Preoperative Single-photon Emission Computed Tomography Research Articles

Monitoring of regional cerebral oxygenation by near-infrared spectroscopy in carotid arterial stenting: preliminary study

In carotid arterial stenting (CAS), ischemic complications and cerebral hyperperfusion are recognized as devastating complications. To detect these complications in early stages, we assessed the feasibility for real-time measurement of regional oxygen saturation (rSO2) of the brain in 24 patients with symptomatic extracranial carotid artery stenosis in CAS. The rSO2 changes were easy to evaluate and significantly correlated with the ischemic neurological symptoms as well as postoperative hyperperfusion detected by single-photon emission computed tomography (SPECT). Moreover, the pattern of changes in rSO2 was significantly correlated with the asymmetry index and the cerebral vasoreactivity examined by preoperative SPECT. Therefore, simultaneous monitoring of rSO2 is feasible in detecting early hemodynamic complications in CAS.

Improvement of Myocardial Stress Perfusion After Off-Pump Revascularization Using Bilateral Internal Thoracic In Situ Grafts Versus Y-Composite Grafts

There is a concern that revascularization using bilateral internal thoracic arteries (ITA) as a composite graft may not supply sufficient blood flow to a wider area of myocardium when compared with grafting using bilateral in situ ITAs. One-hundred three patients who underwent off-pump coronary artery bypass using bilateral ITAs for revascularization of the left coronary system were studied prospectively. Bilateral ITAs were used as in situ grafts in 49 patients (group 1) and as a Y-composite graft in 54 patients (group 2). Resting and stress myocardial single-photon emission computed tomography (SPECT) was performed preoperatively and 3 months postoperatively. Myocardial perfusion was automatically quantified and expressed as a percentage of the maximal uptake. The left coronary territory was divided into 16 segments. A total of 379 segments (154 segments in group 1; 225 segments in group 2) that indicated decreased stress perfusion preoperatively were included in this study. Resting myocardial perfusion revealed no significant differences with regard to both the preoperative (77.5 +/- 9.3% vs 78.8 +/- 8.8%) and postoperative SPECT (78.3 +/- 10.0% vs 77.2 +/- 10.5%) between groups 1 and 2 (p = not significant [NS]). However, stress myocardial perfusion was significantly lower in group 1 preoperatively (62.5 +/- 10.8% vs 65.4 +/- 10.1%, p < 0.01). Although it improved postoperatively, there were no differences regarding postoperative stress myocardial perfusion between the two groups (75.5 +/- 11.3% vs 75.0 +/- 11.7%; p = NS). The degree of improvement regarding stress myocardial perfusion (difference between the preoperative and postoperative values) was higher in group 1 than in group 2 (13.0 +/- 9.4% vs 9.6 +/- 10.0%, p < 0.005). Myocardial SPECT demonstrated that revascularization using bilateral in situ ITAs exhibited a greater level of improvement with regard to stress perfusion postoperatively compared with Y-composite grafts. However, because there was no considerable difference with regard to postoperative stress perfusion between the two groups, revascularization using a Y-composite graft might also be sufficient for revascularization of the left coronary territory.

Effect of calcium channel blockers on the sensitivity of preoperative 99mTc-MIBI SPECT for hyperparathyroidism

Technetium 99m ( 99m Tc)-methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) is frequently used in the evaluation of patients with hyperparathyroidism. Calcium channel blockers (CACBs) may affect 99m Tc-MIBI uptake by parathyroid cells. This study examines the effect of CACB therapy on the sensitivity of 99m Tc-MIBI SPECT localization for hyperparathyroidism. Two hundred fifty-three operated patients with hyperparathyroidism were retrospectively reviewed. The potential effect of CACB therapy on 99m Tc-MIBI scan sensitivity was examined by using logistic regression analysis. Possible confounding factors were considered. Among 235 patients, those with multiple endocrine neoplasia, type I (MEN-I), MEN-IIA, 4-gland hyperplasia, secondary hyperparathyroidism, and tertiary hyperparathyroidism exhibited no difference associated with CACB use. Of the remaining 198 patients with primary hyperparathyroidism, 7/30 (23%) with negative 99m Tc-MIBI SPECT scans compared to 24/168 (14%) with positive scans used CACBs. After correcting for age, gender and gland weight, the odds ratio (OR) for a negative study in patients taking CACBs was 2.88 (95% CI, 1.03-8.10; P = .045). Atherosclerosis, hypertension, diabetes mellitus, preoperative calcium and parathyroid hormone levels, and thyroid hormone use were not confounding factors. CACB therapy reduces the sensitivity of 99m Tc-MIBI parathyroid SPECT in patients with primary hyperparathyroidism. Further studies are required to determine the potential reversibility of this effect with termination of CACB therapy.

