Superficial temporal artery-to-middle cerebral artery anastomosis with encephalo-duro-myo-synangiosis as a modified operative procedure for moyamoya disease

Comparison of Operative and Conservative Treatment for Asymptomatic Moyamoya Disease: Preliminary Experience in Small Retrospective Series

OBJECTIVE

The best management of asymptomatic moyamoya disease (MMD) remains controversial. In this study, the authors aimed to explore an experience for treatment modality for asymptomatic MMD.

METHODS

The authors retrospectively reviewed a total of 23 patients (age range 30-58 years) with asymptomatic MMD during the past 5 years at their institutions. The patients were divided into 2 groups: The surgical group included 11 patients, and the conservative group included 12 patients. The demographic, radiologic, and clinical findings of the patients were evaluated. At follow-up over 13-65 months, the future clinical and radiologic progression events were evaluated.

RESULTS

During the follow-up period, 3 patients suffered from future clinical progression events in the conservative group: 1 experienced stroke, and 2 experienced transient ischemic attack. Among the patients in the surgical group, only 1 experienced transient ischemic attack. Kaplan-Meier analysis showed that patients undergoing surgeries had longer clinical progression-free survival times compared with patients in the conservative group (P = 0.002).

CONCLUSIONS

Surgical treatment may be an alternative choice for patients with asymptomatic MMD. However, the best strategy for asymptomatic MMD in order to reduce future cerebrovascular risks still needs to be further explored.

Extracranial to intracranial by-pass anastomosis: Review of our preliminary experience from a low volume center in Egypt

Background:

Cerebral revascularization is a useful microsurgical technique for the treatment of steno-occlusive intracranial ischemic disease, complex intracranial aneurysms that require deliberate occlusion of a parent artery and invasive skull base tumors. We describe our preliminary experience with extracranial-to-intracranial by-passes at a low volume center; and discuss clinical indications and microsurgical techniques, challenges in comparison to large advanced referral centers.

Materials and Methods:

Twenty-seven patients with hemodynamic ischemia or complex aneurysms or skull base tumors were operated at Cairo University Hospitals in the period between May 2009 and June 2014. All patients operated by a low flow by-pass were operated through a superficial temporal artery to middle cerebral artery (MCA) anastomosis. All patients chosen for a high flow by-pass were operated using a radial artery graft interposed between the MCAs distally and the common or the external carotid artery proximally. Patency was confirmed at the end of surgery using appearance on the table and confirmed after surgery by transcranial color-coded duplex or computed tomography angiography. All patient data were prospectively collected and retrospectively analyzed at the end of surgery.

Results:

Nineteen patients (70.4%) were operated upon for flow augmentation and eight patients (29.6%) were operated upon for flow replacement. A total of 30 anastomoses were performed. All except one were patent which gives a patency rate of 96.3%. There was one death in the present series resulting from a hyperperfusion syndrome. 89.5% of patients with hemodynamic ischemia stopped having symptoms after surgery. All but one patient operated for hemodynamic ischemia showed a considerable cognitive improvement after surgery. None of the patients operated upon for flow replacement showed improvement of oculomotor nerve function in spite of adequate intraoperative decompression. All patients treated for flow replacement showed the absence of recurrence on follow-up.

Conclusion:

Our initial results for both low and high flow by-pass procedures in our low volume center indicate that such complex surgical procedures are possible with results comparable to those obtained in other larger referral centers throughout the world. This procedure not only represents a more definitive treatment when compared to other endovascular or radiation treatments but is also much less costly when compared to other treatment modalities.

Clinical course of asymptomatic adult moyamoya disease

BACKGROUND

As regular medical check-ups are becoming more common, the prevalence of asymptomatic moyamoya disease (MMD) is increasing. However, the definition and clinical features are still unclear. The lack of precision has hampered the establishment of guidelines for the management of asymptomatic MMD. The purpose of this study was to define and clarify the clinical characteristics of asymptomatic MMD in adults.

METHODS

We identified all adults (aged ≥18 years) with MMD who underwent digital subtraction angiography or magnetic resonance angiography at our institution from 1995 through 2010. The authors defined asymptomatic MMD as asymptomatic or nonspecific symptom without any infarction or ischemia on magnetic resonance imaging. In our MMD registry, 40 patients (74 hemispheres) were identified and enrolled in this retrospective cohort study. Their demographic, radiological and clinical findings were evaluated. The log-rank test was used to assess prognostic factors. Pearson's correlation test and the Mann-Whitney U test were used to identify correlation angiographic staging and age or perfusion status.

