Procedural blood pressure and contrast extravasation on dual energy computed tomography after endovascular stroke treatment.

BACKGROUND: Blood brain barrier disruption (BBBD) can be visualized by contrast extravasation (CE) after endovascular treatment (EVT) in patients with acute ischemic stroke. Elevated blood pressure is a risk factor for BBBD. However, the association between procedural blood pressure and CE post-EVT is unknown. METHODS: In this single-center retrospective study, we analyzed 501 eligible patients who received a dual energy CT (DECT) immediately post-EVT for acute ischemic stroke. Procedural blood pressure values (SBPmean, SBPmax, SBPmax-min, and MAPmean) were collected. CE was quantified by measuring the maximum parenchymal iodine concentration on DECT iodine overlay map reconstructions. As a measure for the extent of BBBD, we created CE-ASPECTS by deducting one point per hyperdense ASPECTS region on iodine overlay maps. The association between blood pressure and CE was assessed using multivariable linear regression. RESULTS: The procedural SBPmean, SBPmax, and MAPmean were 150 ± 26 mmHg, 173 ± 29 mmHg, and 101 ± 17 mmHg, respectively. The median maximum iodine concentration on post-EVT DECT was 1.2 mg/ml (IQR 0.7-2.0), and median CE-ASPECTS was 8 (IQR 5-11). The maximum iodine concentration was not associated with blood pressure. SBPmean, SBPmax, and MAPmean were significantly associated with CE-ASPECTS (per 10 mmHg, ß = -0.2, 95 % CI -0.31 to -0.09, ß = -0.15, 95 % CI -0.25 to -0.06, ß = -0.33, 95 % CI -0.49 to -0.17, respectively). CONCLUSION: In acute ischemic stroke patients undergoing EVT, particularly in patients achieving successful recanalization, SBPmean, SBPmax, and MAPmean are associated with the extent of BBBD on immediate post-EVT DECT, but not with maximum iodine concentration.

Risk Factors for Contrast Media Extravasation in Intravenous Contrast-Enhanced Computed Tomography: An Observational Cohort Study.

RATIONALE AND OBJECTIVES: To identify the risk factors for contrast media (CM) extravasation and provide effective guidance for reducing its incidence. MATERIALS AND METHODS: We observed adult inpatients (n = 38 281) who underwent intravenous contrast-enhanced computed tomography between January 1, 2018, and December 31, 2022. Risk factors for CM extravasation were evaluated using univariate and multivariate logistic regression. RESULTS: Among the 38 281 inpatients who underwent enhanced computed tomography angiography, 3885 received peripherally inserted central venous catheters (PICCs) and 34 396 received peripheral short catheters. In 3885 cases of PICCs, no CM extravasation occurred, but in five cases, ordinary PICCs that are unable to withstand high pressure were mistakenly used; three of those patients experienced catheter rupture, and eventually, all five patients underwent unplanned extubation. Among 34 396 cases of peripheral short catheters, 224 (0.65%) had CM extravasation. Female sex (odds ratio [OR]=1.541, 95% confidence interval [CI]: 1.111-2.137), diabetes (OR=2.265, 95% CI: 1.549-3.314), venous thrombosis (OR=2.157, 95% CI: 1.039-4.478), multi-site angiography (OR=9.757, CI: 6.803-13.994), and injection rate ≥ 3 mL/s (OR=6.073, 95% CI: 4.349-8.481) were independent risk factors for CM extravasation. Due to peripheral vascular protection measures in patients with malignant tumor, there was a low incidence of CM extravasation (OR=0.394, 95% CI: 0.272-0.570). CONCLUSION: Main risk factors for CM extravasation are female, diabetes, venous thrombosis, multi-site angiography, and injection rate ≥ 3 mL/s. However, patients with malignant tumor have a low incidence of CM extravasation. CLINICAL IMPACT: Analysis of these risk factors can help reduce the incidence of CM extravasation.

Hypotension in the Emergency Department and Contrast Extravasation on Computerized Tomography Predict Blood Transfusion in Low-Energy Pelvic Fractures.