Radio-guided brain tumorectomy using a gamma detecting probe and a mobile solid-state gamma camera

Background We herein report a technique to distinguish brain tumors from normal brain tissue during surgery using a gamma probe and a solid-state mobile gamma camera after 99mTc-hexakis-2-methoxy-isobutyl-isonitrile ( 99mTc-MIBI) is administered to patients immediately before operation. Methods We examined 13 patients with brain tumors. Before the operation, 99mTc-MIBI single photon emission computed tomography (SPECT) was performed to assess accumulation in the tumors. On the day of the operation, 99mTc-MIBI was administered intravenously and craniotomy for tumor resection was performed. During the operation, the tumor was localized with a gamma probe and preremoval scintigraphy images were taken with a mobile gamma camera. After tumor resection was completed, residual tumors were confirmed using it again. We compared accumulation found in the preoperative SPECT images and intraoperative scintigraphy images, performed a histologic examination of adjacent tissues, and measured the dose the personnel was exposed to per operation. Results In all patients, tumors were confirmed by a gamma probe and scintigraphy during the operation. Intraoperative accumulation in tumors was significantly related to accumulation found in the preoperative 99mTc-MIBI SPECT images. In 9 out of 13 patients, accumulation disappeared in the postremoval scintigraphy images, and no tumor tissue was found by histologic examination. Residual tumor tissue was found in 4 patients. Average exposure of the personnel per operation was 22.9 ± 4.0 μSv. Conclusion Resection of brain tumors with a gamma probe and a mobile gamma camera was very useful since the area to be removed was easily identified and residual tumors could be detected.

逆行性脳表静脈流出路を有する硬膜動静脈ろうのＭＲＩ／ＳＰＥＣＴ所見の検討

We studied retrograde leptomeningeal venous drainage (RLVD) in 20 patients with dural arteriovenous fistulas (DAVFs) with special reference to symptoms, findings of magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) and treatment results. In 11 patients there was an accessory route in the RLVD route that was angiographic evidence into the other sinus as well as the involved sinus. There were no hyperintensity areas on T2-weighted MRI. The 9 other patients did not have the accessory route. T2-weighted MRI revealed hyperintensity areas on the involved side of the brain in these patients. In 5 of the 9 patients, the hyperintense areas disappeared and symptoms improved after treatment. Their pre-operative SPECT study demonstrated hypoperfusion in these areas, and vasoreactivity to Diamox was preserved. In the 4 other patients the abnormal hyperintensity areas persisted and the symptoms persisted after treatment. Their pre-operative SPECT study had shown hypoperfusion, and there was no Diamox vasoreactivity. In DAVFs patients with no accessory route in the RLVD we consistently observed hyperintensity areas on MRI, reflecting venous congestion. The preservation of Diamox vasoreactivity on SPECT study appears to be a good prognostic indicator.

Invited commentary

Invited commentary

Correlation of single photon emission computed tomography with pathology and seizure outcome in children undergoing epilepsy surgery

Introduction: Single photon emission computed tomography (SPECT) imaging regional cerebral blood flow (rCBF) can help localize the seizure focus in partial epilepsies during presurgical evaluation. Few studies have explored the possible relationship between preoperative SPECT and underlying pathology, or any relationship to postsurgical outcome. Study group: Thirty-five children with medically intractable epilepsy undergoing resective surgery between the ages of 11 months and 18 years had presurgical ictal and interictal rCBF and post surgery follow up of 3–6 years. Results: Pathological examination revealed 13 to have hippocampal sclerosis (HS): of these 11 had relatively low interictal rCBF perfusion on the side of seizure onset, and eight had hyperfusion ictally. Eight children had morphological evidence of cortical dysplasia: all had a localizing ictal rCBF concordant with the area resected whereas only six demonstrated localized reduction in perfusion on interictal rCBF. All three patients with Rasmussens encephalitis had informative rCBF scans, concordant with the seizure focus. However, infarct, tumours and nonspecific pathology demonstrated poor localization of the seizure focus. No SPECT parameter correlated independently with outcome, although overall the HS group had the best outcome, particularly those with localizing ictal SPECT. Comment: Ictal SPECT appears predictive of underlying cortical dysplasia. Although in this small group of HS in children, ictal SPECT added little to interictal SPECT for seizure localization, it may be useful in the prediction of outcome. SPECT adds little to the evaluation of children being considered for hemispherectomy over and above the abnormalities detectable on MRI scan.

