Superficial Temporal Artery-middle Cerebral Artery Bypass Research Articles

Intraoperative evaluation of local cerebral hemodynamic change by laser speckle contrast imaging for predicting postoperative cerebral hyperperfusion during STA-MCA bypass in adult patients with moyamoya disease.

Cerebral hyperperfusion (CHP) occurred frequently after direct superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery for moyamoya disease (MMD). We analyzed cortical microvascular density (CMD) and the change of cerebral blood flow (LΔCBF) using intraoperative laser speckle contrast imaging (LSCI) on 130 hemispheres of 95 consecutive adult patients with MMD. The demographic characteristics, cortical hemodynamic sources, bypass methods, intraoperative blood flow data, and relative CBF changes on single-photon emission computed tomography (SPECT) examination (SΔrCBF) were compared between the groups with and without CHP. The median values for CMD, LΔCBF, and SΔrCBF were significantly higher in the CHP group than in the non-CHP group (CMD 0.240 vs 0.206, P = 0.004; LΔCBF 2.285 vs 1.870, P < 0.001; SΔCBF 1.535 vs 1.260, P < 0.001). Multivariate analysis revealed that hemodynamic sources of recipient parasylvian cortical arteries from MCA (M-PSCAs), end-to-side (E-S) bypass method, CMD ≥ 0.217, and LΔCBF ≥ 1.985 were the risk factors for CHP. Intraoperative LSCI was useful for evaluating hemodynamics and predicting CHP in patients with MMD.

Flow-augmentation STA-MCA bypass for acute and subacute ischemic stroke due to internal carotid artery occlusion and the role of advanced neuroimaging with hemodynamic and flow-measurement in the decision-making: preliminary data.

A major clinical challenge is the adequate identification of patients with acute (<1 week) and subacute (1-6 weeks) ischemic stroke due to internal carotid artery (ICA) occlusion who could benefit from a surgical revascularization after a failure of endovascular and/or medical treatment. Recently, two novel quantitative imaging modalities have been introduced: (I) quantitative magnetic resonance angiography (qMRA) with non-invasive optimal vessel analysis (NOVA) for quantification of blood flow in major cerebral arteries (in mL/min), and (II) blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging to assess cerebrovascular reactivity (CVR). The aim of this study is to present our cohort of patients who underwent surgical revascularization in the acute and subacute phase of ischemic stroke as well as to demonstrate the importance of hemodynamic and flow assessment for the decision-making regarding surgical revascularization in patients with acute and subacute stroke and ICA-occlusion. Symptomatic patients with acute and subacute ischemic stroke because of persistent ICA-occlusion despite optimal medical/endovascular recanalization therapy who were treated at the Neuroscience Clinical Center of the University Hospital Zurich underwent both BOLD-CVR and qMRA-NOVA to study the hemodynamic and collateral vessel status. Patients selected for surgical revascularization according to our previously published flowchart were included in this prospective cohort study. Repeated NOVA and BOLD-CVR investigations were done after bypass surgery as follow up as well as clinical follow up. Continuous BOLD-CVR and qMRA-NOVA variables were compared using paired Student t-test. Between May 2019 and September 2022, superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery was performed in 12 patients with acute and subacute stroke because of ICA-occlusion despite of optimal endovascular and/or medical treatment prior to the surgery. Impaired BOLD-CVR in the occluded vascular territory [MCA territory: ipsilateral vs. contralateral: -0.03±0.07 vs. 0.11±0.07 %BOLD/mmHgCO2, P<0.001] as well as reduced hemispheric flow with qMRA-NOVA (ipsilateral vs. contralateral: 228.00±54.62 vs. 384.50±70.99 mL/min, P=0.01) were measured indicating insufficient collateralization. Post-operative qMRA-NOVA showed improved hemispheric flow (via bypass) (pre-bypass vs. post-bypass: 236.60±76.45 vs. 334.20±131.33 mL/min, P=0.02) and the 3-month-follow-up with BOLD-CVR showed improved cerebral hemodynamics (MCA territory: pre-bypass vs. post-bypass: -0.01±0.05 vs. 0.06±0.03 %BOLD/mmHgCO2, P=0.02) in all patients studied. Quantitative assessment with BOLD-CVR and qMRA-NOVA allows us to evaluate the pre- and post-operative cerebral hemodynamics and collateral vessel status in patients with acute/subacute stroke due to ICA occlusion who may benefit from surgical revascularization after failure of endovascular/medical treatment.

