Superficial temporal artery duplex ultrasonography for improved cerebral hemodynamics after extracranial-intracranial bypass surgery

Pulsatility index of superficial temporal artery was associated with cerebral infarction after direct bypass surgery for moyamoya disease

OBJECTIVE

Direct bypass surgery by superficial temporal artery (STA) - middle cerebral artery anastomosis is an established procedure for moyamoya disease (MMD). However, some patients may develop cerebral infarction (CI) due to the watershed shift phenomenon after the surgery. This study sought to investigate the correlation between the postoperative changes of STA flow as well as cerebral blood flow (CBF) and the incidence of CI after direct bypass surgery for MMD.

METHODS

We conducted a retrospective study of 62 hemispheres in 50 subjects who underwent direct bypass surgery for MMD. All subjects underwent pre- and post-operative MR imaging, ultrasound evaluation of STA, and single-photon emission computed tomography. The presence of CI was correlated with preoperative CBF, the delta difference of each value of the STA between before and after the surgery, and the postoperative increase ratio of CBF.

RESULTS

All bypass procedures were patent, and CI was observed in 4 cases (6.4%). There was no significant association between the incidence of CI and both pre- and post-operative CBF. However, there was a significant difference in delta pulsatility index (PI) of the STA between cases with or without CI (-0.38±0.22 and -0.87±0.63, respectively, p=0.03). Whereas, other factors did not show any significant differences between those with or without CI.

CONCLUSIONS

A relatively high postoperative PI of the STA was significantly associated with the incidence of CI after direct bypass surgery for MMD. A larger study is needed to confirm these findings.

Is STA really a low‐flow graft? A quantitative ultrasonographic study of the flow of STA for cerebral revascularization in MMD patients

OBJECTIVE

Direct revascularization remains an important tool in the treatment of patients with Moyamoya disease (MMD). The superficial temporal artery (STA) is the most commonly used donor vessel for direct bypass, and an STA graft has traditionally been considered a low-flow graft for flow augmentation. This study aimed to quantitatively evaluate the blood flow of the STA after direct revascularization.

METHODS

All direct revascularization procedures performed between 2018 and 2021 by one experienced neurosurgeon were screened. Quantitative ultrasound was used to measure the flow data of the patient's bilateral parietal branch of the STA(STA-PB), the bilateral frontal branch of the STA(STA-FB), and the left radial artery. Data on the patients' basic information, Suzuki grade, Matsushima type, anastomosis type, and blood biochemical parameters were collected and analyzed using univariate and multivariate models. An MBC Scale scoring system was proposed to evaluate the recipient artery network of the middle cerebral artery (MCA) tree. The relationship between MBC Scale score and STA graft flow was statistically analyzed.

RESULTS

In total, 81 patients (43 males and 38 females) successfully underwent STA-MCA bypass and were included in this study. The mean flow rates in the STA-PB graft on 1 day preoperatively, 1 day postoperatively, 7 days postoperatively, and >6 months postoperatively (long-term) were 10.81, 116.74, 118.44, and 56.20 mL/min respectively. Intraoperative graft patency was confirmed in all patients. Comparing the preoperative and all postoperative time points, the STA-PB flow rates were statistically significant (p < 0.001). The MCA-C score was significantly associated with postoperative flow rate on day 1 (p = 0.007).

CONCLUSION

The STA is a useful donor artery for direct revascularization inpatients with MMD and can provide sufficient blood supply to the ischemic cerebral territory.

Clinical use of color Doppler ultrasonography to predict and evaluate the collateral development of two common revascularizations in patients with moyamoya disease

Objective

To explore the value of color Doppler ultrasonography (CDU) to predict preoperatively and evaluate postoperatively the collateral development of two common revascularizations in patients with moyamoya disease (MMD).

Methods

We prospectively enrolled 49 patients with MMD who underwent unilateral superficial temporal artery (STA) -middle cerebral artery (MCA) anastomosis or encephalo-duro-arterio-synangiosis (EDAS). The parameters of the extracranial arteries, including STA, internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA), were performed before and at 3–6 months after surgery. DSA results were used to assess surgical collateral development.