Quantitative evaluation of cerebral metabolites and cerebral blood flow in patients with carotid stenosis

We examined the metabolic and hemodynamic status of patients with severe carotid stenosis and evaluated the effectiveness of carotid endarterectomy (CEA) by comparing pre- and post-operative results of quantitative proton magnetic resonance spectroscopy (1H-MRS) and single-photon emission computed tomography (SPECT). Quantitative 1H-MRS and SPECT were performed in 17 patients with severe carotid stenosis before CEA; in 10 patients the examinations were repeated after CEA. There was a significant correlation between the degree of internal carotid artery (ICA) stenosis and the N-acetyl-aspartate (NAA) concentration, and between CBF and NAA in the basal ganglia. In 10 of the 17 patients (58.8%) we noted a decrease of NAA on 1H-MRS. After CEA in these patients, NAA was significantly increased, and in 7 of 8 patients whose pre-operative SPECT had indicated impairment of cerebral vasoreactivity, it was improved. Quantitative 1H-MRS and CBF measurements can indicate the severity of metabolic and hemodynamic impairment in patients with severe carotid stenosis, and can help to assess the effectiveness of CEA. [Neurol Res 2001; 23: 573-580]

Dual phase 99m-technetium Sestamibi imaging with single photon emission computed tomography in primary hyperparathyroidism: influence on surgery.

The purposes of this study were to determine the positive and negative predictive values of 99m Technetium (99mTc) Sestamibi dual phase imaging with single photon emission computed tomography (SPECT) for parathyroid adenomata or hyperplasia and the effect of preoperative localization on duration of surgery. We reviewed 33 adults (14 men, 19 women; mean age 53 years) with newly diagnosed primary hyperparathyroidism who underwent neck exploration. The duration of surgery for this cohort was compared with a group of historical controls (n = 53) who underwent surgery without preoperative SPECT. At surgery, there were 21 adenomata (including one carcinoma), 10 patients with hyperplasia and two with no pathology detected. The positive predictive values (PPV) for adenomata and hyperplasia were 95% and 100%, respectively. The negative predictive values (NPV) for these entities were 67% and 22%, respectively. The mean weight of adenomata detected was 3.4 g (range 0.2-17 g). Mean duration of surgery was 112.6 min as compared with 113 min in the historical controls (P = not significant). We conclude that 99mTc Sestamibi dual phase imaging with SPECT has an excellent PPV for parathyroid adenomata and hyperplasia, but does not contribute to reduced duration of surgery in patients undergoing neck exploration for the first time. The NPV is low, suggesting that a negative result does not exclude an adenoma or hyperplasia.

Can persisting detrusor hyperreflexia be predicted after transurethral prostatectomy for benign prostatic hypertrophy?

Detrusor hyperreflexia (DH) is frequently found in patients with benign prostatic hypertrophy (BPH) and persists in 30-50% of patients after successful removal of bladder neck obstruction by transurethral prostatectomy (TUR-P) or surgical enucleation of the prostate. It would be beneficial for surgeons to be able to identify patients who are at risk of persistent post-operative urinary irritation symptoms and DH. Twenty-three patients who showed DH pre-operatively were included in this study. Of these 23 patients, four had neurogenic bladder because of previous cerebrovascular disease. The other 19 patients were considered to have DH because of BPH. These 19 patients were classified according to their cystometry chart patterns. Pattern 1 was the continual sporadic onset and offset of DH, pattern 2 was a single episode of DH at a bladder volume of <160 mL, and pattern 3 was a single DH episode at a bladder volume >160 mL. Preoperative single-photon emission computed tomography (SPECT) was performed on 14 patients. Cystometric findings at 3 to 6 months after surgery were compared with the pre-operative findings. Four of the six patients with pattern 2 (67%) and all patients with pattern 3 (100%) showed an absence of DH after surgery. In contrast, all five patients with pattern 1 and all four patients with neurogenic bladder showed persistent DH. Compared with pattern 3 patients, pattern 1 patients more frequently complained of urgency before surgery, and their symptoms and uroflowmetry parameters did not improve afterward. Among 14 patients who had pre-operative SPECT, all eight patients with low cerebral blood flow in the frontal region showed persisting DH. Conversely, all six patients with normal SPECT results showed no DH after surgery. When DH occurs repeatedly (pattern 1) or occurs at a bladder volume of <160 mL (pattern 2), there is a greater risk of post-operative irritation symptoms. Abnormal SPECT findings can also predict the post-operative persistence of DH. Combing these two pre-operative examinations allows us to predict better post-operative DH in patients with BPH.

