Basilar Artery Infarct

What is Basilar Artery Infarct?

The basilar artery, which is created on the surface of the pons by two vertebral arteries, is responsible for supplying critical areas of the brain and brainstem with blood. In terms of anatomy, it is divided into three sections: proximal, middle, and distal. These portions stretch from the vertebral artery to various other arteries in the brain. A basilar artery infarct or occlusion is a condition which occurs when the blood supply to the back part of the brain, also known as the vertebrobasilar system, is blocked. It was first identified by a Scottish doctor, John Abercrombie, in 1828.

Among the most common causes for this are atherosclerosis and blood clots from large vessel blockage or from the heart. The symptoms may range from very mild, like feeling nauseous, dizzy, getting headaches, confusion, and feeling off-balance, to severe manifestations like difficulty with speech, swallowing, paralysis to one side or all limbs, loss of consciousness, comatose state, irregularities with cranial nerves, vision loss, and even severe heart or respiratory issues. The latter can be lethal if not diagnosed and treated promptly.

A key symptom of basilar artery occlusion is reduced consciousness. When a patient shows these signs, they need to be quickly evaluated, and the stroke and medical imaging teams should be consulted. Urgent scans, such as CT scans of the head, CT angiography of the head and neck, or MRI scans with or without perfusion imaging, are often done. However, this process should not delay the administration of blood clot dissolvers like alteplase or tenecteplase. Furthermore, the patient may need to be moved to the angiography room for mechanical thrombectomy, a procedure to remove the clot, if they are eligible. This approach can lead to potentially good clinical outcomes.

What Causes Basilar Artery Infarct?

The things that often cause stroke can also result in damage to the basilar artery’s area in the brain. If something like hardening of the arteries or a clump of blood cells (known as an embolus) blocks blood supply from the heart to the basilar artery, it can stop blood reaching the brainstem or the brain region that the basilar artery feeds. The most common regions affected are the beginning and middle parts of the basilar artery.

Hardening of the arteries is caused by factors like abnormal lipid levels in the blood, diabetes, smoking and high blood pressure. This can injure the inside layer of the blood vessels, leading to the release of factors that attract platelets, which are a type of blood cell. This process can eventually form a clot or blockage. The accumulation of oxidized fats can turn certain immune cells into ‘foam cells’ filled with lipids. If the clot breaks apart, it can either block the vessel partially or fully, or smaller pieces of the clot can block smaller vessels downstream. In both cases, it can cause the obstruction of several vessels, leading to damage in the respective brain regions. Another way this can happen is if a clot forms in the heart and moves into the brain circulation. This is often due to conditions that affect the heart’s rhythm, artificial heart valves, severe narrowing of the heart’s valves, severe heart attacks, acute heart failure, and problems with the heart’s motion.

In rare cases, external pressure on the vertebral artery can cause a type of stroke that influences the back part of the brain’s circulation. This requires either treatment through a catheter, decompression via a surgical process, or a surgical bypass.

COVID-19 infection has been found to increase the risk of clotting during pregnancy and result in basilar artery blockage. Other rare causes of basilar artery blockage include a rare malformation of the basilar artery, acute myelogenous leukemia (a type of blood cancer), and Crohn disease (an inflammatory bowel disease).

Risk Factors and Frequency for Basilar Artery Infarct

Basilar artery occlusion is a lesser-known condition and is estimated to be behind 1% of all strokes caused by a blood clot, known as ischemic strokes. Despite this, it’s hard to pin down the exact number of people this condition affects each year – one study suggests it could be around four in every 100,000. According to the Basilar Artery International Cooperation Study (BASICS) registry which included 592 patients with the condition, the average age of patients was 63. The study also found that 37% of the patients were female, and the severity of their symptoms varied quite a bit.

In our current age of innovative diagnosis techniques, scientists are calling for more study into how common basilar artery occlusion really is. This is especially important now that there are more treatment options available to these patients.

