The usefulness of super-selective arterial spin labeling for postoperative evaluation of pediatric moyamoya disease: technical note

Moyamoya disease is characterized by progressive internal carotid artery (ICA) occlusion. Extracranial-intracranial bypass surgery is effective, particularly in pediatric patients; imaging plays a crucial role in evaluating intracranial perfusion pre- and post-surgery. Arterial spin labeling (ASL) is a magnetic resonance technique employed for noninvasive, whole-brain perfusion assessment by magnetically labeling inflowing blood. However, ASL cannot evaluate the territories and development of each vessel perfusion compared with digital subtraction angiography (DSA). Recently, super-selective ASL (SS-ASL) has been developed, performing pinpoint labeling on a specific artery at a time, and offering a tomographic view that distinctly displays blood supply areas for each vessel. Unlike DSA, SS-ASL is noninvasive and can be repeatedly performed in pediatric patients. In conclusion, SS-ASL is useful for evaluating bypass development over time and understanding the pathophysiology of pediatric moyamoya disease.

Wide Arterial Sparing Encephalo-Duro-Synangiosis for Moyamoya: Surgical Technique and Outcomes

BACKGROUND

Moyamoya is managed by surgical revascularization, but no standardized method has yet been universally adopted.

OBJECTIVE

To describe a new indirect bypass technique for pediatric moyamoya, wide arterial sparing encephalo-duro-synangiosis (WASEDS), which provides a much wider area of revascularization with minimal compromise to the middle meningeal arterial tree compared with traditional procedures. Initially used as a salvage technique after failed encephalo-duro-arterio-synangiosis, its success later motivated its use as a first-line procedure.

METHODS

Clinical and radiographic records of patients who underwent WASEDS for moyamoya from 2009 to 2020 were reviewed. Brain perfusion relative cerebral blood volume on the side of the WASEDS procedure was calculated. Two-tailed paired t tests were performed to identify the statistically significant differences ( P ≤ .05).

RESULTS

WASEDS was successfully performed on 8 patients for a total of 14 cerebral hemispheres. Age ranged from 2 to 25 years. There were no mortalities. The average clinical and radiographic follow-up was 49.79 months (range 2-126 months), demonstrating improvement in neurological condition and no postoperative stroke and significant diminution or cessation of transient ischemic attacks in all patients. Relative cerebral blood volume increased 9.24% after the WASEDS procedure ( P = .012). There were no neurological complications. There were 2 pseudomeningoceles related to the extensive dural openings.

CONCLUSION

WASEDS is a safe and effective indirect revascularization technique for both primary and salvage techniques. It provides an extensive area of cortical revascularization with no compromise of the middle meningeal vasculature and subjective reports of early improvement in cognition and behavior. The main disadvantage is elevated risk of pseudomeningocele secondary to the large craniotomy.

Angiographic Characteristics of Cerebral Perfusion and Hemodynamics of the Bridging Artery After Surgical Treatment of Unilateral Moyamoya Disease

Purpose

To investigate the characteristics of cerebral perfusion and hemodynamics of bypass grafting in the treatment of moyamoya disease (MMD) using the iFlow color-coded flow map in comparison with magnetic resonance imaging–perfusion-weighted imaging (MRI–PWI) and computational fluid dynamic (CFD) analysis.

Materials and Methods

Patients with MMD treated with bypass grafting who had undergone MRI PWI and digital subtraction angiography for iFlow color-coded map was retrospectively enrolled and CFD was performed for calculating the hemodynamic stresses around the bypass grafting.

Results

Forty-five patients with unilateral MMD treated with bypass surgery were enrolled. The bypass surgery was successful in all patients, with no severe neurological complications during the periprocedural period. Followed up for 4–12 months (median 5.5), the neurological function was good in all patients. The cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) were significantly (p < 0.05) improved in the middle cerebral artery distribution area on the surgical side before and after vascular bypass, and the difference of TTP (s) measured from the proximal bifurcation of common carotid artery to the confluence of sinus was also significant (p < 0.05). A significant (p < 0.05) positive correlation existed in the perfusion parameters between the iFlow blood perfusion and the MRI–PWI perfusion, with r-value for TTP of 0.765 (p < 0.01). The iFlow color-coded blood flow map showed warm color changes on the diseased side, similar to those on the contralateral side. In CFD analysis, the hemodynamic stresses were all improved, in and around the bypass grafting and distal vessels, which were beneficial to blood flow entering distal arterial branches.

Conclusion

The iFlow color-coded flow map can be used to analyze cerebral perfusion after bypass grafting for MMD, similar to MRI–PWI, and CFD can be used to analyze the hemodynamics after bypass grafting, revealing improved hemodynamics to promote blood flow entering distal arteries.

Salvage multiple burr hole surgery in patients with Moyamoya disease: efficacy evaluation using probabilistic independent component analysis of dynamic susceptibility contrast perfusion MRI

PURPOSE

Multiple burr hole surgery is considered to be an option for achieving indirect revascularization in patients with ischemic Moyamoya disease (MMD). We aimed to investigate the efficacy of stand-alone multiple burr hole surgery for salvage revascularization in patients with MMD by assessing the hemodynamic changes via normalized time-to-peak (nTTP) analysis and independent component analysis (ICA) of preoperative and postoperative dynamic susceptibility contrast (DSC) perfusion MRI data.

METHODS

The DSC perfusion MRI data of 25 hemispheres from 21 patients with MMD, who underwent multiple burr hole surgery for salvage revascularization due to persistent or recurrent symptoms after primary revascularization with modified encephaloduroarteriosynangiosis (mEDAS), were analyzed. The nTTP, which was measured using the region of interests covering the entire surgical hemisphere, was compared between the preoperative and postoperative images. ICA was used to compare the relative arterial and venous components of the surgical hemispheres between the respective preoperative and postoperative images.

RESULTS

The median postoperative nTTP (1.80 s) was significantly shorter than the median preoperative nTTP (4.10 s) (P < 0.001). The postoperative relative arterial component of the surgical hemisphere (median: 0.04) was significantly higher than the preoperative relative arterial component (median: - 0.02, P < 0.001). In contrast, the postoperative relative venous component of the surgical hemisphere (median: - 0.05) was significantly lower than the preoperative value (median: 0.05, P < 0.001).

CONCLUSION

The improvement in cerebral perfusion parameters observed on postoperative DSC perfusion MRI demonstrated that stand-alone multiple burr hole surgery could be a favorable salvage revascularization technique after mEDAS failure in patients with ischemic MMD.