Clinical effect of a modified superficial temporal artery-middle cerebral artery bypass surgery in Moyamoya disease treatment

BackgroundCerebral extracranial-intracranial (EC-IC) revascularization technique (superficial temporal artery-middle cerebral artery (STA-MCA) bypass grafting) has become the preferred surgical method for the treatment of Moyamoya disease (MMD). We attempted to completely free the two branches of the superficial temporal artery without disconnection. Extracranial and intracranial blood flow reconstruction were then modified by selectively performing a direct bypass technique on one branch and a patch fusion technique on the other of the STA based on the blood flow and the vascular diameter of the intracranial surface blood vessels.MethodsA series of modified STA-MCA bypass surgeries performed consecutively between March 2022 and March 2023 were reviewed and compared to conventional combined bypass surgeries performed during the same period. The following information was collected from all enrolled patients: demographic characteristics, clinical symptoms, and preoperative and postoperative imaging, including Suzuki stage and Matsushima grade. The modified Rankin scale (mRS) was used to assess the changes in neurological status before and after surgery.ResultsA total of 41 patients with Moyamoya disease (MMD) who underwent cerebral revascularization were included in this study, of which 30 were conventional revascularization and 11 were modified revascularization. The mean age was 49.91 years, and 18 (43.9%) of the patients were women. The modified group had a lower incidence of cerebral hyperperfusion syndrome (18.2%) than the conventional group (23.3%). After at least 3 months of follow-up, the bypass patency rate remained 100% in the modified group and 93.3% in the conventional group. All patients in the modified group achieved a better Matsushima grade (A + B), with six (54.5%) having an A and five (45.5%) having a B. In contrast, four patients (13.3%) in the conventional group had a Matsushima grade of C. In all, 72.8% of the modified group had postoperative mRS scores of 0 and 1, which was higher than that of the traditional group (63.3%).ConclusionThe improved STA-MCA bypass could provide blood flow to multiple cerebral ischemic areas, reduce excessive blood perfusion, and ensure blood supply to the scalp, with lower complications and better clinical benefits than the traditional combined bypass.

Double-barrel STA-MCA bypass for a giant thrombosed supraclinoid ICA aneurysm with gangliocapsular infarct – A case report

Extracranial-intracranial (EC-IC) bypass is an essential tool for cerebral revascularization procedure. Superficial temporal artery–middle cerebral artery (STA-MCA) bypass was usually performed using one stem of the STA only. In an attempt to augment the flow and to direct the flow to different ischemic areas of the brain, a “double-barrel” technique is used, in which both branches of the STA are used to revascularize distinct MCA territories. Though there are many advancements in endovascular procedures, still STA MCA bypass plays a role in selected cases. We report a 50 years old female with giant thrombosed supraclinoid segment internal carotid artery (ICA) aneurysm with gangliocapsular infarct presented with vision loss, and limb weakness. Patient underwent double barrel STA-MCA bypass, post operatively patient improved of symptoms and patient was discharged in a stable condition. Though endovascular techniques have evolved exponentially over the last few years, and most of these complex aneurysms can be treated using flow-diverting techniques.Though the need for microsurgical intervention is diminished iin this endovascular era, still the surgeons should think about these revascularization procedures as it gives life-long durable solution.

167 STA-MCA Bypass for Symptomatic Moyamoya Disease—Lessons Learnt From 89 Revascularisations

INTRODUCTION: Efficacy of surgical revascularisation procedures over conservative management in moyamoya disease (MMD) has been established in the past. However there is dearth of literature on comprehensive evaluation of impact of age and Suzuki staging on clinical and angiographic outcome in symptomatic MMD patients undergoing direct revascularisation (DR) via superficial temporal artery – middle cerebral artery (STA-MCA) bypass. METHODS: We analysed consecutive MMD patients who underwent direct-revascularisation (DR) via STA-MCA bypass. Primary outcome measures were mRS scale and stroke risk reduction. Secondary outcome measure was angiographic outcome score (AOS). RESULTS: 70 patients (89 DR procedures), including 37.9% adults (&gt;18 yr), were operated over a duration of 8 years and followed up for 2 years (mean). Long-term bypass-patency rates were deemed 83.3% and 88.8% in children and adults respectively. In pediatric age group, median mRS scores improved from 3 to 2 (p = 0.001), 97.3% were free of recurrent strokes and AOS scores improved significantly (p = 0.002). Amongst adult MMD patients, median mRS score marginally improved from 3 to 2 (p = 0.25), 100% were free of recurrent strokes and AOS improved significantly (p=0.02). On comparing pediatric and adult patients, improvement in mRS scores (p = 0.14) and AOS scores (p = 0.65) were similar across the two age groups. Overall late stage MMD patients (Suzuki stages IV-VI) showed better improvement in mRS scores when compared with early stage MMD patients (Suzuki stages I-III; p = 0.04). Recurrent stroke rates were similar in both groups (p = 0.26). AOS scores improved significantly in both early and late stage MMD (p &lt; 0.001 in both), though the improvement amongst the two groups was similar (p = 0.88). CONCLUSIONS: Using meticulous surgical technique, excellent long-term bypass patency rates can be achieved to facilitate optimal clinical and angiographic outcome in symptomatic MMD patients, irrespective of the age group and stage of disease.

