CT perfusion assessment of Moyamoya syndrome before and after direct revascularization (superficial temporal artery to middle cerebral artery bypass)

Longitudinal evaluation of cerebral perfusion evolution after revascularization surgery in moyamoya disease by CT perfusion

OBJECTIVE

To assess the longitudinal evolution of cerebral perfusion after revascularization surgery in patients with moyamoya disease (MMD) by CT perfusion (CTP).

MATERIALS AND METHODS

Thirty-one clinically confirmed MMD patients (12 males and 19 females, average age: 33.26 y, Suzuki stages 3 and 4: 19 and 11, respectively) who underwent revascularization surgery (bilateral (n=13) or unilateral (n=18)) were studied retrospectively. All patients underwent CTP examinations before and in the week after surgery and long-term (>3 months). CTP metrics (CBF, CBV, MTT, TTP, and delay TTP) were derived. The corresponding CTP metric values of the ROIs, which were manually drawn in the white matter (WM) and gray matter (GM), were recorded.

RESULTS

Six patients developed a new or progressive cerebral infarction/hemorrhage. In all patients, compared with the preoperative level, the TTP of GM and WM decreased in the short term after the surgery (P ≤ 0.005). Concurrently, the WM CBF increased significantly a week after surgery (P =0.02). However, in the long-term follow-up, the CBV and CBF in the GM and WM decreased to equal to or lower than the preoperative level, especially for CBV in the WM (P =0.012). Furthermore, cerebral perfusion began to decrease in the sixth month, and a continuous decline was observed over the next two months. It returned to the presurgical level after one year. In addition, the improvement in postsurgical perfusion was greater in Suzuki stage 3 patients than stage 4 patients.

CONCLUSION

Cerebral perfusion in patients with MMD improved shortly after surgery. However, in the long-term, brain perfusion decreased, most seriously in 6-8 months postoperatively, which might indicate that patients with MMD need timely follow-up and long-term intervention.

Evaluation of surgical revascularization procedure outcomes for adult Moyamoya disease: a computed tomography perfusion-based study

BACKGROUND

The effectiveness of surgical interventions, whether direct or indirect, for Moyamoya disease (MMD) remains controversial. This study aims to investigate CT perfusion (CTP) as an objective method to evaluate the outcomes of different surgical modalities for adult MMD.

METHODS

The clinical and imaging data of 41 patients who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass and 43 who received encephaloduroarteriosynangiosis (EDAS) were retrospectively analyzed. Intra- and intergroup differences in the Modified Rankin Scale (mRS) score, the change in clinical symptoms, collateral grade, and CTP parameters pre- and postoperatively were compared.

RESULTS

The overall level of the change in clinical symptoms in the STA-MCA group was higher than in the EDAS group (p < 0.05). In the operative area, the relative cerebral blood flow (rCBF) was significantly higher whereas the relative time to peak (rTTP) and the relative mean transit time (rMTT) were significantly lower in the STA-MCA and EDAS groups postoperatively than preoperatively (all p < 0.05). In the ipsilateral frontal lobe and basal ganglia, the postoperative rCBF was significantly higher, and the rTTP was significantly lower than the preoperative in the STA-MCA group (all p < 0.05). The postoperative rCBF improvement was higher in each brain area for STA-MCA than in the EDAS group (all p < 0.05).

CONCLUSION

Highlighting the utility of CTP, this study demonstrates its effectiveness in assessing postoperative cerebral hemodynamic changes in adult MMD patients. STA-MCA yielded a larger postoperative perfusion area and greater improvement compared to EDAS, suggesting CTP's potential to elucidate symptom variation between two surgical revascularization procedures.

CRITICAL RELEVANCE STATEMENT

We analyzed computed tomography perfusion parameters in pre- and postoperative adult Moyamoya disease patients undergoing superficial temporal artery-middle cerebral artery bypass and encephaloduroarteriosynangiosis. Our findings suggest computed tomography perfusion's potential in objectively elucidating symptom variations between these surgical revascularization approaches for MMD.

KEY POINTS

• Postoperative perfusion improvement is only confined to the operative area after EDAS. • Besides the operative area, postoperative perfusion in the ipsilateral frontal lobe and basal ganglia was also improved after STA-MCA. • The degree of perfusion improvement in each brain area in the STA-MCA group was generally greater than that in the EDAS group.

Predictive value of CT perfusion-derived parameters in Moyamoya disease

OBJECTIVE

To explore the applicability of CT perfusion-derived parameters and collateral index in prediction of functional and clinical outcomes in patients with Moyamoya disease (MMD) who have not been treated surgically.

METHODS

All hemispheres were categorized into four groups: those with ischemic (IS) lesions, hemorrhagic (HE) lesions, subarachnoid hemorrhage (SAH) and normal hemisphere (NH). The clinical review included primary outcomes (whether a patient survived the cerebrovascular event) and secondary outcomes (the modified Rankin scale [mRS] and Katz-activity of daily living [ADL] scale). CTP-derived parameters of the frontal, temporal lobe and basal ganglia were calculated. Collateral index of the hypointensity ratio (HIR) was defined as a volume of Tmax >10 s/ Tmax >4 s.