Moyamoya disease and syndrome: a review

Moyamoya disease is a chronic occlusive cerebrovascular disease that is non-inflammatory and non-atherosclerotic. It is characterized by endothelial hyperplasia and fibrosis of the intracranial portion of the carotid artery and its proximal branches, leading to progressive stenosis and occlusion, often clinically manifesting as ischemic or hemorrhagic stroke with high rates of morbidity and mortality. On cerebral angiography, the formation of collateral vessels has the appearance of a puff of smoke (moyamoya in Japanese), which became more conspicuous with the refinement of modern imaging techniques. When there is associated disease, it is known as moyamoya syndrome. Treatments are currently limited, although surgical revascularization may prevent ischemic events and preserve quality of life. In this review, we summarize recent advances in moyamoya disease, covering aspects of epidemiology, etiology, presentation, imaging, and treatment strategies.

Surgical Management of Failed Revascularization in Moyamoya Vasculopathy

Objectives: Moyamoya vasculopathy (MMV) is a rare stenoocclusive cerebrovascular disease associated with increased risk of ischemic and hemorrhagic stroke, which can be treated using surgical revascularization techniques. Despite well-established neurosurgical procedures performed in experienced centers, bypass failure associated with neurological symptoms can occur. The current study therefore aims at characterizing the cases of bypass failure and repeat revascularization at a single center.

Methods: A single-center retrospective analysis of all patients treated with revascularization surgery for MMV between January 2007 and December 2019 was performed. Angiographic data, cerebral blood flow analysis [H₂O PET or single-photon emission CT (SPECT)], MRI, and clinical/operative data including follow-up assessments were reviewed.

Results: We identified 308 MMV patients with 405 surgically treated hemispheres. Of the 405 hemispheres treated, 15 patients (3.7%) underwent repeat revascularization (median age 38, time to repeat revascularization in 60% of patients was within 1 year of first surgery). The most common cause of repeat revascularization was a symptomatic bypass occlusion (80%). New ischemic lesions were found in 13% of patients prior to repeat revascularization. Persistence of reduced or progressive worsening of cerebrovascular reserve capacity (CVRC) compared with preoperative status was observed in 85% of repeat revascularization cases. Intermediate-flow bypass using a radial artery graft was most commonly used for repeat revascularization (60%) followed by re-superficial temporal artery to middle cerebral artery (re-STA-MCA) bypass (26%). High-flow bypass using a saphenous vein graft and using an occipital artery to MCA bypass was each used once. Following repeat revascularization, no new ischemic events were recorded.

Conclusion: Overall, repeat revascularization is needed only in a small percentage of the cases in MMV. A rescue surgery should be considered in those with neurological symptoms and decreased CVRC. Intermediate-flow bypass using a radial artery graft is a reliable technique for patients requiring repeat revascularization. Based on our institutional experience, we propose an algorithm for guiding the decision process in cases of bypass failure.

Additional Revascularization Using Multiple Burr Holes for PCA Involvement in Moyamoya Disease

In specific cases of moyamoya disease (MMD), posterior cerebral artery (PCA) stenosis can develop after treatment of the anterior circulation and require additional revascularization. Here, we report two cases that underwent additional posterior indirect revascularization with multiple burr holes for PCA involvement after bilateral revascularization treatment of the anterior circulation. They presented with transient ischemic attack even after bilateral superficial temporal artery-middle cerebral artery bypass, and magnetic resonance angiography (MRA) showed that PCA stenosis had worsened. Indirect revascularization with multiple burr holes using Benz-marked skin incisions was performed. After surgery, the symptoms improved without perioperative complications, and cerebral angiography showed collateral circulation via the burr hole. Indirect revascularization for MMD is often combined with direct revascularization, and there are only a few reports on the use of multiple burr hole surgery alone. In addition, there are few reports of posterior circulation, despite the emphasis on the importance of PCA involvement in MMD. Indirect revascularization with multiple burr holes alone can be performed in multiple areas and applied to patients who cannot undergo direct revascularization using the occipital artery. The procedure is simple and less invasive than traditional direct revascularization procedures. Therefore, it can be effective, especially in pediatric cases of MMD with PCA involvement.

Preoperative Risks of Cerebral Infarction in Pediatric Moyamoya Disease

[Figure: see text].

Specific clinical features and one-stage revascularization surgery for moyamoya disease with severe cerebral ischemia in the territory of posterior cerebral artery

BACKGROUND

There are no reports describing the surgical procedure for moyamoya disease (MMD) patients with severe cerebral ischemia in the territory of the posterior cerebral artery (PCA) at initial presentation. In this study, therefore, we describe their clinical and radiological features and clinical results of one-stage revascularization surgery for both anterior and posterior circulation.

METHODS

This study included 6 MMD patients who had severe cerebral ischemia in the PCA territory and underwent one-stage revascularization surgery for both anterior and posterior circulation. Of these, one patient underwent it on both sides. Their clinical and radiological data were precisely analyzed. Compared with usual procedure, craniotomy was extended towards the temporo-parietal area more widely. The parietal branch of superficial temporal artery (STA) was anastomosed to the angular or posterior temporal artery, while the frontal branch was anastomosed to the frontal branch of MCA. Ultimate indirect bypass was added. Their clinical and radiological outcomes were evaluated.

RESULTS

Their neurological symptoms included visual and speech disturbance as well as numbness of the extremities. Cerebral infarct was distributed in the posterior temporal, parietal, and/or occipital lobe. Cerebral hemodynamics and metabolism were also impaired in the same regions. These findings were completely different from those in MMD patients without PCA lesion. Postoperative course was uneventful, and none of them recurred stroke during a mean follow-up period of 10.5 years. Surgical collaterals widely provided blood flow to the entire hemispheres, including the occipital lobe. Cerebral hemodynamics and metabolism markedly improved after surgery.

CONCLUSION

One-stage revascularization surgery for both anterior and posterior circulation is feasible and effective to prevent future stroke in MMD patients with severe cerebral ischemia in the PCA territory at initial presentation.

Occipital artery to middle cerebral artery bypass in pediatric moyamoya disease: rescue therapy after failed revascularization

OBJECTIVE

Patients with pediatric moyamoya disease (PMMD) showing recurrent symptoms or decreased cerebral blood flow after initial revascularization therapy may require additional revascularization to improve their clinical condition. The authors evaluated the clinical and hemodynamic benefits of an occipital artery (OA)-middle cerebral artery (MCA) bypass for patients with PMMD who have undergone an initial revascularization procedure.

