What is Vertebrobasilar Insufficiency?
Vertebrobasilar insufficiency (VBI) refers to a condition where there is not enough blood reaching the back part of the brain. This part of the brain is supplied blood by two arterial channels that join to form one main artery, namely the basilar artery. These arteries nourish important parts of the brain like the cerebellum, medulla, midbrain, and occipital cortex. When these areas don’t get enough blood, it can result in serious health deterioration and in severe cases, even death.
Because this issue affects the cerebellum, parts of the brain that control different body functions, survivors can experience a disruption in organ functions. This may include lack of muscle control or coordination, weakness on one side of the body, abnormal eye movements, difficulty in speech and swallowing, and impaired cranial nerve function. Fortunately, in many cases, patients show mild and localized neurological deficits due to the involvement of smaller blood vessels.
The term, VBI, came into use in the 1950s when C. Miller Fisher used ‘carotid insufficiency’ to describe temporary lack of sufficient blood supply in the carotid region. Therefore, VBI is often used to describe temporary periods of insufficient blood supply in the vertebrobasilar region. This region, also known as the posterior circulation, supplies blood to areas such as the brainstem, thalamus, hippocampus, cerebellum, occipital, and medial temporal lobes.
While patients may not show symptoms initially, the build-up of plaque in the arteries over time can cause blocks, leading to ‘ischemic events’ – periods when tissues do not get enough blood and oxygen. This could eventually result in a stroke. Either due to the blockage in the vertebral or basilar artery, or due to a clot that gets lodged nearer to the brain.
In emergency medical situations, it’s important to be aware of VBI as its symptoms can seem like other less serious conditions such as labyrinthitis (inflammation of the inner ear), vestibular neuritis (inflammation of the vestibular nerve), and benign paroxysmal positional vertigo (a condition where a person develops a sudden sensation of spinning).
What Causes Vertebrobasilar Insufficiency?
Some factors can increase a person’s chances of developing VBI (vertebrobasilar insufficiency), particularly those that make atherosclerosis worse. Atherosclerosis is a condition where your arteries get narrow due to the build-up of fats, cholesterol, and other substances. Factors that can increase your risk of VBI include smoking, high blood pressure, age, gender, family history and genes, and high levels of fat in your blood, known as hyperlipidemia.
Additionally, if you already have a condition that affects your blood vessels, such as coronary artery disease (CAD) or peripheral artery disease (PAD), your risk for VBI may be higher. CAD is a condition that affects the blood vessels supplying your heart, while PAD affects blood vessels outside of your heart, often in your legs.
There are also other conditions that could cause VBI, such as atrial fibrillation, which is an irregular and often fast heart rate; infective endocarditis, an infection of the inner lining of your heart chambers and heart valves; vertebral artery dissection, which is a serious condition caused by a tear in one of the major arteries in the neck; and systemic hypercoagulable states, which is a condition where your blood clot too much. These all can lead to getting VBI.
Risk Factors and Frequency for Vertebrobasilar Insufficiency
Approximately 25% of strokes and Transient Ischemic Attacks (TIAs), temporary blockages of blood flow to the brain, happen in an area called the vertebrobasilar distribution. This condition, known as vertebrobasilar disease, is similar to atherosclerotic disease – the build-up of fats in blood vessels. It typically occurs later in life, usually around the ages of 70-80, and is more common in males.
- Up to a quarter of older people show symptoms like poor balance and a higher risk of falls due to this condition.
- Like many stroke-related conditions, African Americans are more commonly affected than other ethnic groups.
- This higher prevalence can be attributed to various factors, such as genetic tendencies, a higher prevalence of high blood pressure, and differences in the availability and quality of healthcare.
Signs and Symptoms of Vertebrobasilar Insufficiency
Vertebral Basilar Insufficiency (VBI) is a condition that commonly occurs due to cardiovascular diseases like atherosclerosis or as a result of old age. The symptoms of VBI come about due to inadequate blood flow in certain parts of the brain. If VBI continues to progress, it can result in multiple syndromes depending on its location within the brain. Other factors such as reproducing certain symptoms when the head changes positions should also be considered during a physical exam.
