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Stroke

Vertebrobasilar Insufficiency

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Vertebrobasilar insufficiency: posterior circulation ischemia causes, symptoms including dizziness and visual disturbances, diagnostic imaging, and treatment approaches.

2026-03-29

At a Glance

Vertebrobasilar insufficiency: posterior circulation ischemia causes, symptoms including dizziness and visual disturbances, diagnostic imaging, and treatment approaches.

Definition and Overview

Vertebrobasilar insufficiency (VBI) is a condition in which reduced blood flow through the vertebral artery or basilar artery causes ischemia in the regions these arteries perfuse, including the brainstem, cerebellum, thalamus, and occipital lobe.

Posterior circulation ischemia accounts for approximately 20-25% of all ischemic strokes and approximately 25-30% of TIAs [1]. Posterior circulation strokes tend to be diagnosed later compared to anterior circulation strokes, and the early mortality rate for brainstem infarction is approximately 20-30%, higher than anterior circulation [3].

Causes

Atherosclerosis

Atherosclerotic stenosis at the vertebral artery origin is the most common cause. Intracranial vertebral artery and basilar artery atherosclerosis are also major causes [2].

Embolism

Emboli originating from the heart (atrial fibrillation, valvular disease) or aortic arch can travel to the posterior circulation and occlude vessels.

Arterial Dissection

Vertebral artery dissection is an important cause of posterior circulation stroke in younger patients. Neck hyperextension, rotation, chiropractic manipulation, and trauma are triggering factors.

Small Vessel Disease

Small vessel disease of perforating arteries within the brainstem causes brainstem lacunar infarction.

Other Causes

Subclavian steal syndrome, vasculitis, coagulation disorders, and fibromuscular dysplasia rarely cause VBI.

Symptoms

Transient Symptoms (TIA)

Typical symptoms of posterior circulation TIA are as follows.

  • Vertigo: The most common symptom, though isolated vertigo has low probability of VBI [5]
  • Diplopia: Ischemia of brainstem oculomotor nuclei or their connecting pathways
  • Dysarthria: Slurred speech
  • Dysphagia: Difficulty swallowing
  • Ataxia: Balance impairment and gait instability due to cerebellar ischemia
  • Bilateral or alternating unilateral motor weakness/sensory abnormalities
  • Transient visual field disturbance: Homonymous visual field defects

Warning Signs of Brainstem Ischemia

According to the Oxford study, approximately 60% of posterior circulation stroke patients experienced transient brainstem symptoms before the stroke, many of which were mild dizziness or diplopia [5].

Diagnosis

Vascular Imaging

  • MRA (magnetic resonance angiography): The first-line non-invasive study for evaluating vertebrobasilar stenosis, occlusion, and dissection.
  • CTA (CT angiography): Complementary to MRA, with superior assessment of calcified plaques.
  • Digital subtraction angiography (DSA): The gold standard, but used primarily for interventional planning due to its invasive nature.

Brain Imaging

  • Brain MRI (including DWI): Sensitively detects acute brainstem and cerebellar infarction. MRI is preferred as CT has limitations in evaluating posterior fossa lesions.

Cardiac Evaluation

ECG, 24-hour Holter monitoring, and echocardiography are used to evaluate cardiogenic embolic sources such as atrial fibrillation and valvular disease.

Differential Diagnosis

When dizziness is the chief complaint, differentiation from peripheral vestibular disorders is important.

  • BPPV: Triggered by positional changes, positive Dix-Hallpike test, no neurological abnormalities
  • Vestibular neuritis: Acute persistent vertigo, nystagmus, unilateral vestibular hypofunction
  • Meniere's disease: Recurrent vertigo + aural fullness + hearing loss + tinnitus
  • VBI: Accompanying brainstem symptoms, presence of vascular risk factors, vascular abnormalities on imaging

The HINTS examination (Head Impulse, Nystagmus type, Test of Skew) has been reported to be more sensitive than MRI in differentiating central from peripheral causes in acute vertigo.

