Transzygomatic – Subtemporal Approach for Middle Meningeal to P2 Segment of The Posterior Cerebral Artery Bypass: An Anatomical and Technical Study

Cagatay Han ULKU1, Mehmet Erkan USTUN2, Mustafa BUYUKMUMCU3 Önder GUNEY2, Ahmet SALBACAK2

Departments of 1Otolaryngology Head and Neck Surgery, 2Anatomy, 3NeurosurgerySelcuk University, School of Medicine, Konya - Turkey

IntroductionIn patients complaining vertigo or dizziness, thepathology can originate central or peripheralcompartments. Such patient often seek treatment in Neurology, Neurosurgery or Otolaryngology clinics. Vertebro-basilar insufficiency is one of the mostcommon causes of central vertigo or dizziness, andseveral bypass procedures have been described forıts treatment. The most common posterior circulationbypass between P2 segment of the posteriorcerebral artery (PCA) and external carotid artery(ECA) or vertebral artery (VA). Because it providehigh blood flow, the P2 segment has been used as an anastomosis site. Either the VA or the ECA is used for the proximal anastomosis. (1-5) However, these techniques are limited by the graft materials(saphenous vein or radial artery) which are long andtend to be associated with a low patency rate. (3,5,6)

In this study, we examined the suitability of thediameter and length of the middle meningeal artery(MMA) for use in an MMA to PCA bypass as an alternative to an ECA to PCA anastomosis in cadavers.

Subjects and MethodsFive adult cadavers were dissected bilaterally. Cadeveric dissection protocol that was approved bythe Selcuk University Institutional Review Board. Inthe supine position the head was turned about 70°away from the side of dissection and tilted towardthe floor. A preauricular temporal craniotomy skin incision was used. The deep fascia and periosteumare dissected from the bone of the zygomatic arch, and the zygoma is completely exposed from it is rootto the zygomatico - maxiller suture. In the fascialregion, the deep fascia is dissected away from themasseter muscle. The skin flap can then be dissected and reflected forward, along with thesuperficial temporal artery (STA) and the superiorbranches of the fasial nerve. The masseter muscle is divided from its attachment to the zygomatic bone, and the temporal muscle is elevated from thetemporal fossa. A temporal craniotomy extendingfrom just above the external ear canal to the keyhole area is performed. The bone is then cut andremoved. The temporalis muscle is dissected awayfrom the temporal bone and zygomatic arch. A zygomatic osteotomy is then performed as fallow. Anteriorly, a V – shaped is performed just posteriorto the zygomatico-maxiller suture, including thelateral rim of the orbit. Posteriorly, the osteotomywas lateral to the condylar fossa.

The calibers of the MMA and P2 were wellmatched. Furthermore, the mean caliber of thesearteries was more than 2 mm so the bypass is likely to provide sufficient blood flow. But such an anastomosis is performed, preoperativeangiography would help to ases the diameter of theMMA and PCA to woure that they were largeenough to serve as a usable bypass. Subtemporaltranszygomatic approach was found to be suitablefor such a bypass procedure.The MMA to P2 segment of PCA bypass haveseveral adventage;1. It provides sufficient bloodflow because the mean diameter of the MMA is more than 2 mm (3). 2. It may have a high patencyrate because it is a single and arterial -to- arterialbypass. Artery – to - artery anastomoses have beenreported to have patency rates of were 90%. (14,15)

3. Such a bypass is more simple to perform than an ECA – to - P2 bypass: no second incision oranastomosis in the cervical region is needed. Finally is an ECA to P2 segment of PCA bypass, the graft bends where it enters the cranium , However, the anastomosis between the MMA andPCA follows an almost a straight course which is important in creating a patent bypass. The disadvantage of an MMA to P2 bypass is thatthe anastomosis is performed at a considerabledepth, unlike a superficial STA to MCA (middlecerebral artery) bypass. To prevent cerebrospinalfluid leakage, the dura over the hole can be sealedwith fibrin glue.