Results

To predict good collateral development before STA-MCA anastomosis, the preoperative D > 1.75 mm in the STA had the highest area under the Receiver Operating Characteristic curve (AUC). To predict good collateral development before EDAS, the preoperative EDV > 12.00 cm/s in the STA had the highest AUC. To evaluate the good collateral development after STA-MCA anastomosis, the postoperative EDV > 16.50 cm/s in the STA had the highest AUC. To evaluate the good collateral development after EDAS, an increase of D of 0.15 mm in the STA had the highest AUC. Logistic regression analysis showed that the preoperative RI and EDV in the STA were highly correlated with collateral development. Besides, the preoperative RI was an independent risk factor for collateral development.

Conclusion

CDU could predict preoperatively and evaluate postoperatively the collateral development of STA-MCA anastomosis and EDAS surgery postoperatively by detecting ultrasound parameters of the STA.

Non-Invasive Evaluation of Cerebral Hemodynamic Changes After Surgery in Adult Patients With Moyamoya Using 2D Phase-Contrast and Intravoxel Incoherent Motion MRI

Objective

To explore the feasibility of 2D phase-contrast MRI (PC-MRI) and intravoxel incoherent motion (IVIM) MRI to assess cerebrovascular hemodynamic changes after surgery in adult patients with moyamoya disease (MMD).

Methods

In total, 33 patients with MMD who underwent 2D PC-MRI and IVIM examinations before and after surgery were enrolled. Postsurgical changes in peak and average velocities, average flow, forward volume, and the area of superficial temporal (STA), internal carotid (ICA), external carotid (ECA), and vertebral (VA) arteries were evaluated. The microvascular perfusion status was compared between the hemorrhage and non-hemorrhage groups.

Results

The peak velocity, average flow, forward volume, area of both the ipsilateral STA and ECA, and average velocity of the ipsilateral STA were increased (p &lt; 0.05). The average flow and forward volume of both the ipsilateral ICA and VA and the area of the ipsilateral VA were increased (p &lt; 0.05). The peak velocity, average velocity, average flow and forward volume of the contralateral STA, and the area of the contralateral ICA and ECA were also increased (p &lt; 0.05), whereas the area of the contralateral VA was decreased (p &lt; 0.05). The rf value of the ipsilateral anterior cerebral artery (ACA) supply area was increased (p &lt; 0.05) and more obvious in the non-hemorrhage group (p &lt; 0.05).

Conclusion

Two-dimensional PC-MRI and IVIM may have the potential to non-invasively evaluate cerebrovascular hemodynamic changes after surgery in patients with MMD. An improvement in the microvascular perfusion status is more obvious in patients with ischemic MMD than in patients with hemorrhagic MMD.

Factors Influencing Long-Term Blood Flow in Extracranial-to-Intracranial Bypass for Symptomatic Internal Carotid Artery Occlusive Disease: A Quantitative Study

BACKGROUND

Maintaining the patency of extracranial-to-intracranial (EC-IC) bypass is critical for long-term stroke prevention. However, reports on the factors influencing long-term bypass patency and quantitative assessments of bypass patency are limited.

OBJECTIVE

To quantitatively evaluate blood flow in EC-IC bypass using four-dimensional (4D) flow magnetic resonance imaging (MRI) and investigate factors influencing the long-term patency of EC-IC bypass.

METHODS

Thirty-six adult Japanese patients who underwent EC-IC bypass for symptomatic internal carotid or middle cerebral artery occlusive disease were included. We examined the relationships between decreased superficial temporal artery (STA) blood flow volume and perioperative complications, long-term ischemic complications, patient background, and postoperative antithrombotic medications in patients for whom STA flow could be quantitatively assessed for at least 5 months using 4D flow MRI.

RESULTS

The mean follow-up time was 54.7 ± 6.1 months. One patient presented with a stroke during the acute postoperative period that affected postoperative outcomes. No recurrent strokes were recorded during long-term follow-up. Two patients died of malignant disease. Seven cases of reduced flow occurred in the STA, which were correlated with single bypass (P = .0294) and nonuse of cilostazol (P = .0294). STA occlusion was observed in 1 patient during the follow-up period. Hypertension, age, smoking, dyslipidemia, and diabetes mellitus were not correlated with reduced blood flow in the STA.

