Youmans Neurological Surgery

1. Revascularization Techniques
for Complex Aneurysms and
Skull Base Tumors
Youmans Chapter 380
Joshua R. Dusick
Nestor R. Gonzalez
Neil A. Martin

2. Outline
• Revascularization for the Treatment of Aneurysms
• Revascularization for the Treatment of Skull Base Tumors
• When Is the Collateral Circulation Inadequate and Bypass Necessary?
• Preoperative Planning and Preparation for Bypass Procedures
• Intraoperative Monitoring and Management
• Type of revascularization procedures
• Postoperative Management
• Complication
• Long-Term Graft Patency

3. Revascularization for the Treatment of Aneurysms
• Clipping or coiling of complex, giant, and fusiform aneurysms
• Calcification or atherosclerotic thickening of the aneurysm neck or
the parent artery
• Recurrent aneurysms after endovascular coil embolization

4. Revascularization for the Treatment of Skull Base
Tumors
• Petrous and cavernous ICA
• Benign
• Meningioma, schwannoma, pituitary adenoma, angiofibroma, chordomas :
benign nature, should not resect artery
• Stereotactic radiosurgery or fractionated stereotactic radiotherapy
• Malignant head and neck
• Radical tumor with ICA sacrifice

5. When Is the Collateral Circulation Inadequate and
Bypass Necessary?
• Anterior circulation
• Posterior circulation
• Distal arterial braches

6. Anterior circulation
• Selective approach
• angiographic evaluation of the competence of the circle of Willis
• balloon test occlusion coupled with measurement of cerebral blood flow
• patient pass balloon occlusion test : 20% chance of stroke with complete
occlusion without a bypass
• Universal approach
• advocate bypass for all patients who undergo ICA occlusion

7. Posterior circulation
• Unclipable and uncoilable posterior circulation
• Unilateral vertebral artery occlusion is well tolerated when
• the contralateral vertebral artery is not hypoplastic
• does not terminate in the posterior inferior cerebellar artery (PICA)
• Bilateral vertebral artery or basilar artery occlusion is associated with
a much higher risk for ischemia and should be considered only if
blood flow through both posterior communicating arteries is
sufficient (>1 mm)

8. Distal arterial braches
• Proximal occlusion : ICA, VA
• Occlusion of branch : MCA, PICA, AICA

9. Preoperative Planning and Preparation for Bypass
Procedures
• Optimal site of arterial occlusion, the collateral circulation, and the
size and location of the intended recipient and donor bypass vessels
• Anticonvulsants
• Aspirin (325 mg daily)

10. Intraoperative Monitoring and Management
• EEG : monitor burst suppression
• Evoked potential : activity of the sensory cortex and subcortical and
brainstem pathways during bypass procedures
• Mild hypothermic : 34-36 C
• Thiopental : cerebral protection during transient focal ischemia
• Local intraluminal anticoagulant irrigation is used
• Do not use systemic heparin

11. Type of revascularization procedures
Interposition Vein Grafts
Extracranial-to-Intracranial Bypass
with a Saphenous Vein Graft or
Radial Artery Graft
Scalp Artery (Superficial Temporal or
Occipital) Extracranial-to-Intracranial
Bypass
Direct Intracranial Revascularization

12. Type I Bypasses—Interposition Vein Grafts
• Interposition graft from the parent artery proximal to the site of the
occlusion to the point immediately distal to the parent artery
• Purely intracranial petrous carotid–to–supraclinoid carotid saphenous
vein interposition graft
• Remove skull base tumors and to treat giant intracavernous carotid
aneurysms
• Disadvantage
• Technically complex
• Lengthy procedure
• Prolonged period of ICA occlusion

13. Type II Bypasses—Extracranial-to-Intracranial Bypass
with a Saphenous Vein Graft or Radial Artery Graft
• Extracranial Carotid Artery–to–Middle Cerebral Artery Saphenous
Vein Interposition Graft
• External Carotid Artery–to–Posterior Cerebral Artery Saphenous Vein
Interposition Graft

14. Type II Bypasses—Extracranial-to-Intracranial Bypass
with a Saphenous Vein Graft or Radial Artery Graft
• Normal blood flow MCA : 250 mL/min, PCA moderate less
• STA graft position
• 15-30 mL/min, may increase with time
• not adequate to the circulation of major artery
• Saphenous vein graft
• 70-140 mL/min,can exceed 250 mL/min, 4-5 mm
• Lower longterm patency rate, higher risk of kinking, caliber mismatch
• Radial artery graft
• Smaller diameter, 3.5 mm
• 40-70 mL/min

