It's helpful in understanding various aspects of revascularization procedures, with good illustrations, easy to learn, no complexity, easy language, conclusion added, short descriptions

1. By
Dr. Himanshu Raval
Neurosurgery resident

2. • Decision about direct/ indirect
• Decide on donor vessel
• Decide on conduit
• Decide on recipient
• Technique of anastomosis

3. Indirect :
Promote new capillary network formation
Revascularization with time
Flow augmentation , smaller volume of flow
Recipient vessel size not important
Ischemic brain unable to accommodate a higher flow
Direct :
Vessel to vessel anastomosis
Immediate revascularization
Quick Flow augmentation/ replacement
Recipient vessel size > 1mm (ideally > 1.5 mm)

4. • EMS (encephalomyosynangiosis)
• EDAS (encephaloduroarteriosynangiosis)
• EDAMS (encephaloduroarteriomyosynangiosis)
• Omental graft
• Multiple burr holes

5. • STA
• STA – MCA/ACA anastamosis
• Arterial / venous graft
• PETROUS ICA – SUPRACLINOID ICA
• CERVICAL ECA/ICA – MCA
• CERVICAL ECA/ICA – SUPRACLINOID ICA
• Bonnet graft (opposite STA – Saphenous graft- MCA )

6. • STA (superficial temporal artery)
• MMA (middle meningeal artery)
• ECA (external carotid artery)
• ICA (internal carotid artery)
• OA (occipital artery)
• VA (vertebral artery V3 segment)

7. • Pedicle grafts
STA ≥ 1mm
OA
MMA
• Free arterial graft
Radial ≥ 2.4mm
• Other
Free venous graft
GSV ≥ 3mm

8. • Low resistance circulation, vein grafts not a disadvantage
• Low flow vessels
STA, OA, MMASTA, OA, MMA
< 50ml/min flow at time of anastomosis
• High flow grafts
Radial artery: 50-150 ml/min at anastomosis
Saphenous vein graft :100-250 ml/min at anastomosis

9. Arterial graft Venous graft
Better suited to high pressure flow Larger diameter, higher flow rates
Short term patency rates are Lower short term patency rates (93% at 6 W)
are better (98% at 6 W) Length is not a limitation
Length is a limitation Almost always available
No valves Valves present
Lumen approximates that of recipient Lumen larger than recipient
May not always be available Higher procedure related complications
(incomplete palmar arch)
Recipient ≥ 2 mm (93% at 6 W) Recipient ≥ 2.5 mm

10. High flow > 50 ml/min Low flow (< 50 ml/min)
Proximal vessel sacrifice No vessel sacrificed
Flow replacement Flow augmentation
Large area to be revascularized Small area to be revascularized
Brain can not handle high flows

11. Type I: Saphenous vein interposition graft for
carotid artery replacement.
Type II: Saphenous vein bypass graft (SVG) from
the extracranial carotid artery (ECA) to the middle
(MCA; A and B) or posterior (PCA; C) cerebral
artery.
Type III: Superficial temporal (STA; A or B) or
occipital (Occ. A; C) artery bypass to intracranial
arterial branch.
Type IV: Anastomosis of one intracranial artery to
an adjacent intracranial artery (A and B) or
primary reanastomosis (C) after aneurysm excision.

12. • Expose at ankle 1 cm anterior
and cranial to medial malleolus
• Follow upwards to medial aspect of leg
• Harvest appropriate length
• Can also be harvested in the thigh
(drains into CFV 3 cm below inguinal ligament)

13. A petrous−supraclinoid carotid skull base
bypass showing a saphenous interposition
graft from the petrous segment of the carotid
artery (exposed by drilling the middle cranial
fossa floor) to the supraclinoid carotid artery
(in this case for treatment of an
intracavernous aneurysm).

14. • Extracranial Carotid Artery−Middle Cerebral
Artery Saphenous Vein Interposition Graft
A: A clamp is passed from the cranial
incision behind the root of the zygomatic
arch to the cervical incision.
B: A chest tube is pulled from the cervical
incision to the cranial incision.
C: The harvested saphenous vein graft is
passed through the chest tube, which is
removed leaving the graft in its
subcutaneous tunnel.
D: The completed bypass after end-to-end
anastomosis to the internal carotid artery
(ICA) and end-to-side anastomosis to the
MCA.
E: Alternative technique showing
end-to-side anastomosis to the external
carotid artery (ECA).
• External Carotid Artery−Posterior Cerebral Artery Saphenous Vein Interposition Graft

15. • Superficial temporal artery (STA)−middle
cerebral artery bypass.
A, After Doppler identification of the STA, a
linear incision is made over its distal aspect.
B, The STA is exposed by cutdown technique.
C, After the temporalis muscle is incised, an
oval or circular craniotomy is made over the
posterior aspect of the sylvian fissure.
D, The completed anastomosis is shown.