Efficacyassessment of superficial temporal artery-middle cerebral artery bypass surgery in treating moyamoya diseasefrom a hemodynamic perspective: a pilot study using computational modeling and perfusion imaging.

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a common surgery in treating moyamoya disease (MMD) with occluded MCA. Computational fluid dynamics (CFD) simulation might provide a simple, non-invasive, and low-cost tool to evaluate the efficacy of STA-MCA surgery. We aim to quantitatively investigate the treatment efficacy of STA-MCA surgery in improving the blood flow of MMD patients using CFD simulation. This retrospective study included 11 MMD patients with occlusion around proximal MCA who underwent STA-MCA bypass surgery. CFD simulation was performed using patient-specific blood pressure and postoperative artery geometry. The volumetric flow rates of STA and the bypass, average flow velocity in the proximal segment of transcranial bypass, transcranial pressure drop, and transcranial flow resistance were measured and compared with a postoperative increment of cerebral blood flow (CBF) in MCA territories derived from perfusion imaging. Per-branch pressure drop from model inlet to bypass branch outlet was calculated. The volumetric flow rates of STA and the bypass were 80.84 ± 14.54mL/min and 46.03 ± 4.21mL/min. Average flow velocity in proximal bypass, transcranial pressure drop, and transcranial flow resistance were 0.19 ± 0.07m/s, 3.72 ± 3.10mmHg, and 6.54 ± 5.65 10-8Pasm-3. Postoperative mean increment of CBF in MCA territories was 16.03 ± 11.72mL·100g-1·min-1. Per-branch pressure drop was 10.96 ± 5.59mmHg and 7.26 ± 4.25mmHg in branches with and without stenosis. CFD simulation results are consistent with CBF observation in verifying the efficacy of STA-MCA bypass, where postoperative stenosis may influence the hemodynamics.

Clinical Efficacy of Superficial Temporal Artery-middle Cerebral Artery Bypass Grafting Surgery Combined With Temporal Muscle Patch on Patients With Moyamoya Disease

To analyze the clinical efficacy of superficial temporal artery-middle cerebral artery (STA-MCA) bypass grafting surgery combined with temporal muscle patch and STA-MCA bypass grafting surgery alone on patients with moyamoya disease. Totally 73 patients confirmed with moyamoya disease in our hospital between January 2019 and December 2021 were enrolled. Among them, 43 patients treated with STA-MCA bypass grafting surgery combined with temporal muscle patch were assigned to the experiment group, whereas 30 patients treated with STA-MCA bypass grafting surgery alone to the control group. The following items of the 2 groups were compared: clinical efficacy, total effective rate, and disease control rate 6 months after surgery, the changes of modified Rankin Scale (mRS) and Karnofsky performance scale (KPS) scores before and on the seventh day and 6 months after surgery, and changes of Glasgow coma scale scores before and 24 hours after surgery. In addition, the incidences of cerebral ischemia and cerebral hemorrhage within 1 year after surgery were counted. The cerebral perfusion-associated indexes including relative mean transit time (rMTT), relative time-to-peak, relative cerebral blood flow (rCBF), and relative cerebral blood volume (rCBV) on the seventh day and 6 months after surgery were compared between the 2 groups, and the predictive value of cerebral perfusion-associated indexes before surgery for clinical efficacy on patients was analyzed. The Glasgow coma scale score after surgery ( P >0.05) was similar between the 2 groups, but the clinical efficacy and total effective rate of the 2 groups were notably different (both P <0.05). Compared with those before surgery, mRS scores of both groups declined, whereas KPS scores increased (both P <0.05) on the seventh day after surgery. In addition, compared with those before surgery and on the seventh day after surgery, mRS scores of both groups decreased 6 months after surgery, whereas KPS scores increased (both P <0.05). Both the groups showed decreased rMTT and rTPP, and increased rCBF and rCBV on the seventh day after surgery than those before surgery (all P <0.05). In addition, both the groups still showed decreased rMTT and rTPP, and increased rCBF and rCBV 6 months after surgery than those before surgery and on the seventh day after surgery (all P <0.05). Most notably, the experimental group displayed improved cerebral perfusion-associated indexes than the control group 6 months after surgery (all P <0.05). The relief group showed notably higher rCBF and rCBV levels than the nonrelief group (both P <0.05). According to ROC analysis, the areas under the curves of rCBF and rCBV in forecasting the clinical efficacy on patients were 0.842 and 0.823, respectively. Superficial temporal artery-middle cerebral artery bypass grafting surgery combined with temporal muscle patch can deliver a higher total clinical curative rate for patients with moyamoya disease and can alleviate their coma.