Brain SPECT imaging and neuropsychological testing in coronary artery bypass patients

Background. Cognitive deficits appear frequently after cardiac operation. While the etiology remains unclear, alterations in cerebral perfusion during cardiopulmonary bypass may be causative. Single photon emission computed tomography (SPECT) scanning utilizes a radiopharmaceutical to provide images of cerebral perfusion. We proposed to study the cerebral circulation of patients during coronary artery bypass operation employing cardiopulmonary bypass.Methods. Thirty-five neurologically normal patients underwent preoperative SPECT brain scanning and neuropsychological testing. A second SPECT brain perfusion scan was obtained by administering the radioisotope during cardiopulmonary bypass, with subsequent scanning upon completion of the procedure. Postoperative neuropsychological testing was performed prior to discharge.Results. Fourteen (40%) of patients demonstrated significant neuropsychological decline. Patients who suffered cognitive impairment were no different in demographic, general health, or surgical variables. Patients who demonstrated neuropsychological decline had significantly poorer cerebral perfusion both at baseline and during operation.Conclusions. Impaired cerebral perfusion at baseline may identify patients at risk for cognitive injury after cardiac operation. Alterations in cerebral perfusion during cardiopulmonary bypass is common, and may be a factor in neuropsychological deficits seen after cardiac operation.

The value of acetazolamide single photon emission computed tomography scans in the preoperative evaluation of asymptomatic critical carotid stenosis

Purpose: Acetazolamide (ACZ)-enhanced single photon emission computed tomography (SPECT) scans can assess both cerebral perfusion and vascular reactivity. Patients with asymptomatic critical carotid artery stenosis were evaluated for cerebral vascular reactivity to determine the effect of extracranial occlusive disease and the effect of carotid endarterectomy (CEA) on intracerebral reactivity. Methods: In 44 patients with asymptomatic critical carotid artery stenosis, cerebral perfusion and vascular reactivity were assessed before CEA with resting and ACZ-enhanced SPECT scans. All patients had a 70% or greater ipsilateral internal carotid artery stenosis. Preoperative ACZ-enhanced SPECT scans were obtained, usually 5 days before CEA. Postoperative ACZ-enhanced SPECT scans were obtained in 30 patients. Results: Preoperative SPECT scans were asymmetric, revealing focal (n = 19) or global (n = 15) decreased reactivity in 34 patients (77%). Ten patients had symmetric or normal reactivity. After CEA, 23 patients demonstrated an improvement in reactivity ipsilateral to the side of surgery. The remaining seven patients failed to improve after surgery. Conclusion: Although all patients had a high-grade internal carotid stenosis, nearly a quarter of the patients had excellent intracerebral collateral flow. Only 71% of patients demonstrated improved intracerebral vasoreactivity after CEA. The lack of improvement in the other patients may have resulted from intracerebral pathology or lack of improvement in the extracranial carotid hemodynamics. (J Vasc Surg 1999;30:599-605.)

