10 Double-Barrel Bypass in Moyamoya Disease
Abstract
This chapter describes the use of two branches of the superficial temporal artery for direct anastomotic bypass in patients with moyamoya disease. Although some surgeons routinely perform a double-barrel bypass, it is typically used when significant superficial temporal artery ischemia is found in addition to middle cerebral artery ischemia. The technical features of the procedure are explained, including the ideal manner of harvesting both superficial temporal artery branches while minimizing wound issues. How to identify the best recipient middle cerebral artery branches for anastomoses is also discussed. Finally, specific perioperative management protocols and complication avoidance as well as management are reviewed.
10.1 History and Initial Description
Since the first superficial temporal artery (STA) to middle cerebral artery (MCA) bypass pioneered by Donaghy and Yaşargil et al in 1967, neurosurgeons have utilized multiple adaptations to augment cerebral blood flow. 1 , 2 Reichman was the first to use both STA branches in a bypass for ischemia in 1975. Sakamoto et al 3 applied the technique of using two STA branches for the treatment of pediatric moyamoya disease in 1997. Ishikawa et al 4 reported using one STA branch to revascularize the anterior cerebral artery (ACA) and the other for the MCA in 2005. Several reports from Hokkaido, Japan, describe large series of patients with moyamoya disease who routinely underwent a double-barrel bypass to the MCA cortical branches as part of a larger, combined, indirect revascularization procedure. 5 , 6 At Barrow Neurological Institute, like other centers, we use a double-barrel bypass in select patients, including those with moyamoya disease, intracranial occlusive cerebrovascular disease, and complex aneurysms. 7 , 8
10.2 Indications
The basic indication for a double-barrel bypass in the setting of moyamoya disease is severe hemispheric hypoperfusion. This circumstance is usually the case when both the MCA and the ACA are involved and frequently when patients have severe bilateral disease. Rapid progression of the clinical course of the patient also lends support to performing a double-barrel bypass because these patients have not had time to develop sufficient collateral vascularization on their own. Since such patients have inadequate cerebral blood flow and rapid disease progression, they need STA branches and recipient cortical MCA arteries of sufficient quality to allow for a double-limbed bypass.
At Barrow Neurological Institute, we evaluate the cerebral blood flow in moyamoya patients using computed tomography (CT) perfusion imaging before and after a 1-g acetazolamide vasodilatory challenge. Patients with symptomatic moyamoya disease who have impaired cerebrovascular reserve on a CT perfusion study upon vasodilatory challenge are candidates for revascularization. In most cases, a six-vessel cerebral angiogram is performed to document the stage of moyamoya disease and to demonstrate donor suitability of the STAs. Patients with severe hemispheric hypoperfusion, usually including both STA and ACA territories, are those typically chosen for two direct anastomoses (Fig. 10‑1). The decision to construct a double-barrel bypass depends, in part, on the philosophy of the surgeon managing the case. Some surgeons would argue for using one STA branch for an indirect onlay instead of using both for direct anastomoses. Others contend that a single direct bypass is sufficient to revascularize a patient. No single best method has been proven. As with moyamoya treatment in most centers, the specific treatment, such as a double-barrel bypass, is chosen for a particular patient on the basis of the clinical condition and specific cerebral blood flow deficits of that patient.
10.3 Key Principles of the Double-Barrel Bypass
The pattern of blood flow deficits on the CT perfusion scan and cerebral angiogram should guide the choice of the type of bypass. For a patient with broad hemispheric hypoperfusion, a double-limbed direct bypass with a frontal branch is used for the lower division of the MCA; above the sylvian fissure, the parietal STA branch is used for the upper MCA division. Since the posterior cerebral artery supply to the temporal lobe frequently augments the lower division MCA flow, it is common for the primary perfusion deficit to involve the upper MCA division; in such cases, both STA branches can be anastomosed to the cortical branches above the sylvian fissure. Although not used at our center, STA bypasses to both the MCA and ACA cortical branches remain options. 4 In addition to the appropriate targeting of the recipient artery, careful preparation of the STA grafts is crucial.
10.4 SWOT Analysis
10.4.1 Strength
The double-barrel STA–MCA bypass provides immediate and robust cerebral blood flow to the ischemic hemisphere.
10.4.2 Weaknesses
The procedure is more complex and requires more operating time than single-vessel bypass.
Theoretical disadvantage is loss of use of one STA branch for an indirect encephalo-duro-arterio-synangiosis (EDAS) bypass, potentially reducing longer-term revascularization.
10.4.3 Opportunity
A potential improvement in the execution of a double-barrel bypass would be the use of the cut flow index to assess the need for two grafts. 9
10.4.4 Threats
Use of two grafts might be more likely to cause hyperperfusion syndrome (not reported as a significant problem in one large series). 6
Two separate grafts might compete for blood flow, which could limit the benefit of a second graft or lead to an occlusion.
10.5 Contraindications
Moyamoya patients who have exceptionally small and fragile cortical MCA branches should not, and likely technically could not, undergo direct STA–MCA bypass. In clinical practice, this group represents about 10% of moyamoya patients who present for revascularization.
10.6 Special Considerations
A careful review of any preoperative CT angiography (CTA) and digital subtraction angiography images is required to ensure that both the frontal and the parietal STA branches are of sufficient size and quality for bypass use. Potential recipient MCA branches should also be assessed.
10.7 Risk Assessment and Complications
The perioperative risk of stroke is 3 to 5% in most large series. Rates of significant hemorrhage are greater than 1%, but they do occur, given the use of antiplatelet treatment and the potential for hyperperfusion. Infection and wound healing complications are less than 1%. Headaches and cosmetic issues such as temporalis wasting remain a possibility.
10.8 Special Instructions, Position, and Anesthesia
10.8.1 Preoperative Workup
A cerebral blood flow study and a catheter cerebral angiogram or a CTA must be evaluated preoperatively. Since patients with moyamoya angiopathy can have associated blood dyscrasias, it is important to verify each patient’s response to antiplatelet therapy. We test patients to determine whether they are responsive to aspirin therapy (325 mg daily), which is our preferred antiplatelet agent before surgery and then for life. We avoid clopidogrel as an antiplatelet medication because of intraoperative bleeding issues. However, we did have a patient who did not respond to aspirin and who had a small stroke on discontinuation of clopidogrel. As a compromise, clopidogrel was withheld for 3 days prior to surgery, and the case proceeded without complication.
10.8.2 Patient Position
The patient is positioned supine with the head parallel to the floor and raised slightly above the heart. The courses of both the frontal and the parietal STA branches are insonated with Doppler ultrasonography and marked on the skin. The frontal STA is followed for at least 7 cm from its origin while the parietal branch is marked clear to the superior temporal line. The surgeon makes an incision along the parietal branch alone and shaves a 1-cm strip of hair along its path. An alternative incision is shaped like a hockey stick, with the parietal branch as the posterior limb and the second limb extending forward along the superior temporal line to the hairline. In addition to appropriate patient positioning, the proper instruments are critical to ensuring optimal technical results (Table 10‑1 , Fig. 10‑2).
Related posts:
11 Occipital ArteryMiddle Cerebral Artery Bypass in Moyamoya Disease
12 STAACA/MCA Double Bypasses with Long Grafts
9 STA–MCA Bypass for Direct Revascularization in Moyamoya Disease
13 Double Anastomosis Using Only One Branch of the Superficial Temporal Artery: Single-Vessel Double Anastomosis
7 Encephalo-duro-arterio-synangiosis: In Adults
16 Combined Direct (STA–MCA) and Indirect (EDAS) EC–IC Bypass
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