A flow self-regulating superficial temporal artery-middle cerebral artery bypass based on side-to-side anastomosis for adult patients with moyamoya disease.

Side-to-side (S-S) superficial temporal artery-middle cerebral artery (STA-MCA) bypass was reportedly used to treat a special moyamoya disease (MMD) patient with collaterals arising from the donor STA. However, the S-S technique is not routinely performed to date, and its benefits are still unknown for adult MMD. The purpose of this study was to investigate the possibility of routine use of the S-S technique for adult MMD. The authors retrospectively analyzed the clinical data of 50 adult patients (65 hemispheres, including 30 in the end-to-side [E-S] group and 35 in the S-S group) with MMD who underwent STA-MCA bypass. The patient demographic characteristics, clinical courses, technical details, intraoperative blood flow data, postoperative and preoperative relative cerebral blood flow (rCBF) values, modified Rankin Scale (mRS) scores, and short-term revascularization results were compared between the 2 groups. There were no significant differences observed in terms of the baseline characteristics, bypass patency rates, postoperative/preoperative rCBF values, incidence of cerebral hyperperfusion syndrome (CHS), mRS scores, and short-term revascularization results between the 2 groups (all p > 0.05). Intraoperative blood flow analysis showed that the increase of STA flow in the E-S group was significantly higher than that of proximal STA flow in the S-S group (p = 0.008). Although the increases of proximal and distal recipient flow in the E-S group seemed greater than those in the S-S group, the results were not statistically significant (p = 0.086 for proximal flow and p = 0.076 for distal flow). CHS symptoms in the S-S group were milder and with much shorter duration. The follow-up angiographic data of the representative case demonstrated that both frontal and parietal STA branches and the occipital artery participated in postoperative collateralization. S-S anastomosis can achieve comparable clinical effects to standard E-S construction. S-S anastomosis used in adult MMD demonstrated mild CHS symptoms with short duration and had the potential to arouse all scalp arteries as donor sources for revascularization through the intact distal STA branch via flow self-regulation.

Evidence of Efficacy of Superficial Temporal Artery-Middle Cerebral Artery Bypass in Japan

The Japanese EC-IC Bypass Trial(JET)Study demonstrated that a superficial temporal artery-middle cerebral artery(STA-MCA)bypass is effective in preventing the recurrence of ischemic stroke in cases of atherosclerotic internal carotid artery or MCA steno-occlusive lesions with symptoms. The JET-2 Study revealed that the hemodynamic criteria for STA-MCA bypass in the JET Study(rest cerebral blood flow < 80% and cerebrovascular reactivity < 10%)were adequate. An STA-MCA bypass was ranked as recommendation B; the level of evidence was moderate under the conditions of quantitative evaluation of cerebral hemodynamics and low frequency of perioperative complications, as described in the Japanese Guidelines for the Management of Stroke 2021. An education system for the accurate assessment of cerebral hemodynamics, meticulous surgical procedures, and perioperative management for STA-MCA bypass is necessary to hand over evidence of STA-MCA bypass efficacy in Japan to future generations. Simultaneously, new evidence of STA-MCA bypass efficacy should be explored with the advancement of medicine and should be disseminated worldwide.

