What is VBI (Vertebral Basilar Insufficiency)?

What is Vertebrobasilar Insufficiency (VBI)?

Vertebrobasilar Insufficiency (VBI) is characterized by transient disruption of blood flow in the posterior (vertebrobasilar) circulation, which supplies the thalami, cerebellum, and brainstem, potentially resulting in frank infarct and permanent disability if blood flow disruption is pronounced or prolonged. 1

Etiology and Pathophysiology

VBI is most commonly caused by:

• Atherosclerotic disease - Most common cause, especially in elderly patients 1
• Vertebral artery dissection - Often accompanied by headache or neck pain, especially following trauma 1
• Positional narrowing of vertebral arteries - Less common cause 1
• External compression - From cervical osteophytes or other structures 2

Clinical Presentation

VBI typically presents with:

• Chronic recurrent vertigo - A hallmark symptom 1
• Associated brainstem neurologic deficits - Distinguishes VBI from other causes of vertigo 1
• Auditory disturbances - Occur in approximately 20% of patients, less common than vestibular symptoms 3
• Tinnitus and/or hearing loss - May occur during vertigo episodes 3
• Equilibrium disorders and nystagmus - Common vestibular manifestations 4

Diagnostic Approach

Imaging Studies

1. MRI Head Without IV Contrast

   • Useful for detecting posterior fossa infarcts 1
   • Note: A negative MRI does not exclude chronic ischemia without completed infarction 1

2. Vascular Imaging (essential)

   • CTA Head and Neck with IV Contrast

     • Highest reported sensitivity (100%) for vertebral artery dissection 1
     • Evaluates course and luminal caliber of arteries 1
     • Can detect luminal filling defects (thrombus, embolus, atherosclerotic plaque, dissection flap) 1

   • MRA Head and Neck

     • Alternative to CTA for evaluating vascular structures 1
     • High-resolution vessel wall imaging may provide both diagnostic and prognostic information 1

3. Advanced Imaging Techniques

   • High-resolution vessel wall imaging - May detect atherosclerotic plaque and stenosis not visible on standard MRA 1
   • Arterial spin labeling - Correlates with presence and severity of vertebrobasilar stenosis 1

Electrophysiologic Studies

• Cerebral evoked potentials - May show changes in VBI regardless of symptom severity 4
• Somato-sensory, auditory, and visual evoked potentials - Can detect changes due to brain stem hypoxia 4

Management

Medical Management

1. Maximal medical therapy - First-line treatment, especially for intracranial atherosclerosis 2

   • Antiplatelet agents
   • Risk factor modification (hypertension, diabetes, hyperlipidemia)
   • Lifestyle modifications

2. Anticoagulation - May be considered in select cases, particularly for dissection 2

Interventional/Surgical Options

1. For extracranial vertebral artery disease

   • Angioplasty and stenting may benefit patients who have failed maximal medical therapy 2
   • Carries relatively low morbidity 2

2. For external compression

   • Surgical decompression and excision of bony structures may be beneficial 2

3. For intracranial atherosclerosis

   • Best managed with medical therapy due to high complication rates with stenting/angioplasty 2

Clinical Pitfalls and Caveats

• Differential diagnosis - Essential to rule out systemic illness as the cause of symptoms before diagnosing VBI 5
• Mimics - Several conditions can mimic VBI; thorough evaluation is necessary 2
• Perioperative risk - Patients with VBI have higher perioperative risk from revascularization procedures compared to similar lesions in anterior circulation 1
• Incomplete evaluation - Vascular imaging is essential even with negative MRI, as chronic ischemia without infarction may be present 1

Monitoring and Follow-up

• Regular follow-up to assess symptom control
• Periodic vascular imaging to monitor disease progression
• Ongoing management of vascular risk factors

By understanding the pathophysiology, clinical presentation, and diagnostic approach to VBI, clinicians can provide appropriate management to reduce the risk of permanent neurological disability from posterior circulation ischemia.