METHODS

The authors retrospectively identified 9 patients with PMMD who had undergone OA-MCA bypass between March 2013 and December 2017, and who had received a previous superficial temporal artery-MCA bypass. The following clinical data were collected: initial revascularization procedure, symptoms (presence or recurrence), pre- and postoperative cerebral blood flow and cerebrovascular reactivity (CVR) changes, posterior cerebral artery (PCA) stenosis, PCA-related and nonrelated symptoms, and latest follow-up.

RESULTS

Preoperatively, all patients (n = 9) suffered non-PCA-related recurrent symptoms, and 4 had PCA-related symptoms. At 1-year follow-up, all patients with PCA-related symptoms showed complete recovery. Additionally, 8 (89%) patients with non-PCA symptoms experienced improvement. Only 1 (11%) patient showed no improvement after the surgical procedure. The mean pre- and postoperative CVR values of the MCA territory were 14.8% and 31.3%, respectively, whereas the respective mean CVR values of the PCA territory were 22.8% and 40.0%.

CONCLUSIONS

The OA-MCA bypass is an effective rescue therapy to improve the clinical condition and hemodynamic changes caused by PMMD in patients who experience recurrent symptoms after initial revascularization.

Late (5-20 years) outcomes after STA-MCA anastomosis and encephalo-duro-myo-arterio-pericranial synangiosis in patients with moyamoya disease

OBJECTIVE

Surgical revascularization is known to reduce the incidence of further ischemic and hemorrhagic events in patients with moyamoya disease, but the majority of previous studies report only short-term (< 5 years) outcomes. Therefore, in this study the authors aimed to evaluate late (5-20 years) outcomes of moyamoya patients after superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis and indirect bypass (encephalo-duro-myo-arterio-pericranial synangiosis [EDMAPS]).

METHODS

Cumulative incidences of late morbidity/mortality and disease progression were evaluated among 93 patients who underwent STA-MCA anastomosis and EDMAPS. All of the patients were prospectively followed up for longer than 5 years postsurgery (10.5 ± 4.4 years). There were 35 pediatric and 58 adult patients. Initial presentation included transient ischemic attack/ischemic stroke in 80 patients and hemorrhagic stroke in 10 patients, and 3 patients were asymptomatic. Surgery was performed in a total of 141 hemispheres. Follow-up MRI/MRA was performed within a 6- or 12-month interval during the follow-up periods.

RESULTS

During the follow-up periods, 92/93 patients were free from any stroke or death, but 1 patient had a recurrence of hemorrhagic stroke (0.10% per patient-year). Disease progression occurred in the territory of the contralateral carotid or posterior cerebral artery (PCA) in 19 hemispheres of 15 patients (1.5% per patient-year). The interval between initial surgery and disease progression varied widely, from 0.5 to 15 years. Repeat bypass surgery for the anterior and posterior circulation resolved ischemic attacks in all 10 patients.

CONCLUSIONS

The study results indicate that STA-MCA anastomosis and EDMAPS would be the best choice to prevent further ischemic and hemorrhagic stroke for longer than 10 years on the basis of the demonstrated widespread improvement in cerebral hemodynamics in both the MCA and ACA territories in the study patients. However, after 10 years postsurgery regular follow-up is essential to detect disease progression in the territory of the contralateral carotid artery and PCA and prevent late cerebrovascular events.

Surgery for Moyamoya Disease in Children

Moyamoya disease is a chronic progressive cerebrovascular occlusive disease of the terminal portion of the internal carotid arteries associated with an acquired abnormal vascular network at the base of the brain, often leading to ischemic or hemorrhagic stroke. Moyamoya disease is a relatively common cause of pediatric stroke with a specific racial and well-identified clinical and imaging phenotype. Moyamoya disease is more prevalent in East Asian countries compared with other geographic regions with a higher incidence of familial cases and clinically more aggressive form. Moyamoya disease is one of the few causes of stroke that is amenable to effective surgical revascularization treatment. There are various surgical options available for revascularization, including the direct, indirect, or combined bypass techniques, each with variable responses. However, due to the heterogeneity of the diseases, different clinical course, geographical variables associated with the disease, and availability of a wide variety of surgical revascularization procedures, optimal selection of a surgical candidate and the surgical technique becomes challenging, particularly in the pediatric population. This brief review presents pertinent literature of clinical options for the diagnosis and surgical treatment of moyamoya disease in children.

Sternocleidomastoid Encephalomyosynangiosis for Treatment-Resistant Moyamoya Disease

BACKGROUND AND IMPORTANCE

Refractory ischemic symptoms in moyamoya disease are a challenging problem, particularly in situations in which multiple direct and indirect revascularization techniques have already been employed. In addition, revascularization of the parietal lobes is difficult, as this area is a watershed between the middle cerebral artery and posterior cerebral artery distributions.

CLINICAL PRESENTATION

This is the case of a 50-yr-old woman with hemibody sensorimotor deficits, who had previously undergone bilateral arterial bypass and temporalis myosynangiosis. A method for indirect surgical cerebral revascularization is described, utilizing a rotated and tunneled sternocleidomastoid flap. The perfused muscle is approximated to the cortical surface, with adjacent sulci dissected to expose the underlying vasculature. After sternocleidomastoid encephalomyosynangiosis, the patient experienced symptomatic improvement, along with the appearance of new pial collateral vasculature on diagnostic cerebral angiography. Pre- and postoperative dynamic perfusion computed tomography with acetazolamide challenge demonstrate an increase in cerebral blood flow and decrease in mean transit time, as well as improved cerebrovascular reserve.

CONCLUSION

Sternocleidomastoid encephalomyosynangiosis using a tunneled muscle flap is a useful method for revascularization of the parietal and occipital lobes, particularly for refractory moyamoya in cases where a variety of other options have been exhausted.