RESULTS

Between December 2020 and December 2021, 21 MMD patients (15 bilateral cases and 6 unilateral cases, for a total of 36 hemispheres) were retrospectively included. Compared with the NH group, the IS group showed obviously abnormal hemodynamics. As for the primary outcomes, HIR showed an excellent area under the curve of 0.955 (95 % CI: 0.886-1.000, p < 0.001). Significant correlations were found between CTP-derived parameters and secondary outcomes. Furthermore, HIR was significantly correlated with mRS (r = 0.576, p = 0.001) and ADL scores (r = 0.644, p < 0.001).

CONCLUSION

Among different imaging types, IS hemispheres were characterized by distinct changes of hemodynamic parameters. Collateral index of HIR could be considered a clinically accessible and promising indictor of functional and clinical outcomes in MMD.

Influence of Patient and Technical Variables on Combined Direct and Indirect Cerebral Revascularization: Case Series

BACKGROUND

Cerebral bypass for flow augmentation is an important technique for selected neurosurgical patients, with multiple techniques used (direct, indirect, or combined).

OBJECTIVE

To assess the impact of patient and technical variables on direct and indirect bypass flow after combined revascularization.

METHODS

This was a retrospective, single-institution review of patients undergoing direct superficial temporal artery-to-middle cerebral artery bypass with indirect encephaloduro-myosynangiosis for moyamoya disease and steno-occlusive cerebrovascular disease over a 2-year period. We evaluated the effect of baseline patient characteristics, preoperative imaging characteristics, and operative variables on direct and indirect patency grades.

RESULTS

Twenty-six hemispheres (8 moyamoya disease and 18 steno-occlusive cerebrovascular disease) in 23 patients were treated with combined revascularization. The mean patient age was 53.4 ± 19.1 years. Direct bypass patency was 96%. Over a mean follow-up of 8.3 ± 5.4 months, there were 3 strokes in the treated hemispheres (11.5%). The mean modified Rankin Scale score improved from 1.3 ± 1.1 preoperatively to 0.7 ± 0.8 postoperatively. Preservation of the nondonor superficial temporal artery branch was associated with a lower direct bypass grade ( P < .01), whereas greater mean time to maximum perfusion (Tmax)> 4 and >6 seconds and mismatch volumes were associated with higher direct bypass grades ( P < .05). Tmax >4-second volume inversely predicted indirect bypass patency.

CONCLUSION

Patient and technical variables may influence the relative contributions of the direct and indirect components of combined revascularizations.

Assessment of bypass patency using transcranial Doppler sonography: correlations with computerized tomography angiography findings in patients with moyamoya disease

To explore the utility of transcranial Doppler (TCD) findings when assessing bypass patency in patients with Moyamoya disease (MMD). Computed tomography angiography (CTA) and TCD sonography (TCDS) were performed before and after surgery to evaluate bypass patency. The peak systolic flow velocity (PSV) of the superficial temporal artery (STA) and the pulsatility index (PI) were compared between the groups that achieved patency and not, and receiver operating characteristic (ROC) curve analyses were used to define the TCDS criteria revealing patency. This study included 35 hemispheres (15 women; mean age 47 years) with Moyamoya disease who underwent STA-middle carotid artery bypass in our institution between January 2022 and October 2022. The PSV first increased on postoperative days 4-5 and then decreased on postoperative days 6-7 and 7-8. Patients with transient neurological diseases (TNDs), compared to those without, evidenced a significantly lower PSV value (P < 0.05). Compared with the non-patency group, the PSV was higher (P < 0.001) in the patency group. The cutoff values reflecting patency with good sensitivity and specificity were PSV > 49.00; PSV ratio (postoperative/preoperative) > 1.218; PSV ratio (operation side/contralateral side) > 1.082; and PSV ratio (adjusted) > 1.202. In the patency group, the PSV and PI significantly increased (P < 0.001) and decreased (P < 0.001) respectively. Bypass patency can be noninvasively and accurately evaluated via TCDS, affording an objective basis for assessment of the effect of revascularization surgery on patients with MMD.

Newer Updates in Pediatric Vascular Diseases

Pediatric neurovascular pathology directly involves or is in close proximity to the central nervous system (CNS). These vascular pathologies can occur in isolation or in association with broader syndromes. While some vascular pathologies are unique to the pediatric population, the full spectrum of adult neurovascular lesions can also affect children however, may present differently both clinically and on diagnostic imaging. Non-invasive (Ultrasound, CT, MRI) imaging plays a critical role in the diagnosis, treatment planning, and follow-up of vascular lesions involving the CNS. The modality can be chosen based on the age of the child, urgency of diagnosis, and local availability. Each modality has sensitivities and specificities which vary based on the location and imaging findings of a specific neurovascular pathology. In addition to non-invasive options, digital subtraction angiography (DSA) may be used as both a diagnostic and therapeutic imaging method for pediatric vascular lesions of the central nervous system. The diagnosis and management of pediatric cerebrovascular disease requires the close collaboration between pediatricians and pediatric specialists including neuroradiologists, neurologists, neurosurgeons, cardiologists, neurointerventionalists, and anesthesiologists among others. A detailed understanding of imaging findings, natural history, and treatment options is essential to guide and monitor imaging and treatment. The goal of this review is to provide the reader with an overview on pediatric neurovascular pathologies, provide examples of pathognomonic imaging findings, and present a brief review of endovascular treatment options, if applicable.

