47 Superficial Temporal Artery – Middle Cerebral Artery Bypass • Symptomatic Moya-Moya disease. To supplement cerebral blood flow due to ongoing poor cerebral perfusion. • Complex aneurysm. To replace native cerebral blood flow when intracranial vessel sacrifice is necessary. • Position: The patient is positioned supine with the head fixed with a Mayfield head holder. • Body: A shoulder roll is placed under the ipsilateral shoulder. • Head: The head is rotated 60° to the contralateral side, ensuring that venous return is not compromised due to excessive neck rotation. • The Sylvian fissure has to be the highest point in the surgical field, and the operative field is parallel to the floor. • From the preoperative angiogram, the most suitable superficial temporal artery (STA) branch (frontal vs parietal branch) is chosen as the donor. • The donor STA branch is transduced using a small Doppler probe above the zygoma, and followed to the convexity for a length of about 9 cm. • The parietal branch is preferred as it is well behind the hair line, has a straighter course, with less risk of damage to the frontal nerve during dissection. • Minimal hair shave. • Linear incision ◦ A superficial skin incision is made over the STA. ◦ Starting point: Incision starts just anterior to the tragus (posterior to the hairline). ◦ Course: It runs along the course of the donor STA. ◦ Ending point: The incision line ends at about 9 cm length of the STA. • Curvilinear incision ◦ To harvest the frontal STA branch, a curvilinear incision behind the hairline is performed. ◦ Starting point: The incision starts just anterior to the tragus (posterior to the hairline). ◦ Course: It runs superiorly, then curves forward to the anterior frontal line. ◦ Ending point: Incision line ends at the mid-pupillary point at the hairline. • Frontal and parietal branches of STA. • Frontal branch of the facial nerve. • Myofascial level ◦ The initial incision is made through the epidermis and partial thickness of dermis along the Doppler-defined projected course under microscopic examination. Fig. 47.1 Patient positioning. Fig. 47.3 The configuration of the frontal and parietal STA branch on a skull model. ◦ A blunt tip and fine curve scissors have to be used to perform the dissection through the remaining dermis and subcutaneous tissue to avoid damage to STA (Fig. 47.4A). ◦ After STA vessel is visualized, dissection proceeds along the loose areolar plane around the STA vessel with a Bovie tip or microscissors (Fig. 47.4B), preserving a cuff of perivascular tissue, and free it from the underlying temporal fascia (Fig. 47.4C, Fig. 47.4D). ◦ For dissection of the frontal STA branch, the vessel is dissected from the underside of the scalp flap. • Muscle ◦ The STA is retracted laterally, and protected with a vein retractor (Fig. 47.5A). ◦ The temporal fascia and muscle are incised in line with the long axis of the STA, then perpendicular to this at the proximal and distal ends (in an H-shaped fashion). ◦ The muscle is retracted after freeing it from the underlying bone (Fig. 47.B). • Bone exposures ◦ Subperiosteal dissection of the temporal muscle attachment is as wide anteriorly and posteriorly as allowed by the scalp incision, also from the superior temporal line superiorly to above the zygoma inferiorly. • Burr holes ◦ I: The first burr hole is made just under the superior temporal line. ◦ II: The second one is placed above the zygomatic process. • Craniotomy landmarks Anatomic landmarks which have to be considered in performing the craniotomy are as follows: ◦ Superiorly: The superior temporal line. ◦ Inferiorly: The area just above the zygomatic process. ◦ Anteriorly and posteriorly: Anterior and posterior limit of the craniotomy are determined by the wideness of scalp exposure. A 6 cm diameter craniotomy is created to maximize the distal peri-Sylvian and recipient vessel exposure, as well to maximize the area for associated indirect revascularization to occur. • Donor artery preparation should be performed under microscopic guidance. • A segment of 1–2 cm of distal STA is dissected free of all soft tissue. • Soft tissue is also dissected off a cuff of the proximal STA for the placement of a proximal temporary clip. • The ideal site for temporary clipping is distal to the take-off of the unused (frontal or parietal) branch of STA. • Dura is opened in a multiple leaflets stellate fashion. • Dural tack-up sutures are used to obliterate epidural space. • Large middle meningeal artery (MMA) vessels are preserved. • Large MMA with extensive extracranial to intracranial collateralization [determined preoperatively on the cerebral angiography, external carotid artery (ECA) injection]. • The arachnoid over the potential recipient middle cerebral artery (MCA) vessel is opened (Fig. 47.9A).
47.1 Indications
47.2 Patient Positioning (Fig. 47.1)
47.3 Skin Incision (Figs. 47.2, 47.3)
47.3.1 Critical Structures
47.4 Soft Tissues Dissection
Abbreviations: SI = skin incision.
Abbreviations: CS = coronal suture; FB = frontal branch; PB = parietal branch; SS = squamosal suture; STA = superficial temporal artery.
47.5 Craniotomy (Fig. 47.6)
47.6 Preparing Donor Artery (Fig. 47.7)
47.7 Dural Opening (Fig. 47.8)
47.7.1 Critical Structures
47.8 Intradural Stage (Figs. 47.9–47.11)
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