Enhanced Recovery After Surgery Consensus Protocol for Cerebral Bypass in Moyamoya Disease

Abstract

BACKGROUND AND OBJECTIVE:

Moyamoya disease (MMD) is a progressive cerebrovascular disorder treated primarily with surgical revascularization to prevent stroke recurrence. Despite established surgical techniques, standardized perioperative care protocols remain limited, potentially leading to variable outcomes and perioperative complications. Enhanced Recovery After Surgery (ERAS) protocols have demonstrated improved outcomes across surgical disciplines but have not been systematically applied to cerebral bypass surgery for MMD. The objective was to develop evidence-based ERAS recommendations for perioperative management of patients undergoing direct cerebral bypass surgery for MMD, based on a systematic literature review and expert consensus.

METHODS:

A multidisciplinary guideline development group was formed including cerebrovascular neurosurgery, neurointensive care, vascular neurology, neurophysiological monitoring, and anesthesiology experts. A comprehensive literature review of PubMed databases was conducted using systematic search strategies. The Grading of Recommendations Assessment, Development, and Evaluation system was used to evaluate evidence quality and recommendation strength.

RESULTS:

Thirty-two studies met inclusion criteria for analysis. Seven primary categories of perioperative care were identified: patient selection, preoperative optimization, anesthesia and analgesia, intraoperative neuromonitoring, surgical strategy, postoperative management, and follow-up and recovery protocols. Strong recommendations were developed for 34 specific interventions across the perioperative continuum.

CONCLUSION:

This consensus statement provides the first comprehensive ERAS protocol for direct cerebral bypass surgery in patients with MMD. Implementation of these evidence-based recommendations may improve patient outcomes, reduce complications, and standardize perioperative care.

ABBREVIATIONS:

ERAS

Enhanced Recovery After Surgery

IV

intravenous

MAP

mean arterial pressure

MMD

Moyamoya disease

POD

postoperative day

STA

superficial temporal artery.

Moyamoya disease (MMD) is characterized by progressive stenosis and occlusion of the cerebral arteries, leading to chronic stenosis of the bilateral internal carotid arteries. This obstruction of blood supply is accompanied by the development of collateral vasculature at the base of the brain, creating the characteristic “puff of smoke” appearance on angiography. Stenosis, decreased perfusion, and the neovascularization itself may cause symptoms including headache, stroke, aneurysm formation, or intracerebral hemorrhage. Owing to its progressive nature, surgical management is usually required to restore cerebrovascular balance and prevent future ischemic and hemorrhagic events.¹

Surgical revascularization methods include direct, indirect, and combined approaches. Direct revascularization involves anastomosis of the donor vessel (frequently the superficial temporal artery) to the middle cerebral artery (STA-MCA bypass), providing immediate restoration of cerebral blood flow (CBF) to ischemic territories. This operation has demonstrated efficacy in preventing stroke recurrence in appropriately selected patients. The STA to MCA bypass represents the workhorse bypass operation for cerebral revascularization.²

Enhanced Recovery After Surgery (ERAS) protocols represent a multidisciplinary, evidence-based approach to perioperative care that aims to reduce surgical stress, minimize complications, and accelerate recovery.³ Originally developed for colorectal surgery, ERAS principles have been successfully adapted across multiple surgical disciplines, demonstrating consistent improvements in patient outcomes, reduced length of stay, and decreased healthcare costs.⁴ Systematic reviews have confirmed that ERAS is a safe and potentially favorable perioperative pathway for select patients undergoing cranial surgery.⁵

Despite the established benefits of ERAS protocols in other surgical fields, standardized perioperative care guidelines for cerebral bypass surgery in MMD remain limited.⁶ Current practice varies significantly among institutions, potentially leading to inconsistent outcomes and suboptimal resource utilization.¹ The unique pathophysiology of MMD, combined with the technical complexity of this surgery, necessitates specialized management considerations.⁷ This article addresses a critical gap in standardized perioperative care for patients undergoing cerebral bypass surgery by providing evidence-based ERAS recommendations that we use at our institution. Our goal is to reduce any harmful variability in care and optimize patient outcomes.

METHODS

Formation of Guideline Development Group

A multidisciplinary Guideline Development Group at our institution was assembled comprised 9 experts in cerebrovascular neurosurgery, neurointensive care, vascular neurology, anesthesiology, and neuromonitoring at an academic medical center with a busy cerebral bypass program. The Guideline Development Group was tasked with topic and recommendation selection for ERAS for cerebral bypass surgery and evidence quality assessment.^8,9

Literature Search Strategy

A comprehensive systematic literature review was performed to assess current evidence regarding perioperative management of patients with MMD undergoing cerebral bypass surgery. Electronic databases including PubMed/MEDLINE were searched using the following terms: “moyamoya disease,” “cerebral bypass,” “extracranial-intracranial bypass,” “superficial temporal artery,” “middle cerebral artery,” “perioperative care,” “enhanced recovery,” and “ERAS protocol.” Search strategies included both controlled vocabulary terms and free-text keywords to maximize sensitivity.¹⁰

Inclusion criteria encompassed peer-reviewed studies published in English between 2000 and 2025 describing perioperative management of adult patients with MMD undergoing direct cerebral bypass surgery. Studies were required to include at least 20 operations per series to ensure adequate sample sizes. Exclusion criteria included pediatric-only populations, indirect bypass procedures without direct anastomosis, and case reports.