Clinical importance of the occipital artery in vascular lesions: A review of the literature

The occipital artery (OA) is a critical artery in vascular lesions. However, a comprehensive review of the importance of the OA is currently lacking. In this study, we used the PubMed database to perform a review of the literature on the OA to increase our understanding of its role in vascular lesions. We also provided our typical cases to illustrate the importance of the OA. The OA has several variations. For example, it may arise from the internal carotid artery or anastomose with the vertebral artery. Therefore, the OA may provide a crucial collateral vascular supply source and should be preserved in these cases. The OA is a good donor artery. Consequently, it is used in extra- to intracranial bypasses for moyamoya disease (MMD) or aneurysms. The OA can be involved in dural arteriovenous fistula (DAVF) and is a feasible artery for the embolisation of DAVF. True aneurysms and pseudoaneurysms can occur in the OA; surgical resection and embolisation are the effective treatment approaches. Direct high-flow AVF can occur in the OA; embolisation treatment is a good option in such cases. The OA can also be involved in MMD and brain arteriovenous malformation (AVM) by forming transdural collaterals. For a patient in the prone position, if occipital and suboccipital craniotomies are performed, the OA can also be used for intraoperative angiography. In brief, the OA is a very important artery in vascular lesions.

Strategy and effect of repeat bypass surgery for anterior/posterior circulation in refractory moyamoya disease

OBJECTIVE

In this study the authors aimed to describe clinical features, surgical techniques, and long-term outcomes of repeat bypass surgery required for a certain subset of patients with moyamoya disease.

METHODS

The authors retrospectively reviewed a total of 22 repeat bypass surgeries for 20 patients (age range 1-69 years) performed during the last 20 years at their institutions. The patients were classified into 2 groups. Group A included 10 patients who underwent repeat bypass surgery for anterior circulation due to insufficient revascularization on the ipsilateral side. Group B included 10 patients who underwent repeat bypass surgery for posterior circulation due to the involvement of the posterior cerebral artery (PCA) after successful initial surgery for anterior circulation.

RESULTS

Preoperative symptoms included headache in 3 patients, transient ischemic attack in 10, cerebral infarction in 3, and intracranial hemorrhage in 4 patients. Intervals between the initial bypass surgery and repeat bypass surgery were 0.3-30 years (median 3 years). In group A, superficial temporal artery to middle cerebral artery (MCA) anastomosis and indirect bypass were performed on 7 hemispheres. Only indirect bypass was performed on 3 hemispheres because of the lack of suitable donor or recipient arteries. In group B, occipital artery (OA) to PCA anastomosis and indirect bypass were conducted on 4 hemispheres, and OA-MCA anastomosis and indirect bypass on 1 hemisphere. Only indirect bypass was conducted on 7 hemispheres because of the lack of suitable recipient arteries. All 22 repeat bypass surgeries were successfully conducted. During follow-up periods (median 4 years), none of the patients suffered repeat stroke except 1 patient who died of recurrent intracerebral hemorrhage 3 years after repeat bypass surgery for anterior circulation.

CONCLUSIONS

Repeat bypass surgery was feasible and effective to reduce further incidence of headache attack, transient ischemic attack, and ischemic/hemorrhagic stroke in moyamoya disease patients. Through precise radiological analysis, surgical procedures should be planned to yield maximal therapeutic effects.

Epidemiology, diagnosis and treatment of moyamoya disease

Moyamoya disease (MMD) is a type of chronic cerebrovascular occlusion disease, which frequently occurs in East Asian populations, including pediatric and adult patients, and may lead to ischemic or hemorrhagic stroke, headache, epilepsy or transient ischemic attack. To date, the underlying mechanisms of MMD have remained to be fully elucidated, but certain studies have indicated that genetic factors may be an important component of its development. Cerebral angiography is the best approach for diagnosing MMD. However, with technological advances, non-invasive techniques are increasingly used to accurately evaluate MMD. MMD is commonly treated via surgery, and an increasing number of patients are benefitting from the intra- and extra-cranial revascularization. The present article provides a comprehensive review of MMD on the basis of previous research.

Progress in moyamoya disease

Moyamoya disease is characterized by progressive stenosis or occlusion of the intracranial portion of the internal carotid artery and their proximal branches, resulting in ischemic or hemorrhagic stroke with high rate of disability and even death. So far, available treatment strategies are quite limited, and novel intervention method is being explored. This review encapsulates current advances of moyamoya disease on the aspects of epidemiology, etiology, clinical features, imaging diagnosis and treatment. In addition, we also bring forward our conjecture, which needs to be testified by future research.

Posterior cerebral artery stenosis and posterior circulation revascularization surgery in pediatric patients with moyamoya disease

OBJECTIVE Some pediatric patients with moyamoya disease (MMD) present with posterior cerebral artery (PCA) stenosis before and after anterior circulation revascularization surgery and require posterior circulation revascularization surgery. This study evaluated the factors associated with PCA stenosis and assessed the efficacy of posterior circulation revascularization surgery, including occipital artery (OA)-PCA bypass, in pediatric patients with MMD. METHODS The presence of PCA stenosis before and after anterior circulation revascularization surgery and its clinical characteristics were investigated in 62 pediatric patients (< 16 years of age) with MMD. RESULTS Twenty-three pediatric patients (37%) with MMD presented with PCA stenosis at the time of the initial diagnosis. A strong correlation between the presence of infarction and PCA stenosis before anterior revascularization was observed (p < 0.001). In addition, progressive PCA stenosis was observed in 12 patients (19.4%) after anterior revascularization. The presence of infarction and a younger age at the time of initial diagnosis were risk factors for progressive PCA stenosis after anterior revascularization (p < 0.001 and p = 0.002, respectively). Posterior circulation revascularization surgery, including OA-PCA bypass, was performed in 9 of the 12 patients with progressive PCA stenosis, all of whom showed symptomatic and/or radiological improvement. CONCLUSIONS PCA stenosis is an important clinical factor related to poor prognosis in pediatric MMD. One should be aware of the possibility of progressive PCA stenosis during the postoperative follow-up period and consider performing posterior circulation revascularization surgery.

Strategies for and Outcome of Repeat Revascularization Surgery for Moyamoya Disease: An American Institutional Series

BACKGROUND

Revascularization for moyamoya disease (MMD) effectively prevents future ischemic events. However, small subsets of patients with persistent or new symptoms due to inadequate collateralization require repeat revascularizations.

OBJECTIVE

To investigate the clinical and radiological outcome of repeat revascularization in MMD patients with previous indirect or direct bypasses.

METHODS

Single institution, retrospective analysis of a prospective MMD database.

