Brain AVM Embolization with Onyx

The treatment of brain arteriovenous malformations (AVMs) is challenging based on a multidisciplinary approach involving neurosurgery, radiosurgery, and interventional neuroradiology. The embolization of brain AVMS was for a long time performed using particles and glue. Onyx has been recently introduced in the armamentarium for AVM embolization, but large, multicenter evaluation is lacking. BRAVO study was conducted to evaluate the clinical and anatomical results of brain AVM embolization with Onyx. WHAT IS BRAIN AVM EMBOLIZATION WITH ONYX? Brain AVM embolization with onyx is the modern treatment of arteriovenous malformation [AVM]. Embolization is a method of blocking the blood vessels of AVM using the onyx glue, also called the only embolic agent. Arteriovenous malformations are vascular lesions that consist of arteriovenous microfistulae [micro links] through a vascular nidus [the infected spot].  AVMs can occur anyplace in the body. Signs and symptoms of AVMs depend on the site, size, and degree of arteriovenous leakage. They are commonly originated or present at birth. Endovascular embolization has been recommended as a treatment option since the early 1970s. Its endeavor is either to give relief to symptomatic patients [who do not want surgery] or to minimize intra-operative hemorrhage.  Endovascular embolization is an invasive surgical process that is used to treat strange blood vessels found in the brain or other areas of the body. It is a substitute to open surgery. The procedure blocks blood vessels from flowing into a particular affected part of the body. Onyx appears to be a relatively safe and efficient material for embolization of cerebral or brain AVMs, also in cases of intracranial bleeding [which occurs when a blood vessel within the skull is ruptured or leaks] associated with AVM.  Curative embolization of small brain AVMs [which happens to be an up-and-coming approach for curing cerebral arteriovenous malformations] is an effectual and harmless replacement to neurosurgical [about the nervous system] and radiological [concerned with using radiation] methods. An onyx [not the gem] is a non-adhesive and translucent [transport to x-rays] compound. When onyx is injected through the affected blood vessels it precipitates to effect closure of the human of the targeted vessel.  The degree of human closure is associated with the location of the vessel. Supratentorial and cortical location is most advantageous. Careful angiographic (x-ray imaging) assessment of individual AVMs should be performed before each onyx administration. AVM may occur sequentially with:

• Hereditary hemorrhagic telangiectasia
• Ehlers-danlos syndrome
• Bonnet-because-Blanc syndrome
• PHACE syndrome

RISKS OF AVM

• Acute Brain AVM embolization with onyx from vertebrobasilar circulation or via perforating feeders.
• Acute hemorrhages via few or insufficient veins.

THE A.V.M EMBOLIZATION WITH ONYX TECHNIQUE There are many ways to assess AVM symptoms. One of such ways is via imaging. The available imaging options include: 

• The assessment of ischemic lesions.
• Approximate imaging of lesion morphology.
• Mapping eloquent cortex areas.

Digital subtraction angiography [DSA] has set a standard in AVM assessment. DSA gives exact information on hemodynamic properties of the malformation, such as: 

• Arterial supply.
• The flow rate in individual components.
• Venous drainages.

DSA also visualizes the morphology of the AVM nidus. Furthermore, DSA visualizes the venous drainage of normal brain tissues. The examination recuperates the visualization of the cranial vessels [external and internal carotid arteries, as well as vertebral arteries] is in required projections and 3D images.   The examination is concluded by a very selective evaluation of the arterial blood supply of the AVM, which might establish the preparation for embolization. THE PREPARATION FOR A.V.M ONYX EMBOLIZATION

• Call on your doctor on the day before the exam, to confirm the time and location of the examination.
• Do not smoke or drink caffeine 24 hours to the test. Smoking and caffeine may introduce complications. They are blood thinners and as such, they hinder the clotting of your blood.
• Come expecting that you will be asked to change into a hospital gown. Come in comfortable clothing. You may likely leave your jewelry at home.
• Obtain advanced instructions from your doctor, to know what you are expected to do before coming for the test.

SPECIALTY: A team of neurologists, neurosurgeons, and neuroradiologists. DURATION: About two and a half to three hours is all it takes for an AVM onyx embolization to complete.

• Before The Procedure

1. 1. You may be asked to:
      1. Change into a hospital gown.
      2. Remove your jewelry.
      3. Be positioned on the examination table.
   2. An intravenous [IV] line will be inserted into one of your veins, for administration.
   3. You will be connected to monitors that track your heart rate, blood pressure, oxygen level, and pulse.
   4. Your body area for the catheter insertion will be sterilized and covered with a surgical drape [DMSO].