INTRODUCTION: Although low-energy pelvic fractures seldom present with significant hemorrhage, early recognition of at-risk patients is essential. We aimed to identify predictors of transfusion requirements in this cohort. METHODS: A 7-y retrospective chart review was performed. Low-energy mechanism was defined as falls of ≤5 feet. Fracture pattern was classified using the Orthopedic Trauma Association/Arbeitsgemeinschaft für Osteosynthesefragen system as A, B, or C. Primary outcome was transfusion of ≥2 units of packed red blood cells in the first 48 h. Univariable analysis and logistic regression analysis were performed. A P value ≤0.05 was considered significant. RESULTS: Five hundred forty six patients were included with median (interquartile range) age of 86 (79-91) and median (interquartile range) Injury Severity Score of 5 (4-8). Five hundred forty one (99%) had type A fractures. Twenty six (5%) had the primary outcome and 17 (3%) died. Logistic regression found that systolic blood pressure <100 mmHg at any time in the Emergency Department, Injury Severity Score, and pelvic angiography were predictors of the primary outcome. Seventeen percent of those who had the primary outcome died compared with 2% who did not (P = 0.0004). Three hundred sixty four (67%) received intravenous contrast for computerized tomography scans and of these, 44 (12%) had contrast extravasation (CE). CE was associated with the primary outcome but not mortality. CONCLUSIONS: Hypotension at any time in the Emergency Department and CE on computerized tomography predicted transfusion of ≥2 units packed red blood cells in the first 48 h in patients with low-energy pelvic fractures.

CT contrast extravasation in children: a single-center experience and systematic review.

BACKGROUND: Extravasation of iodinated contrast material during computed tomography (CT) is a rare complication. A few patients may develop severe complications such as compartment syndrome. OBJECTIVE: The purpose of this study was to retrospectively assess the prevalence, severity, management, and outcome of contrast extravasations in our institution and to perform a comparison to what has been reported in the existing literature. MATERIALS AND METHODS: This is a research ethics board (REB)-approved retrospective study comprising 11 patients who had intravenous contrast-enhanced CT between 2019 and 2022 in a tertiary pediatric center, and experienced extravasation of iodinated contrast as a complication. Age, weight, sex, co-morbidities, angiocatheter size, venous access location, total contrast volume, flow rate, patient's symptoms, severity of injury, and management were collected. For the systematic review, PRISMA guidelines were followed. RESULTS: Only 11 (0.3%) (0.17-0.54 (95%CI)) contrast extravasations occurred in a total of 3638 CTs performed with intravenous contrast during the same period in children. The median age (IQR) was 12.5 (10.0, 15.0) years. In our cohort, 1/11 patients developed compartment syndrome and required fasciotomy. The systematic review assessed 12 articles representing a population of 110 children with extravasations. Pooled prevalence from articles stratified by age was 0.32% (0.06-0.58% (95%CI)). Only three children experienced moderate to severe complications. CONCLUSIONS: We confirm that severe complications of contrast extravasation are rare and can occur at any age. No strong associations were seen with the need for surgical consultation (including age, sex, weight, flow rate, injection site, catheter size, and type of contrast).

Association of Contrast Extravasation Grade With Massive Transfusion in Pediatric Blunt Liver and Spleen Injuries: A Multicenter Retrospective Cohort Study.

BACKGROUND: This study aimed to assess whether the grade of contrast extravasation (CE) on CT scans was associated with massive transfusion (MT) requirements in pediatric blunt liver and/or spleen injuries (BLSI). METHODS: This multicenter retrospective cohort study included pediatric patients (≤16 years old) who sustained BLSI between 2008 and 2019. MT was defined as transfusion of all blood products ≥40 mL/kg within the first 24 h of admission. Associations between CE and MT requirements were assessed using multivariate logistic regression analysis with cluster-adjusted robust standard errors to calculate the adjusted odds ratio (AOR). RESULTS: A total of 1407 children (median age: 9 years) from 83 institutions were included in the analysis. Overall, 199 patients (14 %) received MT. CT on admission revealed that 54 patients (3.8 %) had CE within the subcapsular hematoma, 100 patients (7.1 %) had intraparenchymal CE, and 86 patients (6.1 %) had CE into the peritoneal cavity among the overall cohort. Multivariate analysis, adjusted for age, sex, age-adjusted shock index, injury severity, and laboratory and imaging factors, showed that intraparenchymal CE and CE into the peritoneal cavity were significantly associated with the need for MT (AOR: 2.50; 95 % CI, 1.50-4.16 and AOR: 4.98; 95 % CI, 2.75-9.02, respectively both p < 0.001). The latter significant association persisted in the subgroup of patients with spleen and liver injuries. CONCLUSION: Active CE into the free peritoneal cavity on admission CT was independently associated with a greater probability of receiving MT in pediatric BLSI. The CE grade may help clinicians plan blood transfusion strategies. LEVEL OF EVIDENCE: Level 4; Therapeutic/Care management.