• Basilar artery occlusion is behind roughly 1% of ischemic strokes.
• Its occurrence rate is currently unclear – one estimate suggests around four cases for every 100,000 people per year.
• According to a study, the average patient age is 63, with 37% of them being female.
• The severity of symptoms in patients can vary widely.
• With new, advanced techniques available to diagnose conditions, more research needs to be done to understand how common basilar artery occlusion is, particularly as there are more treatments available now.

Signs and Symptoms of Basilar Artery Infarct

Several symptoms and signs can result from different forms of stroke in the brainstem or basilar artery. These can vary depending on which part of the brain is affected:

• Damage to different cranial nerves and brain areas can lead to difficulties with movement (hemiparesis, quadriparesis), issues with senses (anesthesia, hypesthesia, vertigo), speech problems (aphasia, dysarthria, dysphagia), a variety of other symptoms (nausea, dizziness, headache), and even loss of consciousness or coma.
• A condition known as basilar tip occlusion can lead to confusion, vision loss, eye movement abnormalities, and seizures.
• Problems with certain arteries (VA and PICA) can lead to swallowing issues (dysphagia), coordination problems (ataxia), difficulties with face sensation, and a condition called Horner syndrome, which can affect one side of the face.
• Movement problems that resemble seizures, combined with stiffness and twitching, can also be early symptoms of a stroke.

The signs and symptoms can also be related to the extent of damage in different areas of the brain:

• Different paths within the brain can lead to loss or decrease of sensation (anesthesia, hypesthesia), paralysis (hemiplegia, quadriplegia), and foot muscle contraction.
• Damage to the consciousness control center in the brain can result in coma or impaired consciousness.
• Affected areas related to movement and touch sensation can lead to uncoordinated movements of limbs and poor posture control (ataxia).
• Issues with part of the brain responsible for balance can lead to vertigo, nystagmus (rapid, uncontrollable eye movements), and balance loss.
• Dysfunction in certain brain fibers may cause Horner syndrome, a condition affecting eye and face movements.

There can also be other specific symptoms based on damage to specific brain components:

• Pain in the head and neck, symptoms related to heart and lung function, loss of bladder control, issues with eye movements, impaired eye response, and various visual impairments (ptosis, gaze paresis, reflex loss, etc.).
• Involvement of cranial nerves and different brain tracts can cause facial palsy, speech difficulties (dysarthria, dysphagia), memory issues, confusion, and seizures.
• Difficulties with hearing and balance, disruptions in vision, jerking movements, and extension posturing or rigidity.

Testing for Basilar Artery Infarct

When someone arrives in the emergency department (ED), the first thing to do is a CT scan of the head without contrast. This test is to make sure that the person is not having a hemorrhagic stroke (which is when a blood vessel in the brain has ruptured and bleeds). While waiting for the CT results, other vital information is gathered, such as blood pressure, blood glucose levels, the time when the person was last known to be normal, use of specific medications, medical and surgical history, kidney function, and a person’s risk factors for stroke therapy.

In cases where the CT scan does not indicate bleeding in the brain, and the person may have basilar artery occlusion (a blockage in the main blood vessel at the back of the brain), doctors may suggest additional IV treatments and a CT angiogram of the head and neck. This procedure helps check for a potential blockage of large brain vessels. If a CT angiogram cannot be performed, then an MR angiogram is an alternative, provided the person is fit to undergo this procedure. An MRI scan of the brain is often done to investigate the stroke further. However, such scan should not delay critical stroke treatments like intraarterial thrombolysis (IAT) and mechanical thrombectomy (MT).

There is a unique sign seen on the MRI scan, known as the ‘smog sign.’ If it is present, it indicates a better chance of a good neurological outcome after a mechanical thrombectomy. Another point of significance is the ‘target mismatch’, identified if the initial area of the brain affected by the stroke is less than 70ml and the ratio of brain tissue at risk to stroke volume is more significant or equal to 1.8. This discovery could be a possible selection standard for stent therapy in the brain vessels.

Furthermore, a particular grading system called eTICI can denote successful unblocking of the blood vessels after EVT (endovascular therapy) in patients diagnosed with acute BAO (basilar artery occlusion). After these urgent management measures, doctors need to carry out a full stroke evaluation to find the stroke’s cause, which will guide specific treatment approaches. The doctor will also assess the stability of the plaque (a fatty deposit in the arteries), look for clots, valvular abnormalities, wall motion abnormalities, and PFOs (patent foramen ovale – a hole in the heart that didn’t close after birth).