Emergency Superficial Temporal Artery-Middle Cerebral Artery Bypass for Atherosclerotic Ischemic Stroke

Endovascular recanalization is the primary strategy for the treatment of acute embolic stroke. However, atherosclerotic occlusions are often challenging to recanalize, and only medical therapy can be performed. In these cases, even the best medical treatment may not be effective, and the cerebral infarction progressively worsens. We believe that an emergency superficial temporal artery-middle cerebral artery(STA-MCA)bypass could be effective in these situations, after careful case selection. We use the following eligibility criteria: (1)atherosclerotic infarction; (2)cerebral ischemia with blood flow < 70% of the contralateral side; (3)progressively worsening symptoms or widening of the subcortical infarction despite medical treatment; and(4)surgery availability < 72 h from symptom onset. Among the 35 patients who underwent urgent STA-MCA bypass from 2014 to 2020, 27(77.1%)gained gait independence, and the National Institutes of Health Stroke Scale(NIHSS)scores improved from a preoperative median of 8 to 3 at discharge. The modified Rankin score(mRS)improved from a preoperative median of 5 to 2 at discharge. No intracerebral hemorrhages occurred due to hyper-perfusion syndrome. When we match it with other reports, this emergency surgery allows 76-90% of patients with progressive stroke to achieve gait independency.

Fundamental Surgical Techniques of Superficial Temporal Artery:Middle Cerebral Artery (STA-MCA) Bypass

Superficial temporal artery-middle cerebral artery(STA-MCA)bypass surgery is necessary for vascular reconstruction in patients with hemodynamic ischemia, including moyamoya disease and complex aneurysms. This report introduces the fundamental techniques of STA-MCA bypass surgery practiced in my institute. Preoperative and perioperative management is important to minimize complications. During the procedure, the operator should keep a bloodless surgical field to facilitate the bypass. The vascular lumen and intima must be carefully observed during anastomosis, especially in moyamoya cases. In addition, this study emphasizes the importance of off-the-job training using animal or synthetic arteries because this technique includes special movements compared with that of other microsurgical procedures.

A Preliminary Report of One-Session Treatment with Cranioplasty and Superficial Temporal Artery-Middle Cerebral Artery Bypass for Hemorrhagic Moyamoya Disease Patients with Skull Defect

The objective of this study was to conduct a retrospective analysis of the safety and efficacy of one-session treatment with cranioplasty and superficial temporal artery-middle cerebral artery (STA-MCA) bypass after decompressive craniectomy in hemorrhagic moyamoya disease (MMD). From March 2019 to August 2021, 5 patients with hemorrhagic MMD after DC were admitted in Nanfang Hospital. All patients underwent digital subtraction angiography to exclude any spontaneous revascularization between the cortex and temporal muscle and the preservation of STA. Then one-stage treatment with STA-MCA bypass and cranioplasty were performed. If no suitable recipient artery was available, an encephalo-myo-synangiosis procedure was used as a salvage plan. Four patients underwent direct STA-MCA bypass, while one underwent encephalo-myo-synangiosis due to absence of a suitable recipient artery. All patients had no hemorrhage on postoperative computed tomography, and no new infarcts were detected on magnetic resonance imaging. There were no new recurrent symptoms at clinical follow-up 8 to 24 months after surgery. Three patients had improved Glasgow Outcome Scale scores, and 2 patients had stable Glasgow Outcome Scale scores. Perfusion computed tomography showed improvement in cerebral hemodynamics. Four follow-up digital subtraction angiographies were performed, suggesting graft patency. One-session treatment with extracranial to intracranial bypass and cranioplasty are safe and effective in patients with MMD who have undergone previous decompressive craniectomy due to hemorrhagic attack.

Microsurgical treatment of middle cerebral artery stenosis or occlusion: a single center experience and literature review

BackgroundTo investigate the effect of superficial temporal artery-middle cerebral artery (STA-MCA) bypass in the treatment of MCA stenosis or occlusion.MethodsThe clinical and imaging data of 31 MCA stenosis or occlusion patients with STA-MCA bypass were analyzed retrospectively. The operation was performed by STA-MCA M4 segment bypass via the frontotemporal approach. Modified Rankin Scale (mRS) was used to evaluate the neurological function of patients.ResultsAfter operation, head computed tomography (CT) showed that there was no new infarction or hemorrhage in the operation area. CTA and CTP showed that the bypass vessel was unobstructed in 29 cases and the cerebral perfusion was improved in 31 cases. Among the 31 patients, 7 patients had postoperative complications and 13 patients had improvement of clinical symptoms. The other patients had no complications and the clinical symptoms remained unchanged. The mRs score of 31 patients after operation indicated that the neurological function was significantly improved than pre-operation. Of the 31 patients, 23 cases were followed up. The mRs score showed that the neurological function of these 23 patients was further improved than that at discharge. In addition, DSA (or CTA) and CTP showed that the bypass vessel was unobstructed and the cerebral perfusion was further improved.ConclusionSTA-MCA bypass was an effective method for the treatment of MCA stenosis or occlusion. However, the results should be further verified by large sample, multi-center and long-term follow-up.