Crucial factors for implementing treatment strategies in intractable atonic postpartum haemorrhage: early phase contrast medium extravasation on dynamic CT.

AIM: To identify the relationship between contrast medium extravasation (CME) on dynamic contrast-enhanced computed tomography (DCT) and clinical information in intractable atonic postpartum haemorrhage (PPH) and its relevance to treatment with uterine artery embolisation (UAE). MATERIALS AND METHODS: Of 90 patients who underwent DCT to diagnose PPH, 60 diagnosed with intractable atonic PPH were investigated retrospectively. Maternal background and clinical indicators were analysed to compare the positive and negative factors of early phase CME. Regression analysis was used to investigate the factors associated with CME. The sensitivity, specificity, and positive and negative predictive values of early phase CME for predicting UAE were calculated. Clinical outcomes were compared between the two groups according to the timing of the decision to undergo UAE. RESULTS: Of the 60 patients with intractable atonic PPH, 21 underwent UAE, 20 of whom had early phase CME on DCT. Pre-DCT clinical parameters and clinical indices were not significantly different in presence of early phase CME. Early phase CME was associated with UAE performance, with a sensitivity of 95%, specificity of 87%, positive predictive value of 80%, and negative predictive value of 97%. In cases where UAE was performed after conservative management, there was a significant increase in blood loss and transfusion volume. CONCLUSION: Early phase CME is not indicated by background factors or clinical findings. UAE is not required when CME cannot be detected in the uterine cavity. If early phase CME is present, UAE should be considered immediately.

Pelvic ring fractures with concomitant large hematomas: diagnostic investigation with arteriography and eventual embolization in 157 trauma patients, with or without contrast extravasation at emergency CT.

PURPOSE: This study aims to evaluate the diagnostic value of pelvic arteriography in patients with pelvic ring fractures and associated large hematomas, in both cases of positive or negative findings of contrast agent extravasation at emergency CT; in those patients with positive DSA subsequently treated with embolization, correlations with clinical-radiological parameters were investigated. MATERIALS AND METHODS: In this single-center retrospective study, patients with acute blunt pelvic trauma showing at CT pelvic ring fractures with associated large (> 3 cm) hematoma, with or without signs of arterial bleeding, were investigated with DSA. Technical success was considered radiographic bleeding control with disappearance of angiographic bleeding; clinical success was defined as clinical bleeding control hemodynamically stable, before applying other surgical maneuvers. Pelvic ring fractures were evaluated according to Tile classification system. RESULTS: One hundred and fifty-seven patients, mean age 54years, were analyzed. 70.7% had polytrauma; 14.6% patients assumed antiplatelets and/or anticoagulation therapy. False-negative and false-positive rates at CT were 29.6% and 27.1%, respectively. Polytrauma and B3/C1 Tile pattern fractures were significantly associated with bleeding signs at DSA. Seventy-two patients required embolization: 52.8% showed direct signs of DSA bleeding; among these, technical and clinical successes were 88.8% and 81.9%, respectively. CONCLUSIONS: In this study, patients with pelvic ring fractures and concomitant hematomas > 3 cm, with or without contrast extravasation at CT, have been examined in depth with DSA focusing on both direct and indirect angiographic signs of bleeding, finding polytrauma and Tile fracture patterns B3/C1 predictive factors for arterial hemorrhage detection at DSA despite negative CT findings.

Early post-endovascular treatment contrast extravasation on dual-energy CT is associated with clinical and radiological stroke outcomes: A 10-year single-centre experience.