16. occipital artery−posterior inferior
cerebellar artery (PICA) bypass.
A, The scalp flap and isolation of the
occipital artery.
B, The suboccipital craniotomy and
completed occipital artery−PICA
bypass is apparent.
Trapping of the PICA aneurysm and the occipital
artery−PICA bypass.
• Superficial Temporal Artery−Superior Cerebellar Artery Bypass
• Superficial Temporal Artery−Posterior Cerebral Artery Bypass

17. • pericallosal artery−pericallosal artery
intracranial revascularization.
Illustration of the interhemispheric
approach to the pericallosal arteries.
The arteries are exposed adjacent
to the corpus callosum, and a
side-to-side anastomosis is made.
• Posterior Inferior Cerebellar Artery−Posterior Inferior Cerebellar Artery Anastomosis

18. • Meticulous haemostasis (heparin administration to graft, no systemic
heparinisation)
• Distension of graft to prevent spasm
• Intracranial anastamosis performed first
• Arterial graft retro/ preauricular route
• Venous graft retroauricular route
• Deliver graft without torsion

19. • Hand sewn (commonest)
• Require proximal and distal clamping of the recipient
• Non occlusive anastomosis
• Expensive , learning curve, larger recipient vessel size, Expensive ,
learning curve, larger recipient vessel size, patency rates comparable,
• similar complication rates
• ELNA (Excimer Laser assisted Non occlusive Anastomosis)
• C-Port xA Distal Anastomosis System

20. •Fish mouthing of graft end before anastomosis
•Teardrop arteriotomy of recipient
•Ensure no air in graft (back bleeding/ flushing)
•Verify flow through graft (Doppler/ angiography)
•Bone flap placed without compromising graft

21. • Cerebral ischemia
• Moyamoya disease
• Aneurysms
• Skull base tumours

22. Rational for surgery
Augment blood flow
Improvement in CBF has been demonstrated
Reduction in further ischaemic events
Reduction in haemorrhagic events
Indications for surgery
History of infarct/ haemorrhage
Regions to be addressed
MCA territory : EDAS,EDAMS, STA – MCA bypass
ACA territory : multiple burr holes, STA – ACA bypass,
vascularized dural flap

23. Indirect revascularization
EMS,EDAS,EDAMS
Encephalo – galeo – synangiosis
Multiple burr holes
Omental graft
Direct revascularization
STA – MCA bypass
STA – ACA bypass (technically difficult, poor results)
A higher incidence of symptomatic hyperperfusion with
direct revascularization

24. • Sacrifice of parent vessel or a major branch
• As a temporary measure during prolonged temporary clipping
of complex aneurysm
• Aneurysms requiring bypass
Giant / blister aneurysms
Absence of a neck (fusiform or saccular-fusiform aneurysms)
Severe atherosclerosis or calcification in the neck
Extensive thrombosis
Critical branch origin from neck
Symptomatic dissecting aneurysm
Blister aneurysm

25. • Facilitates tumor removal with better patient outcome
• Allows surgeon to focus on cranial nerve preservation
• High morbidity and mortality
• Performed by few centers
• Being used less frequently

26. • For occlusive cerebrovascular disease not amenable to
carotid endarterectomy
• EC – IC bypass study (coss)
• Not effective preventing ischemia
• Reduction in bypass

27. Inclusion criteria
Complete occlusion of an ICA
TIA or ischemic stroke in the hemispheric territory of an
occluded internal carotid artery
Outcome measures
with medical mx: 21%
with medical + Surgical mx: 22%
Results
no significant benefit

28. CONCLUSION
Several types of EC-IC and IC-IC bypass procedures can provide
revascularization, if the treatment of unclippable aneurysms or skull base
tumors requires major artery occlusion or sacrifice. The selection of the
type of revascularization procedure depends on the demand for blood
flow through the bypass and the anatomy of the vessels associated with
the lesion. Parent artery occlusion (or preferably trapping) by surgical or
endovascular techniques, combined with EC-IC bypass to maintain tissue
perfusion, is an effective strategy for treating aneurysms that are difficult
or impossible to clip. Careful attention to technique yields a high rate
of bypass patency and good clinical outcomes in most patients.