Quality Assessment and Consensus Development

The Grading of Recommendations Assessment, Development, and Evaluation system was implemented to evaluate evidence quality and recommendation strength.¹¹ Evidence quality was classified as high, moderate, low, or very low based on study design, risk of bias, inconsistency, indirectness, and imprecision.¹² Recommendation strength was categorized as strong or weak based on balance of benefits and harms, quality of evidence, values and preferences, and resource considerations.¹³ Further information is provided in Supplemental Digital Content 1, Supplementary Table, https://links.lww.com/NS9/A127. Expert consensus was achieved with multiple rounds of voting until majority agreement was reached.⁹ Recommendations achieving consensus were incorporated into the final ERAS protocol.¹⁴

RESULTS

Literature Review Results

The systematic literature search yielded 1180 abstracts for initial screening. After applying inclusion and exclusion criteria, 115 studies were selected for detailed analysis and evidence synthesis. Of these 115, 83 were eliminated after in-depth analysis because they did not contain a sufficient level of detail to incorporate. The remaining 32 studies (Figure 1) represented a total of 3847 patients undergoing 4512 cerebral bypass operations. Most studies were retrospective case series (68%), with fewer prospective cohorts (22%) and randomized controlled trials (10%). Please see Table 1 for further details.

FIGURE 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram of study selection.

TABLE 1.

Contributions of Current Literature to Enhanced Recovery After Surgery Guidelines for external carotid artery to internal carotid artery Bypass Surgery

RCT, randomized controlled trial.

Operative stage contribution: Preoperative = operative stage I; Intraoperative = operative stage II; Postoperative = Operative stage III.

Category of recommendation: PS, patient selection; PO, preoperative optimization; A/A, anesthesia/analgesia; SS, surgical strategy; PBM, postoperative blood pressure management; OFR, outpatient follow-up and recovery.

The comprehensive literature review revealed a wide variety of practices relating to patient selection, preoperative optimization, anesthesia and analgesia practices, surgical strategy, blood pressure management, postoperative management, and outpatient follow-up and recovery. Please see Table 2 for further details.

TABLE 2.

Literature Review Results for Direct Cerebral Bypass Surgery Patient Selection, Preoperative Optimization, Anesthesia and Analgesia Practices, Surgical Strategy, Blood Pressure Management, Postoperative Management, and Outpatient Follow-Up and Recovery