OBJECTIVE: To determine the association between early post-endovascular treatment (EVT) contrast extravasation (CE) on dual-energy CT (DECT) and stroke outcomes. METHODS: EVT records in 2010-2019 were screened. Exclusion criteria included the occurrence of immediate post-procedural intracranial haemorrhage (ICH). Hyperdense areas on iodine overlay maps were scored according to the Alberta Stroke Programme Early CT Score (ASPECTS), thus forming a CE-ASPECTS. Maximum parenchymal iodine concentration and maximum iodine concentration relative to the torcula were recorded. Follow-up imaging was reviewed for ICH. The primary outcome measure was the modified Rankin Scale (mRS) at 90 days. RESULTS: Out of 651 records, 402 patients were included. CE was found in 318 patients (79%). Thirty-five patients developed ICH on follow-up imaging. Fourteen ICHs were symptomatic. Stroke progression occurred in 59 patients. Multivariable regression showed a significant association between decreasing CE-ASPECTS and the mRS at 90 days (adjusted (a)cOR: 1.10, 95% CI: 1.03-1.18), NIHSS at 24-48 h (aß: 0.57, 95% CI: 0.29-0.84), stroke progression (aOR: 1.14, 95% CI: 1.03-1.26) and ICH (aOR: 1.21, 95% CI: 1.06-1.39), but not symptomatic ICH (aOR 1.19, 95% CI: 0.95-1.38). Iodine concentration was significantly associated with the mRS (acOR: 1.18, 95% CI: 1.06-1.32), NIHSS (aß: 0.68, 95% CI: 0.30-1.06), ICH (aOR: 1.37, 95% CI: 1.04-1.81) and symptomatic ICH (aOR: 1.19, 95% CI: 1.02-1.38), but not stroke progression (aOR: 0.99, 95% CI: 0.86-1.15). Results of the analyses with relative iodine concentration were similar and did not improve prediction. CONCLUSIONS: CE-ASPECTS and iodine concentration are both associated with short- and long-term stroke outcomes. CE-ASPECTS is likely a better predictor for stroke progression.

An audit of contrast extravasation in patients undergoing contrast enhanced CTs at radiology department in a tertiary care hospital in Pakistan.

OBJECTIVE: To audit the radiology department of a health facility, focusing on contrast extravasations management pre- and post-implementation of a standard protocol. METHODS: The audit was conducted at the Radiology Department of Shifa International Hospital, Islamabad, Pakistan and comprised reported computed tomography contrast extravasation incidents from January 2017 to December 2019 in the retrospective phase before the implementation of a standard protocol. Post-implementation, re-audit was done prospectively to assess compliance from January 2020 to May 2021. Overall score of >80% was chosen arbitrarily as a qualifying standard for adequate documentation. RESULTS: Of the 49 total cases, 26(53%) related to the first phase and 23(47%) to the second. In the first phase, 2(20%) of the 10 parameters cleared the cut-off mark; 'study performed' 25(96%) and 'limb assessment by technician' 26(100%). In the second phase, 2(20%) parameters failed to clear the cut-off mark; site of cannula/extravasation' 18(78.3%) and 'volume of contrast' 15(65%). CONCLUSIONS: Lack of early identification and appropriate management, especially in cases of large-volume extravasation, may result in significant morbidity.

Angiography in patients with pelvic fractures and contrast extravasation on CT following high-energy trauma.

INTRODUCTION: Pelvic fracture may be accompanied by severe bleeding. Computed tomography (CT) is a gold standard diagnostic tool in stable trauma patients. Contrast extravasation detected on CT of pelvis is a sign of hemorrhage, but its significance is not clear. We aimed to evaluate the need for angiography in patients with pelvic fracture and CT revealed contrast extravasation. We tried to identify parameters that might help to choose patients who will benefit from therapeutic angiography. METHODS: Electronic medical records of patients with pelvic fracture admitted to Level II Trauma Center during 10 years were retrospectively reviewed. Patients who had contrast extravasation on CT were included. Data base consisted of demographics, injury severity, initial physiologic parameters, laboratory data, results of CT and angiography. RESULTS: Forty out of 396 patients had contrast extravasation detected by CT. Twelve patients underwent angiography and 4 of them benefited from embolization. The sensitivity of contrast extravasation in evaluating the need for embolization was 1.0 (95% CI 0.398, 1.0), positive predictive value was 0.1 (95% CI 0.028, 0.237), and the negative predictive value was 1.0 (95% CI 0.990, 1.0). CONCLUSION: The role of angiography in stable patients with pelvic fracture and CT identified contrast extravasation remains questionable. Most of these patients are not in need of angioembolization.

Contrast extravasation on computed tomography angiography in patients with hematochezia or melena: Predictive factors and associated outcomes.