An ECG, telemetry (long-term heart monitoring), event monitor or loop recorder may be necessary to rule out heart rhythm abnormalities. Blood tests would also be carried out, including HbA1c (measures blood sugar over three months), lipid panel (measures fats in the blood), homocysteine (an amino acid that can cause blood clots) and other tests depending on the suspected cause like antiphospholipid antibody syndrome, verify-now for platelet function, and cancer screening.

Treatment Options for Basilar Artery Infarct

If a patient arrives at the hospital within 3 to 4.5 hours after noticing stroke symptoms and there is no reason why they shouldn’t take tPA, a type of medication, they should receive it promptly. Afterwards, they can be moved to a special room for a procedure known as mechanical thrombectomy (MT), even up to 24 hours after first noticing the symptoms. This procedure should be considered for all patients who arrive at the hospital within the 4.5 hour “window” and are suitable for the tPA treatment.

After these treatments, patients should be looked after in a specialist neuroscience unit. There they can receive close monitoring, help with breathing, careful management of their blood pressure, and other supportive care. The patient’s condition should be managed by a team of different healthcare professionals in a stroke unit, rather than a general hospital ward.

The “First-pass effect” (FPE), where a patient’s blood flow is successfully restored with a single attempt using a device called a stent retriever, without needing any extra treatment, has been linked to better outcomes after 90 days, especially for patients who had the procedure within 24 hours.

Interestingly, using the stent retriever as an initial treatment has been found to have better success rates than direct aspiration, another treatment method which involves sucking the blood clot out. However, the stent retriever approach might have a slightly higher risk of complications.

Recent studies have suggested that the procedure for removing the clot (mechanical thrombectomy) should be attempted at least three times, as this might help restore blood flow better among stroke patients.

Patients who can’t take tPA and have an accumulation of fatty deposits in the blood vessels behind the brain can be managed with medications to prevent blood clots or reduce blood stickiness (antiplatelet drugs). Recent research has also suggested that for patients with a large area of damage from a stroke, a single or dual antiplatelet therapy might be more effective than anticoagulation. In cases of intracranial atherosclerosis (narrowing of the brain’s blood vessels due to fat build-up), it’s recommended to use dual antiplatelet therapy for 90 days after the stroke, then switch to aspirin only.

Prevention of further strokes may include using aspirin, atorvastatin (a type of cholesterol-lowering medication), and blood thinners, if indicated. When a patient is ready to be discharged from the hospital, they should get advice on managing their stroke risk factors. This could include aiming for a cholesterol level below 70, blood pressure reading less than 130/80, and good control of blood sugar with an A1c level under 6.5. The medical team might suggest other treatments depending on the cause of the stroke. Healthy lifestyle changes, like a Mediterranean diet, quitting smoking, limiting alcohol, and avoiding illegal drugs, have also been shown to help prevent another stroke.

What else can Basilar Artery Infarct be?

Here are several health conditions that can have similar symptoms to a stroke:

• Basilar meningitis: an inflammation of the brain covering
• Basilar migraine: a severe form of headache
• Cerebellar infarct: a condition where a part of the brain lacks adequate blood supply
• Drug intoxication: overexposure to certain drugs
• Encephalopathy: a general term for brain disease
• Hemorrhagic stroke: this could be caused by brainstem compression or abnormal blood vessels in the brain bleeding
• Multiple sclerosis: a disease that affects nerve cell coverings in the brain and spinal cord
• Seizures: sudden, abnormal electrical disturbance in the brain
• Tumors in the back part of the brain: these can cause increases pressure and compression on the brainstem

Since these conditions have similar symptoms to a stroke, doctors would run various tests to accurately diagnose the issue.