Category	Recommendation	Supporting studies
Patient selection	Preop DSA	Rice et al16, Kan et al18, Pena-Tapia et al31, Nielson et al33, Fujimoto et al40
	Per JET study [rCBF of the ipsilateral MCA <32 mL/100 g/min (corresponding to 80% of normal value), and a CVR <10% in a quantitative SPECT study with a ACZ challenge]	Hirai et al21, Nomura et al24, Nakamizo et al22, Murai et al35, Fujimoto et al40, Wessels et al44, Mikami et al38
	Steno-occlusive disease	Teo et al15, Yamaguchi et al20, Kim et al26, Nishizawa et al28, Horn et al29, Pena-Tapia et al31, Park et al32, Nielson et al33, Murai et al35, Garrett et al36, Fluri et al37, Fujimoto et al40, Murai et al35, Wang et al41, Wessels et al44, White et al45, Burbridge et al46, Mikami et al38
	Abnormal cerebral vasodilatory reserve on TCD/ACZ/I-IMP challenged SPECT or PET	Teo et al15, Kan et al18, Yamaguchi et al20, Jussen et al23, Fujimara et al25, Nishizawa et al28, Hirai et al21, Nomura et al24, Nakamizo et al22, Pena-Tapia et al31, Nielsen et al33, Powers et al19, Fujimura et al25, Katsuki et al39, Fujimoto et al40, Murai et al et al35, Wessels et al44, Mikami et al38, Garrett et al36, Park et al32
	Multidisciplinary review with neurology and neurosurgery	Rice et al16
	Preop MRI	Kan et al18, Yamaguchi et al20, Jussen et al23, Nishizawa et al28, Horn et al29
	Recurrent TIAs	Horn et al29, Jussen et al23, Pena-Tapia et al31, Hirai et al21, Nomura et al24, Nakamizo et al22, Murai et al35, Fujimoto et al40, Wessels et al44, Mikami et al38, Park et al32
Preop optimization	LDL 100 mg/dL or lower	Powers et al19
	Triglycerides 150 mg/dL or lower	Powers et al19
	Hemoglobin A1C 7% or lower	Powers et al19
	Baseline blood pressure 130/85 or better	Powers et al19
	Stop antiplatelet 1 wk prior	Yamaguchi et al20
	Low molecular weight dextran prior to procedure	Yamaguchi et al20
	Aspirin prior to the case with aspirin function testing	Jussen et al23
	Antiplatelet until day of surgery and then held until postoperative day 5	Nomura et al24
	Preop hemoglobin ≥10	Mendez et al27
	Aspirin 325 d of surgery	Mendez et al27, Khan et al17
	Aspirin preoperatively	Kan et al18
	Dual antiplatelet therapy, tight blood pressure control, glycemic control, and statin	White et al45
Anesthesia and analgesia	Propofol anesthesia	Yamaguchi et al20, Fujimura et al25, Nielsen et al33
	Fentanyl, propofol, and thiamylal sodium	Hirai et al21, Nakamizo et al22, Fujimoto et al40
	General anesthesia with propofol and remifentanil	Li et al34, Wessels et al44
	Intraop SBP 120-140	Li et al34
	Intraop SBP <130	Fujimura et al25
	Intraop SBP >110	Mendez et al27
	Intraop SBP >120	Horn et al29
	MAPs normal	Horn et al29
	MAP 100-120	Park et al32
	Arterial pressure monitoring	Mendez et al27
	Burst suppression with propofol during M4 clamping	Nielsen et al33, Rice et al16
	Total IV anesthesia propofol and sufentanil or combined inhalation/IV with sevoflurane and propofol	Mendez et al27
	Normothermia	Horn et al29
	Normovolemia	Horn et al29, Li et al34
	End tidal carbon dioxide 35-39	Horn et al29
	Propofol 6-10 mg/kg/h, Fentanyl 2-5 μg/kg	Horn et al29
	100 mg/day acetylsalicylic acid in the perioperative period	Horn et al29
	Normotension	Biswas et al30
	Mild hypothermia	Biswas et al30
	Normocapnia	Biswas et al30, Park et al32, Li et al34, Wessels et al44
	Fentanyl PRN or morphine drip	Park et al32
	Arterial blood gas every 30 min, Inspired fraction of oxygen at 1.0 (100%) during suturing of anastomosis	Wessels et al44
	Target body temp 33°C then rewarmed to >35°C for extubation; Preincision dexamethasone 8 mg; Premed w/1-2 mg midazolam; Induction fent 7-9 mcg/kg then 0.5 mg/kg propofol and 0.6 mg/kg roc; Induction fent 7-9 mcg/kg then 0.5 mg/kg propofol and 0.6 mg/kg roc; Maintenance w/50% NO, 50% O2, 0.5 MAC iso or sevo, remi gtt 0.05-0.2 mcg/kg/min	Burbridge et al46
	MAP >20% baseline during anastomosis	Biswas et al30
Surgical strategy	Doppler probe	Rice et al16, Yamaguchi et al20, Nomura et al24, Nishizawa et al28, Murai et al35, Mikami et al38, Katsuki et al39
	ICG angiography	Rice et al16, Kan et al18, Nomura et al24, Nishizawa et al28, Horn et al29, Pena-Tapia et al31, Nielsen et al33, Murai et al35, Mikami et al38, Katsuki et al39, Wang et al41, Zhao et al42, Wessels et al44
	Neuromonitoring	Khan et al17, Yamaguchi et al20
	Silicone stent	Yamaguchi et al20
	STA-M4 followed by EDMS	Fujimura et al25, Nishizawa et al28
	Intraoperative minocycline	Fujimura et al25, Nishizawa et al28
	3-8 arachnoid sutures	Kim et al26
	STA-MCA direct bypass	Mendez et al27, Horn et al29, Park et al32, Murai et al35, Katsuki et al39, Fujimoto et al40, Wang et al41, Zhao et al42, Antonucci et al43, Wessels et al44, White et al45