CONCLUSION

Double anastomoses and cilostazol resulted in long-term STA blood flow preservation. No recurrence of cerebral infarction was noted in either STA hypoperfusion or occlusion cases.

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.

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.

Flow evaluation of STA-MCA bypass using quantitative ultrasonography: An alternative to standard angiography for follow up of bypass graft

PURPOSE

To date, digital subtraction angiography (DSA) has been considered as the gold imaging modality for assessing graft patency after extracranial-intracranial bypass. The utility of a noninvasive and quantitative method of assessing graft flow postoperatively was evaluated by using quantitative ultrasonography.

METHOD

All STA-MCA bypass surgery performed over a 5-year period at a single institution were reviewed. Measured by duplex ultrasonography, pre-operative (day1) and post-operative (day1, day7, 3month and 6 month) graft blood flow rates were recorded and analyzed. Results were correlated to Matsushima grade determined by DSA performed within 24 h when ultrasonography was conducted to confirm the graft function.

RESULTS

100 patients with 131 operated hemispheres were included in this study. The mean flow rates in the STA graft on pre-operative day1, post-operative day 1 and 7, at 3- and 6-month postoperatively were 24.1, 106.7, 112.6, 97.4 and 79.7 ml/min respectively. The mean post-operative flow in the STA graft graded as A/B/C were significantly different (168.0 ± 34.8 ml/min, 91.0 ± 15.5, 42.1 ± 17.2 ml/min, respectively, p = 0.000). 124.5 ml/min and 65.5 ml/min are good cut-off value for predicting post-operative graft Matsushima grade. The analysis also showed excellent agreement between ultrasonography and DSA for assessing bypass function (κ = 0.78).

CONCLUSIONS

The patency of the STA grafts can be assessed noninvasively by quantitative ultrasonography, which results are comparable to those of conventional DSA. This, therefore, suggest that quantitative ultrasonography may be an alternative method to standard DSA for serial follow up of STA grafts.

Time-of-flight MRA signal intensity predicts the cerebral hemodynamic status after superficial temporal artery to middle cerebral artery anastomosis

Arterial signal intensities on magnetic resonance angiography (MRA) correlate with the relevant hemisphere's hemodynamics in patients with cerebrovascular diseases. We evaluated whether superficial temporal artery (STA) signal intensities (SI) on MRA were useful to evaluate the postoperative cerebral hemodynamics of patients with symptomatic internal carotid artery (ICA) or middle cerebral artery (MCA) steno-occlusive disease who underwent unilateral STA-MCA anastomosis. Twenty-one consecutive patients undergoing unilateral STA-MCA anastomosis for symptomatic ICA or MCA steno-occlusive disease were enrolled. All patients underwent MRA and superficial temporal artery duplex ultrasonography (STDU) at 3 months and 1 year postoperatively. Bilateral region of interests (ROIs) on time-of-flight (TOF)-MRA source images were placed on the STA just before its bifurcation. The STA-SI ratio, which was the ratio of the SI on the operated STA to that of the contralateral STA, was calculated; the correlation between the ratio and STDU parameters was investigated. The STA diameter and flow velocities (systolic, end-diastolic, and mean) significantly correlated with the STA-SI ratio at 1 year postoperatively (p = .0302, p = .0002, p = .0029, p = .002). The end-diastolic flow velocity ratio was significantly correlated with the STA-SI ratio at 1 year postoperatively (p = .0014, r = 0.6518). The STA-SI ratio can be used to predict the extent of postoperative collateral bypass flow, and it may help predict postoperative cerebrovascular reserve.

Increased Ratio of Superficial Temporal Artery Flow Rate After Superficial Temporal Artery-to-Middle Cerebral Artery Anastomosis: Can It Reflect the Extent of Collateral Flow?