Treatment

Medical Treatment

First-line treatment for posterior circulation ischemia is medical therapy [1].

  • Antiplatelet agents: Aspirin or clopidogrel for non-cardiogenic causes
  • Anticoagulation therapy: NOAC or warfarin for cardiogenic causes such as atrial fibrillation
  • Vascular risk factor management: Hypertension (target <130/80 mmHg), hyperlipidemia (statin, LDL <70 mg/dL), diabetes, smoking cessation

Endovascular Treatment

Stenting for symptomatic vertebral artery origin stenosis is technically feasible; however, the VIST study did not demonstrate superiority of stenting over optimal medical therapy [4]. Current guidelines recommend consideration only after failure of medical therapy.

Acute Treatment

In acute posterior circulation stroke, as with anterior circulation, intravenous thrombolysis (IV tPA) within 4.5 hours of onset and mechanical thrombectomy for large vessel occlusion are applicable. In basilar artery occlusion, mechanical thrombectomy may be considered within a longer time window (up to 24 hours).

Prognosis

Aggressive medical treatment after posterior circulation TIA can significantly reduce the risk of stroke within 90 days. However, when brainstem infarction occurs, the prognosis varies greatly depending on the location and extent of infarction, and basilar artery occlusion has a mortality rate of 85-95% without treatment [3].

Frequently Asked Questions

It is possible, but the most common causes of dizziness are peripheral conditions such as BPPV or vestibular neuritis. Dizziness due to VBI is usually accompanied by other brainstem symptoms such as diplopia, dysarthria, dysphagia, or limb weakness. However, in approximately 20% of cases, dizziness may be the only symptom, so careful evaluation is needed in elderly patients with vascular risk factors [5].

In the past, it was explained that neck rotation physically compresses the vertebral artery causing ischemia (bow hunter syndrome), but this is an extremely rare condition. Most dizziness with neck rotation is caused by BPPV, cervicogenic dizziness, or vestibular dysfunction. If VBI is suspected, vascular imaging (MRA/CTA) should be performed for confirmation.

Transient symptoms of VBI (posterior circulation TIA) can be a precursor to stroke. The risk of stroke within 90 days after posterior circulation TIA is approximately 10-15%, similar to anterior circulation TIA [1]. Therefore, immediate medical evaluation is necessary when VBI symptoms are suspected.

Aggressive management of vascular risk factors including hypertension, diabetes, hyperlipidemia, and smoking is key. Antiplatelet agents (aspirin, clopidogrel) are used for recurrence prevention, and anticoagulation therapy is needed for atrial fibrillation [1].

Endovascular stenting for symptomatic vertebral artery stenosis is technically feasible, but the randomized controlled trial (VIST) found insufficient evidence that stenting is superior to medical therapy alone in preventing stroke recurrence [4]. Currently, medical therapy remains the first-line treatment.

References

  1. [1] Markus HS, van der Worp HB, Rothwell PM (2013). "Posterior circulation ischaemic stroke and transient ischaemic attack: diagnosis, investigation, and secondary prevention." Lancet Neurology, 12: 989-998. DOI PubMed
  2. [2] Caplan LR (2015). "Vertebrobasilar ischemia and hemorrhage: clinical findings, diagnosis, and management of posterior circulation disease." Cambridge University Press: 1-650. DOI
  3. [3] Savitz SI, Caplan LR (2005). "Vertebrobasilar disease." New England Journal of Medicine, 352: 2618-2626. DOI PubMed
  4. [4] VIST Investigators, Compter A, van der Worp HB, Schonewille WJ, Vos JA, Boer BJ, Nederkoorn PJ, Algra A, de Borst GJ, Kappelle LJ (2015). "Stenting versus medical treatment in patients with symptomatic vertebral artery stenosis: a randomised open-label phase 2 trial." Lancet Neurology, 14: 606-614. DOI PubMed
  5. [5] Paul NLM, Simoni M, Rothwell PM (2013). "Transient isolated brainstem symptoms preceding posterior circulation stroke: a population-based study." Lancet Neurology, 12: 65-71. DOI PubMed

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