Moyamoya Disease-Standards and Advances in Revascularization Procedure and Peri-operative Management.

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with unknown etiology characterized by progressive stenosis at the terminal portion of the internal carotid artery and the abnormal vascular network formation at the base of the brain. Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a preferred surgical procedure for ischemic-onset MMD patients by improving cerebral blood flow. Recent evidence further indicates that flow-augmentation bypass has a potential role for preventing re-bleeding in hemorrhagic-onset MMD patients. Based on such cumulative evidence, there is a worldwide increase in the number of MMD patients undergoing bypass surgery, thus thorough understanding of the basic pathology of MMD including peri-operative hemodynamics is critical for avoiding surgical complications. The author sought to demonstrate the standard surgical procedure of STA-MCA bypass with indirect pial synangiosis for adult MMD patients and its pitfall in the early postoperative period, introducing the characteristic peri-operative hemodynamic condition of adult MMD after surgery, such as local cerebral hyperperfusion and intrinsic hemodynamic ischemia caused by watershed shift phenomenon.

Pre- and Postoperative Cerebral Haemodynamic Assessments and Multidisciplinary Team Management for Patients Undergoing Cerebral Revascularization Procedures: 2 Case Reports

Background: Cerebrovascular bypasses are complex neurosurgical procedures with specific indications. Surgical risks and outcome are associated with the type of bypass intended and patient&rsquo;s underlying conditions. A multidisciplinary team approach is therefore pivotal in the management of these bypass patients. Objective: The aim of this study is to provide an overview of the perioperative haemodynamic assessments and management of patients undergoing cerebral revasculaization with 2 illustrative cases. Case Report: Case 1: A 40-year-old male with cerebrovascular occlusive condition and recurrent transient ischaemic attacks (TIA&rsquo;s) affecting his left side. Preoperative computed tomography (CT) brain perfusion and carbon dioxide (CO2) inhalation technique revealed poor cerebrovascular reserve (CVR) in the right middle cerebral artery (MCA) territory. The patient underwent a right superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery. Case 2: A 56-year-old female with a left giant cavernous sinus aneurysm presented with left-sided intractable facial pain. Preoperative cerebral digital subtraction angiography (DSA) with carotid compression test revealed inadequate collateral circulation. She underwent a high flow, common carotid-middle cerebral artery bypass with saphenous vein graft and trapping of the giant aneurysm. Results: Case 1: Postoperative computed tomography angiography (CTA) brain scan on day 1 confirmed graft patency. The patient improved rapidly in strength of the left arm and right leg. CT brain perfusion scan at 3 months showed improved brain perfusion and CVR. Case 2: Postoperative CTA brain on day 1 confirmed graft patency. On day 3 post-operatively, she developed self-limiting left-sided ophthalmoplegia, which completely resolved by 6 weeks. CTA brain at 5 months showed patency of the bypass graft. There was no further facial pain or ophthalmoplegia at the last follow-up. Conclusion: Although many new surgical techniques had been developed, the outcome for patients undergoing bypass surgery remains highly dependent on multidisciplinary teamwork, detailed preoperative haemodynamic assessment, patient selection and perioperative care. Keywords: Cerebrovascular bypass; EC-IC bypass; STA-MCA bypass; Cerebral ischaemia; Cerebrovacular reserve; Balloon occlusion test

Blood volume flow in the superficial temporal artery assessed by duplex sonography: predicting extracranial-intracranial bypass patency in moyamoya disease.

