Begin with an anesthetized patient, positioned to ensure adequate cerebral venous drainage. The patient has a cerebral arteriovenous malformation (AVM), a lesion with abnormal artery-to-vein connections.
Incise the skin and connective tissue and remove the pericranium layer to expose the skull. Drill holes and connect them to create a bone flap.
Expose the dura mater, the outermost brain layer, and suture it to the skull to close the epidural space.
Open the dura to expose the AVM.
Identify the arteries feeding blood to the AVM and the veins draining blood away.
Use electrocautery to apply heat that seals the feeding arteries and blocks the inflow.
Dissect the AVM circumferentially, occlude the draining veins, and remove the AVM.
Use electrocautery and hemostatic agents to control residual bleeding.
Perform angiography to confirm complete AVM removal.
Close the dura, reposition the bone flap using a plating system, suture the scalp, and monitor the patient for recovery.
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.
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