	Bone-flap cut to allow graft to pass underneath during reimplantation; MCA branch at least 1 mm in diameter; 3 mm arteriotomy	Horn et al29
	8-12 interrupted stitches using 10-0 nylon	Horn et al29, Wang et al41, Wessels et al44
	End-to-side	Biswas et al30, Pena-Tapia et al31, Antonucci et al43, Wessels et al44
	Two anchoring stitches at heel and toe	Biswas et al30, Park et al32, Wessels et al44
	Slit arteriotomy (instead of tear drop arteriotomy)	Biswas et al30
	Circumferential dural opening	Pena-Tapia et al31
	Radial dural opening	Zhao et al42
	Galea cut parallel to STA; Interrupted or running stitches	Park et al32
	3-4 cm craniotomy	Pena-Tapia et al31, Wessels et al44
	6 cm craniotomy	Park et al32, Nielsen et al33, Li et al34
	8 cm craniotomy	Katsuki et al39
	8-9 cm graft	Nielsen et al33
	10 cm graft	Wang et al41
	Double bypass (after one anastomosis with larger STA, other branch of STA connected to the arterial line)	Murai et al35, Mikami et al38
	Local papaverine	Mikami et al38
	IV heparin	Mikami et al38
	Operative microscope	Fujimoto et al40, Wessels et al44
	Stump of donor shaved obliquely to fit recipient side	Wang et al41, Wessels et al44
	EDS with dura inverted and inserted under bone edge	Zhao et al42
	Outside-in-inside-out stitches	Wessels et al44
Blood pressure management	SBP 130-150 intraoperatively and for 48 hours postop	Teo et al15
	SBP 120-160 postoperatively	Rice et al16
	SBP 110-140 postoperatively	Yamaguchi et al20, Mendez et al27
	Strict <120 if evidence of hyperperfusion	Yamaguchi et al20, Katsuki et al39
	SBP <130 with Cardene drip	Fujimura et al25
	Intraop SBP <130	Fujimura et al25
	BP <150/90 using nitroglycerin and/or diltiazem for 7 d postoperatively	Hirai et al21, Nakamizo et al22, Fujimoto et al40
	BP <140/100	Zhao et al42
	SBP 110-130 postoperatively ×7-10 d	Nishizawa et al28, Katsuki et al39
	SBP >120	Horn et al29
	Cardene drip	Mendez et al27, Fujimura et al25, Katsuki et al39
	Normotension until anastomosis then MAP >20% above baseline then normotension again after	Biswas et al30
	Intraoperative MAP 100-120 mm Hg	Park et al32
	Intraoperative MAP 5-10 mm Hg above baseline	Nielsen et al33
	Complex SBP guidance intra/postop	Li et al34
	MAP 85%-100% baseline for 7 d postoperatively	Murai et al35
	Normotension with BP within 20% of baseline	Mikami et al38
	SBP 120-140 postoperatively	Wessels et al44, White et al45
	Intraoperative MAP 90-100 mm Hg	Wessels et al44
	Intraoperative MAP 80-110 mm Hg	Burbridge et al46
	SBP >120 intraoperatively	White et al45
Postop management	SBP 130-150 intraoperatively and for 48 h after	Teo et al15
	SBP 120-160 postoperatively	Rice et al16
	SBP 110-140 postoperatively	Yamaguchi et al20, Mendez et al27
	Strict <120 if evidence of hyperperfusion	Yamaguchi et al20, Katsuki et al39
	SBP <130 with Cardene drip	Fujimura et al25
	Intraop SBP<130	Fujimura et al25
	BP <150/90 using nitroglycerin and/or diltiazem for 7 d postoperatively	Hirai et al21, Nakamizo et al22, Fujimoto et al40
	BP <140/100	Zhao et al42
	SBP 110-130 postoperatively ×7-10 d	Nishizawa et al28, Katsuki et al39
	SBP >120	Horn et al29
	Cardene drip	Mendez et al27, Fujimura et al25, Katsuki et al39
	Normotension until anastomosis then MAP >20% above baseline then normotension again after	Biswas et al30
	Intraoperative MAP 100-120 mm Hg	Park et al32
	Intraoperative MAP 5-10 mm Hg above baseline	Nielsen et al33
	Complex SBP guidance intra/postop	Li et al34
	MAP 85%-100% baseline for 7 d postoperatively	Murai et al35
	Normotension with BP within 20% of baseline	Mikami et al38
	SBP 120-140 postoperatively	Wessels et al44, White et al45
	Intraoperative MAP 90-100 mm Hg	Wessels et al44
	Intraoperative MAP 80-110 mm Hg	Burbridge et al46
	SBP >120 intraoperatively	White et al45
Outpatient follow-up/recovery	MRI and DSA at 12 mo follow-up	Wessels et al44
	Quantitative ultrasound monitoring, preop, day 1, 7, 3 mo, 6 mo	Wang et al41
	STA Doppler, SPECT preop and 14 d/3 mo postop	Fujimoto et al40
	CTA, MRA, or DSA follow-up with frequent clinic visits	Khan et al17
	First follow-up 30 d postop	Powers et al19, Rice et al16
	Perfusion scan at 30-60 d	Powers et al19
	6 mo follow-up: MRI with Diamox, DSA PRN	Nielsen et al33
	DSA, MRI, STA Doppler before and 14 d postop	Hirai et al21
	Angiographic confirmation at 14 d, long-term imaging	Nakamizo et al22
	Angiogram before and 3 mo postop	Jussen et al23
	Test aspirin resistance and prothrombotic disorders	Jussen et al23
	DSA 7-10 d postop	Pena-Tapia et al31
	DSA 14 d postop	Fujimoto et al40
	MRI with DWI within 1 wk of bypass	Antonucci et al43
	30 d CTA/DSA/QMRA	White et al45
	DSA at 6-12 mo postop	Zhao et al42
	Clinic/phone follow-up 3-6 mo and yearly	Zhao et al42