PURPOSE: The purpose of this study was to identify variables associated with extravasation on computed tomography angiography (CTA) in patients with hematochezia/melena and compare the outcome of patients with extravasation on CTA to those without extravasation. MATERIAL AND METHODS: Ninety-four patients (51 men, 43 women; mean age, 69 ± 16 [SD] years) who underwent CTA within 30 days of hematochezia/melena were included. Variables associated with extravasation on CTA were searched using univariable and multivariable analyses. Outcomes of patients with visible extravasation on CTA were compared with those without visible extravasation. RESULTS: One hundred and one CTA examinations were included. Extravasation was observed on 26/101 CTA examinations (26%). At multivariable analysis the need for vasopressor drugs (odds ratio [OR], 7.6; P = 0.040), high transfusion requirements (> 2 blood units) (OR, 7.1; P = 0.014), CTA performed on the day of a hemorrhagic event (OR, 46.2; P = 0.005) and repeat CTA (OR, 27.8; P = 0.011) were independently associated with extravasation on CTA. Extravasation on CTA was followed by a therapeutic procedure in 25/26 CTAs (96%; 26 patients) compared to 13/75 CTAs (17%; 68 patients) on which no extravasation was present (P < 0.001). No patients (0/26; 0%) with contrast extravasation on CTA died while 8 patients (8/61; 13%) without contrast extravasation died, although the difference was not significant (P = 0.099). CONCLUSION: Extravasation on CTA in the setting of hematochezia or melena is especially seen in clinically unstable patients who receive more than two blood units. Presence of active extravasation on CTA leads to more frequent application of a therapeutic procedure; however, this does not significantly affect patient outcome.

Clinical Significance of Hyperdense Lesions on Non-enhanced Brain CT Obtained Immediately after Arterial Revascularization in Acute Ischemic Stroke Patients.

PURPOSE: To analyze the characteristics of hyperdense lesions on brain CT conducted immediately after arterial revascularization (AR) in patients with acute ischemic stroke (AIS), track the outcome of those lesions and investigate their clinical significance. MATERIALS AND METHODS: 97 AIS patients were enrolled in our study. Among them, 52 patients showed hyperdense lesions and were divided into three categories: type I, type II and type III according to the morphologic characteristics of hyperdense lesions. All patients underwent several follow-up CT/MR examinations to visualize the outcomes of the lesions. RESULTS: Among the 52 patients, 22 showed contrast extravasation, 23 displayed contrast extravasation combined with hemorrhagic transformation (HT) and 7 confirmed symptomatic intracranial hemorrhage (SICH) in follow-up CT/MR. Among the without hyperdense lesions group, only 7 converted to hemorrhage, and no SICH occurred. All type I lesions showed contrast extravasation; 23 type II lesions turned to hemorrhage, 2 revealed SICH and 6 were pure contrast extravasation; all of the type III developed into SICH. CONCLUSION: Hyperdense lesions on non-enhanced brain CT obtained immediately after arterial revascularization (AR) exhibited varying features. Type I indicated a pure contrast extravasation. Type II and type III hyperdense lesions suggested higher incidence of HT, the presence of type III lesions indicated an ominous outcome.

Optical tissue clearing and machine learning can precisely characterize extravasation and blood vessel architecture in brain tumors.

Precise methods for quantifying drug accumulation in brain tissue are currently very limited, challenging the development of new therapeutics for brain disorders. Transcardial perfusion is instrumental for removing the intravascular fraction of an injected compound, thereby allowing for ex vivo assessment of extravasation into the brain. However, pathological remodeling of tissue microenvironment can affect the efficiency of transcardial perfusion, which has been largely overlooked. We show that, in contrast to healthy vasculature, transcardial perfusion cannot remove an injected compound from the tumor vasculature to a sufficient extent leading to considerable overestimation of compound extravasation. We demonstrate that 3D deep imaging of optically cleared tumor samples overcomes this limitation. We developed two machine learning-based semi-automated image analysis workflows, which provide detailed quantitative characterization of compound extravasation patterns as well as tumor angioarchitecture in large three-dimensional datasets from optically cleared samples. This methodology provides a precise and comprehensive analysis of extravasation in brain tumors and allows for correlation of extravasation patterns with specific features of the heterogeneous brain tumor vasculature.

Intraperitoneal Barium From Gastrointestinal Perforations: Reassessment of the Prognosis and Long-Term Effects.

