Comparative anatomy of dissected optic lobes, optic ventricles, midbrain tectum, collicular ventricles, and aqueduct: evolutionary modifications as potential explanation for non-tumoral aqueductal anomalies in humans.

PURPOSE: An extensive literature has postulated multiple etiologies for aqueductal stenosis. No publications were found, discussing that evolutionary modifications might explain aqueductal anomalies. This study's objectives were to review the evolutionary modifications of vertebrates' tectum structures that might explain human aqueduct anomalies. Undertaking vertebrate comparative study is currently not feasible in view of limitations in obtaining vertebrate material. Thus, vertebrate material collected, injected, dissected, and radiographed in the early 1970s was analyzed, focusing on the aqueduct and components of the midbrain tectum. METHODS: Photographs of brain dissections and radiographs of the cerebral ventricles and arteries of adult shark, frog, iguana, rabbit, cat, dog, and primate specimens, containing a barium-gelatin radiopaque compound, were analyzed focusing on the aqueduct, the optic ventricles, the quadrigeminal plate, and collicular ventricles. The anatomic information provided by the dissections and radiographs is not reproducible by any other radiopaque contrast currently available. RESULTS: Dissected and radiographed cerebral ventricular and arterial systems of the vertebrates demonstrated midbrain tectum changes, including relative size modifications of the mammalian components of the tectum, simultaneously with the enlargement of the occipital lobe. There is a transformation of pre-mammalian optic ventricles to what appear to be collicular ventricles in mammals, as the aqueduct and collicular ventricle form a continuous cavity. CONCLUSIONS: The mammalian tectum undergoes an evolutionary cephalization process consisting of relative size changes of the midbrain tectum structures. This is associated with enlargement of the occipital lobe, as part of overall neocortical expansion. Potentially, aqueductal anomalies could be explained by evolutionary modifications.

Utility of MRI for cervical spine clearance after blunt traumatic injury: a meta-analysis.

OBJECTIVES: To quantify the rate of unstable injuries detected by MRI missed on CT in blunt cervical spine (CS) trauma patients and assess the utility of MRI in CS clearance. METHODS: We undertook a systematic review of worldwide evidence across five major medical databases and performed a meta-analysis. Studies were included if they reported the number of unstable injuries or gave enough details for inference. Variables assessed included severity, CT/MRI specifications, imaging timing, and outcome/follow-up. Pooled incidences of unstable injury on follow-up weighted by inverse-of-variance among all included and obtunded or alert patients were reported. RESULTS: Of 428 unique citations, 23 proved eligible, with 5,286 patients found, and 16 unstable injuries reported in five studies. The overall pooled incidence is 0.0029 %. Among studies reporting only obtunded patients, the pooled incidence is 0.017 %. In alert patients, the incidence is 0.011 %. All reported positive findings were critically reviewed, and only 11 could be considered truly unstable. CONCLUSIONS: There is significant heterogeneity in the literature regarding the use of imaging after a negative CT. The finding rate on MRI for unstable injury is extremely low in obtunded and alert patients. Although MRI is frequently performed, its utility and cost-effectiveness needs further study. KEY POINTS: • There were 16 unstable injuries on follow-up MRI among 5286 patients. • The positive finding rate among obtunded patients was 0.12 %. • The positive finding rate among alert, awake patients was 0.72 %. • MRI has a high false-positive rate; its utility mandates further studies. • The use and role of "confirmatory" tests shows wide variations.

Cost-Effectiveness of Tomosynthesis in Annual Screening Mammography.

