Progressive PCA steno-occlusive changes after revascularization for moyamoya disease: A neglected phenomenon
Journal
Neurosurgery
Journal Volume
67
Journal Issue
6
Pages
E1865-E1866
Date Issued
2010
Author(s)
Abstract
To the Editor: We read with great interest the article by Hayashi et al entitled “Additional Surgery for Postoperative Ischemic Symptoms In Patients With Moyamoya Disease: The Effectiveness of Occipital Artery−Posterior Cerebral Artery Bypass With an Indirect Procedure: Technical Case Report.”1 This article addressed an important cause of cerebral ischemia after revascularization that deserves attention because these patients may benefit from additional revascularization surgery. The authors observed this phenomenon in 3 of the 44 patients (6.8%) who underwent revascularization. In a retrospective study, our group evaluated the phenomenon of posterior circulation changes after revascularization2 and found that progressive posterior cerebral artery (PCA) steno-occlusive changes after revascularization caused cerebral hemodynamic compromise and clinical deterioration in at least 27.8% of the revascularized patients. In our study, 23 moyamoya disease patients who presented with ischemic symptoms, underwent revascularization, and were then followed up clinically with complete angiography and xenon computed tomography for a minimum of 3 years were evaluated. Preoperative and postoperative angiographs were reviewed to determine the internal carotid artery stage, PCA stage, leptomeningeal collateral grade, and Matsushima synangiosis grade. The postoperative regional cerebral blood flow and cerebral vascular reserve were recorded and compared with angiographic findings and clinical outcome; as a result of which, progression of internal carotid artery staging was noted in 23 cases (55.2%) and progression of PCA staging was noted in 18 cases (47.4%). Among the 18 cases of PCA stage progression, an associated decrease in leptomeningeal collateral grade was noted in 12 cases (66.7%); these changes were associated with decreased regional cerebral blood flow and cerebral vascular reserve, which also explained the recurrent ischemic symptoms in 27.8% of these patients. We speculate that this rate would have been higher with greater clinical vigilance and serial documentation of higher cortical and visual function. Our study also stressed the importance of serial documentation of the angiography grading and staging to appreciate the dynamic process of the disease and collateral formation. The importance of collateral assessment of these patients via imaging studies performed at follow-up cannot be overemphasized.3,4 In the study by Hayashi et al, progression of PCA steno-occlusive disease was demonstrated in only 3 cases; 1 patient had typical symptoms (visual impairment) in that territory, whereas the other 2 patients had symptoms arising from the anterior cerebral artery (ACA) territory (lower-extremity monoparesis). This may be explained by the fact that the PCA provides important collaterals to the ACA territory via the posterior pericallosal artery, and when steno-occlusive lesions of the PCA progress, these collaterals diminish, causing ischemic symptoms. In our study, however, cerebral ischemia or infarct of the MCA, posterior watershed, or PCA territory was observed in most patients with PCA stage progression by xenon computed tomography study. These patients presented with recurrent transient ischemic attacks, visual field abnormalities, parietal syndrome, neuropsychological deficits, and sensory and motor deficits. It is reasonable to assume that revascularization of the PCA territory might benefit patients with progressive PCA steno-occlusion before cerebral infarction ensues. Miyamoto et al5 reported 5 patients with impending blindness who received transplantation of the omentum to the occipital lobe, leading to visual improvement. Muscle-free flaps such as the latissimus dorsi and serratus anterior could also be considered for use in the revascularization of this region.6 Finally, Hayashi et al demonstrated elegantly in their study that occipital artery-PCA bypass was effective for postoperative cerebral ischemia involving the ACA and PCA territories.1 Last but not least, we hope to increase awareness of this frequently neglected phenomenon that is responsible for cerebral ischemia after apparently successful revascularization because prompt recognition and treatment may prevent neurological deterioration and subsequent stroke in this group of patients. Abel Po-Hao Huang Yong-Kwang Tu Taipei, Taiwan
SDGs
Type
letter