OBJECTIVE

There are several ways to identify donor artery patency and success of surgery after an anastomosis of the superficial temporal artery (STA) to the middle cerebral artery (MCA). The purpose of this study was to evaluate the ratio of bilateral STA mean flow rate (MFR) with the use of color Doppler ultrasonography (CDUS) after bypass surgery and to confirm the possibility of this value as a predictor of the extent of collateral flow.

METHODS

Eleven consecutive patients who had undergone STA-MCA anastomosis were included. In every case, bilateral STA MFR, mean velocity, and cross-sectional diameter were measured preoperatively and postoperatively at 1 week, 1 month, and 2 months via CDUS. We measured the bilateral STA MFR ratio changes to compensate for systemic hemodynamic variables.

RESULTS

One month after surgery, 9 of the 11 patients who underwent STA-MCA anastomosis had good patency on DSA. In patients with good patency, there was a significant increase in the baseline STA MFR ratio compared with those at 1 week, 1 month, and 2 months postoperatively (2.88, 3.07, and 4.38, respectively, P < 0.05). The mean STA cross-sectional diameter ratio also was significantly increased postoperatively in the good patency group (1.35, 1.41, and 1.49, respectively, P = 0.044). In addition, the mean STA mean velocity ratio was increased postoperatively in the good patency group (1.48, 1.40, and 1.67, respectively, P = 0.042).

CONCLUSIONS

We conclude that using CDUS to measure both STA MFR ratio is a potential method to predict the extent of collateral flow through an STA-MCA anastomosis.

Effect of Adventitial Dissection of Superficial Temporal Artery on the Outcome of Superficial Temporal Artery-Middle Cerebral Artery Bypass in Moyamoya Disease

Superficial temporal artery-middle cerebral artery (STA-MCA) has been used for the treatment of occlusive cerebrovascular disease including moyamoya disease. The effect of STA-MCA bypass depends not only on the patency of anastomosis, but also on integrity and functional capacity of the donor artery. In the present prospective study, we investigated the effect of extensive stripping STA adventitia and fasciae on hemodynamic function in STA-MCA bypass of moyamoya disease patients. Twenty patients (n=8 in control group, n=12 in stripping group) of moyamoya disease were subjected to STA-MCA end-to-side direct anastomosis. Perfusion unit (PU) values of the cortex were measured and recorded using a Laser Doppler flowmetry (LDF) for 5 days. Computed tomography perfusion was performed to determine blood flow before and after bypass. No patient experienced significant neurologic deficits associated with neurosurgical complications. LDF demonstrated that adventitial stripping group had higher cerebral blood flow increase than control group. The adventitia stripping group tends to have higher rate of increased cerebral perfusion after bypass than non-stripping group. Furthermore, the ultrasound examination at 3 days after bypass demonstrated that the adventitial stripping group has a tendency of bigger STA and higher peak systolic velocity than control group. Our result suggests that stripping adventitia of STA improves hemodynamics of STA-MCA bypass in moyamoya disease.

Hemodynamic study with duplex ultrasonography on combined (direct/indirect) revascularization in adult moyamoya disease

BACKGROUND

To evaluate the hemodynamic changes by duplex ultrasonography in adult moyamoya disease (MMD) patients who underwent combined direct and indirect revascularization surgery.

METHODS

Seventeen adult patients underwent direct and indirect revascularization surgery in our hospital. Hemodynamic parameters, peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistance index (RI), were determined by color Doppler at the baseline, 2 weeks, and 6 months after bypass.

RESULTS

Both the PSV and EDV of direct bypass were lower at 6 months after surgery compared with those at 2 weeks postoperatively. The EDV of indirect revascularization surgery of the maxillary artery (MA) at 6 months after surgery was higher and the RI of the MA lower compared with the baseline levels. Decreased PSV and EDV in the bypass vessel did not significantly correlate with increased EDV or decreased RI of the MA.

CONCLUSIONS

Duplex ultrasonography is a reliable, noninvasive tool to assess hemodynamic changes and evaluate the therapeutic performance of combined bypass surgery in adult MMD.