RESULTS

From 1991 to 2014, this institution performed 1244 revascularization bypasses (1107 direct, 137 indirect) in 765 patients, of whom 57 were repeat revascularizations (38 indirect, 19 direct bypass). When initially performed at the institution, the repeat revascularization rate was 4% for indirect and 1% for direct bypasses (P = .03). Cohorts with previous indirect vs direct bypass were slightly younger (mean age 23 vs 30 yr), with fewer females (61% vs 84%, P = .08), and a similar mean duration between initial bypass and repeat revascularization (49 vs 47 mo). Both groups had similar repeat revascularization due to transient ischemic attacks (66% vs 63%). One acute graft occlusion in the previous direct bypass group was revised within 1 wk postoperatively. Over 50% of the repeat revascularizations in both groups were direct bypasses; the major difference being that the repeat bypass in the direct group was to augment another vascular territory. At nearly 5 yr mean follow-up, over 80% of patients in both groups are well, free from stroke/transient ischemic attack symptoms, with excellent radiological results.

CONCLUSION

Repeat revascularization can safely and effectively prevent future ischemic events. Indirect bypass has a higher rate of repeat revascularization than direct bypass.

Noninvasive Assessment of Hemodynamic Stress Distribution after Indirect Revascularization for Pediatric Moyamoya Vasculopathy

BACKGROUND AND PURPOSE

Indirect revascularization surgery is an effective treatment in children with Moyamoya vasculopathy. In the present study, we hypothesized that DSC-PWI may reliably assess the evolution of CBF-related parameters after revascularization surgery, monitoring the outcome of surgical pediatric patients with Moyamoya vasculopathy. Thus, we aimed to evaluate differences in DSC-PWI parameters, including the hemodynamic stress distribution, in surgical and nonsurgical children with Moyamoya vasculopathy and to correlate them with long-term postoperative outcome.

MATERIALS AND METHODS

Pre- and postoperative DSC parameters of 28 patients (16 females; mean age, 5.5 ± 4.8 years) treated with indirect revascularization were compared with those obtained at 2 time points in 10 nonsurgical patients (6 females; mean age, 6.9 ± 4.7 years). We calculated 4 normalized CBF-related parameters and their percentage variance: mean normalized CBF of the MCA territory, mean normalized CBF of the proximal MCA territory, mean normalized CBF of cortical the MCA territory, and hemodynamic stress distribution. The relationship between perfusion parameters and postoperative outcomes (poor, fair, good, excellent) was explored using 1-way analysis of covariance (P < .05).

RESULTS

A significant decrease of the mean normalized CBF of the proximal MCA territory and hemodynamic stress distribution and an increase of the mean normalized CBF of the cortical MCA territory were observed after revascularization surgery (P < .001). No variations were observed in nonsurgical children. Postoperative hemodynamic stress distribution and its percentage change were significantly different in outcome groups (P < .001).

CONCLUSIONS

DSC-PWI indices show postoperative hemodynamic changes that correlate with clinical outcome after revascularization surgery in children with Moyamoya disease.

The Occipital Artery as an Alternative Donor for Low-Flow Bypass to Anterior Circulation After Internal Carotid Artery Occlusion Failure prior to Exenteration for an Atypical Cavernous Sinus Meningioma

BACKGROUND

In skull base tumors involving the cavernous sinus, indications for aggressive resection are sparse and must be carefully examined because of their invasiveness. With careful evaluation, techniques including internal carotid artery sacrifice with or without extracranial-intracranial bypass may still be an option in some cases. Moreover, previous surgery with the sacrifice of potential donor vessels requires adjusting the revascularization strategy. We describe an occipital artery-middle cerebral artery bypass before skull base tumor resection.

CASE DESCRIPTION

A 47-year-old woman with a recurrent cavernous sinus meningioma was referred to our department. Because of tumor recurrence after radiotherapy and its rapid progression, radical resection, including part of the cavernous sinus, was planned. A balloon test occlusion was performed and showed good tolerance. An endovascular internal carotid artery occlusion was performed. The patient eventually experienced motor deficits and aphasia after surgery. Therefore, bypass surgery using an occipital artery-middle cerebral artery anastomosis was performed. The patient showed no exacerbation of symptoms after bypass surgery and subsequently underwent tumor resection.

CONCLUSIONS

The reliability of balloon test occlusion in the management of giant aneurysms may not be similarly applicable to skull base tumors. If hypoperfusion symptoms occur after occlusion of the internal carotid artery, a surgical revascularization procedure should be considered because of the risk of ischemic stroke following tumor resection. For patients whose superficial temporal artery is not available, the occipital artery can be a valuable alternative donor for low-flow bypass.

Can Combined Bypass Surgery at Middle Cerebral Artery Territory Save Anterior Cerebral Artery Territory in Adult Moyamoya Disease?

Background

Patients with moyamoya disease are frequently encountered with improved symptoms related to anterior cerebral artery territory (ACAt) and middle cerebral artery territory (MCAt) after bypass surgery at MCAt.

Objective

To evaluate hemodynamic changes in MCAt and ACAt after bypass surgery in adult moyamoya disease.

Methods

Combined bypass surgery was performed on 140 hemispheres in 126 patients with MCAt symptoms. Among them, 87 hemispheres (62.1%) accompanied preoperative ACAt symptoms. Clinical, hemodynamic, and angiographic states were evaluated preoperatively and approximately 6 months after surgery.

Results

Preoperative symptoms resolved in 127 MCAt (90.7%) and 82 ACAt (94.3%). Hemodynamic analysis of total patients showed a significant improvement in MCAt basal perfusion and reservoir capacity ( P < .001 and P = .002, respectively) and ACAt basal perfusion ( P = .001). In a subgroup analysis, 82 hemispheres that completely recovered from preoperative ACAt symptoms showed a significant improvement in MCAt basal perfusion and reservoir capacity ( P < .001 and P = .05, respectively) and ACAt basal perfusion ( P = .04). Meanwhile, 53 hemispheres that had never experienced ACAt symptoms significantly improved MCAt basal perfusion and reservoir capacity ( P < .001 and P = .05, respectively); however, no ACAt changes were observed. A qualitative angiographic analysis demonstrated a higher trend of leptomeningeal formation from MCAt to ACAt in the former subgroup ( P = .05). During follow-up, no ACAt infarctions were observed.

Conclusion

Combined bypass surgery at MCAt resulted in hemodynamic improvements in ACAt and MCAt, especially in patients with preoperative ACAt symptoms.

