Ec ic bypass indications and techniques

EC IC BYPASS INDICATIONS AND TECHNIQUESHistory of revascularizationAuthor (year)Event Kredel , 1942EDAMSWoringer & Kunlin, 1963CCA-ICA bypass with saphenous vein graftDonaghy & Yasargil, 1968STA MCA bypassLoughheed 1971CCA- IC ICA bypassKikuchini & Karasawa1973EC-IC bypass for moyamoyaKarasawa , 1977Encephalomyosynangiosis for moyamoyaStory , 1978ICA-MCA bypass, saphenous vein graftSundt , 1982Saphenous vein graft for posterior circulationEC/IC bypass study group, 1985No benefit of STA-MCA bypass in reducing ischemic events compared to best medical therapyCOSS ,2010Study stopped for futilityRevascularization Indirect : Promote new capillary network formation Revascularization with timeFlow augmentation , smaller volume of flowRecipient vessel size not importantIschemic brain unable to accommodate a higher flow

Direct Vessel to vessel anastamosisImmediate revascularizationFlow augmentation/ replacementRecipient vessel size > 1mm (ideally > 1.5 mm)

Indirect revascularization EMS (encephalomyosynangiosis)EDAS (encephaloduroarteriosynangiosis)EDAMS (encephaloduroarteriomyosynangiosis)Omental graftMultiple burr holes

Direct revascularizationSTASTA MCA anastamosisArterial / venous graftPETROUS ICA SUPRACLINOID ICACERVICAL ECA/ICA MCA CERVICAL ECA/ICA SUPRACLINOID ICA Bonnet graft (opposite STA Saphenous graft- MCA )

Revascularization Decision about direct/ indirectDecide on donor vesselDecide on conduitDecide on recipientTechnique of anastamosisRevascularization Direct Indirect Immediate flow required (vessel sacrifice)The brain can handle the high flow ratesAvailability of acceptable recipient vessel

Immediate flow not required (3- 4 months to mature)Collaterals may not develop in 40 50 % adultsMass effect of muscle (aphasia)Revascularized area dependent on craniotomy size and site (only local revascularization)No acceptable recipient

Donor vesselSTA (superficial temporal artery)MMA (middle meningeal artery)ECA (external carotid artery)ICA (internal carotid artery)OA (occipital artery)VA (vertebral artery V3 segment)Conduit Pedicled graftsSTA 1mmOAMMAFree arterial graftRadial 2.4mmOther arteriesFree venous graftGSV 3mmJ Neurosurg 102:116131, 2005Flow characteristics of graftsLow resistance circulation, vein grafts not a disadvantage Low flow vesselsSTA, OA, MMA< 50ml/min flow at time of anastamosisHigh flow graftsRadial artery50-150 ml/min at anastamosisSaphenous vein graft100-250 ml/min at anastamosis Vein Vs arterial graftArterial graftVenous graftBetter suited to high pressure flowShort term patency rates are better (98% at 6 W)Length is a limitationNo valvesLumen approximates that of recipient May not always be available (incomplete palmar arch)Recipient 2 mmLarger diameter, higher flow ratesLower short term patency rates (93% at 6 W)Length is not a limitationAlmost always availableValves presentLumen larger than recipientHigher procedure related complications Children < 12 yearsRecipient 2.5 mm

Neurosurgery 69:308314, 2011Graft flow characteristicsHigh flow > 50 ml/minLow flow (< 50 ml/min)Proximal vessel sacrificeFlow replacementLarge area to be revascularized

No vessel sacrificeFlow augmentationSmall area to be revascularizedBrain can not handle high flows

Recipient vessel M1 tolerates temporary occlusion poorly (lenticulostriate perforators)Implant into a bifurcationImplant into a 2.5 mm vessel MCAIf M1 segment short , MCA unsuitable recipient, use supraclinoid ICA if aneurysm infraclinoidIf supraclinoid ICA used as recipient collateral from ACA essential (temp PCA occlusion required)Suturing started at the heel end

Anastomotic techniqueHand sewn (commonest)Require proximal and distal clamping of the recipient Non occlusive anastamosisExpensive , learning curve, larger recipient vessel size, patency rates comparable, similar complication ratesELNA (Excimer Laser assisted Non occlusive Anastamosis)C-Port xA Distal Anastomosis System

STA MCA bypassSTAParietal branch preferred (frontal has collaterals with ophthalmic )Location of craniotomyJunction of the anterior 2/3 and posterior 1/3 of a line joining lateral canthus to ipsilateral tragusA line perpendicular to this Craniotomy 3-5 cm in diameter 6 cm above this lineAnastomose to temporal M4 branchesAvoid ischemia to frontal branches during occlusionGood collaterals with PCAMore consistent good M4 branches