The most common symptoms of VBI include:
- Vertigo, the most common sign of VBI
- Dizziness or fainting
- Sudden weakness in the knees, causing falls
- Double or lost vision
- Strange sensations or numbness, especially on one side of the body
- Confusion
- Difficulty swallowing or talking
- Headache
- Altered consciousness
- Loss of coordination or unsteady walk
- Weakness on one side
- Loss of temperature and pain
- Incontinence
Physical examination after a vertebral artery stroke can reveal:
- Changes in consciousness
- Weakness on one side of the body
- Changes in pupil size and reaction
- Cranial nerve paralysis
- Different types of eye movement abnormalities
- Facial nerve paralysis
- Muscle weakness of the tongue or other mouth muscles
- Loss of ability to feel temperature or pain
Certain similar symptoms can also occur as a result of less severe conditions like labyrinthitis, vestibular neuritis, and benign paroxysmal positional vertigo (BPPV). Hence, it becomes crucial to differentiate these conditions from VBI, especially in emergency situations. This distinction, however, cannot be made based solely on vertigo. It needs to be accompanied by other brainstem signs or symptoms.
Syndromes associated with vertebral artery strokes can include conditions such as:
- Locked-in syndrome
- Lateral medullary syndrome
- Internuclear ophthalmoplegia
- Cerebellar infarction
- Medial medullary syndrome
- Posterior cerebral artery occlusion
Testing for Vertebrobasilar Insufficiency
Imaging techniques are vital for diagnosing and managing conditions related to the vertebral and basilar arteries. Non-invasive methods such as CTA or MRA (which use X-rays or magnetic fields respectively to create pictures of your blood vessels) are usually used to provide images of the vertebral-basilar system. These images can help determine if there are narrowings (stenoses) or blockages (occlusions) in the vessels. CTA is beneficial as it captures clear pictures of both the vessels within the brain (intracranial) and outside it (extracranial).
However, imaging the extracranial vessel could need a technique called contrast-enhanced MRA. This involves using a contrast agent to make the blood vessels more visible, but the swallowing motion can sometimes make the images less clear.
One needs to be careful when using CTA, though, as the contrast used can cause kidney damage (nephrotoxicity), and the procedure involves exposure to radiation. MRI scans using a contrast agent called gadolinium can also impact kidney function and very rarely cause a condition called nephrogenic systemic fibrosis if your kidney function is impaired. In terms of viewing problems occurring in the brainstem and the posterior fossa, an area at the back of your skull, MRI usually offers better images. It is particularly effective for spotting acute infarctions (areas of dead tissue due to a lack of blood) in the brainstem.
Other issues, such as cavernomas (clusters of abnormal blood vessels), dermoid/epidermoid cysts (non-cancerous growths that arise at birth) in the cerebellopontine angle (the area between the cerebellum and pons), and schwannomas (tumors that develop on the covering of nerve) can also be effectively identified by an MRI.
An ultrasound of the arteries in the neck could be useful for identifying abnormalities in the vertebral artery. However, it’s not always ideal, as it can be challenging to view certain sections of the artery or identify changes in blood flow caused by blockages. For patients over the age of 45, doctors will also look for risk factors for VBI such as cholesterol levels, blood sugar levels, blood pressure, and smoking habits. In younger patients, further investigations are needed to rule out causes such as heart-related problems, excess blood clotting, vertebral dissection (tear of the vertebral artery), and fibromuscular dysplasia (an abnormal growth or position of the artery wall).
Other routine tests include blood tests to check blood cell counts, electrolyte levels, kidney and liver functions, and a coagulation profile and lipid profile which measures the blood’s ability to clot and the amounts of various types of fat respectively. Younger patients will also need to be evaluated for a specific mutation called factor V Leiden, Protein C, S, and lupus anticoagulant. An ECG (tests the electrical activity of the heart) may be done to reveal changes in the heart’s normal rhythm, damage to the heart muscle, or a heart attack. An echocardiogram (an ultrasound of the heart) may be needed to rule out heart-related conditions.
Treatment Options for Vertebrobasilar Insufficiency
Just like in cases of ischemic strokes (a stroke due to blocked blood flow to the brain), managing vertebrobasilar disease (a condition affecting the blood vessels at the back of the brain) requires immediate action. Past instances of transient ischemic attacks (TIAs, which are temporary blockages of blood flow to the brain) might point to a future, more serious stroke.