What to expect with Basilar Artery Infarct

The outlook for patients suffering from BAO (basilar artery occlusion), a type of stroke, greatly depends on various factors such as the severity of the stroke, the time taken from symptom onset to treatment, the effectiveness of the treatment, and the accessibility to specialized stroke centers. Unfortunately, the death rate is generally very high among these patients. However, patients with successful restoration of blood flow after a procedure called thrombectomy have a comparatively lower mortality rate (33 to 50%) than those without this procedure or if it is unsuccessful (74 to 100%).

Timely arrival and proper treatment can lead to better results, with minimum harm to the patients. On the other hand, delays in treatment and unsuccessful blood flow restoration typically lead to poor outcomes, such as severe neurological damage and high mortality rate.

Interestingly, an imaging technique called diffusion-weighted imaging on the cerebellum, a part of the brain, before starting endovascular treatment (a minimally invasive procedure), can predict the mortality of the patient 90 days ahead. This serves as a useful tool for doctors to tailor the treatment plan according to the patient’s needs.

Possible Complications When Diagnosed with Basilar Artery Infarct

Some common complications that can arise after surgery include:

• Death
• Bleeding within or outside the brain
• Reperfusion syndrome, a condition where blood flow returns to the tissue after a period of ischemia, or lack of oxygen
• Ischemic stroke, a type of stroke that occurs when the blood supply to the brain is blocked
• Complications at the puncture site in the groin, such as a hematoma (a solid swelling of clotted blood), a fistula (an abnormal connection between two body parts), and internal bleeding within the abdomen
• Infections which can occur in different regions such as the urinary tract and lungs (pneumonia)
• Pressure ulcers, or sores that develop from prolonged pressure on the skin
• Contractures, or shortening and hardening of muscles, tendons, or other tissues
• Dysphonia, a condition characterized by difficulty speaking or abnormal voice quality
• Dysphagia, a term used to describe difficulty swallowing
• Deep vein thrombosis or pulmonary embolism, conditions characterized by blood clots in the deep veins of the legs that can travel to the lungs

Recovery from Basilar Artery Infarct

Various types of therapies exist for different health concerns, these include: respiratory, physical, occupational, and speech therapy. Another type of therapy, acupuncture, has been researched for its potential benefits in improving blood flow within the arteries at the back of the neck in patients suffering from vertigo due to blockage of blood supply to the back of the brain (posterior circulation infarction vertigo).

Preventing Basilar Artery Infarct

Advice for patients and their families on how to lower the risk of a stroke includes properly managing health conditions such as diabetes, hypertension, high cholesterol, heart diseases, and obesity. It’s also crucial to quit smoking, limit the consumption of alcohol, and incorporate physical activity regularly. They should also learn and remember the BE-FAST signs of a stroke – balance loss, eyesight issues, facial droop, arm weakness, slurry speech. Spreading awareness about these signs through media and public education campaigns is extremely important. Prompt action is key. If these symptoms appear, the person should get medical help immediately.

The risk of stroke can be minimized by managing certain conditions like high blood pressure, high cholesterol, diabetes, heart disease, and obesity. Other effective measures include quitting smoking, reducing alcohol intake, and remaining physically active over time. The quicker the treatment starts after noticing the initial symptoms of stroke, the better. Ideally, treatment should start between 3 to 4.5 hours from the start of symptoms. This is when clot-dissolving medicines are most effective. Even if the exact time of symptom onset is unknown, it’s crucial to get medical assistance as soon as possible.

Once the 4.5-hour window has passed, treatment may include resting, oxygen, fluids given through a vein (IV), and medications to prevent the blood from clotting too much. The specific treatment for a stroke depends on how long the symptoms have lasted, how severe they are, and what caused them. It might also involve addressing dietary needs or administering medication to manage diabetes, high blood pressure, and other risk factors.

After a stroke, a team of physical, speech, and occupational therapists might work with the patient to improve any functions that the stroke has impaired. They will also implement preventative measures to avoid potential short-term and long-term complications. These could include infection from accidentally inhaling foreign matter into the lungs (known as aspiration pneumonia), developing blood clots in the legs, sores from staying in bed too long (bedsores), and falls. In some rare cases, surgery may be required to remove large blood clots or to clear blocked arteries.