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery is an important therapy for symptomatic moyamoya disease. Its success depends on bypass function, which may be impaired by primary or secondary bypass insufficiency. Catheter angiography is the current gold standard to assess bypass function, whereas the diagnostic value of ultrasonography (US) has not been systematically analyzed so far. The authors analyzed 50 STA-MCA bypasses in 39 patients (age 45 ± 14 years [mean ± SD]; 26 female, 13 male). Bypass patency was evaluated by catheter angiography, which was performed within 24 hours after US. The collateral circulation through the bypass was classified into 4 types as follows: the bypass supplies more than two-thirds (type A); between one-third and two-thirds (type B); or less than one-third (type C) of the MCA territory; or there is bypass occlusion (type D). The authors assessed the mean blood flow velocity (BFV), the blood volume flow (BVF), and the pulsatility index (PI) in the external carotid artery and STA by duplex sonography. Additionally, they analyzed the flow direction of the MCA by transcranial color-coded sonography. US findings were compared between bypasses with higher (types A and B) and lower (types C and D) capacity. Catheter angiography revealed high STA-MCA bypass capacity in 35 cases (type A: n = 22, type B: n = 13), whereas low bypass capacity was noted in the remaining 15 cases (type C: n = 12, type D: n = 3). The BVF values in the STA were 60 ± 28 ml/min (range 4-121 ml/min) in the former and 12 ± 4 ml/min (range 6-18 ml/min) in the latter group (p < 0.0001). Corresponding values of mean BFV and PI were 57 ± 21 cm/sec (range 16-100 cm/sec) versus 22 ± 8 cm/sec (range 10-38 cm/sec) (p < 0.0001) and 0.8 ± 0.2 (range 0.4-1.3) versus 1.4 ± 0.5 (range 0.5-2.4) (p < 0.0001), respectively. Differences in the external carotid artery were less distinct: BVF 217 ± 71 ml/min (range 110-425 ml/min) versus 151 ± 41 ml/min (range 87-229 ml/min) (p = 0.001); mean BFV 47 ± 17 cm/sec (range 24-108 cm/sec) versus 40 ± 7 cm/sec (range 26-50 cm/sec) (p = 0.15); PI 1.5 ± 0.4 (range 1.0-2.5) versus 1.9 ± 0.4 (range 1.2-2.6) (p = 0.009). A retrograde blood flow in the MCA was found in 14 cases (9 in the M1 and M2 segment; 5 in the M2 segment alone), and all of them showed a good bypass function (type A, n = 10; type B, n = 4). The best parameter (cutoff value) to distinguish bypasses with higher capacity from bypasses with lower capacity was a BVF in the STA ≥ 21 ml/min (sensitivity 100%, negative predictive value 100%, specificity 91%, positive predictive value 83%). Duplex sonography is a suitable diagnostic tool to assess STA-MCA bypass function in moyamoya disease. Hemodynamic monitoring of the STA by US provides an excellent predictor of bypass patency.

Double-barrel STA-MCA bypass for cerebral revascularization: lessons learned from a 10-year experience.

In select patients, extracranial-intracranial (EC-IC) bypass remains an important tool for cerebral revascularization. Traditionally, superficial temporal artery-middle cerebral artery (STA-MCA) bypass was performed using one limb of the STA only. In an attempt to augment flow and to direct flow to different ischemic areas of the brain, the authors adopted a "double-barrel" technique in which both branches of the STA are used to revascularize distinct MCA territories. A series of consecutive double-barrel STA-MCA bypasses performed between 2010 and 2020 were reviewed. Each anastomosis was directed to augment flow to a territory most at risk based on preoperative perfusion studies, cerebral angiography, and intraoperative indocyanine green data. CT perfusion and CTA were routinely used to evaluate postoperative augmentation and graft patency. Patient perioperative outcomes, surgical complications, and modified Rankin Scale (mRS) scores at the last follow-up were reported. Forty-four patients (16 males, 28 females) successfully underwent double-barrel STA-MCA bypass on 54 cerebral hemispheres: 28 operations were for moyamoya disease, 23 for atherosclerotic disease refractory to medical therapy, 2 for complex cerebral aneurysms, and 1 for carotid occlusion as a sequela of cavernous meningioma growth. Ten patients underwent multiple operations, 9 of whom had moyamoya disease/syndrome, with the subsequent operation on the contralateral hemisphere. The average patient age at surgery was 45.1 years (range 14-73 years), with a mean follow-up time of 22.1 months. Intraoperative graft patency was confirmed in 100% of cases, and 101 (98.1%) of the 103 anastomoses with imaging follow-up were patent. Perfusion to the revascularized hemisphere was improved in 88.2% of cases. Perioperative ischemic and hemorrhagic complications occurred in 8 procedures (2 were asymptomatic), whereas remote ischemic and hemorrhagic events occurred in 7 cases. There was no mortality in the series, and the mean patient mRS scores were 1.72 at presentation and 1.15 at the last follow-up. The high rates of intraoperative and postoperative patency support the feasibility of dual-anastomosis STA-MCA bypass for revascularization. The perioperative complication rate is not significantly different from that of single-anastomosis bypass. The functional outcomes at follow-up and perfusion improvement postoperatively support the efficacy and safety of this method as a treatment strategy.

Outcome Following Surgical Revascularization in Patients of Moyamoya Disease with Focus on Graft Patency and Angiographic Changes.

