Alan B. Sanderson, MD
DESCRIPTION
- Vertebrobasilar insufficiency (VBI) refers to a transient or intermittent diminished blood flow in the posterior cerebral circulation, causing ischemia in areas of the brain supplied by these arteries and their branches.
- Major symptoms are referable to areas of the brain supplied by the posterior circulation, including the occipital lobes, thalamus, brainstem, and cerebellum.
- Occasionally VBI can be elicited by certain neck positions or postures, such as hyperextension. There are case reports of VBI in women having their hair washed at a salon.
- VBI can be the first warning of impending ischemic stroke in the posterior cerebrovascular territories.
- Systems affected: CNS, cardiovascular system
- Synonyms: An episode of VBI may be termed a transient ischemic attack (TIA).
EPIDEMIOLOGY
Incidence
20% of stroke/TIA events involve the posterior circulation. Of these, about 25% have >50% stenosis involving the vertebrobasilar system (1).
Prevalence
The age and gender profiles mimic that of atherosclerosis, with increasing prevalence with age and in the male gender.
RISK FACTORS
VBI shares risk factors for atherosclerosis and stroke, namely smoking, hypertension, diabetes, dyslipidemia, heart disease, hypercoagulable states, and age.
Genetics
No genetic syndromes reported.
GENERAL PREVENTION
- Smoking cessation, medical management of vascular risk factors, including hypertension, diabetes, and dyslipidemia.
PATHOPHYSIOLOGY
- Atherosclerotic stenosis of the vertebral artery most commonly occurs at the origin of the vessel from the subclavian artery, sometimes related to atherosclerosis also involving the parent vessel.
ETIOLOGY
- The most common causes are atherosclerosis of the vertebral or basilar arteries, embolism, and penetrating small vessel disease.
- Many different processes can contribute to VBI, including mechanical compression of the arteries related to neck positioning, subclavian steal syndrome, intrinsic vessel diseases, and embolic phenomena.
- VBI may be a manifestation of dolichoectasia of the basilar artery.
COMMONLY ASSOCIATED CONDITIONS
Vascular disease in other locations, including carotid artery stenosis, coronary artery disease, and peripheral vascular disease.
HISTORY
- Patients will often describe vertigo, nausea, lightheadedness, diplopia, nystagmus, and other symptoms which relate to brainstem ischemia. More severe presentations can include coma, paralysis, or death.
- Symptoms typically will last several minutes at a time.
PHYSICAL EXAM
- Vital signs: Check blood pressure in both arms to screen for subclavian steal syndrome.
- Cardiovascular: Take note of murmurs or abnormal rhythms. Listen for bruits in the neck.
- Neurologic: A full screening neurologic exam should be performed, with special attention to the cranial nerves and the visual system. Usually the neurologic exam is normal between episodes unless the patient has had a stroke.
DIAGNOSTIC TESTS AND INTERPRETATION
Lab
Initial Lab Tests
- There are no specific laboratory tests.
- Screen for dyslipidemia and diabetes.
Follow-Up & Special Considerations
- Consider screening for less common causes of vascular disease, including vasculitis.
- Consider screening for hypercoagulable states, especially in younger patients with fewer risk factors.
Imaging
Initial Approach
- MRI with diffusion-weighted imaging is the preferred initial study to evaluate for many conditions which can cause symptoms of VBI.
- Noninvasive angiography using CT and MRI can often identify a structural cause of VBI, but may be insensitive to stenosis at the origin of the vertebral arteries (1)[A].
Follow-Up & Special Considerations
Consider conventional angiography when noninvasive imaging is equivocal and a high index of suspicion remains, especially if the patient may be a candidate for intervention (2)[C].
Diagnostic Procedures/Other
Carotid Doppler ultrasound may be useful to evaluate the carotid arteries or to screen for subclavian steal syndrome (3)[C].
Pathological Findings
There is no significant role for biopsy in the diagnosis of VBI. Histology typically shows atherosclerosis at the site of occlusion.
DIFFERENTIAL DIAGNOSIS
- Other causes of neurologic symptoms: Vertebral or basilar artery stenosis, thromboembolic disease, basilar migraine, infectious, inflammatory, or neoplastic disease involving the brainstem, toxic or metabolic conditions such as hypo- or hyperglycemia, syncope, seizure, trauma
- Presyncope
- Other causes of vertigo: Vestibulitis, vestibular neuronitis, Meniere's disease, etc.
MEDICATION
First Line
Aspirin (3)[A]
Second Line
ADDITIONAL TREATMENT
General Measures
- Optimal medical therapy including management of underlying vascular risk factors, including hypertension, diabetes, dyslipidemia, and smoking (3)[A]
Issues for Referral
Patients should be followed by a stroke neurologist or vascular neurosurgeon.
Additional Therapies
Where applicable, patients can be counseled to avoid neck positions or postures which reproduce symptoms.
COMPLEMENTARY AND ALTERNATIVE THERAPIES
There are case reports of successfully using Chinese herbal remedies and acupuncture to treat VBI (4)[C].
SURGERY/OTHER PROCEDURES
- Various surgical bypass procedures have been reported, and generally have high morbidity and mortality (2)[B].
- Endovascular approaches with angioplasty with or without stenting generally have low morbidity and mortality, but have a high restenosis rate of about 30–40%. Restenotic patients are symptomatic only
of the time (2)[B]. - Endovascular approaches have not been shown to be superior to medical therapy alone (5)[B].
IN-PATIENT CONSIDERATIONS
Initial Stabilization
- Once ischemic stroke has been ruled out, patients should be stabilized with blood pressure normalization.
- In cases of impaired consciousness or other causes of poor airway protection, patients should be intubated to prevent aspiration.
Admission Criteria
- Most patients can be managed as outpatients.
- Reasons for admission may include TIA, stroke, or planned intervention.
IV Fluids
If indicated for hypotension in the setting of active symptoms. There is no preference for one type of IV hydration.
Nursing
- Assure glucose control in diabetic patients.
- Manage accurate administration of medications.
- Provide patient education on VBI and comorbid conditions.
Discharge Criteria
Asymptomatic patients may be discharged as soon as a diagnostic workup is complete and outpatient follow-up plans have been made.
FOLLOW-UP RECOMMENDATIONS
- Patients should be followed by a stroke neurologist or vascular neurosurgeon.
- Primary care doctors or medical specialists should provide treatment for underlying medical risk factors.
Patient Monitoring
- There are no recommendations for follow-up imaging in asymptomatic patients.
DIET
- Diets shown to be helpful in other atherosclerotic vascular diseases are likely to be helpful in VBI, but there are no research studies addressing this topic.
- Diabetic diet as applicable.
PATIENT EDUCATION
- Patients should be educated regarding the cause of their symptoms and treatment options.
- Patients should be informed of underlying risk factors for VBI and counseled regarding smoking cessation and compliance with medical therapies for hypertension, dyslipidemia, and diabetes.
- Patients should know what symptoms should prompt them to seek medical care.
PROGNOSIS
- Variable, depending on the etiology and presence of associated infarction.
- After posterior circulation stroke the risk of death is about 3–4%, and major disability is about 20%.
COMPLICATIONS
The most important complication of VBI is ischemic infarction in the posterior cerebrovascular territories.