• During The Procedures

The radiologist will do the below:

1. Numb the area for the catheter insertion with local or general anesthesia.
2. Make a small incision on the numbed area of your body.
3. Flush the guiding microcatheter via a pressure bag, with saline containing 2500 U heparin/L.
4. Guide the microcatheter to the nidus of the AVM, with the aid of a 0.008-inch guidewire [Mirage, ev3], until the tip of the microcatheter gets to the desired position.
5. Flush the microcatheter with 5ml of normal saline.
6. Inject 0.25ml of DMSO into the microcatheter, to fill the dead space.
7. Aspirate onyx into 1ml syringe.
8. Inject 0.25ml of onyx for 40 seconds [slowly], to fill the microcatheter and fill up the dead space.
9. Continue the slow injection of onyx under fluoroscopy.
10. Carry out single injections of onyx for up to 90 minutes.

The injection is expected to be done from time to time, to obtain an angiogram after each pause. Long injection times are possible, due to the less adhesiveness of onyx.

1. Withdraw the catheter when reflux exceeds about 1.5 to 2cm of the catheter’s tip.

• After the Procedures

1. 1. You will remain in the procedure room for some hours, for close monitoring.
   2. The health workers will use an ultrasound or external labor monitor, to track your heartbeats after the procedure.
   3. You will be:
      1. Transferred into a hospital room until your doctor makes certain your discharge to go home.
      2. Advised to avoid smoking and caffeine.
   4. Call on your doctor if any emergency health condition springs up.
   5. Value your follow-up appointments with your doctor.
   6. Take your medications as recommended.

RESULTS The procedure for the cranial AVM onyx embolization is challenging and doesn’t go without complications.  The most common complication is hemorrhage, occurring in about 9.7% of patients undergoing the procedure.  A hemorrhage occurs if the catheter is glued to the nidus. Sometimes, the catheter or the guidewire can injure the vessel as it navigates through the blood vessel to the nidus of the AVM. The lesion may bleed.  Despite all these, curative embolization of AVM with Onyx has proven to be the best noninvasive treatment approach to AVM. MORTALITY RATE Brain AVM onyx embolization has witnessed an overall clinical complication rate of 24.1%, with hemorrhage being 9.7%. The mortality following rupture of AVM and left untreated stands at 4.6%. However, procedure-related mortality was 1.5%.  

Symptoms

Inconsistent data are available regarding the incidence of AVM symptoms. In most cases, the disorder may show no symptom [asymptomatic]. However, the most common symptoms include:

• Bleeding.

• Seizures. 

• Recurring headaches.

• Severe headache.
• Weakness, numbness or paralysis.
• Vision loss.
• Difficulty speaking.
• Confusion or inability to understand others.
• Severe unsteadiness.

Causes

The factors that promote arteriovenous malformation [AVM] raptures include:

• Presence of aneurysms.
• Size of the blood vessels [if the diameter is <3cm].
• Deep or periventricular location.
• High pressure in supplying arteries.
• Pregnancy.

The cause of cerebral AVM is unknown. An AVM occurs when arteries in the brain connect directly to nearby veins without having the normal small vessels (capillaries) between them. AVMs vary in size and location in the brain. An AVM rupture occurs because of pressure and damage to the blood vessel.

FAQ

What is the recovery period of brain AVM embolization surgery?
Full recovery takes few months, but normal day to day activities can be resumed after 4 to 6 weeks. If side effects are seen, rehabilitation programmes may also be advised during this period.

What is the survival rate of an AVM?

In observational studies, the mortality rate after intracranial hemorrhage from AVM rupture ranges from 12% – 66.7% and 23% – 40% of survivors have a significant disability.

• Is AVM brain completely curable?

Once an AVM is completely taken out surgically, the patient is cured. An AVM doesn't grow back.

• Can you live with an AVM?

AVM affects around 1 in 2000 people. Although most people with the condition can lead relatively normal lives, they live with the risk that the tangles can burst and bleed into the brain at any time, causing a stroke. Around one in every hundred AVM patients suffer a stroke each year.

• Can I drink alcohol with an AVM?

Do not drink alcohol. Alcohol may also raise your blood pressure or thin your blood. Blood-thinning can cause hemorrhage.

• Is embolization a surgical procedure?

Endovascular embolization (EE) is an invasive surgical procedure. It's used to treat abnormal blood vessels found in your brain, as well as other cases of your body.