RESULTS

Overall, 6 patients underwent indirect bypass surgery and 36 received antiplatelet medication. On initial single positron emission tomography (35 patients, 67 affected hemispheres), basal and acetazolamide stress brain perfusion were decreased in 19 (28.4%) and 22 (32.8%) hemispheres, respectively. Among 70 angiographically evaluated hemispheres, 6 were unilateral MMD; 27 of 64 affected hemispheres (42.2%) had transdural collateral at evaluation. Age (p = 0.309, Pearson's correlation test) and hemodynamic impairment (p = 0.614, Mann-Whitney U test) did not correlate with angiographic staging. During a median 32-month (range 6-203) clinical follow-up, 3 nonsurgically treated patients had a transient ischemic attack, which was associated with decreased vascular reserve (p < 0.001, log-rank test) and smoking (p = 0.017). Other variables did not show a significant association with clinical progression. During a median 24-month (range 12-108) radiological follow-up, 3 patients displayed angiographic progression and 3 displayed new hemodynamic abnormalities. Radiological progressions were related to hypertension only (p = 0.022). In this case series, there was no case of ischemic or hemorrhagic stroke.

CONCLUSION

The findings suggest that asymptomatic MMD in adults is not a stable disease in our definition. However, stroke rate (0%) was lower than previous reports. Lifestyle modification, stroke risk factor control and/or antiplatelet medication seem to be appropriate initial treatments for patients with normal cerebrovascular reserve. A clear definition of asymptomatic MMD and further clarification of its clinical course are needed to set precise treatment guidelines.

Neurosurgical Advances in the Treatment of Moyamoya Disease

Background and Purpose—

Moyamoya disease is characterized by chronic stenoocclusive vasculopathy involving the distal supraclinoid internal carotid arteries and presents with ischemic or hemorrhagic symptoms. We review advances in the understanding and management of moyamoya disease.

Summary of Review—

Cerebral revascularization, either direct or indirect, is the cornerstone of treatment for moyamoya disease. Recent advances have been made in understanding the molecular biology and pathophysiology of moyamoya disease, and new genetic mutations and deletions have been identified. Imaging for moyamoya disease is also rapidly improving with new sequences of MRI and better methods of assessing ischemia and cerebrovascular reserve. Positron emission tomography has emerged as an important tool to measure cerebrovascular reserve. Novel surgical techniques assess patency and ischemia during superficial temporal to middle cerebral artery bypass, including indocyanine green videoangiography to evaluate anastomosis patency, and various methods to monitor intraoperative blood flow. Newer methods of indirect revascularization have been described with placement of more tissues supplied by the external carotid artery on the brain surface. Postoperative hyperperfusion to the chronically ischemic brain tissue is a recently identified causative factor of complications. Interestingly, complications from hyperperfusion mimic those caused by ischemia, although they have different treatments, making the role of postoperative blood flow assessment important in distinguishing between the two. Awareness has also increased that even asymptomatic patients can experience significant cognitive decline attributable to chronic ischemia. Whether this reverts after successful revascularization requires investigation.

Conclusions—

Surgical revascularization with direct, indirect, and combined methods remains the preferred procedure for patients with moyamoya disease.

Changes in Bypass Flow during Temporary Occlusion of Unused Branch of Superficial Temporal Artery

OBJECTIVE

Some neurosurgeons intentionally ligate the branches of the superficial temporal artery (STA) that are not used in standard STA-to-middle cerebral artery (MCA) anastomosis for the purpose of improving the flow rate in the bypass graft. We investigated changes in bypass flow during temporary occlusion of such unused branches of the STA.

METHODS

Bypass blood flow was measured by a quantitative microvascular ultrasonic flow probe before and after temporary occlusion of branches of the STA that were not used for anastomosis. We performed measurements on twelve subjects and statistically assessed changes in flow. We also examined all the patients with digital subtraction angiography in order to observe any post-operative changes in STA diameter.

RESULTS

Initial STA flow ranged from 15 mL/min to 85 mL/min, and the flow did not change significantly during occlusion as compared with pre-occlusion flow. The occlusion time was extended by 30 minutes in all cases, but this did not contribute to any significant flow change.

CONCLUSION

The amount of bypass flow in the STA seems to be influenced not by donor vessel status but by recipient vessel demand. Ligation of the unused STA branch after completion of anastomosis does not contribute to improvement in bypass flow immediately after surgery, and furthermore, carries some risk of skin necrosis. It is better to leave the unused branch of the STA intact for use in secondary operation and to prevent donor vessel occlusion.