Vertebrobasilar insufficiency

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: VBI

Overview

Vertebrobasilar insufficiency (VBI), or vertebral basilar ischemia, refers to a temporary set of symptoms due to decreased blood flow in the posterior circulation of the brain. The posterior circulation supplies blood to the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex (responsible for vision). Therefore, the symptoms due to VBI vary according to which portions of the brain experience significantly decreased blood flow. In the United States, 25% of strokes (see stroke) and transient ischemic attacks (see transient ischemic attack) occur in the vertebrobasilar distribution. These must be separated from strokes arising from the anterior circulation, which involves the carotid arteries.

Causes

Causes by Organ System

Cardiovascular	Intracranial atherosclerosis , vertebral artery dissections ,
Chemical / poisoning	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	No underlying causes
Ear Nose Throat	No underlying causes
Endocrine	No underlying causes
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	No underlying causes
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	No underlying causes
Musculoskeletal / Ortho	Cervical spondylosis ,
Neurologic	No underlying causes
Nutritional / Metabolic	No underlying causes
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Opthalmologic	No underlying causes
Overdose / Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	No underlying causes
Renal / Electrolyte	No underlying causes
Rheum / Immune / Allergy	No underlying causes
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	head rotation or extension |-

Epidemiology and Demographics

The incidence of VBI increases with age and typically occurs in the seventh or eighth decade of life. Reflecting atherosclerosis, which is the most common cause of VBI, it affects men twice as often as women and is more prevalent in African Americans. Patients with hypertension, diabetes, smoking, and dyslipidemias also have a higher risk of developing VBI.

Natural History, Complications and Prognosis

Complications

One of the complications is vertebral artery dissection. It is the development of dissection (a flap-like tear) in the vertebral artery. It is commonly associated with physical trauma but may also develop spontaneously. It is a major cause of stroke in young people.

Diagnosis

The evaluation for VBI starts with a history and physical exam, with great emphasis on the cardiovascular and neurologic exam. It also includes a work-up to exclude benign conditions (such as labyrinthitis, vestibular neuronitis, and benign paroxysmal positional vertigo) that have overlapping signs and symptoms. However, the exact work-up largely depends on the patient’s age and known risk factors. For middle-aged patients, a cardiovascular risk factor evaluation is important. This often includes a cholesterol level, lipid profile (see this [2] to determine what your cholesterol level means), ECG, and echocardiogram. If a person with VBI is under age 45 and has no evidence for atherosclerosis, a work-up for hypercoagulable states (Lupus anticoagulant, anti-cardiolipin antibodies, protein C, protein S, antithrombin III deficiencies) is indicated.

Imaging studies are rarely required to diagnose VBI, but sometimes computed tomography (CT) is performed first. The CT is extremely sensitive in detecting hemorrhage. However, magnetic resonance imaging (MRI) is superior to the CT in detecting ischemic changes in the vertebrobasilar distribution. Magnetic resonance angiography (MRA) also can be used to identify vertebrobasilar occlusions, but it can often overestimate the degree of occlusion.

Symptoms

Vertigo (commonly described as the environment spinning or as if the person is twirling in space) is the most recognizable and quite often the sole symptom of decreased blood flow in the vertebrobasilar distribution. The vertigo due to VBI rarely is brought on by head turning, which could occlude the ipsilateral vertebral artery and result in decreased blood flow to the brain if the contralateral artery is occluded. When the vertigo is accompanied by double vision (diplopia), graying of vision, and blurred vision, patients often go to the ophthalmologist. If the VBI progresses, there may be weakness of the quadriceps and, to the patient, this is felt as a buckling of the knees. The patient may suddenly become weak at the knee and crumple (often referred to as a “drop attack”). Such a fall can lead to significant head and orthopedic injury, especially in the elderly.

Transient ischemic attacks due to VBI will, by definition, have symptoms resolved within 24 hours. More often, however, the symptoms are very brief, lasting a few seconds to half an hour. These symptoms are often provoked by sudden and temporary drops in blood pressure. Postural changes (see orthostatic hypotension), such as getting out of bed too quickly or standing up after sitting for extended periods of time, often provoke these attacks. Exercise of the legs may also bring on the symptoms of VBI. For the sedentary older subject, going up a flight of stairs or walking the dog may be enough to cause pooling of blood in the legs and a drop in blood pressure in the distal arteries of the head. Heat and dehydration may also be contributing causes.