References1. Ausman JI, Diaz FG, de los Reyes RA, Pak H, Patel S, Mehta B, Boulos R. Posterior circulationrevascularisation. Superficial temporal artery to superior cerebellar artery anastomosis. J Neurosurg. 1982;56:766-776.2. Heros RC, Ameri AM. Rupture of a giant basilar aneurysm after saphenous vein interposition graft to theposterior cerebral artery: Case report. J Neurosurg. 1984;61:387-390.3. Sekhar LN, Wright DC, Olding M. Brain revascularization by saphenous vein and radial artery bypass graft. In: Sekhar LN, Olivera ED, eds. Cranial Microsurgery. New York, Thieme, 1999:581-600.4. Sundt TM, Piepgras DG, Houser OW, Campbell JK. Interposition saphenous vein grafts for advanced occlusivedisease and large aneurysms in the posterior circulation. J Neurosurg. 1982;56:205-215.5. Sundt TM, Piepgras DG, Marsh WR. Bypass vein grafts for giant aneurysms and severe intracranial occlusivedisease in the anterior and posterior circulation; in Sundt TM, ed. Occlusive cerebrovascular disease, diagnosisand surgical management. Philadelphia, WB Saunders, 1987:439-464.6. Diaz FG, Pearce JE, Ausman JI. Complications of cerebral revascularization with autogenous vein grafts. Neurosurgery. 1985;17:271-276.7. Ausman JI, Nicoloff DM, Chou SN. Posterior fossa revascularization: Anastomosis of vertebral artery to PICA with interposed radial artery graft. Surg Neurol. 1978;9:281-286.8. Ausman JI, Diaz FG, de los Reyes RA, Pak H, Patel S, Boulos R. Superficial temporal to proximal superiorcerebellar arteryanastomosis for basilar artery stenosis. Neurosurgery. 1981;9:56-60.9. Ausman JI, Diaz FG, de los Reyes RA, Pak H, Patel S, Boulos R. Anastomosis of occipital artery to anteriorinferior cerebellar artery for vertebrobasilar junction stenosis. Surg Neurol. 1981;16:99-102.10. Ausman JI, Diaz FG, Dujovny M. Posterior circulation revascularization. Clin Neurosurg.1986;33:331-343.

ConclusionWhen an arterial – to - arterial bypass and an sufficient blood flow are needed, an MMA – to - P2 segment of PCA bypass may be a good alternative– to - ECA – to - PCA bypass using long grafts.

DiscussionVertebrobasilar insufficiency is one of the mostcommon causes of central vertigo or dizziness. Several techniques are aveible for a posteriorcirculation bypass (1-5, 7-16) The diameters of thedonor (OA and STA) and recipient (PICA, AICA orSCA) arteries less than 2 mm, which unite thereabsolute to provide sufficient blood flow. Procedures has of the proximal PCA as therecipient and the ECA or VA as the donor vesselsin the bypass are reported to be more protective. (5,14,15) .

Figure 1.MMA: Middle meningeal arteryPCA(P2): Posterior cerebral arteryMCA: Middle cerebral artery

Figure 2.MMA: Middle meningeal arteryPCA: Posterior cerebral arteryICA: Internal carotid arteryPcom: Posterior communicating arteryBA: Basilar arteryOcN: Oculomotor nerveTN: Trigeminal nerve

The VA is used as the proximal vessel if it is thesame size as and is well connected to the other VA. If the VA is markedly dominant and the other VA is small the ECA is used as the proximal artery. (14)

The use of the middle meningeal artery as a donorsite for bypass surgery was described previously in detail. The middle meningeal artery – middlecerebral artery bypass has been performedespecially when the superficial temporal artery wasnot useful as a donor artery (17-20). We performed the anatomical study to determinedwhether the diameter and length of the MMA aresuitable for performed an anastomosis betweenthe MMA and P2 segment of PCA and todetermined the feasibility whether this surgery. Inthe present study, we found that a short length of MMA about 3 cm was sufficient to create a bypass between the MMA and P2 .