CT perfusion-based delta-radiomics models to identify collateral vessel formation after revascularization in patients with moyamoya disease

Purpose

To build CT perfusion (CTP)-based delta-radiomics models to identify collateral vessel formation after revascularization in patients with moyamoya disease (MMD).

Methods

Fifty-three MMD patients who underwent CTP and digital subtraction angiography (DSA) examination were retrospectively enrolled. Patients were divided into good and poor groups based on postoperative DSA. CTP parameters, such as mean transit time (MTT), time to drain (TTD), time to maximal plasma concentration (Tmax), and flow extraction product (FE), were obtained. CTP efficacy in evaluating surgical treatment were compared between the good and poor groups. The changes in the relative CTP parameters (ΔrMTT, ΔrTTD, ΔrTmax, and ΔrFE) were calculated to evaluate the differences between pre- and postoperative CTP values. CTP parameters were selected to build delta-radiomics models for identifying collateral vessel formation. The identification performance of machine learning classifiers was assessed using area under the receiver operating characteristic curve (AUC).

Results

Of the 53 patients, 36 (67.9%) and 17 (32.1%) were divided into the good and poor groups, respectively. The postoperative changes of ΔrMTT, ΔrTTD, ΔrTmax, and ΔrFE in the good group were significantly better than the poor group (p < 0.05). Among all CTP parameters in the perfusion improvement evaluation, the ΔrTTD had the largest AUC (0.873). Eleven features were selected from the TTD parameter to build the delta-radiomics model. The classifiers of the support vector machine and k-nearest neighbors showed good diagnostic performance with AUC values of 0.933 and 0.867, respectively.

Conclusion

The TTD-based delta-radiomics model has the potential to identify collateral vessel formation after the operation.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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%).

CONCLUSIONS

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.

Can Evoked Potential Changes during the Superficial Temporal Artery-Middle Cerebral Artery Bypass Surgery Predict Postoperative Improvement of Cerebral Perfusion and Functional Status?

BACKGROUND

We investigated evoked potential (EP) changes during superficial temporal artery to middle cerebral artery (STA-MCA) bypass surgery and their correlations with imaging and clinical findings postoperatively.

METHODS

This retrospective study included patients who underwent STA-MCA bypass surgery due to ischemic stroke with large artery occlusion (MB group). Patients who underwent unruptured MCA aneurysm clipping were enrolled in the control group (MC group). Median and tibial somatosensory evoked potentials (SSEP), and motor evoked potentials recorded from the abductor pollicis brevis (APB-MEP) and abductor hallucis (AH-MEP) were measured intraoperatively. Modified Rankin scale (mRS) and perfusion-weighted imaging (PWI) related variables, i.e., mean transit time (MTT) and time to peak (TTP), were assessed.

RESULTS

Δmedian SSEP, ΔAPB-MEP, and ΔAH-MEP were significantly higher in the MB group than in the MC group (p = 0.027, p = 0.006, and p = 0.015, respectively). APB-MEP and AH-MEP amplitudes were significantly increased at the final measurement (p = 0.010 and p < 0.001, respectively). The ΔTTP asymmetry index was moderately correlated with ΔAPB-MEP (r = 0.573, p = 0.005) and ΔAH-MEP (r = 0.617, p = 0.002). ΔAPB-MEP was moderately correlated with ΔMTT (r = 0.429, p = 0.047) and ΔmRS at 1 month (r = 0.514, p = 0.015).

CONCLUSIONS

MEP improvement during STA-MCA bypass surgery was partially correlated with PWI and mRS and could reflect the recovery in cerebral perfusion.

Imaging methods for surgical revascularization in patients with moyamoya disease: an updated review

Neuroimaging is crucial in moyamoya disease (MMD) for neurosurgeons, during pre-surgical planning and intraoperative navigation not only to maximize the success rate of surgery, but also to minimize postsurgical neurological deficits in patients. This is a review of recent literatures which updates the clinical use of imaging methods in the morphological and hemodynamic assessment of surgical revascularization in patients with MMD. We aimed to assist surgeons in assessing the status of moyamoya vessels, selecting bypass arteries, and monitoring postoperative cerebral perfusion through the latest imaging technology.