Neurosurgery 61:ONS-74ONS-78, 2007Radial artery harvestRadial artery graft

Allens test

Expose at wrist between FCR and brachioradialis tendon

Follow upwards between Pronator Teres and brachioradialisJ Neurosurg 102:116131, 2005GSV harvestExpose at ankle 1 cm anterior and cranial to medial malleolusFollow upwards to medial aspect of legHarvest appropriate lengthCan also be harvested in the thigh (drains into CFV 3 cm below inguinal ligament)

J Neurosurg 102:116131, 2005Anastomosis Meticulous haemostasis (heparin administration)Distension of graft to prevent spasmVein graft not reversedIntracranial anastomosis performed firstArterial graft retro/ preauricular routeVenous graft retroauricular routeDeliver graft without torsion

Hand sewn anastomosisFish mouthing of graft end before anastamosis

Teardrop arteriotomy of recipient

Ensure no air in graft (back bleeding/ flushing)

Verify flow through graft (Doppler/ angiography)

Bone flap placed without compromising graft

Indications for bypassCerebral ischemia

Moyamoya disease

Aneurysms

Skull base tumorsBypass after major vessel sacrificeSelective approach: only if test occlusion is positive22% risk of TIA, infarctsNeurosurgery 35:351363, 1994.TIA 10% ,stroke rate of 5% and mortality of 5% after ICA occlusion following test occlusion Neurosurgery 36:2630, 1995A high flow bypass if fails test occlusion, low flow if passesSpetzler RF . Comments Neurosurgery 62[SHC Suppl 3]:SHC1373SHC1410, 2008Universal approach: irrespective of test occlusion resultsNeurosurgery 62[SHC Suppl 3]:SHC1373SHC1410, 2008

Moyamoya diseaseRationale for surgeryAugment blood flowImprovement in CBF has been demonstratedReduction in further ischaemic eventsReduction in hemorrhagic eventsIndications for surgeryHistory of infarct/ haemorrhageRegions to be addressed MCA territory : EDAS,EDAMS, STA MCA bypassACA territory : multiple burr holes, STA ACA bypass, vascularized dural flap

Moyamoya diseaseIndirect revascularizationEMS,EDAS,EDAMS, EDMAPS (Neurosurgery 66:1093-1101, 2010)Encephalo galeo synangiosis Multiple burr holesOmental graft

Direct revascularizationSTA MCA bypassSTA ACA bypass (technically difficult, poor results)A higher incidence of symptomatic hyperperfusion with direct revascularization as compared to atherosclerotic diseaseAneurysms Only level III evidence availableSacrifice of parent vessel or a major branchAs a temporary measure during prolonged temporary clipping of complex aneurysmAneurysms requiring bypassGiant / blister aneurysmsAbsence of a neck (fusiform or saccular-fusiform) aneurysmsSevere atherosclerosis or calcication in the neckExtensive thrombosis Critical branch origin from neck or sacSymptomatic dissecting aneurysmBlister aneurysm

Cranial base tumorsFacilitates tumor removal with better patient outcome and tumor removal

Allows surgeon to focus on cranial nerve preservation

High morbidity and mortality

Performed by few centers

Being used less frequently (GKRS)Cerebral ischemia(occlusive cerebrovascular disease not amenable to carotid endarterectomy)EC IC bypass study 1985Not effective preventing ischemiaReduction in bypassCriticism Only half of the patients received antiplatelet agents at entry into studyNo evaluation preop for cerebrovascular hemodynamic status.. Both the patient and the therapist were not blindedRandomization-to-treatment bias could have occurredNo angiographic determinants for entry. A large percentage of patients had no symptoms between the angiographic demonstration of ICA occlusion and randomization. large number of patients underwent surgery outside the study. A high percentage of patients had tandem lesionsCOSS studyInclusion criteriaComplete occlusion of an ICATIA or ischemic stroke in the hemispheric territory of an occluded internal carotid artery in the preceding 120 daysOutcome measuresSurgery armDeath or stroke 30 days from surgeryIpsilateral stroke within 2 yearsMedical armDeath or stroke 30 days from randomizationIpsilateral stroke within 2 yearsResults Study stopped on 24 June 2010 for futility

Present status of revascularizationCerebral ischemia: most RCT have shown no benefitMoyamoya disease: only class III evidence of benefitComplex aneurysms : class III data. Evidence of benefitIC IC bypass, lower morbidity, comparable patency ratesSkull base tumors: class III evidence of benefitalternative strategies for treatment of residual disease,