Assessment of the cortical artery using computed tomography angiography for bypass surgery in moyamoya disease

Computed tomography angiography (CTA) is often used to assess the vascular status in moyamoya disease. The purpose of the study is to identify the characteristics of cortical arteries (M4) of moyamoya disease on CTA; the clinical significance of which is also discussed. A total of 38 hemispheric sides of 27 patients with moyamoya disease were included in this study. The number of M4 was visualized on CTA using cortical surface imaging and compared between the moyamoya disease group and the non-moyamoya disease group or the control group. Then, the clinical and radiological factors associated with the number of M4, the distribution of M4, and collateral circulation were examined. The number of M4 was lower in the moyamoya disease group than in the non-moyamoya disease group and in the control group (p < 0.05). There are few predictive clinical factors of the number of M4 except male sex. The prefrontal artery, precentral artery, central artery, and angular artery had a significantly higher prevalence in moyamoya disease (p < 0.05). The durocortical and periventricular anastomosis had a significantly higher prevalence in moyamoya disease (p < 0.05). The prevalence and distribution pattern of cortical arteries in moyamoya disease differed from that of the non-moyamoya disease group, and the distribution patterns of M4 might be influenced by collateral circulation. It is thus essential to recognize M4 to assess the recipient artery so as to ensure superficial temporal artery-middle cerebral artery bypass.

Direct Anastomosis Using Occipital Artery for Additional Revascularization in Moyamoya Disease After Combined Superficial Temporal Artery–Middle Cerebral Artery and Indirect Bypass

BACKGROUND: The posterior cerebral artery (PCA) is involved in approximately 30% of moyamoya disease (MMD) cases. However, there have been insufficient reports describing revascularization techniques in the posterior portion of the brain, particularly of direct anastomosis.

OBJECTIVE: To perform a technical assessment in patients with MMD who underwent either occipital artery (OA)–PCA bypass or OA–middle cerebral artery (MCA) bypass.

METHODS: A total of 428 revascularization procedures in 368 patients were retrospectively assessed by reviewing clinical charts and radiological data.

RESULTS: Ten patients (3.5%) were treated with direct bypass after the anterior revascularization with a median interval of 30 months (range, 5 months-16 years). Seven patients were &lt; 18 years of age (average age, 17.5 ± 15.6 years). Preoperative symptoms included transient motor deficits involving the lower extremities (n = 5), visual disturbances (n = 6), and cerebral infarctions (n = 6). A favorable outcome (modified Rankin Scale score &lt; 3) was achieved in 9 of these 10 patients. Direct anastomosis was performed in 3 hemispheres with an OA-MCA bypass and in 8 hemispheres with an OA-PCA bypass. Patency of the direct bypass was confirmed on angiogram in 7 of 7 patients who underwent conventional angiogram performed within 1 year after the surgery. None of the 10 patients demonstrated cerebral infarctions after the posterior revascularization.

CONCLUSION: In MMD, symptomatic PCA regression after anterior revascularization was found predominantly in children and young adults. Direct anastomosis in the posterior portion of the brain can be successfully achieved and is effective in preventing ischemic events.

Moyamoya Disease: Treatment and Outcomes

Although the pathogenesis of moyamoya disease (MMD) has not been fully elucidated, the effectiveness of surgical revascularization in preventing stroke has been addressed by many studies. The main mechanism of surgical revascularization is augmenting the intracranial blood flow using an external carotid system by either direct bypass or pial synangiosis. This can improve resting cerebral blood flow as well as vascular reserve capacity. For direct revascularization, the superficial temporal artery is used as the donor artery in most cases, although the occipital artery may be used in limited cases. Usually, the cortical branch of the middle cerebral artery is selected as the recipient of direct anastomosis. As for indirect revascularization, various techniques using different kinds of connective tissues have been introduced. In some cases, reinforcing the anterior cerebral artery and the posterior cerebral artery territories can be considered. The effectiveness of surgical revascularization for preventing ischemic stroke had been generally accepted by many studies. However, for preventing hemorrhagic stroke, new evidence has been added by a recent randomized controlled trial. The incidence of peri-operative complications such as stroke and hyperperfusion syndrome seems to be high due to the nature of the disease and technical demands for treatment. Preventing and adequately managing these complications are essential for ensuring the benefits of surgery.

Posterior Cerebral Artery Insufficiency in Pediatric Moyamoya Disease

The majority of clinical studies on moyamoya disease (MMD) have focused on anterior circulation. The disease involvement of posterior circulation in MMD, mainly in the posterior cerebral artery (PCA), has been mentioned since the early 1980s, and it has been repeatedly emphasized as one of the most important factors related to poor prognosis in MMD. However, its clinical features and outcome have only been elucidated during the last few years. In this review, the angiographic definition of PCA stenosis is summarized. The clinical features are elucidated as being either early-onset or delayed-onset, according to the time of PCA stenosis diagnosis in reference to the anterior circulation revascularization surgeries. The surgical strategy and hypothesis on the mechanism of PCA stenosis is also briefly mentioned. It appears that some MMD patients may show PCA stenosis during the early or late course of the disease and that the presenting symptoms may vary. Because the hemodynamic compromise caused by PCA stenosis may respond well to surgical treatment, clinicians should be aware of the condition, especially during follow-up of MMD patients.

Posterior auricular artery as an alternative donor vessel for extracranial-intracranial bypass surgery

BACKGROUND

Sometimes the superficial temporal artery (STA) is not available for an extracranial-intracranial (EC-IC) bypass procedure. An alternative vessel for an EC-IC bypass is the posterior auricular artery (PAA) if it extends to the temporoparietal area with a diameter large enough. We assessed the prevalence of an appropriate PAA as an alternative donor vessel and report three illustrative cases in which the PAA was used for EC-IC bypass surgery.

METHODS

A literature search was performed on the use of the PAA as a donor vessel for bypass surgery. Secondly, a prospective database of bypass surgeries was reviewed to calculate the prevalence of a PAA with a diameter of at least 1 mm in the parietotemporal area. Finally, three illustrative cases are reported that describe various indications for the revascularisation procedures with their clinical, surgical and imaging features.

RESULTS

Two articles have previously described the use of the PAA for bypass surgery and their results are summarised. The prevalence of a PAA that would be appropriate for an EC-IC bypass in patients with intracranial vascular pathology is 5.7%. The presented cases demonstrate that the PAA can be successfully used for EC-IC bypass surgery with good flow velocities and patency.