ACZ, acetazolamide; BP, blood pressure; CTA, computed tomography angiography; CVR, cerebrovascular reserve; DSA, digital subtraction angiography; DWI, diffusion-weighted imaging; EDMS, extradural/microvascular skeletonization; EDS, extradural dissection/suturing; ICG, indocyanine green; ¹²³I-IMP, iodine-123 N-isopropyl-p-iodoamphetamine; IV, intravenous; JET, Japan Extracranial-Intracranial Bypass Trial; LDL, low density lipoprotein; MAP, mean arterial pressure; MCA, middle cerebral artery; MRA, magnetic resonance angiography; PET, positron emission tomography; postop, postoperative; preop, preoperative; PRN, Pro Re Nata; QMRA, quantitative magnetic resonance angiography; rCBF, regional cerebral blood flow; SBP, systolic blood pressure; SPECT, single photon emission computed tomography; STA, superficial temporal artery; TCD, transcarotid Doppler; TIA, transient ischemic attack.

Recommendations

The final ERAS protocol for our institution encompasses 6 primary categories spanning the full perioperative continuum: patient selection, preoperative optimization, anesthesia and analgesia, surgical strategy, postoperative management, and recovery protocols. These can be seen in Figure 2. Each category contains specific evidence-based recommendations with accompanying rationale and implementation guidance.

FIGURE 2.

Recommendations for cerebral artery bypass surgery enhanced recovery after surgery. BP, blood pressure; CT, computed tomography; ERAS, Enhanced Recovery After Surgery; HTN, hypertension; MAP, mean arterial pressure; MRI/A, magnetic resonance imaging/angiography; SBP, systolic blood pressure; SSEP, somatosensory-evoked potentials.

Patient Selection Before Scheduling Surgery

Recommendation 1: Comprehensive Preoperative Imaging

Preoperative MRI, digital subtraction angiography, and perfusion studies with acetazolamide challenge are recommended for all patients being considered for cerebral bypass surgery.^{15,16,18-25,28,29,31-33,35,36,38-40,44} These studies should demonstrate steno-occlusive disease with compromised cerebrovascular reserve.^{15,20,26,28,29,31-33,35-38,40,41,44-46} Of note, recent stroke as demonstrated by diffusion-weighted hyperintensity on MRI is associated with perioperative stroke.⁴³ Strong recommendation, moderate-quality evidence.

Recommendation 2: Multidisciplinary Team Review

Complex cases should undergo multidisciplinary review involving cerebrovascular neurosurgery, vascular neurology, neurointensive care, and anesthesiology to optimize patient selection and perioperative planning.^16,47 Strong recommendation, low-quality evidence.

Recommendation 3: Patient and Family Education

Comprehensive preoperative education regarding the surgical operation, expected course, and potential complications should be provided to patients and families.⁴⁸ Patient counseling to set appropriate expectations is an established ERAS element.⁴⁹ Strong recommendation, low-quality evidence.

Preoperative Optimization

Recommendation 4: Blood Pressure Management

Patients should maintain individualized high-normal blood pressure targets tailored to their baseline perfusion status. Individualized perioperative blood pressure management can decrease the incidence and extent of cerebral infarction in adult patients with MMD after revascularization.^{15,16,20-22,25,27-30,32,33,35,38-40,42,44-46,50} Strong recommendation, moderate-quality evidence.

Recommendation 5: Antiplatelet Therapy

The patient should be on low-dose aspirin both preoperatively and postoperatively. This may be held the morning of surgery at the discretion of the attending surgeon.^{17,18,23,24,27,45,51,52} Strong recommendation, moderate-quality evidence.

Recommendation 6: Medical Optimization

Comprehensive diabetes management, treatment of anemia, and management of hyperlipidemia are recommended. We target a hemoglobin A1c ≤7%, with the caveat that this threshold should not be the sole reason to delay urgent revascularization.⁵³ Qualifying patients should receive high- or moderate-intensity statin therapy per American Heart Association and American Stroke Association secondary prevention guidelines.⁵⁴ Preoperative hemoglobin should be optimized; values <11 g/dL are associated with significantly increased cranial surgical morbidity and mortality.⁵⁵ Strong recommendation, moderate-quality evidence.

Recommendation 7: Smoking Cessation

Smoking cessation counseling and support should be provided to all current smokers; smoking approximately doubles the risk of postoperative symptomatic stroke after cerebral bypass.⁵⁶ Cessation also reduces respiratory, cardiac, and wound-healing complications.⁵⁷ We aim for 4 weeks or more of preoperative abstinence when feasible.⁵⁸ Strong recommendation, moderate-quality evidence.

Recommendation 8: Nutritional Assessment

Preoperative nutritional evaluation and supplementation should be provided as indicated. Malnutrition is one of the few modifiable preoperative risk factors with meaningful impact on surgical outcomes, and nutritional assessment is an established ERAS cornerstone.^59,60 Strong recommendation, moderate-quality evidence.

Recommendation 9: Anesthesia Evaluation

Comprehensive preoperative anesthesia evaluation is recommended, including functional capacity assessment, obstructive sleep apnea screening, cardiovascular risk stratification, and medication optimization.⁶¹ Strong recommendation, low-to-moderate quality evidence.

