11 Occipital ArteryMiddle Cerebral Artery Bypass in Moyamoya Disease

10.1055/b-0039-172625

11 Occipital Artery–Middle Cerebral Artery Bypass in Moyamoya Disease

Ken Kazumata

Abstract

The posterior cerebral artery (PCA) is involved in approximately 30% of moyamoya disease (MMD) cases. Symptomatic PCA regression following anterior revascularization was predominantly found in children and young adults. Occipital artery–middle cerebral artery (OA–MCA) bypass can be used as one of the option for revascularization in the posterior portion of the brain. OA–MCA bypass demonstrates a several advantages over conventional OA–PCA bypass. Technical points are described in this chapter.

11.1 History and Initial Description

Occlusive lesions in the posterior cerebral artery (PCA) are observed in 26 to 43% moyamoya disease (MMD) patients at the initial diagnosis, which is associated with disease advancement and poor prognosis. ¹ Although majority of the patients with PCA involvement is asymptomatic, revascularization in the anterior circulation occasionally advances PCA involvement in certain patients. ² PCA regression causes several clinical issues such as follows: (1) additional PCA lesions can cause extensive cerebral ischemia beyond the territory of the PCA, (2) ischemic injury to frontoparietal connection fibers potentially impairs cognitive function, and (3) surgical treatment involves more complex procedures. Nevertheless, revascularization in the posterior portion of the brain is generally difficult. While source for blood supply through indirect procedure is limited in the posterior portion of the head, the direct anastomosis may be less competent than the superficial temporal artery–middle cerebral artery (STA–MCA) bypass. Previous literatures describe indirect methods for revascularization in the posterior half of the brain ³ ^, ⁴ as well as occipital artery-posterioer cerebral artery (OA–PCA) bypass for the direct anastomosis in the posterior circulation. ⁵ Alterative approach such as OA–MCA bypass is described.

11.2 Indications

We consider that anterior revascularization as the first treatment choice at the time of diagnosis, regardless of the PCA involvement. Accordingly, patients who persistently demonstrated ischemic symptoms attributable to PCA lesions or “delayed” PCA involvement following the anterior revascularization is selected as candidates for posterior revascularization. Hemodynamic compromise is evaluated such as using single-photon emission computed tomography (SPECT) and acetazolamide test. Symptomatic occlusive lesions in PCA territories were identified by their decreased cerebrovascular reserve, an avascular area on a cerebral angiogram, or hyperintense vessels on fluid-attenuated inversion recovery (FLAIR). ⁶

11.3 Key Principles

OA–MCA bypass procedure is not commonly used. However, it can be effective when posterior part of the brain requires additional source of blood supply. OA–MCA bypass does not require prone position and may be effective when combined with indirect procedure. Although source of indirect procedure is limited, a large craniotomy may facilitate neovascularization from the dura matter. Pericranial flap is also available.

11.4 SWOT Analysis

11.4.1 Strengths

OA-MCA bypass can effectively alleviate recurrent ischemia due to PCA involvement. ² Furthermore, improving cerebral perfusion in the posterior portion of the brain may ultimately lead to improved revascularization in the anterior circulation territory as well. ⁷ Furthermore, surgical revascularization in the posterior portion of the brain may not only be effective in stroke prevention, but also potentially improve cognitive outcomes by preventing ischemic injury in frontoparietal association fibers. ⁸

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