Clinical Management of Moyamoya Patients

Moyamoya angiopathy (MMA) is a peculiar cerebrovascular condition characterized by progressive steno-occlusion of the terminal part of the internal carotid arteries (ICAs) and their proximal branches, associated with the development of a network of fragile collateral vessels at the base of the brain. The diagnosis is essentially made by radiological angiographic techniques. MMA is often idiopathic (moyamoya disease-MMD); conversely, it can be associated with acquired or hereditary conditions (moyamoya Syndrome-MMS); however, the pathophysiology underlying either MMD or MMS has not been fully elucidated to date, and this poor knowledge reflects uncertainties and heterogeneity in patient management. MMD and MMS also have similar clinical expressions, including, above all, ischemic and hemorrhagic strokes, then headaches, seizures, cognitive impairment, and movement disorders. The available treatment strategies are currently shared between idiopathic MMD and MMS, including pharmacological and surgical stroke prevention treatments and symptomatic drugs. No pharmacological treatment able to reverse the progressive disappearance of the ICAs has been found to date in both idiopathic and syndromic cases. Antithrombotic agents are usually prescribed in ischemic MMA, although the coexisting hemorrhagic risk should be considered. Surgical revascularization techniques, which are currently the best available treatment in symptomatic MMA, are associated with good long-term outcomes and reduced ischemic and hemorrhagic risks. Given the lack of dedicated randomized clinical trials, current treatment is mainly based on observational studies and physicians’ and surgeons’ expertise.

Encephaloduroarteriosynangiosis (EDAS) treatment of moyamoya syndrome: evaluation by computed tomography perfusion imaging

OBJECTIVE

To explore the value of computed tomography perfusion (CTP) imaging for evaluating the efficacy of encephaloduroarteriosynangiosis (EDAS) treatment of moyamoya syndrome (MMS).

METHODS

Forty-three patients with MMS (48 hemispheres) who received EDAS treatment were examined using CTP and DSA before and after surgery. CTP of the ipsilateral cortex, contralateral mirror area, and pons region were measured, and the relative cerebral blood flow (rCBF) and volume (rCBV), mean transit time (rMTT), and time-to-peak (rTTP) were calculated. Based on postoperative DSA, 48 hemispheres were apportioned to two groups based on rich (grades 2, 3) or poor (grades 0, 1) collateral vessel formation, and the pre- and post-operative differences in perfusion changes were compared. The association between clinical outcome, CTP, and the degree of DSA collateral vessels was explored.

RESULTS

rCBF and rMTT significantly improved in both the poor and rich collateral vessel formation groups (n = 21 and 27, respectively), while rTTP significantly improved only in the latter. Postoperative CTP improved in the rich and the grade 1 collateral vessel groups (p < 0.01). The clinical improvement was consistent with the improvement of CTP (p = 0.07), but less consistent with the degree of collateral angiogenesis (p = 0.003).

CONCLUSION

CTP can quantitatively evaluate the improvement of brain tissue perfusion in the operated area after EDAS. Brain tissue perfusion in operated areas improved regardless of postoperative rich or poor collateral vessel formation observed via DSA. A significant improvement in rTTP in the operated area may indicate the formation of abundant collateral vessels.

KEY POINTS

• CTP showed that brain tissue perfusion in the operated area after EDAS improved regardless of rich or poor collateral vessel formation observed via DSA. • Significant improvement of rTTP in the operated area may indicate the formation of abundant collateral vessels.

Color Doppler ultrasonography for predicting the patency of anastomosis after superficial temporal to middle cerebral artery bypass surgery

BACKGROUND

Color Doppler ultrasonography (CDUS) is used to evaluate the surgical success and postoperative hemodynamic changes of patients who receive superficial temporal to middle cerebral artery (STA-MCA) bypass surgery. Previous studies enrolled small populations, and difficulties interpreting the results have limited their use in clinical settings.

OBJECTIVE

We attempted to determine the feasibility of using CDUS to evaluate STA hemodynamics and identify the most reliable parameter as a new clinical implication for determining bypass patency.

METHOD

Twenty-six patients who underwent STA-MCA bypass surgery were prospectively enrolled. Four times CDUS and two times digital subtraction angiography (DSA) were performed. The CDUS parameters were compensated using the ratio of the operated to the non-operated sides (R1) and compared before and after surgery (R2). The CDUS parameters are then compared with the patency on DSA by statistical analyses.

RESULTS

Increased CDUS parameters of the mean flow rate (MFR) and cross-sectional diameter (CSD) showed significant correlations with good patency on DSA. The R2 at 1 month was identified as the most reliable parameter for predicting the patency in both MFR and CSD. Their cutoff values were 1.475 and 1.15, respectively.

CONCLUSION

CDUS can be utilized for predicting the patency after STA-MCA bypass surgery; if the postoperative (compensated and compared) CDUS parameters increased by more than 47.5% in the MFR or 15% in the CSD, the patency of the anastomosis on DSA would be good.

Computed tomographic angiography may be used for assessing the dilatation of the anterior choroidal and posterior communicating arteries in patients with moyamoya syndrome

OBJECTIVE

To evaluate the feasibility of CT angiography (CTA) for assessing anterior choroidal artery (AChA) and posterior communicating artery (PComA) dilatation in patients with moyamoya syndrome (MMS).

METHODS

Eighty-eight MMS patients who underwent digital subtraction angiography (DSA) and CTA within 1 month were enrolled. The AChA was graded using both DSA and CTA. Given the features of dual blood supply, DSA was firstly used for grading of the PComA. Then, the calibers of PComA, P1 or P2 segment of the posterior cerebral artery (PCA), were recorded from CTA. Taking DSA as a reference standard, the optimal cutoff values of the PComA/P1 or PComA/P2 were calculated to determine the dilatation of PComA. Both the AChA and PComA were classified as extreme dilatation (ED, grade 2) or non-extreme dilatation (NED, grade 0 or 1).

