Neuroendovascular surgery (AKA endovascular neurosurgery), which overlaps with interventional neuroradiology, employs techniques of catheter-based diagnosis and treatments. This chapter addresses some general aspects of importance to the management of these patients that are not covered in other sections. For endovascular issues related to specific entities (e.g. aneurysms), see the chapter on that subject (listed below).
CONDITIONS TREATED
Conditions that are sometimes amenable to endovascular techniques include:
1. aneurysms: coiling, stent assisted coiling (see page 1059)
2. arteriovenous malformations (AVMs): embolization
A. pial AVMs: see page 1098
B. dural AVMs (considered to be fistulas by some): see page 1109
C. spinal AVMs: see page 507
3. arteriovenous fistulas: CCFs (see page 1113)
4. acute embolic stroke: intraarterial clot lysis (see page 1018) or mechanical clot disruption/removal (see page 1018)
5. cerebrovascular arterial dissections: see page 1160
6. internal carotid artery stenosis: angioplasty/stenting in high-risk patients (see page 1151)
7. tumors: embolization. Primarily used before surgery as an adjunct to decrease vascularity, e.g. with some meningiomas, hemangioblastomas…
8. intracranial atherosclerosis
9. inferior petrosal sinus/cavernous sinus sampling for localizing pituitary microadenomas: see page 646
PHARMACOLOGIC AGENTS
Some drugs that are used almost exclusively in endovascular procedures are shown below. Other drugs (e.g. heparin, Plavix®…) are covered in other sections (see index).
Platelet glycoprotein IIb/IIIa receptor binding drugs: All are parenteral
eptifibatide (Integrilin®)DRUG INFO
Rx: bolus 180 mcg/kg IV (up to a max of 22.6 mg) over 1-2 minutes followed by infusion of 2 mcg/kg/min (duration of therapy depends on indication - for some up to 96 hrs).
abciximab (ReoPro®)DRUG INFO
Made from the Fab fragment of a monoclonal antibody. Platelet inhibition lasts up to 48 hours.
Rx: bolus with 0.25 mg/kg IV 10-60 minutes prior to procedure (e.g. stenting) followed by infusion of 0.125 mcg/kg/min.
tirofiban (Aggrastat®)DRUG INFO
A synthetic nonpeptide antiplatelet drug. Platelet inhibition lasts 4-8 hours.
Rx: bolus with 0.4 mcg/kg/min IV x 30 minutes, followed by infusion of 0.1 mcg/kg/min.
9.1. Neuroendovascular procedure basics
The femoral artery is punctured just below the inguinal ligament (which lies on the line connecting the anterior superior iliac spine and the anterior superior pelvic tubercle) to avoid bleeding at a non-compressible location (which can lead to significant retroperitoneal hematoma). An 18-19 gauge needle is usually employed.
The Seldinger technique is then used to place a wire in the artery with removal of the percutaneous needle and the introduction of the sheath1.
A guiding catheter is usually used to access the target vessel (carotid or vertebral artery). A microcatheter is inserted co-axially within the guiding catheter to access the lesion (aneurysm, AVM nidus…)
Sheaths and catheters are all kept under pressurized heparinized saline flush. An arterial line flush system may be used.
Systemic anticoagulation with heparin is frequently used during the procedure and reversal is not always performed.
FEMORAL SHEATH MANAGEMENT
Except as indicated below, the sheath is removed at the end of the procedure. If the patient has not had systemic anticoagulation during the procedure, then manual compression should be performed for 10-20 minutes to achieve hemostasis. This minimizes the risk of local and embolic complications.
If the sheath is to remain in place for an intraoperative examination or a subsequent interventional procedure, then it should remain on heparinized flush. Remove the sheath only when the aPTT has returned to normal (< 36 secs) or when the ACT is < 170.
There are a number of femoral arterial closure devices, including: Starclose, Perclose, Angioseal, Minx…
STENTING
Indications for stent placement:
1. to assist in the coiling of wide necked aneurysms where there is risk of coil herniation into the parent artery. ✖ Stent-assisted coiling is not recommended for ruptured aneurysms because of the need for dual antiplatelet therapy and the increased risk of hemorrhage if EVD placement is required on this regimen2
2. treatment of intracranial stenosis due to atherosclerosis
3. cerebrovascular arterial dissections
Initially, only cardiac stents were available, however, they are being replaced by stents which are FDA approved for CNS use and are more suitable3. Currently available stents approved for CNS use:
• Wingspan: (Boston Scientific, Natick, MA) self-expanding nitinol microstent used for intracranial atherosclerosis, exerts greater outward radial force than stents used for aneurysm coiling
• Neuroform: (Boston Scientific, Natick, MA) self-expanding flexible stent used for stent-assisted coiling of wide necked saccular aneurysms
• Enterprise: (Cordis Neurovascular, Miami, FL) self-expanding nitinol stent used for stent-assisted coiling of wide necked intracranial aneurysms
• Pipeline: (ev3, Plymouth, MN) self-expanding flow directed bimetallic microstent with braided tubular design that will exclude aneurysms. May also be useful for arterial dissections4. Currently awaiting FDA approval
Post stenting medical management
Aspirin is usually recommended indefinitely following stent placement to prevent stent thrombosis. Plavix® is prescribed for at least 6 weeks following stent placement to allow for endothelialization of the stent.
9.2. References
1. Osborn A: Diagnostic cerebral angiography. Lippincott, Williams and Wilkins, Philadelphia, 1999.
2. Ross I B, Dhillon G S: Ventriculostomy-related cerebral hemorrhages after endovascular aneurysm treatment. AJNR Am J Neuroradiol 24 (8): AJNR Am J Neuroradiol: 1528-31, 2003.
3. White J B, Ken C G, Cloft H J, et al.: Coils in a nutshell: A review of coil physical properties. AJNR Am J Neuroradiol 29 (7): AJNR Am J Neuroradiol: 1242-6, 2008.
4. Ansari S A, Thompson B G, Gemmete J J, et al.: Endovascular treatment of distal cervical and intracranial dissections with the neuroform stent. Neurosurgery 62 (3): Neurosurgery: 636-46; discussion 636-46, 2008.