Surgical revascularization is the mainstay of treatment in symptomatic patients of moyamoya disease (MMD). The present study analyzed the postoperative angio-architecture in pediatric and adult patients of moyamoya disease. Patients with MMD, both ischemic and hemorrhagic, were subjected to surgery. A superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis was attempted in all. It was augmented by an encephalo-duro-myo-synangiosis), this was labelled as the combined surgical group. In patients where a direct bypass was not possible encephalo-duro-arterio-myo-synangiosis (EDAMS) was performed and these patients were put in the indirect surgery group. In the postoperative period, MRA was performed in all patients to look for (a) graft patency, (b) regression of moyamoya vessels, and (c) degree of surgical neovascularization (as quantified on adapted Matsushima and Inaba grading system). Eighty-two patients underwent 131 surgical revascularization procedures. A combined surgery (STA-MCA bypass and EDAMS) was performed in 100 hemispheres and indirect surgery (EDAMS) on 31 sides. In children less than 5 years of age, STA-MCA anastomosis was possible in more than 50% of patients. Clinical improvement was seen in 85.4% of patients. Postoperative MRA demonstrated a patent bypass graft in 97% of cases. Regression of moyamoya vessels was seen in half of the cases and good surgical revascularization (type A and B) was seen in more than 80% of hemispheres in the combined surgery and indirect surgery group. Revascularization procedures led to a regression of moyamoya collaterals, appearance of surgical neo angiogenesis, and a graft patency rate of 97%. Surgical group with combined revascularization had a trend towards better collateral development.

Changes in Evoked Potentials during Superficial Temporal Artery-Middle Cerebral Artery Bypass Surgery: A Case Series Report

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a surgical treatment for ischemic stroke caused by large artery occlusion. Intraoperative neuropsychological monitoring (IONM) is useful for ensuring cerebral perfusion. Herein, we report 5 cases of patients with ischemic stroke who underwent STA-MCA bypass with IONM. We investigated whether the improved cerebral perfusion was reflected in real time on the evoked potentials (EP) of IONM. To measure changes in cerebral perfusion, all patients underwent pre- and post-operative perfusion-weighted imaging (PWI). Additionally, functional assessments were performed before and after the surgery. We found that the motor evoked potential (MEP) amplitudes showed a consistent increase at the end of surgery. The somatosensory evoked potential (SSEP) latencies decreased consistently, but this change was not large. SSEP amplitudes showed no consistent change. Most of the PWI findings and functional assessments of our patients also improved after the surgery. After bypass surgery, MEP showed more reliable and consistent changes than SSEP. Keywords: Cerebral revascularization; Cerebral blood flow; Intraoperative neurophysiological monitoring

Non-invasive assessment of cerebral microvascular changes for predicting postoperative cerebral hyperperfusion after surgical revascularisation for moyamoya disease: an arterial spin labelling MRI study

Cerebral hyperperfusion syndrome (CHPS) can result after anastomotic surgery as the reperfusion is established in chronically ischemic cerebral territories in patients of moyamoya disease (MMD). In this study, we have evaluated the feasibility of arterial spin labelling (ASL) perfusion MRI to predict cerebral hyperperfusion syndrome based on changes of cerebral blood flow (CBF) after revascularisation surgery in patients of MMD. Our prospective study included 25 patients with MMD who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass with or without dural/muscle synangiosis. ASL MRI was performed before and 1-7days after surgery. On the side planned for operation, 5-mm ROI circle was drawn on the predetermined regions in frontal lobe, temporal lobe, parietal lobe and basal ganglia in proximal and distal territories of MCA to calculate ipsilateral CBF values (CBFi). An attempt was made to select the same location on contralateral side (non-operative) (CBFc) for each measurement for calculation of hemispheric normalised CBF (nCBFh) ratios. To adjust for inter individual variation among MR imagers and CBF, additional regions of interest were drawn within the cerebellum (CBFcbl) for cerebellar CBF normalised ratios (nCBFCbl). Of the 25 patients (26 operated hemispheres), 5 patients showed significant immediate postoperative symptoms suggestive of CHPS. Based on our findings, sensitivity and specificity of ASL perfusion to detect CHPS were evaluated. ASL was found to have 47-100% sensitivity and 45-88% specificity to detect CHPS. We have tried to calculate the prevalence of CHPS in postoperative patients of moyamoya disease, which in our study ranged from 6.83 to 40.70%. Based on our results, we concluded that ASL perfusion is an appropriate alternative to standard nuclear medicine studies to monitor the changes in perfusion after STA-MCA bypass surgery in moyamoya patients. ASL MR perfusion can be used to identify changes in cerebral blood flow (CBF) for early detection of cerebral hyperperfusion syndrome in patients with otherwise normal conventional MRI sequences with very high sensitivity but moderate specificity.