RESULTS

The AChA was evaluated in 149 affected hemispheres of 88 patients while the PComA was evaluated in 70 affected hemispheres of 49 patients. The sensitivity and specificity of CTA in diagnosing AChA-ED were 92% and 93.5% respectively. Both the PComA/P1 (p < 0.001) and PComA/P2 (p = 0.4) ratios were increased in the PComA-ED group with the former yielding a better detecting performance than the latter (AUC = 0.92 vs 0.85, p = 0.046). When using 0.71 as a cutoff value, the sensitivity and specificity of the PComA/P1 ratio for diagnosis of PComA-ED cases were 91.3% and 83.3% respectively.

CONCLUSIONS

CTA could be used for the AChA classification in MMS patients, while a PComA/P1 ratio greater than 0.71 indicates the existence of PComA-ED.

KEY POINTS

• CTA showed a high sensitivity, specificity, and accuracy in diagnosing AChA-ED in patients with MMS. • PComA/P1 ratio greater than 0.71 on CTA signified an extremely dilated PComA. • CTA could be used to assess the dilatation of AChA and PComA in MMS patients, especially for routine postoperative follow-up.

Preoperatively estimated graft flow rate contributes to the improvement of hemodynamics in revascularization for Moyamoya disease

OBJECTIVES

Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass operation is an effective treatment for patients with Moyamoya disease, and the hemodynamic parameters are reported to be improved after operation. However, there is no report concerning hemodynamic changes from the viewpoint of the preoperative anatomical structure of grafts. In this study, we evaluated the correlation between the preoperatively estimated blood flow of the graft obtained through image-based computational fluid dynamics (CFD) analysis and the hemodynamic changes in the acute phase after revascularization.

MATERIALS AND METHODS

A total of 30 hemispheric sides of 23 patients were examined. The blood flow, that is, flow rate (FR) of the STA branches that were anastomosed to the MCA was evaluated using CFD analysis based on computed tomography (CT) angiography imaging data. The correlations between the FR and the hemodynamic changes in the acute phase after revascularization obtained through CT perfusion were assessed.

RESULTS

The preoperatively estimated FR of the graft was moderately correlated with the changes in the mean transit time significantly and weakly correlated with those in the cerebral blood flow and cerebral blood volume. In addition, the FR was strongly correlated with age and the diameter of the STA from the origin to the bifurcation.

CONCLUSION

The preoperatively estimated FR of the graft obtained through image-based CFD analysis contributed to the improvement of the mean transit time after revascularization. Because the FR of the graft was associated with the diameter of the STA, the size of the STA might be an important factor in postoperative hemodynamic changes. This might lead to the risk assessment of acute drastic hemodynamic changes as cerebral hyperperfusion, and consequently, better surgical outcomes might be expected.

Cerebral Hemodynamic Changes After Revascularization in Patients With Hemorrhagic Moyamoya Disease

Objective: To explore the cerebral hemodynamic changes after revascularization in patients with hemorrhagic moyamoya disease (MMD).

Materials and Methods: We retrospectively included 57 hemorrhagic MMD patients in a high-volume stroke center from January 2016 to December 2018. All subjects were evaluated with whole-brain CT perfusion (CTP) before and after surgical revascularization. Absolute and relative CTP values in the regions of cortical middle cerebral artery territory (CMT) and deep brain area (DBA) of hemorrhagic hemispheres were measured. Differences between pre- and post-operative CTP values were assessed comprehensively. The patients were categorized into subgroups based on revascularization subtypes and postoperative CTP intervals.

Results: The relative cerebral blood volume (rCBV) in DBA and CMT significantly reduced in postoperative CTP (P < 0.05). The median and interquartile range of the proportion of rCBV decrease (rCBVc%) were 7.2% (2.3–13.2%). The rCBV reduction retained statistical significant in patients who received subtypes of revascularization, and in patients with variable intervals of follow-up (P < 0.05). There was no significant difference of rCBVc% between patients who received different revascularization and among patients with different postoperative CTP intervals (P > 0.05). The relative mean transit time (rMTT) and relative time to peak (rTTP) also showed downward trends, but without retainable statistical significance in stratified analysis. There was no significant change in relative cerebral blood flow (rCBF) (P > 0.05).

Conclusion: In patients with hemorrhagic MMD, the CBV appeared to decrease and be relatively stable in the chronic phase after revascularization, with varying degrees of MTT and TTP shortening. However, there was no significant change in CBF.

