The overall goal of this combined intervention is to safely treat intracranial arteriovenous malformations. This is accomplished via preoperative embolization to first reduce blood flow and remove high-risk arteriovenous malformation features. This is followed by surgical resection with the preceding embolization potentially significantly reducing the technical challenges of the surgery.
The goal of this protocol is to allow for the safe and comprehensive treatment of intracranial arteriovenous malformations. Using a combination of endovascular techniques and open surgery, we begin to develop a greater understanding of these intricate and complex lesions. With each progressive arterial embolization, we develop a higher risk of a loss of venous outflow and hemorrhage.
We therefore are in a position with our final embolization, under a single setting of anesthesia, to take the patient after that embolization immediately to surgery for a complete resection. Our case is a 22-year-old gentleman who presented with an intracranial hemorrhage from a ruptured AVM. This Spetzler-Martin grade III AVM left him with a visual field cut on the left side.
He presents for treatment today after a series of staged embolizations by my interventional partner. We're going to perform a final stage of embolization with the goal to reduce the AVM to one arterial distribution and then proceed with definitive surgical resection. His indication for the procedure are his young age, the Spetzler-Martin grade, and his personal history of rupture.
Position the patient supine on the fluoroscopy table after administration of general anesthesia with assistance from the anesthesiology team. Prepare the patient for embolization surgery with the neuromonitoring team. Establish baseline and continuous neuromonitoring signals via somatosensory evoked potentials, transcranial motor evoked potentials, auditory brainstem responses, and/or electroencephalography.
After preparing the patient for surgery, begin by placing the right femoral artery sheath. Prepare to use a modified Seldinger technique with a micropuncture groin access kit. To begin, clean the groin with alternating solution scrubs, and drape the surrounding area.
Next, inject one to two milliliters of 1%lidocaine subcutaneously. Then, palpate the femoral artery at the inguinal crease. After applying the local anesthetic, insert the microneedle into the femoral artery lumen at a 45 degree angle.
Next, insert the microwire, and advance it into the artery lumen. Then remove the microneedle, make a small skin incision, and insert a vessel dilator over the microwire. Then remove the microwire and inner portion of the vessel dilator, and insert a J-wire into the artery.
Remove the vessel dilator, keeping the J-wire in place. Now, introduce a size five or six French sheath over the J-wire and into the vessel lumen. Once in place, remove the J-wire.
Next, set up a mono-or biplane fluoroscope updating at three to five frames per second. To proceed with the AVM embolization, introduce a preassembled coaxial system into the femoral sheath. Now, under fluoroscopy, advance the coaxial system cephalad into the ascending aorta.
Along the way, inject small boluses of radiopaque contrast agent for visualization. In the ascending aorta, selectively catheterize the large caliber vessel from which the desired feeding AVM vessel originates with a diagnostic catheter, and advance the guide catheter to the appropriate cervical segment for support. Then, remove the diagnostic catheter and guide wire, and perform a diagnostic angiogram by injecting a radiopaque contrast agent.
Overlay guidance or roadmap images are then created to assist with microcatheterization of the target AVM vessel. Next, introduce a microcatheter and microwire into the guide catheter, and selectively catheterize the desired feeding artery under overlay or roadmap guidance. Embolize the nidus and desired feeding artery, using a controlled injection of radiopaque contrast agent.
In the highlighted case, a pedicle off the right fetal variant posterior cerebral artery was selected as the first target for embolization. The volume of solution needed depends on the size of the lesion. Be careful during this process, as there is a risk of embolizate reflux into non-AVM arteries or distal embolization into draining veins.
Repeat a guide catheter run to evaluate the embolization and patency of the parent vessels. Perform repeat microcatherizations and embolizations of all desired AVM pedicles, prioritizing arterial feeders that are the least surgically accessible. As the risk of venous outflow obstruction and rupture increases with progressive AVM embolizations, a final aggressive embolization should only be performed when a craniotomy and resection is planned to immediately follow.
In the highlighted case, two posterior cerebral artery pedicles and three middle cerebral artery pedicles in total were embolized prior to immediate transfer to the operating room for resection of the AVM. Perform a final diagnostic angiogram of involved vessels to evaluate overall AVM embolization and ensure patency of parent vessels. Finally, withdraw the coaxial system and sheath, and secure the femoral artery with a sealant device.
If the patient is being taken directly to the OR for resection, the femoral sheath may be left in place or exchanged for a flexible sheath for intraoperative angiogram. This procedure begins by performing a wide craniotomy at the AVM location. Ideally, the craniotomy site will be chosen to allow early access to cerebrospinal fluid cisterns for drainage if needed.
The patient is positioned to ensure adequate cerebral venous drainage. Neuromonitoring signals are established or continued if already established during embolization. Neuronavigation is synced with preoperative imaging and registered.
A planned incision is marked, the surgical site is prepped, local anesthetic is administered, and the field is draped. First, incise the skin and galea, using a number 15 blade. Then, obtain hemostasis, using electrocautery and Raney clips.
Elevate a soft tissue flap, using a combination of electrocautery and blunt dissection to the level of the cranium or pericranium. If desired, a pericranial flap can be harvested at this point and used later for closure. Hooks are used for soft tissue retraction to maximize surgical exposure.