Anesthesia and Analgesia

Recommendation 10: Hemodynamic Monitoring

Continuous intra-arterial blood pressure monitoring is essential throughout the perioperative period, including during anesthetic induction. Disrupted autoregulation in MMD renders CBF pressure dependent; intermittent measurement fails to detect critical hypotensive episodes, and minimizing the duration and magnitude of mean arterial pressure (MAP) drops below each patient's autoregulatory threshold directly reduces stroke risk.⁶² Strong recommendation, moderate-quality evidence.

Recommendation 11: Blood Pressure Targets

Intraoperative MAP should be maintained at individualized levels approximately 10% above each patient's baseline (typically 85-100 mm Hg), balancing adequate perfusion pressure against hyperperfusion risk in a brain with chronically altered autoregulatory reserve.⁶³ Strong recommendation, low-to-moderate quality evidence.

Recommendation 12: Normocapnia and Normovolemia

Normocapnia (target partial pressure of carbon dioxide in arterial blood 36-42 mm Hg) and normovolemia should be maintained throughout surgery. Hypocarbia promotes steal phenomenon by vasoconstricting nonischemic territories; hypercarbia impairs autoregulation and increases hyperperfusion risk. Hypovolemia reduces MAP and CBF in collateral-dependent regions while worsening steal through pressure redistribution. Euvolemia should be maintained with attentive crystalloid infusion rather than restrictive fluid protocols.⁶³ Strong recommendation, moderate-quality evidence.

Recommendation 13: Neuroprotection During Anastomosis

Burst suppression may be used immediately before recipient vessel clamping to reduce the cerebral metabolic rate of oxygen and provide theoretical neuroprotection during temporary arterial occlusion.^64,65 Weak recommendation, low-quality evidence.

Recommendation 14: Temperature Management

Normothermia should be targeted with active temperature monitoring throughout surgery. Although mild hypothermia (33-35°C) reduces the cerebral metabolic rate of oxygen and offers theoretical neuroprotection, clinical trials (Mild Intraoperative Hypothermia during Surgery for Intracranial Aneurysm, Effect of Early Sustained Prophylactic Hypothermia on Neurologic Outcomes Among Patients With Severe Traumatic Brain Injury) have not demonstrated improved neurological outcomes, and hypothermia carries risks of immune suppression, coagulopathy, dysrhythmia, and delayed emergence.^66-70 Strong recommendation, moderate-quality evidence.

Intraoperative Neuromonitoring

Recommendation 15: Multimodal Monitoring

Intraoperative neurophysiological monitoring should be used when available, including bilateral median and posterior tibial somatosensory-evoked potentials and 8-channel electroencephalography. Half minimum alveolar concentration steady state is used with avoidance of sedation boluses; the surgical team should provide advance warning to achieve electroencephalography burst suppression before vessel clamping and anastomosis.^71-73 Strong recommendation, low-quality evidence.

Surgical Strategy

Recommendation 16: Graft Preparation

Donor grafts should be carefully prepared with preservation of unused branches. Meticulous attention to technical detail is required for successful completion of the bypass and subsequent patency.⁷⁴ Ideally, the graft should be 10 cm or more in length to maximize anastomosis options and facilitate indirect revascularization.^75,76 Strong recommendation, moderate-quality evidence.

Recommendation 17: Surgical Technique

The surgical technique should follow established microsurgical principles for direct cerebral bypass. The operation involves microdissection of the donor artery in the scalp and microdissection of the recipient MCA branches near the Sylvian fissure.⁷⁴ Unused scalp branches (eg, frontal STA) should be preserved.⁷⁶ Larger craniotomy maximizes anastomosis options and is associated with bypass durability. We aim for craniotomy >6 cm.^32-34 Strong recommendation, moderate-quality evidence.

Recommendation 18: Combined Revascularization, Direct with Indirect

Direct anastomosis combined with indirect revascularization should be performed when appropriate vessel caliber allows. Combined bypass procedure, especially STA to MCA anastomosis plus indirect bypass, has been shown to be a safe and effective option for improving outcomes in patients with MMD.² In our experience, direct bypass is technically feasible and highly likely to remain patent when the recipient and graft are ≥0.8 mm. A healthy galeal cuff and dural inversion may encourage indirect anastomosis formation.⁷⁷ Strong recommendation, moderate-quality evidence.

Recommendation 19: Anastomosis Technique

Microsurgical anastomosis should be performed using established microvascular techniques.⁷⁴ The graft may be beveled and fish mouthed. Anchoring stitches are placed at the graft heel and the toe followed by interrupted or running 10-0 or 11-0 suture. In the case of the side-to-side anastomosis, entry and exit stitches with intraluminal suture technique is required for the back wall.⁷⁶ Strong recommendation, low-quality evidence.

Recommendation 20: Flow Enhancement

Side-to-side anastomosis or double-barrel bypass may be considered when higher flow augmentation is needed.⁷⁸ Double-barrel anastomosis should be reserved for cases with large or bilateral perfusion deficits, borderline individual branch caliber (≤0.8 mm), or after insufficient flow augmentation is demonstrated intraoperatively after the first anastomosis. The trade-off is longer operative time and competitive flow risk. Both indocyanine green angiography and flow probe confirmation of both limbs are essential. Weak recommendation, low-quality evidence.