Quantitative Angiographic Hemodynamic Evaluation After Revascularization Surgery for Moyamoya Disease

The corresponding hemodynamic changes of the internal carotid artery (ICA) after the revascularization surgery for moyamoya disease (MMD) remain unclear. The aim of this study was to analyze the hemodynamic changes of the ipsilateral ICA after the combined direct and indirect extracranial-intracranial (EC-IC) bypass. MMD patients undergoing combined EC-IC bypass were retrospectively reviewed. The mean transit time (MTT) of ICA was evaluated by color-coding angiography before revascularization and at follow-up. The MTT defined as the blood transit time between the end of cervical portion (C1) and the C7 segment of ICA. The clinical prognosis was assessed with Matsushima grading system, moyamoya vessel reduction system, and modified Rankin Scale (mRS). The correlation between hemodynamic parameter and prognosis was analyzed. Subgroup analysis was conducted between different presentations and different ages. Fifty-one patients were identified and the mean imaging follow-up interval was 5.5 months. The ICA-MTT was increased after the combined revascularization (P < 0.001) compared with contralateral ICA. Faster preoperative ICA-MTT was significantly associated with improved mRS in the ischemic group (P = 0.05). The increased ICA-MTT was significantly associated with favorable neoangiogenesis (P = 0.04), moyamoya vessel reduction (> 50%) (P = 0.023), and improved mRS score (P = 0.008). In subgroup analysis, the correlation in the ischemic subgroup and adult subgroup remained significant. In this cohort, the ICA-MTT increased after the combined EC-IC bypass, and there was a positive correlation between the increased blood transit time and favorable outcomes. Color-coding DSA proved to be useful as a quantitative and serial method to monitor postoperative courses after revascularization in MMD.

Collateral Circulation in Moyamoya Disease: A New Grading System

Background and Purpose- Predicting the risk of stroke and determining intervention indications are highly important for patients with Moyamoya disease (MMD). Here, we evaluated a novel MMD grading system based on collateral circulation and Suzuki stage to evaluate symptoms and predict prognosis. Methods- In total, 301 idiopathic MMD patients were retrospectively analyzed between 2014 and 2016. A collateral circulation grading system with scores ranging from 1 to 12 was established: the anatomic extent of pial collateral blood flow from posterior cerebral artery to middle cerebral artery and anterior cerebral artery was scored from 1 to 6; perforator collateral and internal cerebral artery flow were scored as 6 to 1, which corresponded to Suzuki stages 1 to 6. Dynamic susceptibility contrast-magnetic resonance imaging was used to evaluate hemodynamic status. We assessed the association between the grading system and clinical characteristics. Results- We analyzed 364 symptomatic hemispheres of 301 patients (146 males, 28±16 years). Ischemic patients who presented with infarction were more likely to score <8 points (P<0.001), whereas those with ischemia symptoms (transient ischemic attack and headache) were more likely to score >8 points. Hemorrhagic patients who presented with intraparenchymal hemorrhage were more likely to score <8 points, whereas those who presented with intraventricular hemorrhage were more likely to score >8 points (P<0.001). According to dynamic susceptibility contrast-magnetic resonance imaging, lower scores were correlated with more severe time to peak delay (P<0.001) and worse relative cerebral blood volume ratio (P=0.016) and cerebral flow ratio (P=0.002). Encephaloduroarteriosynangiosis was performed in 348 symptomatic hemispheres. Patients who had collateral scores <4 points were more likely to have a postoperative stroke and a worse prognosis during the follow-up. Conclusions- This new MMD collateral grading system correlated well with clinical symptoms, hemodynamic status, and therapeutic prognosis and may facilitate risk stratification and prognosis predictions in patients with MMD.

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.

Evaluation of Hemodynamics Before and After Revascularization in Hemorrhagic Moyamoya Disease: A Computed Tomography Perfusion Imaging Case Study

OBJECTIVE

To explore the feasibility of computed tomography perfusion imaging (CTP) for evaluating hemodynamics in hemorrhagic moyamoya disease (MMD).

METHODS

The retrospective analysis included 25 patients with hemorrhagic MMD who underwent brain CTP examination. Two experienced radiologists manually delineated regions of interest (ROIs) in the bilateral frontal lobe, temporal lobe, brain tissue adjacent to the hemorrhagic foci, and brainstem as a control region. The perfusion values for all ROIs were extracted, including cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP). Subsequently, the differences in perfusion values for different brain tissues were compared between the hemorrhagic side and the nonhemorrhagic side. For patients who underwent revascularization surgery, differences in perfusion values from before to after surgery were determined in brain tissues on the ipsilateral side.

RESULTS

CBF in the area around the hematoma and the lateral temporal lobe on the hemorrhage hemisphere was lower than that on the contralateral side, whereas TTP and MTT were higher. Among the 14 patients who underwent revascularization, CBF and CBV in the postoperative temporal lobes were higher than the preoperative values, whereas TTP and MTT were lower. CBF and CBV in the frontal lobe were higher after the operation.

CONCLUSIONS

Hemorrhagic MMD results in cerebral ischemia, and CTP could be used to localize such ischemic brain tissue and objectively evaluate the changes in cerebral hemodynamics with revascularization.

Modified encephalo-duro-periosteal-synangiosis (EDPS) for the revascularization of anterior cerebral artery territory in moyamoya disease: A single-center experience

OBJECTIVES

Anterior cerebral artery (ACA) territory, a crucial area of intellectual development in children, is frequently involved in the progress of moyamoya disease (MMD). However, revascularization surgeries for this area are not as established as surgeries for middle cerebral artery (MCA) territory. This study aimed to describe our experience and study the effect of revascularizing ACA territory with periocranium and dural leaflets, which is referred to as 'encephalo-duro-periosteal-synangiosis (EDPS)'.