OBJECTIVE. The purpose of this study was to reassess the outcome and potential consequences of intraperitoneal barium leakage during radiologic evaluation of the gastrointestinal tract. MATERIALS AND METHODS. This retrospective study included 18 patients who had significant intraperitoneal leakage of barium from gastrointestinal perforations that were not suspected or diagnosed before the radiologic procedures. This complication occurred during a barium enema examination in nine patients, an upper gastrointestinal study in seven, and a small bowel series in two patients. All patients underwent urgent laparotomy for repair of perforation, with vigorous peritoneal lavage and antibiotic therapy. RESULTS. All patients had an uneventful recovery and were followed for 4-17 years (mean, 8.5 years). Radiographs obtained during this interval showed that a significant amount of residual barium was retained in the abdominal cavity. Six patients had a total of 10 subsequent abdominal operations for unrelated conditions, and some had developed barium granulomas and peritoneal adhesions. However, none of the patients in this series experienced intestinal obstruction or any clinical symptoms related to barium deposits in the abdominal cavity. CONCLUSION. Intraperitoneal leakage of barium is a rare complication of radiologic gastrointestinal examinations, and this series of 18 cases reflects 3 decades of experience at two major medical centers. The presented data indicate that the commonly held and perpetuated concept about the high rate of morbidity and mortality of this complication would not be valid in the modern era of medical and surgical management.

The feasibility of dual-energy CT to predict the probability of symptomatic intracerebral haemorrhage after successful mechanical thrombectomy.

AIM: To study the ability of dual-energy computed tomography (DECT) after successful mechanical thrombectomy (MT) to predict symptomatic intracerebral haemorrhage (sICH) in anterior circulation acute ischaemic stroke (AIS). MATERIALS AND METHODS: From June 2018 to February 2020, 102 AIS patients with DECT performed immediately after successful MT were enrolled prospectively. According to the presence of iodine contrast media extravasation (ICME) on DECT and subsequent sICH development, patients were classified into four groups. The neurological outcome was compared among groups. Imaging parameters, together with clinical factors, were investigated for sICH prediction based on a linear logistic regression model after class-imbalance resolved by Synthetic Minority Sampling Technique (SMOTE) method. RESULTS: Among 102 patients, patients (14.7%, 15/102) with the presence of sICH experienced worse outcomes than others without sICH (p<0.001). No case without ICME was observed with sICH development (0/102). The parameters derived from DECT have excellent performance for sICH prediction after successful MT, which is better than clinical predictive model boosted data (area under the curve [AUC]: DECT 0.87 versus clinical prediction 0.65), cross-validation results (AUC: DECT 0.87 versus clinical prediction 0.65), and original data (AUC: DECT 0.85 versus clinical prediction 0.68). By combining clinical and radiological parameters, the predictive performance for sICH could be further improved with an AUC of 0.90 (95% CI: 0.85-0.96). CONCLUSIONS: Based on DECT parameters acquired immediately after successful MT, the present model was more efficient than the clinical model for accurate prediction of sICH. Rho and ICME volume appeared to be the best parameters for predicting sICH using DECT.

Case series of fluoroscopic findings and 3D reconstruction of human spinal MRIs of the space of Okada.

OBJECTIVE: To better understand the unexpected spread of contrast medium observed by conventional fluoroscopic X-ray images during standard neuraxial techniques used in the treatment of pain. The support of 3D reconstruction of MRI images of structures within the lumbar spine was used to better understand the space of Okada. METHODS: Lumbar facet joint and epidural corticosteroid injections in five patients under fluoroscopic guidance with loss of resistance to air or saline to identify the facet joints or epidural space. Next, in a retrospective study, the authors examined the retrodural space of Okada and the neighboring tissues with 3D reconstruction of spinal MRIs of seven patients without any demonstrable spinal pathology to better understand the characteristics of the space of Okada. RESULTS: Contrast medium spread to the ipsilateral and contralateral sides was observed in five patients. The contralateral spread was thought to be through the retrodural space of Okada, which is a potential space between the anterior surface of the vertebral lamina and the posterior surface of the ligamentum flavum. It facilitates communication between the contralateral articular facet joints of the spine. CONCLUSIONS: This study provides new evidence for the existence of the space of Okada where an unexpected contralateral spread occurred following facet joint and attempted epidural injection. The 3D reconstructions of MRIs may help us better understand the nature of the retrodural space of Okada and its clinical implications.