Treatment

Patients should discuss with their physician possible causes for their VBI symptoms. As discussed above, postural changes, exercise, and dehydration are some of the likely culprits. Treatment usually involves lifestyle modifications. For example, if VBI is attributed mainly to postural changes, patients are advised to slowly rise to standing position after sitting for a long period of time. An appropriate exercise regimen for each patient can also be designed in order to avoid the excessive pooling of blood in the legs. Dehydrated patients are often advised to increase their water intake, especially in hot, dry climates. Finally, when applicable, patients are often advised to stop smoking and to control their hypertension, diabetes, and cholesterol level.

In the event that a patient suffers a “drop attack,” and especially for the elderly population, the most important action is to be evaluated for associated head or other injuries. To prevent drop attacks, patients are advised to “go to the ground” before the knees buckle and shortly after feeling dizzy or experiencing changes in vision. Patients should not be concerned about the social consequences of suddenly sitting on the floor, whether in the mall or sidewalk, as such actions are important in preventing serious injuries.

Sometimes, to prevent further occlusion of blood vessels, patients are started on an antiplatelet agent (aspirin, clopidogrel, or aspirin/dipyridamole) or sometimes an anticoagulant (warfarin) once hemorrhage has been excluded with imaging.

For treatment of vertebrobasilar stenosis due to atherosclerosis, researchers from Stanford University found that intracranial angioplasty can be performed with an annual stroke rate in the territory of treatment of 3.2% and 4.4% for all strokes, including periprocedural events. Randomized control trials need to be performed.

2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS Guideline on the Management of Patients With Extracranial Carotid and Vertebral Artery Disease (DO NOT EDIT)

Vascular Imaging in Patients with Vertebral Artery Disease (DO NOT EDIT)

Class I

"1. Noninvasive imaging by CTA or MRA for detection of vertebral artery disease should be part of the initial evaluation of patients with neurological symptoms referable to the posterior circulation and those with subclavian steal syndrome. (Level of Evidence: C)"

"2. Patients with asymptomatic bilateral carotid occlusions or unilateral carotid artery occlusion and incomplete circle of Willis should undergo noninvasive imaging for detection of vertebral artery obstructive disease. (Level of Evidence: C)"

"3. In patients whose symptoms suggest posterior cerebral or cerebellar ischemia, MRA or CTA is recommended rather than ultrasound imaging for evaluation of the vertebral arteries. (Level of Evidence: C)"

Class IIa

"1. In patients with symptoms of posterior cerebral or cerebellar ischemia, serial noninvasive imaging of the extracranial vertebral arteries is reasonable to assess the progression of atherosclerotic disease and exclude the development of new lesions. (Level of Evidence: C)"

"2. In patients with posterior cerebral or cerebellar ischemic symptoms who may be candidates for revascularization, catheter-based contrast angiography can be useful to define vertebral artery pathoanatomy when noninvasive imaging fails to define the location or severity of stenosis. (Level of Evidence: C)"

"3. In patients who have undergone vertebral artery revascularization, serial noninvasive imaging of the extracranial vertebral arteries is reasonable at intervals similar to those for carotid revascularization. (Level of Evidence: C)"

Management of Atherosclerotic Risk Factors in Patients with Vertebral Artery Disease (DO NOT EDIT)

Class I

"1. Medical therapy and lifestyle modification to reduce atherosclerotic risk are recommended in patients with vertebral atherosclerosis according to the standards recommended for those with extracranial carotid atherosclerosis. (Level of Evidence: B)"

"2. In the absence of contraindications, patients with atherosclerosis involving the vertebral arteries should receiveantiplatelet therapy with aspirin (75 to 325 mg daily) to prevent MI and other ischemic events. (Level of Evidence: B)"

"3. Antiplatelet drug therapy is recommended as part of the initial management for patients who sustain ischemic stroke or TIA associated with extracranial vertebral atherosclerosis. Aspirin (81 to 325 mg daily), the combination of aspirin plus extended-release dipyridamole (25 and 200 mg twice daily, respectively), and clopidogrel (75 mg daily) are acceptable options. Selection of an antiplatelet regimen should be individualized on the basis of patient risk factor profiles, cost, tolerance, and other clinical characteristics, as well as guidance from regulatory agencies. (Level of Evidence: B)"

Class IIa

"1. For patients with atherosclerosis of the extracranial vertebral arteries in whom aspirin is contraindicated by factors other than active bleeding, including those with allergy to aspirin, either clopidogrel (75 mg daily) or ticlopidine (250 mg twice daily) is a reasonable alternative. (Level of Evidence: C)"