11. Hopkins LN, Martin NA, Hadley MN, Spetzler RF, Budny J, Carter LP. Vertebrobasilar insufficiency. Part 2. Microsurgical treatment of intracranial vertebrobasilar disease. J Neurosurg. 1987;66:662-674.12. Khodadad G. Occipital artery-posterior inferior cerebellar artery anastomosis. Surg Neurol. 1976;5:225-227.13. Little JR, Furlan AJ, Bryerton B. Short vein grafts of cerebral revascularization. J Neurosurg. 1983;59:384-388.14. EC/IC Bypass Study Group. Failure of extracranial – intracranial arterial bypass to reduce the risk of ischemic stroke(1985). Results of an international randomized trial. N Engl J Med. 1985; 313(19):1191-1200.15. Sekhar LN, Schramm Jr VI, Jones NF, Yonas H, Horton J, Latchaw RE, Curtin H. Operative exposure andmanagement of the petrous and upper cervical internal carotid artery. Neurosurgery. 1986;19:967-982.16. Sen C, Sekhar LN. Direct vein graft reconstruction of the cavernous, petrous, and upper cervical internal carotidartery:lessons learned from 30 cases. Neurosurgery 1992; 30:732-743.17. Golby AJ, Marks MP, Thomspon RC, Steinberg GK. Direct and combined revascularization in pediatric moyamoyadisease. Neurosurgery 1999;45:50-60.18. Miller CF, Spetzler CF, Kopaniky DJ. Middle meningeal to middle cerebral arterial bypass for cerebralrevascularization. Case report. J Neurosurgery 1979;50:802-804.19. Nishikawa M, Hashi K, Shiguma M. Middle meningeal-middle cerebral artery anastomosis for cerebral ischemia. Surgical Neurology 1979;12:205-208.20. Owers NO. Anatomic pathways facilitating middle cerebral artery bypass.Am Surg. 1987;53(5):282-4.

ResultsThe mean caliber of the MMA at theanastomosis site (before the exit of theanterior and posterior branches) was 2.1 ±0.25 mm (range1.5 to 2.5 mm). The meancaliber of the P2 segment was 2.2 ± 0.2 mm (range 2.0 to 2.4 mm). The meanlength of the MMA need to perform a bypass was 32 ± 4.1 mm (range 28 to 36 mm). The mean length of the MMA trunkwas 39.5 ± 4.4 mm (range 35 to 44 mm). Inall cadavers we were able to create a tension-free anastomosis between theMMA and P2.

AbstractObjectives: To investigate the use of a bypass between the middle meningeal artery (MMA) and P2 segment of the posterior cerebral artery (PCA) as an alternative to an external carotid artery (ECA-to-PCA) anastomosis. Study Design: We conducted an anatomical study at a university hospital. Subjects and Methods: Five adult cadaveric heads (10 sides) were used. After a temporal craniotomy and zygomatic arch osteotomy were performed, the dura of the floor of the middle cranial fossa was separated and elevated. The MMA was dissected away from the durauntil the foramen spinosum was reached. Intradurally, the carotid and sylvian cisterns were opened. After the temporal lobe was retracted, the interpeduncular and ambient cisterns were opened and the P2 segment of the PCA was exposed. The MMA trunk was transsected just before the bifurcation of its anterior and posterior branches where it passes inside the dura and over the foramen spinosum. It was anastomosed end to side with the P2 segment of the PCA. Results: The mean caliber of the MMA trunk before its bifurcation was 2.1 +/- 0.25 mm, and the mean caliber of the P2 was 2.2 +/- 0.2 mm. The mean length of the MMA used to perform the bypass was 32 +/- 4.1 mm, and the mean length of the MMA trunk was 39.5 +/- 4.4 mm.Conclusion This bypass procedure is simpler to perform than an ECA-to-P2 revascularization using long grafts. The caliber and length of the MMA trunk are suitable to provide sufficient blood flow. Furthermore, the course of the bypass is straight. An MMA to PCA bypass may provide a simple alternative to an ECA to PCA bypass.Key words: Artery graft, bypass procedure, middlemeningeal artery, posterior cerebral artery.

The zygomatic bone is removed andpreserved for subsequent reattachment. The dura of the floor of the middle cranialfossa is then separeted under the surgicalmicroscop. The MMA can be found bytracing the vessels from the dural surfacemedially then the MMA was dissected awayfrom the dura until to the foramen spinosumwas reached extradurally. Intradurally theslyvian and carotid cisterns were opened. After the temporal lobe was retracted theinterpeduncular and ambient cisterns wereopened, and the P2 segment of the PCA was exposed. The MMA trunk wastranssected just before bifurcating toanterior and posterior branches and passedinside the dura over the foramen spinosumuntil it reached the P2 segment to which it was anastomosed end-to side (Figures 1 and 2).