Now, create one or multiple burr holes on the periphery of the desired craniotomy with a perforator drill bit attached to a high-powered drill. Around the burr hole, strip the dura from the inside of the skull using a bone elevator or footplate attachment. If the craniotomy is over a venous sinus, burr holes are planned to allow complete stripping of underlying dura at the sites where the craniotomy crosses the sinus.
Then, complete the craniotomy by connecting the burr holes. Use a tapered drill bit and, for dural protection, a footplate attachment on the high-speed drill. Great care is taken when cutting over a venous sinus.
Remove the bone after detaching it from the underlying dura. Irrigate and obtain hemostasis, using bipolar electrocautery. Next, place dural tack-up sutures to close off the epidural space by drilling small holes in the bone around the craniotomy with a C1 drill bit and securing the dura to the bone at these sites using 4-0 sutures.
Then, open the dura sharply and carefully, using a number 11 blade. Do not injure the underlying cortex or vessels. Then, open the remaining exposed dura in either a cruciate or C-shaped fashion, using Metzenbaum scissors and Gerald forceps.
Use the forceps to elevate the dural edge and visualize the tips of the scissors while cutting. Obtain hemostasis after dural opening, using irrigation and bipolar electrocautery. While not the case in this procedure, in the setting of an acute rupture and emergent surgery, it's important to actually decompress the clot only sufficiently to allow for brain relaxation and microdissection of the arterial feeders.
Complete resection of the clot should be reserved after all potentially angiographically occult components of the AVM have been identified at the time of surgery. Now, under an operating microscope or exoscope, excise the AVM. Start by first dissecting within the subarachnoid space, using a combination of blunt and sharp technique to define the AVM anatomy by exposing its margins and free draining veins.
Also obtain proximal control by identifying and dissecting free all of the feeding arteries. Take great care to identify and preserve the draining veins, as occlusion of the venous drainage prior to the arterial feeders results in engorgement of the AVM and increases rupture risk. After defining the anatomy, coagulate the arterial feeding arteries as they enter the AVM in a proximal to distal fashion, using bipolar electrocautery.
Gently hold the vessel between the tips of the bipolar forceps, and run up to 30 watts of current. Dissect circumferentially within the brain parenchyma immediately around the AVM nidus, using bipolar forceps and a variable action suction tip. A brain retractor may be used to facilitate visualization for deep dissections.
After completing the dissection, coagulate or clip draining vessels as needed. Then, remove the AVM from the resection cavity. Obtain meticulous hemostasis, using bipolar electrocautery as before and by gently lining the resection cavity with absorbable hemostatic agents.
After removing the AVM, perform an intraoperative angiogram, using the previously placed arterial sheath and intraoperative single or biplane angiography or C-arm fluoroscopy. Intraoperative angiogram of the right internal carotid and vertebral artery in the highlighted case demonstrated a complete AVM resection. Following a satisfactory resection, close or reapproximate the dura using 4-0 sutures and, if needed, a dural graft.
Replace and secure the bone flap, using a plating system, and close the galea and skin, using interrupted absorbable sutures for the deep layers and either staples or running suture for the skin. Finally, remove the groin sheath, and secure the groin. Extubate the patient if able, and transfer to the ICU for neurologic monitoring and recovery.
After this dual procedure, the patient was discharged after a short hospital stay at his neurologic baseline. To reiterate the applications of this technique, another case where combined endovascular and open surgical approach was used for AVM resection is reviewed. A 22-year-old, previously health female presented with new onset seizures.
Non-contrast head CT was negative for acute hemorrhage but revealed an incompletely characterized right front lesion. MRI demonstrated an approximately 2.9 by 2.4 centimeter Spetzler-Martin grade III AVM within the right superior frontal gyrus with large draining cortical veins going to the superior sagittal sinus and an arterial supply via large branches off the right middle cerebral artery. The patient underwent multiple staged endovascular embolizations, culminating in an embolization of a right anterior cerebral artery pedicle.
At the completion of these staged embolizations, there was residual supply to the nidus via the distal right middle and anterior cerebral artery branches and an indirect supply from the left external carotid artery via the distal superior temporal artery branches that anastomosed to the middle meningeal artery via transosseous collaterals. The patient then underwent a frontotemporal craniotomy, wherein the medial draining veins were identified early and protected. All arterial feeders were also identified, bipolared, and cut to achieve sequential devascularization prior to removal of the AVM nidus.
Intraoperative and postoperative catheter angiogram confirmed complete resection. One month postoperatively, the patient was neurologically stable and being weaned from antiseizure medications, with plans for delayed cerebral vascular imaging at one year. Our case today and the featured case in our figure example demonstrate the value of a combined endovascular and surgical approach for these complex lesions.
We've demonstrated the value of developing an intricate understanding of the pathophysiology and anatomy and protecting the patient from risks of rupture, progressive occlusion, or stroke. No less important are the neuroanesthesiologist, neuromonitoring, and neurointensive care professionals that carry the patient through their operative journey. For these reasons, we believe this technique should be best applied in high-volume experience centers.