Postoperative changes in the superficial temporal artery and the external carotid artery duplex sonography after extra-intracranial bypass surgery in European Moyamoya disease

INTRODUCTION

Despite Duplex ultrasonography being a noninvasive, easily repeatable, readily available and economical tool, this examination and its normal ranges are rarely described in Moyamoya disease (MMD).

METHODS

Duplex ultrasonography examinations of the superficial temporal artery (STA) and external carotid artery (ECA) were performed preoperatively, postoperatively (within 30 days) and as follow-up exams (6 months postoperatively) after 32 cerebral revascularization procedures in 20 European patients with MMD.

RESULTS

A significant higher mean diastolic flow of STA compared to preoperative values was found in postoperative (p<.000) and follow-up exams (p<.001) in Duplex ultrasonography. Postoperative and follow-up Duplex sonography of STA also showed a significantly higher mean systolic flow compared to preoperative values (p<.05 and p<.05). Also ECA showed significantly changes after bypass surgery (p<.05).

CONCLUSION

Duplex ultrasonography of STA is a reliable and non-invasive tool to investigate hemodynamic changes after bypass surgery and to detect bypass patency in European patients with MMD.

Postoperative evaluation of changes in extracranial-intracranial bypass graft using superficial temporal artery duplex ultrasonography

BACKGROUND AND PURPOSE

Extracranial-intracranial (ECIC) bypass grafts have been assessed postoperatively by various neuroradiologic techniques. The aim of this prospective study was to evaluate postoperative changes in ECIC bypass graft by using superficial temporal artery duplex ultrasonography (STDU). Furthermore, this study assessed the ability of STDU to predict cerebrovascular reserve capacity (CVR).

MATERIALS AND METHODS

Forty-five consecutive patients who underwent ECIC bypass procedure for atherosclerotic internal carotid artery occlusion were enrolled in this prospective study. All patients underwent single-photon emission CT and STDU preoperatively, 14 days after, 3 months after, 1 year after, and 2 years after ECIC bypass.

RESULTS

The diameter and flow velocities of the ipsilateral superficial temporal artery (STA), and regional cerebral blood flow (rCBF) showed increase during the first 2 weeks and then remained stable, whereas CVR showed a constant improvement up to 2 years after surgery. The STA diameter and mean STA flow velocity correlated significantly with CVR at 1 year after surgery (r2 = 0.1232 and r2 = 0.08716, respectively; P < .05). A cutoff value of 1.8 mm STA diameter was determined as the most reliable value to predict CVR greater than 10% at 1 year after surgery. The positive predictive value was calculated as 96.6%, the negative predictive value as 43.8%, the sensitivity as 75.7%, the specificity as 87.5%, and the likelihood ratio as 6.056.

CONCLUSIONS

ECIC bypass grafts can be assessed postoperatively in a noninvasive fashion with STDU. This technique provides information regarding patency as well as quantitative assessment of bypass function. Moreover, STDU is useful to predict CVR improvement.

The efficacy of direct extracranial-intracranial bypass in the treatment of symptomatic hemodynamic failure secondary to athero-occlusive disease: a systematic review

OBJECTIVE

The 1985 International Extracranial-Intracranial (EC-IC) Bypass Trial failed to show a benefit following surgery in patients with varying degrees of angiographic ICA stenosis. More recent studies using modern technology to identify appropriate candidates, however, have generated promising findings. As a result, controversy exists regarding the role of this technique in the treatment of symptomatic athero-occlusive disease. To this end, we performed a systematic review and quantitative analysis of the literature to determine if a subset of patients with symptomatic hemodynamic failure secondary to athero-occlusive disease may benefit from direct EC-IC bypass.

METHODS

We performed a MEDLINE (1985-2007) database search using the following keywords, singly and in combination: EC-IC bypass, hemodynamic failure and misery perfusion. Additional studies were identified manually by scrutinizing references from identified manuscripts, major neurosurgical journals and texts, and personal files. Our literature search divided studies into three categories: natural history of patients with stage I hemodynamic failure (16 studies, 2320 patients), natural history of patients with stage II hemodynamic failure (3 studies 163 patients), and outcomes of patients with hemodynamic failure treated by EC-IC bypass (23 studies 506 patients).