PATIENTS AND METHOD

Fourteen hemispheres of 9 MMD patients who had undergone EDPS from November 2015 till July 2017 in our hospital were retrospectively included. Clinical characteristics and procedure-related information were recorded. Cerebral perfusion was evaluated by computed tomography perfusion (CTP). Absolute and relative (r) CTP parameters of ROIs in ACA territory at the level of centrum semiovale and middle basal ganglia were calculated. Preoperative and postoperative parameters were compared.

RESULTS

All EDPS procedures were technically successful with no postoperative complications. The mean operating time was 75.00 ± 22.53 min per hemisphere. Postoperative absolute cerebral blood flow (CBF), rCBF were significantly increased and absolute time to peak (TTP), rTTP, absolute mean transit time (MTT) were significantly reduced in ACA territory at centrum semiovale level (P = 0.002, 0.045, 0.007, 0.005 and 0.039 respectively). Improved outcomes were achieved in five patients, stabilization in three and one patient had deterioration out of intracerebral hemorrhage during follow-up.

CONCLUSION

EDPS is a simple but effective technique to revascularize ACA territory for MMD. EDPS significantly improved cerebral blood perfusion of frontal lobe in the majority of patients without increasing procedure-related risks.

An acute stroke CT imaging algorithm incorporating automated perfusion analysis

In this paper, we propose a CT imaging algorithm for patients presenting with suspected acute stroke that incorporates automated CT perfusion (CTP) imaging. The algorithm details evaluation of the non-contrast CT (NCCT) for hemorrhage and acute ischemia, calculation of ASPECTS, with performance and interpretation of CTP if appropriate. In particular, we consider the key steps in expeditious interpretation of non-contrast CT and CT angiography in the context of suspected acute ischemic stroke. Given the recent expansion of the "imaging based" treatment window for thrombectomy from 6 to 24 h in the 2018 American Heart Association stroke guidelines, we consider the key criteria in the decision to perform CT perfusion and the patient cohorts in which this might be most helpful. We also describe how imaging findings might be incorporated into the treatment paradigm for suspected with acute ischemic stroke and we allude to some of the most frequently encountered pitfalls associated with CTP which we think will be particularly helpful for radiologists and stroke physicians who are considering adding CT perfusion to their work-up for acute stroke.

Quantifying Hemodynamic Changes in Moyamoya Disease Based on Two-Dimensional Cine Phase-Contrast Magnetic Resonance Imaging and Computational Fluid Dynamics

OBJECTIVE

To investigate hemodynamic changes in moyamoya disease (MMD) via two-dimensional cine phase-contrast magnetic resonance imaging and computational fluid dynamics.

METHODS

In 18 patients with MMD and 10 healthy control subjects, phase-contrast magnetic resonance imaging was performed to quantify flow rate of main supplying arteries, including internal carotid arteries (ICAs) and vertebral arteries. Mean flow rate in these vessels was adopted as the patient-specific boundary condition for computational fluid dynamics simulation of the circle of Willis in MMD and control groups. Pressure drop in both ICAs and their difference, wall shear stress and secondary flow in the carotid siphon of ICAs, and flow rate and size of posterior communicating arteries (PComAs) were compared between MMD and control groups. Four patients with MMD underwent follow-up scans for longitudinal comparison.

RESULTS

Phase-contrast magnetic resonance imaging data revealed significantly different flow rate in the left ICA and right vertebral arteries between MMD and control groups. Computational fluid dynamics simulation demonstrated similar wall shear stress and similar secondary flow of both ICAs but significantly higher pressure drop in left ICA, higher pressure drop difference between left ICA and right ICA, and higher flow rate in PComAs in patients with MMD compared with control subjects. Significantly increased size of left PComA in patients with MMD was also found. Follow-up results confirmed that the combination of pressure drop difference, flow rate, and size of PComAs can potentially assist long-term prognosis after surgery.

CONCLUSIONS

Pressure drop difference, flow rate, and size of PComAs can be used to evaluate impairments in cerebrovascular reserve and indicate long-term prognosis in MMD.

Application of CT perfusion to assess hemodynamics in symptomatic Moyamoya syndrome: focus on affected side and parameter characteristic

OBJECTIVE

Vascular and hemodynamic changes were not consistent in symptomatic and non-symptomatic cerebral hemisphere in patients with symptomatic moyamoya syndrome (MMS). Thus, the purpose of this study is to evaluate the hemodynamic difference between symptomatic and non-symptomatic cerebral hemisphere in patients with symptomatic MMS.

METHODS

Patients who were diagnosed with symptomatic MMS were retrospectively collected. All cases underwent CTP examination. Regions of interest (ROIs) were chosen in the mirroring bilateral frontal lobes, temporal lobes, the basal ganglia, and the brainstem as control region. The relative perfusion parameter values of symptomatic side were compared with non-symptomatic side.

