Collateralization and ischemia in hemodynamic cerebrovascular insufficiency

The Development and Effect of Systemic Hypertension on Clinical and Radiological Outcome in Adult Moyamoya Angiopathy Following Revascularization Surgery: Experience of a Single European Institution

Patients with Moyamoya Angiopathy (MMA) display structurally altered vessels with decreased cerebral autoregulatory capacity, so aggressive lowering of systemic hypertension may aggravate ischemic symptoms, whereas uncontrolled hypertension may promote hemorrhage. This study provides an in-depth analysis of the role of hypertension in adult MMA patients including long-term analysis of clinical and radiological development. In this single-center retrospective analysis of 137 adult MMA patients with 206 surgically treated hemispheres angiographic images, clinical/operative data were reviewed and scored. Univariate Cox-regression analysis was performed to evaluate hypertension as a predictor for negative angiographic and clinical outcomes following revascularization surgery. A total of 50% of patients were being treated for hypertension prior to the first surgery. Patients with and without hypertension did not differ in terms of age, gender, diagnosis, symptom onset or disease severity (Berlin and Suzuki Grades). Although hypertension did not statistically significantly affect postoperative collaterals, moyamoya vessels or STA-MCA bypass patency, patients with hypertension showed higher rates of bypass patency and better bypass filling compared to those without hypertension. No significant differences in adverse events were found in patients with and without systemic hypertension and the presence of systemic hypertension was not found to predict negative clinical or radiological outcomes. In conclusion, the rate of systemic hypertension in MMA patients appears to be higher than the general population; however, this is not associated with an increased risk of postoperative complications or negative angiographic development following revascularization procedures. Systemic hypertension may also positively influence the rate of bypass patency and filling following revascularization procedures.

Longitudinal angiographic characterization of the efficacy of combined cerebral revascularization using minimally invasive encephalodurosynangiosis in patients with moyamoya angiopathy

Moyamoya angiopathy (MMA) can be treated using direct, indirect, or combined revascularization procedures. We perform combined revascularization using the STA-MCA bypass and minimally invasive encephalodurosynangiosis (MIS-EDS). Due to lack of systematic analyses to date it remains unclear whether and to which extent this limited EDS serves as a growth source for extracerebral blood vessels into the brain. The objective of the current study is to characterize the extent of angiographic filling of MIS-EDS and STA-MCA bypass development over time and to determine possible predictors of EDS development in adult MMA patients. Single-center retrospective analysis of 81 MMA patients (139 hemispheres) treated with a MIS-EDS and STA-MCA bypass was performed. Angiographic images and clinical/operative data were reviewed and scored. Uni-/ and multivariate Cox regression analyses identified preoperative predictors of good EDS vascularization. At 3-6 months after surgery EDS showed moderate and high angiographic filling in 40% and 5% of hemispheres, respectively. After 12 months moderate and high filling was found in 57% and 4% of hemispheres, respectively. STA-MCA bypass filling was moderate in 47% and high in 7% of hemispheres at 3-6 months and 45% moderate and 9% high after 12 months. High STA-MCA bypass filling on angiography was a negative predictor of EDS development. MIS-EDS is a simple technique and serves as a source of vessel growth into the brain. EDS development lags behind that of STA-MCA bypass and can be recommended as an additive revascularization source when combined with a direct bypass.

STA-A3 Bypass Using Radial Artery Graft for Progressive Cerebral Infarction of Bilateral ACA Region after STA-MCA Bypass Surgery for Moyamoya Disease

Direct revascularization surgery, such as superficial temporal artery (STA)-middle cerebral artery (MCA) bypass, is effective in preventing ischemia and hemorrhage for moyamoya disease. On the other hand, when ischemia of the anterior cerebral artery (ACA) region progresses after ipsilateral STA-MCA bypass, it is difficult to perform revascularization from the viewpoint of the donor artery. A 55-year-old woman with right hemiparesis was diagnosed with cerebral infarction due to moyamoya disease. Left STA-MCA bypass was performed with no postoperative complications, but memory impairment and decreased motivation were observed 2 months after the operation. Magnetic resonance imaging and angiography revealed new infarction in the bilateral ACA area and deterioration in the signal intensity of bilateral ACAs. Revascularization of the bilateral ACA regions was considered necessary, but the left STA was already used in the previous surgery. Therefore, STA-radial artery (RA)-A3 bypass using RA graft combined with right STA-MCA bypass was performed. STA-A3 bypass using an RA graft may be the optimal treatment for ischemia of the ACA region that progresses after STA-MCA bypass.