Recommendation 21: Flow Confirmation

Intraoperative confirmation of graft patency using available methods is recommended.³⁸ Doppler probe, flow probe, and indocyanine green angiogram with Flow 800 (Zeiss) may be used to confirm and measure optimal flow.⁷⁶ Strong recommendation, moderate-quality evidence.

Recommendation 22: Complication Prevention

Special techniques should be used to safely complete bypass surgery and avoid perioperative complications. A topical calcium channel blocker or papaverine may be used to prevent and treat mechanical vasospasm.⁷⁶ During closure, we apply a small amount of subgaleal vancomycin powder to prevent infection. Moderate recommendation, low-quality evidence.

Postoperative Care

Recommendation 23: Specialized Unit Care

Postoperative care should be provided in an experienced neuroscience intensive care unit for 24 hours or longer if needed.⁷⁹ Strong recommendation, moderate-quality evidence.

Recommendation 24: Postoperative Blood Pressure Management

Continue arterial line monitoring for ≥24 hours postoperatively. Target MAP 85 to 100 mm Hg; use continuous infusion rather than intravenous (IV)-push agents for acute hypertension to mitigate the risk of precipitous pressure drops and consequent ischemic events.⁸⁰ Strong recommendation, moderate-quality evidence.

Recommendation 25: Antiplatelet Resumption

We recommend resumption or continuation of aspirin 81 mg daily by at least postoperative day (POD) 1.⁵² Strong recommendation, moderate-quality evidence.

Recommendation 26: Prophylactic Antiseizure Medication

We recommend prophylactic antiepileptic therapy perioperatively with continuation for 10 days postoperatively. Although evidence for routine antiseizure prophylaxis after craniotomy is inconsistent,⁸¹ the frequency of transient neurological events after cerebral bypass supports this practice at our institution. Weak recommendation, low-quality evidence.

Recommendation 27: Prophylactic Antibiotics

We recommend prophylactic antibiotics for 72 hours postoperatively, extended to 10 days in patients with diabetes. The use of the STA reduces scalp blood supply and, in our experience, increases infection risk beyond what standard guidelines anticipate for clean procedures.⁸² Weak recommendation, low-quality evidence.

Recommendation 28: Judicious Use of Postoperative Imaging

The use of transcranial ultrasound to look at graft patency may be considered as a low-cost and noninvasive means of assessing bypass function. We otherwise do not perform routine postoperative imaging, but postoperative imaging can be obtained as needed for clinical changes. Weak recommendation, low-quality evidence.

Recommendation 29: Maintain Euvolemia

IV fluids were continued as tolerated with the goal of euvolemia. Oral hydration was encouraged to wean IV fluids.⁸³ Strong recommendation, moderate-quality evidence.

Recommendation 30

Patient mobilization should begin as soon as neurologically appropriate, ideally the day of surgery or POD 1. Early mobilization is an important postoperative ERAS element.⁶⁰ Strong recommendation, moderate-quality evidence.

Recovery and Follow-Up

Recommendation 31: Discharge Criteria and Instructions

Standardized discharge criteria should be implemented: ambulation, adequate oral fluid tolerance, and acceptable pain control.⁸⁴ Instructions should encourage continued hydration, gentle early aerobic activity, showering from POD 3, and avoidance of constrictive headwear. Patients and families should be instructed to call immediately with any wound concern. Strong recommendation, low-quality evidence.

Recommendation 32: Structured Follow-Up

Long-term follow-up should be arranged to monitor outcomes and detect late complications.⁸⁵ We recommend nurse navigator telephone follow-up 1 week after discharge, office follow-up at 30 days, a diagnostic cerebral angiogram, computed tomography perfusion Diamox, and MRI/magnetic resonance angiography at 6, 12 months, 3, 10, 20 years, etc. We recommend a yearly MRI/magnetic resonance angiography for unilateral moyamoya.⁸⁶ Strong recommendation, low-quality evidence.

Recommendation 33: Quality Monitoring

Systematic outcome measurement should be implemented to evaluate the effectiveness of the ERAS protocol. Strong recommendation, low-quality evidence.

Recommendation 34: Continuous Improvement

Regular review and updating of protocols should be performed based on emerging evidence. Strong recommendation, moderate-quality evidence.

DISCUSSION

To our knowledge, this article represents the first ERAS protocol, specifically designed for cerebral bypass surgery in patients with MMD. The recommendations synthesize the best available evidence to provide standardized, evidence-based perioperative care guidelines.

The pathophysiology of MMD creates unique perioperative challenges that distinguish it from other neurosurgical operations.⁷⁹ The tenuous cerebral perfusion status of these patients requires meticulous attention to hemodynamic management throughout the perioperative period. Maintaining adequate cerebral perfusion pressure while avoiding hyperperfusion represents a delicate balance that requires experienced multidisciplinary care.

