosis. Four-vessel cerebral angiography is not usually required.

Treatment

Address atherosclerosis risk factors; commence antiplatelet therapy. Surgery (stenting/repair of a stenosis) is a specialist decision. No specific therapy exists for isolated vertigo/disequilibrium episodes — physiotherapy-based rehabilitation may help.