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Motor excitability in bilateral moyamoya vasculopathy and the impact of revascularization

OBJECTIVE

Motor cortical dysfunction has been shown to be reversible in patients with unilateral atherosclerotic disease after cerebral revascularization. Moyamoya vasculopathy (MMV) is a rare bilateral stenoocclusive cerebrovascular disease. The aim of this study was to analyze the corticospinal excitability and the role of bypass surgery in restoring cortical motor function in patients by using navigated transcranial magnetic stimulation (nTMS).

METHODS

Patients with bilateral MMV who met the criteria for cerebral revascularization were prospectively included. Corticospinal excitability, cortical representation area, and intracortical inhibition and facilitation were assessed by nTMS for a small hand muscle (first dorsal interosseous) before and after revascularization. The clinically and/or hemodynamically more severely affected hemisphere was operated first as the leading hemisphere. Intra- and interhemispheric differences were analyzed before and after direct or combined revascularization.

RESULTS

A total of 30 patients with bilateral MMV were examined by nTMS prior to and after revascularization surgery. The corticospinal excitability was higher in the leading hemisphere compared with the non-leading hemisphere prior to revascularization. This hyperexcitability was normalized after revascularization as demonstrated in the resting motor threshold ratio of the hemispheres (preoperative median 0.97 [IQR 0.89-1.08], postoperative median 1.02 [IQR 0.94-1.22]; relative effect = 0.61, p = 0.03). In paired-pulse paradigms, a tendency for a weaker inhibition of the leading hemisphere was observed compared with the non-leading hemisphere. Importantly, the paired paradigm also demonstrated approximation of excitability patterns between the two hemispheres after surgery.

CONCLUSIONS

The study results suggested that, in the case of a bilateral chronic ischemia, a compensation mechanism between both hemispheres seemed to exist that normalized after revascularization surgery. A potential role of nTMS in predicting the efficacy of revascularization must be further assessed.

Gelatinolytic activity of autocrine matrix metalloproteinase-9 leads to endothelial de-arrangement in Moyamoya disease

Moyamoya disease (MMD) is a rare steno-occlusive cerebrovascular disorder. Mechanisms driving the formation of aberrant MMD vessels remain elusive. We collected serum and vessel specimens from MMD and atherosclerotic cerebrovascular disease (ACVD) patients serving as controls due to the same hypoxic stimulus but substantial differences in terms of vascular features. Based on patient material and an in vitro model mimicking ACVD and MMD conditions, matrix metalloproteinase-9 (MMP-9) and vascular-endothelial growth factor (VEGF) were tested for their potential involvement in cerebrovascular disintegration. While serum concentration of both molecules did not significantly differ in both patient groups, excessive collagenase activity and lowered collagen IV protein amount in MMD vessels pointed to a focal MMP-9 activity at the affected vessel sites. We observed overexpressed and autocrinely secreted MMP-9 and VEGF along with disturbances of EC-matrix interactions in MMD but not ACVD serum-treated cEND cells. These seemingly brain-specific effects were partially attenuated by VEGF signaling inhibition suggesting its role in the MMD etiology. In conclusion, our findings support the understanding of the high incidence of hemorrhagic and ischemic events in MMD and provide the basis for novel therapeutic strategies stopping or slowing the development of fragile cerebrovasculature or micro-bleeds characterizing the disease.

Berlin Grading System Can Stratify the Onset and Predict Perioperative Complications in Adult Moyamoya Disease

BACKGROUND

The grading system for moyamoya disease is not established.

OBJECTIVE

To assess the usefulness of a recently proposed grading system for stratifying the clinical severity and predicting postoperative morbidity in adult moyamoya disease.