RESULTS

Of the 40 patients, 33 patients were taken into assessment. In all cases (n = 33), rCBF, rMTT, and rTTP in all regions of interest (ROIs) of the symptomatic side were significantly different from those of contralateral side. In unilateral MMS patients (n = 7), rCBF values were not significantly different between two sides in the temporal lobe and basal ganglia area; rTTP values were significantly higher in the symptomatic side. rMTT values were significantly higher only in the temporal lobe of symptomatic side. In bilateral MMS patients (n = 26), rCBF and rMTT in all ROIs of the symptomatic side were significantly different from those of contralateral side. However, there were no significant differences between two sides in all ROIs on rTTP values.

CONCLUSIONS

This study demonstrates that rCBF and rMTT were more sensitive than rTTP for evaluating hemodynamic changes in patients with symptomatic bilateral MMS. Furthermore, patients with unilateral MMS may have a preserved rCBF compared to those with bilateral disease.

Characteristics of cerebral hemodynamics assessed by CT perfusion in moyamoya disease

Due to the recent development of multidetector row computed tomography (CT), hemodynamic parameters can now be conveniently obtained with CT perfusion. The purpose of this study is to characterize the hemodynamic parameters of CT perfusion in moyamoya disease, and to discuss the differences in collateral circulation between moyamoya disease and atherosclerotic disease. A total of 16 hemispheric sides of 15 patients with moyamoya disease and 10 hemispheric sides of 9 patients with atherosclerotic disease who underwent bypass surgery were included. CT perfusion was performed with ¹²³I-IMP SPECT. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) values obtained by CT perfusion using standard singular value decomposition as the deconvolution algorithm in moyamoya disease were calculated. Preoperative values of these parameters were compared with those of atherosclerotic disease. Then, the postoperative changes of these parameters were analyzed. In the impaired side, CBF as measured by CT perfusion was correlated with that measured by ¹²³I-IMP SPECT. In moyamoya disease, CBV as measured by CT perfusion was significantly increased compared to in atherosclerotic disease, yet CBF was significantly decreased in atherosclerotic disease. Postoperatively, the asymmetry ratios of MTT were significantly improved, especially in atherosclerotic disease compared with moyamoya disease. On CT perfusion, the parameters included transit time and arrival time. CBV increase in moyamoya disease and postoperative improvement of MTT, especially in atherosclerotic disease, were unique characteristics in each. This might be due to the difference of collateral circulation and compensatory mechanisms between moyamoya disease and atherosclerotic disease.

One sided bypass for bilateral Moyamoya disease, a case report and review of the literatures

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Moyamoya disease (MMD) is a rare condition which can present both in children and adults.

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Diagnosis is usually established after imagine.

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Treatment is aiming at stroke prevention by improving blood flow.

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When surgical intervention is considered, unilateral revascularisation might be sufficient even for patients with bilateral lesion.

Background

Moyamoya disease (MMD) is a rare condition, where the most appropriate treatment for it is yet to be determined. Surgery remains an important method of choice although it is considered a form of palliative care. The outcome following surgery is very difficult to judge, and there is no standardised measurement to assess it. It is therefore important to know which approach for such patient is adequate.

Clinical presentation

A 21-year-old male patient presented with signs and symptoms of intracranial haemorrhage. Upon investigation, a diagnosis of bilateral MMD was made, and one sided direct bypass surgery was subsequently performed. At 3-year follow-up, there is no evidence of recurrent cerebral vascular event.

Conclusion

This case provided further evidence that direct bypass surgery is beneficial for patient in terms of blood flow improvement and symptom relieve. Although there is no consensus on whether bilateral surgical intervention is mandatory for patient with bilateral MMD, unilateral bypass might be sufficient enough. Further study is required to evaluate the best approach for such group of patient.

Progress on Complications of Direct Bypass for Moyamoya Disease

Moyamoya disease (MMD) involves progressive occlusion of the intracranial internal carotid artery resulting in formation of moyamoya-like vessels at the base of the brain. It can be characterized by hemorrhage or ischemia. Direct vascular bypass is the main and most effective treatment of MMD. However, patients with MMD differ from those with normal cerebral vessels. MMD patients have unstable intracranial artery hemodynamics and a poor blood flow reserve; therefore, during the direct bypass of superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis, perioperative risk factors and anesthesia can affect the hemodynamics of these patients. When brain tissue cannot tolerate a high blood flow rate, it becomes prone to hyperperfusion syndrome, which leads to neurological function defects and can even cause intracranial hemorrhage in severe cases. The brain tissue is prone to infarction when hemodynamic equilibrium is affected. In addition, bypass vessels become susceptible to occlusion or atrophy when blood resistance increases. Even compression of the temporalis affects bypass vessels. Because the STA is used in MMD surgery, the scalp becomes ischemic and is likely to develop necrosis and infection. These complications of MMD surgery are difficult to manage and are not well understood. To date, no systematic studies of the complications that occur after direct bypass in MMD have been performed, and reported complications are hidden among various case studies; therefore, this paper presents a review and summary of the literature in PubMed on the complications of direct bypass in MMD.