RESULTS

Patients with severe stage I and stage II hemodynamic failure are at higher risk of cerebral infarction than those with mild disease (p=.014, OR 1.17-4.08 and p=0.10, OR 0.89-3.63, respectively). Additionally, patients with severe hemodynamic failure respond better to surgery than those with mild disease (p=0.03, OR 0.16-0.92).

CONCLUSIONS

Patients with severe hemodynamic failure secondary to athero-occlusive disease appear to benefit from direct EC-IC bypass surgery. As a result, the conclusions of the 1985 International EC-IC Bypass Trial may not be applicable to this subset of patients. A randomized clinical trial involving this patient population is warranted.

The extracranial-intracranial bypass trial: implications for future investigations

The 1985 International Extracranial-Intracranial (EC-IC) Bypass Trial failed to show a surgical benefit of EC-IC bypass in patients with varying degrees of angiographic stenosis. This study was limited by the technology available at the time it was conducted. In the 20 years since, there has been considerable progress in imaging techniques that now enable the identification of a subset of stroke patients with hemodynamic ischemia. In the present study, the authors review the relevant literature and propose a reevaluation of the benefits of the EC-IC bypass procedure using these new imaging techniques. The authors reviewed the admission criteria for the EC-IC Bypass Trial in the light of more recently discovered neurovascular physiology and showed that the imaging criteria used in that trial are not physiologically adequate. A MED-LINE (1985-2007) database search for EC-IC case studies was conducted, and additional studies were identified manually by scrutinizing references from identified manuscripts, major neurosurgical journals and texts, and personal files.

Changes in brain volume after EC-IC bypass surgery

We studied changes in brain volume on magnetic resonance imaging in 10 patients with and without EC-IC bypass surgery who met the inclusion criteria for the Japanese EC-IC bypass trial, a multicenter, randomized, double-blind, prospective study of patients with hemodynamic brain ischemia due to cerebral artery occlusive disease. We also examined the association of cerebral hemodynamics on single photon emission computed tomography with the changes in brain volume. As a result, the affected/unaffected ratio of the % brain volume declined in patients without EC-IC bypass surgery (p < 0.02, n = 4), and the affected/unaffected % rCBF ratio increased in patients with the surgery (p < 0.03, n = 6). Acetazolamide reactivity increased in the affected hemisphere of patients with surgery (p < 0.01). And also two-year increase (decrease) in acetazolamide reactivity of the affected hemisphere showed a significant positive correlation with 2-year changes in the affected/unaffected % brain volume ratio (R2 = 0.737, p = 0.0007). Change in acetazolamide reactivity might be a good predictor for brain atrophy in cerebral artery occlusive disease.

Changes in Brain Volume 2 Years after Extracranial-Intracranial Bypass Surgery: A Preliminary Subanalysis of the Japanese EC-IC Trial

BACKGROUND AND METHODS

We studied changes in brain volume on magnetic resonance imaging in 10 patients with and without extracranial-intracranial (EC-IC) bypass surgery who met the inclusion criteria for the Japanese EC-IC Bypass Trial, a multicenter, randomized, prospective study of patients with hemodynamic brain ischemia due to cerebral artery occlusive disease. We also examined the association of cerebral hemodynamics on single-photon emission computed tomography with the changes in brain volume.

RESULTS

The affected/unaffected ratio of the percent brain volume declined in patients without EC-IC bypass surgery (p < 0.02, n = 4), and the affected/unaffected percent regional cerebral blood flow ratio increased in patients with the surgery (p < 0.03, n = 6). Acetazolamide reactivity increased in the affected hemisphere of patients with surgery (p < 0.01). Two-year increase (decrease) in acetazolamide reactivity of the affected hemisphere showed a significant positive correlation with 2-year changes in the affected/unaffected percent brain volume ratio (R2 = 0.737, p = 0.0007).

CONCLUSIONS

Change in acetazolamide reactivity might be a good predictor for brain atrophy in cerebral artery occlusive disease.