The recommendations emphasize individualized blood pressure targets informed by baseline perfusion status rather than rigid numeric thresholds.⁵⁰ This approach recognizes that patients with chronic cerebrovascular insufficiency may require specific hemodynamic management strategies.

Our emphasis on multidisciplinary care reflects the complexity of managing these patients safely. Practice variability in perioperative moyamoya care highlights the need for standardized protocols, such as the one we have proposed here based on the review of the currently available evidence and own institutional practices.⁶

Microsurgical technique recommendations emphasize elements that have been associated with improved outcomes in the literature. However, surgeons will appropriately bring their own unique strengths to optimize outcomes for their patients in this technically demanding operation. Technical excellence is paramount in achieving optimal results.

Although this protocol focuses on direct bypass, direct anastomosis is not always feasible due to inadequate vessel caliber, unfavorable anatomy, or previous radiation, necessitating indirect techniques. Outside of operative technique, perioperative management is nearly identical. The risk of hyperperfusion is lower with indirect bypass given the gradual nature of neovascularization, but hypotension is equally if not more dangerous, as the brain remains entirely dependent on native collateral flow until new vessels mature. Patients can still experience transient neurologic events postoperatively and require the same meticulous perioperative care described in this protocol.

The evidence for acute bypass performed within days of stroke or during crescendo transient ischemic attack is limited, and perioperative stroke risk seems substantially elevated in this setting.⁴³ For the rare patient with rapidly recurrent ischemic events refractory to medical management, acute bypass may be considered but requires rigorous patient selection, full multidisciplinary consensus, and extensive counseling regarding the markedly elevated operative risk. In the vast majority of patients, the safer approach is medical stabilization followed by elective bypass approximately 1 month after stroke, allowing infarct maturation and partial restoration of autoregulatory reserve before surgical intervention.

Postoperative management recommendations focus on early recognition and prevention of complications, particularly perioperative stroke and cerebral hyperperfusion. The emphasis on specialized monitoring reflects the importance of detecting complications early.⁸⁷ Supportive care through  transient neurologic events with close attention to hydration is particularly important.⁸⁸

The present ERAS draws on recovery protocols that incorporate principles of enhanced recovery shown to be successful in other surgical disciplines while addressing the specific needs of cerebral bypass patients.⁸⁹ Enhanced recovery strategies for elective craniotomy include a wide range of evidence-based interventions to improve recovery.⁶⁰ Implementation for patients undergoing cerebral bypass may prevent misses or near misses when navigating a complex operative journey and improve outcomes.⁹⁰

Limitations

Several limitations must be acknowledged in these recommendations. Most of the supporting evidence comes from retrospective case series rather than randomized controlled trials. The heterogeneity of MMD presentations and surgical techniques creates challenges in developing universally applicable recommendations. In addition, resource availability and institutional expertise may limit the feasibility of some recommendations.

The recommendations are based on adult populations, and their applicability to pediatric patients requires careful consideration.⁹¹ Recent pediatric moyamoya consensus statements provide specific guidance for pediatric perioperative care that should be considered alongside these recommendations.

We acknowledge this work represents a hybrid of systematic review, consensus voting, and institutional protocol; it does not fully satisfy the formal reporting requirements of any single methodology, and a prospectively registered protocol was not used.

Future Directions

Prospective studies comparing this ERAS protocol to conventional perioperative care are needed to quantify its clinical impact.⁹² On publication, we will plan to compare pre- and postprotocol cohorts. Development of quality metrics will facilitate adoption of these recommendations across institutions. Educational initiatives targeting multidisciplinary teams caring for moyamoya patients could accelerate dissemination of best practices.⁹³ Future research should focus on identifying patient-specific factors that predict optimal perioperative management strategies.⁹⁴ For example, advanced age, recent infarct, and large volume perfusion deficits are potential risk factors for postoperative complications that require specific management approaches.⁹⁵

CONCLUSIONS

This article provides evidence-based recommendations for enhanced recovery protocols in direct cerebral bypass surgery for MMD. The multidisciplinary approach spans the entire perioperative continuum from patient selection through long-term follow-up. Implementation of these recommendations has the potential to improve patient outcomes, reduce complications, and standardize care delivery across institutions.

The success of ERAS protocols in other surgical disciplines suggests that similar benefits may be achieved in cerebral bypass surgery with appropriate adaptation to the unique requirements of patients with MMD.⁹⁶ However, successful implementation requires commitment from multidisciplinary teams, adequate resources, and ongoing quality improvement efforts.⁹⁷

These recommendations provide a foundation for standardized care adaptable to local resources and expertise. Regular updates will be necessary as new evidence emerges and surgical techniques continue to evolve.⁹⁸ The ultimate goal is to optimize outcomes for patients with MMD undergoing cerebral bypass surgery while reducing variability in care delivery.

Supplementary Material

neuopen-7-e000286-s001.docx ^{(20.3KB, docx)}

Funding

This study did not receive any funding or financial support.

Disclosures

The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

Supplemental Digital Content

Supplemental Digital Content 1: Supplementary Table. GRADE justification for recommendations.