If the cause of the blockage is determined to come from the heart, most likely due to conditions like atrial fibrillation (an irregular heart rhythm) or mechanical heart valves, blood thinners are usually recommended. Sometimes, a trauma leading to the damage in vertebral arteries can also be the source of the blood clot; in such cases, antithrombotic medication, which helps to prevent blood clots, is used.
Apart from this, managing risk factors such as smoking, high cholesterol, and high blood pressure is crucial. Initially, when the symptoms are severe, doctors may use IV fluids to ensure that enough blood is reaching the brain and try to avoid lowering the blood pressure too much. In the long term, strict control of blood pressure is essential to prevent future strokes.
Other important preventive measures include lifestyle changes like quitting smoking, maintaining a healthy diet and regular exercise, controlling blood sugar levels, and using cholesterol-lowering medications known as statins.
Surgical options for this condition are limited and depend on where the blockage is located and how effective a repair would be. Surgery becomes a more likely option if the blockage is located further away from the brain.
Criteria for surgery include severe narrowing (more than 60%) in both vertebral arteries or in the dominant vertebral artery. Also, if an artery problem is causing symptoms, or if an aneurysm (a weakened, bulging spot in the artery) is present and is larger than 1.5 cm, surgery might be needed.
There are two types of surgical treatments: open surgical repair and endovascular treatment. Open surgical repair involves using a graft to bypass the area of narrowing while endovascular repair involves inserting a balloon and a stent to open up the blocked artery, using a small tube inserted into a blood vessel in the groin.
Patients who experience a stroke because of vertebral artery problems need to be closely monitored in an intensive care unit (ICU), especially if they are medically unstable, have variable neurological symptoms (relating to the brain and nervous system), have other medical conditions, or are potential candidates for clot-dissolving medication treatments (thrombolytic therapy).
Once the patient achieves stability, the course of treatment depends on how quickly the patient received medical attention after the onset of symptoms. If the patient receives medical attention within 4.5 hours of the stroke symptoms, a clot-dissolving drug called tPA has been shown to be effective. Blood thinners might be used, but studies have not shown definitive evidence of their effectiveness in improving outcomes after a stroke.
Another procedure, angioplasty (which uses a balloon to open up a blocked artery), is often performed for patients with narrowed blood vessels at the base of the brain. However, its use in treating vertebral artery stroke still needs to be figured out.
What else can Vertebrobasilar Insufficiency be?
When dealing with certain medical conditions, doctors consider other diseases that might share similar symptoms. These conditions might include:
- Benign positional vertigo in emergency medicine
- Labyrinthitis
- MELAS (Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes)
- Multiple Sclerosis
- Posterior fossa tumour
- Subclavian steal syndrome
- Stroke haemorrhage
- Stroke ischemic
- Transient ischemic attack
- Transtentorial herniation
- Vertebral artery dissection
- Vasculitis
- Vestibular neuronitis
It’s important for doctors to distinguish between these possibilities to make a correct diagnosis.
What to expect with Vertebrobasilar Insufficiency
How well a person recovers after having a stroke in the vertebral artery (the arteries in the neck that supply blood to the brain), depends on how severe the stroke was, the age of the patient, and any other existing health conditions they might have. There’s also a 10-15% chance the stroke might happen again.
Even if the stroke was a minor one, the path to recovery can be really tough. Many people who survive often need a lot of physical therapy and rehabilitation that could last several months. Even after this intensive recovery period, some people may still experience lingering effects on their nervous system.
Possible Complications When Diagnosed with Vertebrobasilar Insufficiency
- Deep vein thrombosis: A condition where a blood clot forms in the deeper veins of your body, usually in your legs.
- Aspiration pneumonia: An infection that happens when you accidentally inhale food, drink, or saliva into your lungs.
- MI (Myocardial Infarction): Commonly known as a heart attack. It happens when blood flow to the heart muscle is blocked.
- Pulmonary embolism: A blockage in one of the pulmonary arteries in your lungs, often caused by blood clots from the legs.
- Pressure sores: Also known as bed sores, these are injuries to your skin and underlying tissue caused by prolonged pressure on the skin.
- Gastritis: An inflammation or irritation of the stomach lining.