CONCLUSIONS

The PAA is a rarely described as an appropriate donor vessel for an EC-IC bypass. Its prevalence is 5.7% and it can successfully be used as an alternative donor vessel. The awareness among cerebrovascular surgeons about the presence of a PAA and knowledge about its anatomy may be valuable.

Recent advances in moyamoya disease: pathophysiology and treatment

Moyamoya disease is a progressive intracranial arteriopathy characterized by bilateral stenosis of the distal portion of the internal carotid artery and the proximal anterior and middle cerebral arteries, resulting in transient ischemic attacks or strokes. The pathogenesis of moyamoya disease remains unresolved, but recent advances have suggested exciting new insights into a genetic contribution as well as into other pathophysiological mechanisms. Treatment that may halt progression of the disease or even reverse the intracranial arteriopathy is yet to be found. There are strong indications that neurosurgical intervention, through direct, indirect, or combined revascularization surgery, can reduce the risk of ischemic stroke and possibly also cognitive dysfunction by improving cerebral perfusion, although randomized clinical trials have not been performed. Many questions regarding the indication for and timing of surgery remain unanswered. In this review, we discuss recent developments in the pathogenesis and treatment of moyamoya disease.

Incidence of late cerebrovascular events after direct bypass among children with moyamoya disease: a descriptive longitudinal study at a single center

BACKGROUND

The potential for late cerebrovascular events following surgical revascularization presents a challenge in the treatment of pediatric moyamoya disease. Limited information is available on the incidence of such events after direct bypass. The objective of this descriptive study was to examine the incidence of late cerebrovascular events after direct bypass for pediatric moyamoya disease.

METHODS

The study cohort comprised consecutive patients with moyamoya disease who had undergone direct bypass at less than 18 years of age in the authors' institute between 1978 and 2003. They were prospectively followed until the end of the study period or, if applicable, the time of death.

RESULTS

Fifty-six of 58 enrolled patients (96.6%) were followed for a mean period of 18.1 years. Four patients experienced late cerebrovascular events, comprising one stroke and three hemorrhages, an average of 13 years after surgery, one of whom experienced a fatal second hemorrhage. The only late ischemic stroke in the cohort occurred after a severe head injury and emergent craniotomy. The incidence of late cerebrovascular events was 0.41% per year (95% confidence interval, 0.15-1.08); 10-year, 20-year, and 30-year cumulative incidences were 1.8%, 7.3%, and 13.1%, respectively.

CONCLUSIONS

Despite the efficacy of surgical revascularization, pediatric patients remain at risk of future cerebrovascular events, especially hemorrhage, after reaching adulthood and thus require careful long-term follow-up.

History of the development of surgical treatments for moyamoya disease

Many surgical treatments for moyamoya disease have been developed over the past 40 years. The optimum treatment for ischemic-type moyamoya disease is almost established. The first surgical treatment for the disease was the superficial temporal artery to middle carotid artery (STA-MCA) anastomosis. The discovery of spontaneous collateral formation following the STA-MCA anastomosis surgery led to the development of various indirect bypass procedures. Collateral formation and clinical outcomes from direct and indirect procedures have been compared to assess the merits and limitations of each technique. Experience and a greater understanding of the surgical effects of moyamoya disease have led to the development of surgical procedures combining various direct and indirect bypass techniques for optimal restoration of perfusion. This review of the historical development and efficacy of each procedure will aid surgeons in selecting the most appropriate surgical procedure for patients of different ages with different symptoms and disease severities.

Effectiveness of burr holes for indirect revascularization in patients with moyamoya disease-a review of the literature

OBJECTIVE

Moyamoya disease (MMD) has inspired the development and refinement of numerous surgical techniques to induce revascularization in hypoperfused territories. Over the last 3 decades, the use of burr hole surgery has progressively gained popularity. Used either in combination with another direct or indirect procedure or as the sole method for revascularization, burr hole surgery can be tailored to each patient's specific needs. We reviewed the conceptual progress, the technical evolution, and the clinical and radiological data following burr hole surgery.

METHODS

Pubmed and Medline databases were searched for publications from 1970 to 2012 relating to the use of burr holes in the surgical management of MMD. The reference sections of each article were reviewed, and pertinent articles were identified.

RESULTS

A review of case reports and case series using burr hole surgery for MMD testifies to the progressive refinement in the decision process and key technical aspects of this procedure. Favorable clinical and angiographic results have been documented in the pediatric and adult MMD population after burr holes, used either in combination with direct or indirect revascularization techniques, or more recently alone in the setting of multiple burr holes. The superficial temporal artery and middle meningeal artery have both been found to contribute to revascularization via burr holes.

CONCLUSIONS

Burr hole surgery is an important and versatile tool in the armamentarium of surgeons treating children and adults with MMD, allowing tailoring of the revascularization. Further studies should help to determine factors that may help predict optimal revascularization from this surgical technique.

Outcome of repeat revascularization surgery for moyamoya disease after an unsuccessful indirect revascularization

Object

Revascularization for moyamoya disease, either by direct anastomosis or indirect procedures, is an accepted and effective form of treatment for prevention of future ischemic events. Indirect procedures do not provide sufficient collateral vessels in a subset of patients, who then have persistent or new symptoms. Repeat revascularization procedures may be recommended for these patients.

Methods

Sixteen patients underwent repeat revascularization after undergoing an indirect procedure in the same hemisphere. These patients were included in the study, and a retrospective review of their clinical details, neuroimaging results, surgical details, and outcome was performed. Direct revascularization was the procedure of choice; however, in patients with no acceptable recipient vessel (> 0.6 mm) the authors added a second indirect procedure for further revascularization.

Results

Over the last 19 years, 16 patients (8 male and 8 female patients, age range 5–48 years, mean 16.7 years, 10 pediatric and 6 adult patients) underwent repeat revascularization for moyamoya disease. Initially all patients presented with ischemic symptoms (4 transient ischemic attacks [TIAs] and 12 strokes; 2 patients had bilateral symptoms). Angiography revealed that 13 patients had bilateral disease, and 3 had unilateral disease. Initial surgery was bilateral encephaloduroarteriosynangiosis (EDAS) in 9, unilateral EDAS alone in 3, unilateral EDAS with contralateral superficial temporal artery–middle cerebral artery (STA-MCA) bypass in 2, bilateral encephalomyosynangiosis (EMS) in 1, and unilateral EMS in 1. Thirteen of the 16 patients continued to have TIAs in the hemisphere ipsilateral to surgery, whereas 1 patient had seizures and cognitive deficit, 1 had asymptomatic infarct on MR imaging, and 1 had visual symptoms. Poor revascularization was seen on angiography studies in all patients. The median duration between the surgeries was 24 months (3 months–10 years).