Postoperative Hyperperfusion in Dural Arteriovenous Fistula Associated with Venous Ischemia: Case Report

Background It is well known that carotid endarterectomy and extracranial-intracranial arterial bypass sometimes cause postoperative hyperperfusion, and vasoparalysis attributable to long-standing ischemia has been suggested as the cause. It is also well known that dural arteriovenous fistula (AVF) sometimes causes cerebral ischemia attributable to venous hypertension. However, there are few reports regarding the postoperative changes of regional cerebral blood flow (rCBF). Methods We report a case of dural AVF of the left transverse/sigmoid sinuses, occurring in a 64-year-old man. Intraoperative transvenous embolization combined with transarterial embolization was performed, and the rCBF was measured pre- and postoperatively using 99mTc-hexamethyl-propylene amine oxime and single-photon emission computed tomography (SPECT). Results Preoperative SPECT disclosed a marked rCBF reduction in the left temporal, parietal, and occipital lobes. Complete obliteration of the AVF was attained after the intraoperative transvenous embolization, without any neurological deterioration. However, postoperative SPECT demonstrated temporary hyperperfusion in these regions. Conclusions Sudden resolution of venous ischemia can lead to postoperative hyperperfusion, and pre- and post-treatment rCBF studies are important to prevent complications related to hyperperfusion.

Intraoperative gamma detection reveals abdominal endocrine tumors more efficiently than somatostatin receptor scintigraphy

[(111)In]-diethylenetriamine pentaacetic acid (DTPA)-D-[Phe1]-octreotide (OctreoScan, Mallinckrodt Medical, Petten, The Netherlands), combined with single photon emission computed tomography (SPECT), has limited possibilities to detect small abdominal endocrine tumors. This study explores the efficacy of OctreoScan and a newly developed handheld gamma detector probe (H-probe2) for the localization of neuroendocrine abdominal tumors.Twenty-one patients with endocrine pancreatic or midgut carcinoid tumors were given 100-200 megabecquerels (MBq) [(111)In]-DTPA-D-[Phe1]-octreotide and underwent preoperative SPECT examination, after which time surgery was undertaken within 24-48 hours. Intraoperatively the radioactivity of tumors and normal tissues was measured with the H-probe2 connected to a portable personal computer. Resected intestinal specimens of ten patients with carcinoid tumors were examined by gamma camera ex vivo. Biopsies of all tumors subsequently were investigated in a wellcounter and by routine histopathology.Disregarding liver metastases, a total of 34 of 60 abdominal tumors were detected by SPECT; however, SPECT failed to visualize any tumor < 9 mm. The shielding of the manual probe allowed intraoperative examination despite the substantial radiation energy of (111)In. The H-probe2 detected 91% of the tumors investigated, and these included all those > 5 mm. In the wellcounter the H-probe2-detected tumors exhibited 4.7-157.7 times higher radionuclide uptake than the surrounding normal tissues. The gamma camera analysis detected 68% of tumors in the resected specimens.The intraoperative H-probe2 examination provided substantial improvement in the detection of small endocrine lesions accumulating [(111)In]-DTPA-D-[Phe1]-octreotide and all lesions with a size > 5 mm in greatest dimension could be identified.

Regional cerebral blood flow measured with 99mTc-HMPAO based on two-dimensional 133Xe study in ischemic brain.

Two-dimensional regional cerebral blood flow (rCBF) was measured using the xenon-133 inhalation method, and used to calibrate the rCBF measured by single photon emission computed tomography (SPECT) in the non-affected middle cerebral artery (MCA) area. The value of the rCBF in the target area could then be measured by SPECT and compared between patients. Technetium-99m-d,l-hexamethyl-propylene-amine-oxime and technetium-99m-diethylenetriaminepenta-acetic acid-human serum albumin D were used to measure rCBF and regional cerebral blood volume (rCBV), respectively, in the ischemic area of 16 patients who underwent surgical revascularization in the chronic stage. No significant increase in rCBF was obtained after the bypass surgery. The delta rCBF and delta CBF/CBV ratio correlated well with the extent of vascularization in the MCA area on postoperative angiograms. Patients with a low CBF/CBV ratio on preoperative SPECT scans tended to show favorable postoperative vascularization and rCBF in the MCA area. Since the angiographic findings and the delta rCBF or delta CBF/CBV were correlated well, this simple and non-invasive method could be used for the analysis of rCBF in a group of patients.