15. Type II Bypasses—Extracranial-to-Intracranial Bypass
with a Saphenous Vein Graft or Radial Artery Graft
• Substiture for STA-MCA bypass
• scalp artery is hypoplastic, diseased, or occluded
• aneurysm that can be occluded only proximally, as in the case of some
dolichoectatic and fusiform aneurysms
• type II bypass may supply too much flow and can be dangerous

16. Extracranial Carotid Artery–to–Middle Cerebral
Artery Saphenous Vein Interposition Graft

17. External Carotid Artery–to–Posterior Cerebral
Artery Saphenous Vein Interposition Graft
• Basilar artery or bilateral vertebral arteries are occluded to treat an
unclippable basilar artery aneurysm
• Subtemporal approach
• The proximal 20 to 25 mm of the P2 segment is isolated, and a
segment free of brainstem perforating vessels is chosen for the
anastomosis
• Subdural hygroma : suggest routine subtemporal subdural-peritoneal
(or atrial) shunt

18. Type III Bypasses—Scalp Artery (Superficial Temporal or
Occipital) Extracranial-to-Intracranial Bypass
• Used
• a giant aneurysm requires occlusion of a single, crucial arterial branch
• carotid occlusion is required (for an aneurysm or tumor) and the circle of
Willis is only marginally inadequate
• Donor vessel : STA, occipital artery
• STA 15 – 30 mL/min
• STA-PCA, STA-SCA
• OA-PICA, OA-AICA

19. Superficial Temporal Artery–to–Middle Cerebral
Artery Bypass
• Parietal branch : Charter’s point (center, 6 cm, above EAC)
• Frontal branch : a second, vertically oriented incision above the ear is required
over Chater’s point

20. Superficial Temporal Artery–to–Middle
Cerebral Artery Bypass
• In patients who have two separate MCA branches that arise from the
dome of an aneurysm : double-barrel STA bypass
• Recipient a. ,> 1 mm diameter, 10 mm length
• Adventitia over the distal end of STA is removed
• Off temporary clip : distal MCA, proximal MCA, STA

21. Occipital Artery–to–Posterior Inferior Cerebellar
Artery Bypass

22. Superficial Temporal Artery–to–Superior Cerebellar
Artery Bypass and Superficial Temporal Artery–to–
Posterior Cerebral Artery Bypass
• Substituted for the saphenous vein graft–to-PCA bypass when some
collateral blood flow is available through small posterior
communicating arteries

23. Type IV Bypasses—Direct Intracranial Revascularization
• Anastomosis between two adjacent cerebral arteries
• Primary Reanastomosis
• intracranial arterial reconstruction involves excision of the aneurysm with
primary reconstruction of the parent artery
• Pericallosal-to-Pericallosal Bypass
• used to treat fusiform aneurysms of the proximal pericallosal artery or for
giant anterior communicating artery aneurysms that require trapping
• side-to-side anastomosis

24. Type IV Bypasses—Direct Intracranial Revascularization
• Posterior Inferior Cerebellar Artery–to–Posterior Inferior Cerebellar
Artery Anastomosis
• used when the occipital artery is small or has been damaged during a
previous surgical procedure
• side-to-side anastomosis

25. Techniques for Occluding or Trapping an Aneurysm
after Bypass
• Trapping
• combined proximal and distal parent artery occlusion
• it isolates the aneurysm from the circulation
• avoids the risk of rupture from retrograde filling
• allows immediate decompression of the aneurysm to relieve any mass effect.
• Proximal occlusion
• induce aneurysmal thrombosis
• Used in giant intracavernous aneurysms and large fusiform or dolichoectatic
vertebrobasilar aneurysms

26. Postoperative Management
• Palpating bypass pulse or by using a Doppler probe
• Continue ASA
• Euvolemia
• Normal SBP
• CTA

27. Complications
• Early graft occlusion
• careful avoidance of twisting, kinking, stretching, or tension of the graft
• avoidance of graft spasm by adventitial papaverine irrigation
• administration of perioperative antiplatelet therapy
• Post operative aneurysmal rupture
• High flow graft
• Emphasize the need to isolate the aneurysm completely from the circulation
by trapping whenever possible

28. Complications
• Ischemic neurological deficits
• Temporary arterial occlusion while the bypass anastomosis
• Cerebral protection with moderate hypothermia, induced arterial
hypertension, and barbiturate administration
• Subdural or epidural hematomas (or both) developed postoperatively
• given heparin in addition to aspirin

29. Long-Term Graft Patency
• Superior temporal artery graft
• Radial artery graft
• Saphenous vein graft