Repeat revascularization was performed in 23 hemispheres (16 patients). Direct revascularization was performed in 14 hemispheres (60.9%): STA-MCA bypass in 10, external carotid artery–MCA vein bypass in 2, occipital artery (OA)–MCA in 1, and OA–posterior cerebral artery in 1 hemisphere. Indirect revascularization was performed for patients without an acceptable recipient vessel, and was done in 9 hemispheres. The procedures included EMS (4 hemispheres), repeat EDAS (2), and omental transposition (3). There was 1 postoperative death in a patient undergoing a high-flow vein graft implantation. None of the other patients experienced any neurological worsening after surgery.

Follow-up was available in all patients, ranging from 3 to 144 months (mean 34 months, median 12 months). Of the 15 patients who survived repeat revascularization surgery, 12 (80%) were free from any TIA, stroke, or any other neurological symptoms. Two patients had occasional TIAs, less frequent than before, whereas 1 patient had frequent TIAs and underwent revision of the revascularization. Angiographic studies were available in 11 patients, and showed improved flow in the hemispheres in 10 patients. Follow-up MR imaging performed at 6 months did not reveal a new infarct in any patient.

Conclusions

Repeat revascularization procedures are effective for patients who are clinically symptomatic and have inadequate collateral vessels following indirect procedures. Although direct procedures are preferred, the choice of procedure depends on the operative findings and the status of donor and recipient vessels.

Indirect revascularization techniques for treating moyamoya disease

There have been many indirect revascularization techniques described by surgeons for the treatment of moyamoya disease. These surgical procedures are typically used more commonly in pediatric, than in adults', cases. Some of the techniques include: cervical sympathectomy, omental transplantation, multiple burr holes, encephalo-myo-synangiosis (EMS), encephalo-arterio-synangiosis (EAS), encephalo-duro-synangiosis (EDS), encephalo-myo-arterio-synangiosis (EMAS), encephalo-duro-arterio-synangiosis (EDAS), encephalo-duro-arterio-myo-synangiosis (EDAMS), encephalo-duro-galeo (periosteal)-synangiosis (EDGS), and combinations of all the above. This chapter will detail the technical aspects of many of these procedures and some of the reported clinical outcomes.

Correlation between focal brain metabolism and higher brain function in patients with Moyamoya disease

BACKGROUND

Moyamoya disease is one of the causes of higher brain dysfunction in younger patients. Fortunately, it may be possible to protect younger Moyamoya disease patients from brain dysfunction via surgical manoeuvres.

AIM

Our group retrospectively analysed the correlation between preoperative positron emission tomography data and the intelligence quotient scores of 60 Japanese Moyamoya disease patients (age range 9-64).

METHOD

All patients underwent a quantitative measurement of the cerebral metabolic rate of oxygen by inhalation of C(15)O(2) and (15)O(2) gas with positron emission tomography. The data was analysed using spm99 software to determine the cerebral regions in which regional cerebral metabolic rate of oxygen was significantly correlated with full-scale intelligence quotient, verbal intelligence quotient, or performance intelligence quotient measured using the Wechsler intelligence scale.

RESULTS

All scores (full-scale intelligence quotient, verbal intelligence quotient, and performance intelligence quotient) showed significant positive correlations with the cerebral metabolic rate of oxygen in the lower part of the bilateral frontal lobe, the right anterior temporal lobe, and the medial occipital lobe. The verbal intelligence quotient was significantly and positively correlated with the cerebral metabolic rate of oxygen in the left inferior frontal lobe, including Broca's area. Infarcted lesions in the left posterior temporal lobe and the right upper frontal lobe influenced the decline of all of the intelligence quotient scores measured.

CONCLUSION

The present analysis indicates that the higher brain function of Moyamoya disease patients tends to be affected by the cerebral metabolism of specific regions. This information may be useful in seeking optimal clinical management to preserve higher brain function in patients with Moyamoya disease.

Postoperative neurological deterioration in pediatric moyamoya disease: watershed shift and hyperperfusion

OBJECT

Young patients with moyamoya disease frequently exhibit extensive cerebral infarction at the time of initial presentation, and even in the early postoperative period. To investigate clinical characteristics in the early postoperative period, the authors prospectively analyzed findings of MR imaging, MR angiography, and SPECT before and after surgery. The authors focused in particular on how postoperative neurological deterioration occurred.

METHODS

Between August 2005 and June 2009, 22 patients younger than 18 years of age with moyamoya disease were treated at Miyagi Children's Hospital. The mean patient age (+/- SD) was 8.58 +/- 4.55 years (range 2-17 years). Superficial temporal artery-middle cerebral artery bypass and indirect bypass of encephalosynangiosis between the brain surface and the temporal muscle, galea, and dura mater were performed in 35 hemispheres. Magnetic resonance imaging and MR angiography were performed before surgery, at 7 days postoperatively, and 3-6 months after surgery. A (123)I-isopropyl iodoamphetamine SPECT scan was also obtained pre- and postoperatively.

RESULTS

During the postoperative period, neurological deterioration was observed after 15 operations (10 cases of motor paresis, 1 of aphasia, and 4 of sensory disturbance) in 13 patients. All symptoms had resolved by the time of discharge, except in 2 patients who suffered cerebral infarction. All patients exhibited disappearance (94.3%) or reduction (5.7%) of transient ischemic attacks (TIAs) during the follow-up period. Perioperative studies revealed 2 different types of radiological findings, focal uptake decrease on SPECT indicative of cerebral ischemia due to dynamic change in cerebral hemodynamics caused by bypass flow, the so-called watershed shift, and perioperative edematous lesions on MR imaging due to cerebral hyperperfusion. The frequent occurrence of preoperative TIAs was significantly associated with watershed shift, whereas preoperative MR imaging findings and preoperative SPECT findings were not. Age at operation was the only factor significantly associated with postoperative hyperperfusion.

CONCLUSIONS

In young patients, moyamoya disease exhibits rapid progression, resulting in poor clinical outcome. The risk of postoperative neurological deterioration in very young moyamoya patients with frequent TIAs should be noted. The findings in this study showed that direct bypass is not completely safe in patients with moyamoya disease because it causes dynamic change in postoperative cerebral hemodynamics.