METHODS

We investigated 176 hemispheres from 89 adult patients who were diagnosed with moyamoya disease in Japan. Their data were analyzed using the Berlin grading system with minor modifications. After summarizing the numerical values for digital subtraction angiography (1-3 points), magnetic resonance imaging (0-1 points), and single-photon emission computed tomography (0-2 points), 3 grades of moyamoya disease were defined: mild (grade I) = 1 to 2 points, moderate (grade II) = 3 to 4 points, and severe (grade III) = 5 to 6 points. In total, 82 of 161 hemispheres underwent superficial temporal artery to middle cerebral artery anastomosis and indirect synangiosis. Postoperative neurological morbidity was included within 30 d after surgery.

RESULTS

Preoperative examinations categorized 87 hemispheres as grade I, 39 as grade II, and 50 as grade III. There was a significant correlation between the Berlin grading system and clinical severity (P < .001). Perioperative complications occurred in 12 of 82 (14.6%) hemispheres, including transient ischemic attack in 3 hemispheres, ischemic stroke in 4 hemispheres, symptomatic hyperperfusion in 4 hemispheres, and intracerebral hemorrhage in 1 hemisphere. The Berlin grading system was related to their occurrence (P < .001).

CONCLUSION

The Berlin grading system facilitates the stratification of clinical severity and predicting postoperative neurological morbidity in adult moyamoya disease, thereby suggesting its general usage in clinical practice.

Adolescents with moyamoya disease: clinical features, surgical treatment and long-term outcomes

BACKGROUND

This study aimed to elucidate the clinical features, surgical treatment and long-term outcomes of adolescent patients with moyamoya disease.

METHODS

We reviewed consecutive patients with moyamoya vasculopathy who were admitted to our hospital from 2009 to 2015 to identify adolescent patients with moyamoya disease. Clinical features, surgical treatment and long-term outcomes were analyzed. Follow-up was performed by face-to-face or structured telephone interviews. Outcome measures were future stroke events. We performed univariate and multivariate time-to-event analyses to identify risk factors associated with future stroke events.

RESULTS

A total of 95 adolescent patients with moyamoya disease (age at onset, 13.1 ± 2.3 years) were included in this study. During follow-up, 12 patients (12.6%) had stroke events. We found that the patients who underwent direct/combined bypass had a significantly lower risk of future strokes [hazard ratio (HR), 0.16; 95% confidence interval (CI), 0.03-0.74; P = 0.019] compared to patients who underwent indirect bypass.

CONCLUSIONS

Our results demonstrate that direct/combined bypass can be more effective in preventing future strokes than indirect bypass in adolescent patients with moyamoya disease.

Autocrine release of angiopoietin-2 mediates cerebrovascular disintegration in Moyamoya disease

Moyamoya disease is a rare steno-occlusive cerebrovascular disorder often resulting in hemorrhagic and ischemic strokes. Although sharing the same ischemic stimulus with atherosclerotic cerebrovascular disease, Moyamoya disease is characterized by a highly instable cerebrovascular system which is prone to rupture due to pathological neovascularization. To understand the molecular mechanisms underlying this instability, angiopoietin-2 gene expression was analyzed in middle cerebral artery lesions obtained from Moyamoya disease and atherosclerotic cerebrovascular disease patients. Angiopoietin-2 was significantly up-regulated in Moyamoya vessels, while serum concentrations of soluble angiopoietins were not changed. For further evaluations, cerebral endothelial cells incubated with serum from these patients in vitro were applied. In contrast to atherosclerotic cerebrovascular disease serum, Moyamoya disease serum induced an angiopoietin-2 overexpression and secretion, accompanied by loss of endothelial integrity. These effects were absent or inverse in endothelial cells of non-brain origin suggesting brain endothelium specificity. The destabilizing effects on brain endothelial cells to Moyamoya disease serum were partially suppressed by the inhibition of angiopoietin-2. Our findings define brain endothelial cells as the potential source of vessel-destabilizing factors inducing the high plasticity state and disintegration in Moyamoya disease in an autocrine manner. We also provide new insights into Moyamoya disease pathophysiology that may be helpful for preventive treatment strategies in future.