Acetazolamide enhanced single photon emission computed tomography (SPECT) evaluation of cerebral perfusion before and after carotid endarterectomy

Twenty-five patients were tested before and after carotid endarterectomy with resting and acetazolamide enhanced single photon emission computed tomography (SPECT) scans with hexamethyl propyleneamine oxine (HMPAO) or iofetamine hydrochloride I123 (123I labeled IMP), both widely available radiopharmaceuticals. Twenty preoperative SPECT studies were asymmetric, revealing focal or diffuse decreased perfusion reserve, and 13 also demonstrated infarcts. Five patients had symmetric (normal) studies.After carotid endarterectomy, 22 cases had changed flow distribution patterns. Usually improvement of reactivity ipsilateral occurred to the area operated on. In four, contralateral improvement was also found. Three of the patients who had preoperative symmetrical scans had increased ipsilateral reactivity after surgery indicating previous global loss of reactivity. Acetazolamide SPECT scans demonstrate a decreased perfusion reserve in 20 patients with carotid artery stenosis, indicating reduced perfusion and poor collateral circulation. Postoperative studies confirm improvement by demonstrating recovery of vascular reactivity in 84% of the patients. Acetazolamide enhanced SPECT scans may be helpful in providing objective evidence for selection of patients for carotid endarterectomy, especially in those who have an 80% carotid artery stenosis, but are asymptomatic.

Value of HM-PAO SPECT in selective temporal lobe surgery for epilepsy

The purpose of this study was to assess the value of interictal 99mTc-hexamethyl-propylenamine oxime (HM-PAO) single-photon emission computed tomography (SPECT) in the preoperative evaluation of epileptic patients with medically refractory seizures of temporal lobe (TL) origin. For this study, we selected 31 patients, who were preoperatively evaluated according to the Zürich presurgical protocol. All patients underwent selective amygdalohippocampectomy. Their surgery was based on ictal and interictal EEG recordings, using scalp and foramen ovale electrodes simultaneously. Postoperatively, 27 patients (87%) were seizure-free or had more than a 90% seizure reduction. All patients had preoperative interictal SPECT and magnetic resonance imaging (MRI) performed. Postoperative SPECT was performed in 18 patients. Preoperative MRI showed structural lesions in 20 cases, and 23 patients had abnormal histopathological findings. Preoperative SPECT determined correctly the primary epileptogenic area in 15 cases (48%), showing a zone of hypoperfusion restricted either to the TL (n = 9; 29%) or exceeding the TL structures (n = 6; 19%). In two patients (6%), the SPECT findings were located contralateral to the affected TL, and in one (3%) there was reduced regional cerebral blood flow in the ipsilateral basal ganglia. Thirteen patients (42%) had normal SPECT. No significant correlations were found among preoperative SPECT findings, MRI and histopathological results, and the postoperative clinical outcome. Based on the results of this study, we regard HM-PAO SPECT to be a useful confirmatory diagnostic tool in presurgical evaluation of epileptic patients. Given the present technological level, it cannot, however, replace the semi-invasive EEG methods.

Syphilis in the Owl Monkey: To the Editor of the British Journal of Venereal Diseases

<h3>Background</h3> The revascularization of carotid stenosis can increase ipsilateral cerebral blood flow (CBF). Occasionally, elevated CBF is also evident on the contralateral side, but this phenomenon is poorly understood. <h3>Objective</h3> To analyze retrospectively the relationship between a contralateral CBF increase and several clinical and radiologic features. <h3>Materials and methods</h3> We retrospectively analyzed 40 patients with unilateral cervical carotid stenosis treated by carotid artery stenting (CAS). Using ¹²³I-iodamphetamine single-photon emission computed tomography (SPECT); we compared pre- and postoperative hemispheric CBF on both sides. We investigated the influence of the following five factors on the increase of the contralateral hemispheric CBF: stenosis grade (≥50% or &lt;50%, according to the North American Symptomatic Carotid Endarterectomy Trial criteria); age; the presence of anterior and posterior communicating arteries; postoperative hyperperfusion on the stenotic side; and the presence of cerebral steal phenomenon during preoperative acetazolamide-challenge SPECT. <h3>Results</h3> Following unilateral CAS, mean hemispheric CBF increased significantly on both sides: from 33.4±5.6 (mean ± SD) to 38.7±7.8 mL/min on the operated side (paired t test, p&lt;0.001) and f35.4±5.4 to 39.2±7.2 mL/min on the contralateral side (p&lt;0.001). In a general linear model, stenosis grade (≥50%) alone was significantly correlated with the increase of the CBF on the contralateral side (p=0.03). <h3>Conclusion</h3> Revascularization by CAS for unilateral carotid stenosis can increase hemispheric CBF on both sides. Increase of the contralateral CBF is correlated with stenosis grade (≥50%).