OBJECTIVE: The purpose of this study was to evaluate the cost-effectiveness of the addition of annual screening tomosynthesis to 2D digital mammography alone for women beginning at 40 years old and to determine differences for age decade subgroups. MATERIALS AND METHODS: Decision-tree analysis comparing annual tomosynthesis versus 2D mammography alone from a federal payer perspective and lifetime horizon was created from published multiinstitutional data, published institutional data, literature values, and Medicare reimbursement rates. Cost-effectiveness was calculated through incremental cost-effectiveness ratios and net monetary benefit calculations. Sensitivity analyses were performed to determine the implication of different variables including changes in recall rate and disutility for false-positives. RESULTS: Base-case analysis showed an incremental cost per quality-adjusted life year gained for tomosynthesis over 2D alone for all ages (≥ 40 years old) of $20,230, 40- to 49-year-old subgroup of $20,976, 50- to 59-year-old subgroup of $49,725, 60- to 69-year-old subgroup of $44,641, and ≥ 70-year-old subgroup of $82,500. Net monetary benefit per decade in the 40- to 49-year-old subgroup was $1,598, 50- to 59-year-old subgroup of $546, 60- to 69-year-old subgroup of $535, and ≥ 70-year-old subgroup of $501. Tomosynthesis was the better strategy in 63.2% of the iterations according to probabilistic sensitivity analysis. CONCLUSION: Addition of annual screening tomosynthesis to 2D mammography beginning at the age of 40 years was cost-effective compared with 2D mammography alone in our analysis. Three times greater net monetary benefits were found in women 40-49 years old compared with those 50-59 years old.

Utility analysis of management strategies for suspected subarachnoid haemorrhage in patients with thunderclap headache with negative CT result.

PURPOSE: To determine the most effective follow-up strategy for evaluation of patients with thunderclap headache and negative initial non-contrast CT for acute subarachnoid haemorrhage (SAH). MATERIALS AND METHODS: Institutional review was performed to assess the frequency of CT angiography (CTA) in screening patients with negative non-contrast CT. A comparative effectiveness analysis based on decision tree modelling was subsequently performed to assess three different strategies--no follow-up, lumbar puncture (LP) and CTA. The clinical probabilities and utilities from literature were used to design the decision tree. Base-case scenario utility calculations, sensitivity analyses and probabilistic Monte Carlo simulation were performed. RESULTS: Institutional review of recent data in the last two years demonstrates frequent use of CTA in patients with thunderclap headache with limited utility. The decision tree analysis shows CT with LP follow-up to be the most effective strategy with the highest expected utility of 0.79926 quality-adjusted life-year (QALY) compared with 0.79875 QALY for no follow-up and 0.79869 QALY for CTA follow-up. Monte Carlo simulation showed LP was the best strategy in 86.4% of all iterations. Sensitivity analyses demonstrate that CT without follow-up is the best strategy only when the sensitivity of CT is very high (99.6%) or the pre-test probability of SAH in a patients with thunderclap headache with negative initial CT is low (1.6%). CONCLUSIONS: CT with no follow-up was shown to be the best strategy when the pre-test probability of SAH is low (<1.6%) or the sensitivity of initial non-contrast CT for blood is high (>99.6%). Otherwise, LP should be the preferred strategy for follow-up.

Use of follow-up imaging in isolated perimesencephalic subarachnoid hemorrhage: a meta-analysis.

BACKGROUND AND PURPOSE: Multiple studies have shown that negative computed tomographic angiograms (CTAs) are reliable in excluding aneurysms in patients with isolated perimesencephalic subarachnoid hemorrhage (pSAH). We evaluate the use of digital subtraction angiography versus CTA for initial diagnosis and of angiographic follow-ups in patients with pSAH by performing an institutional analysis and a meta-analysis of literature. METHODS: Retrospective institutional analysis of patients with pSAH was performed from 2008 to 2014. The number and types of follow-up imaging studies were tabulated. Initial and follow-up studies were evaluated by an experienced neuroradiologist for intracranial aneurysm. Meta-analysis of literature was performed to assess the use of initial digital subtraction angiography and of follow-up imaging. RESULTS: Our institutional review revealed no additional use of initial digital subtraction angiography or of any angiographic follow-up after initial negative CTA in patients with pSAH on noncontrast CT. Meta-analysis of 40 studies yielded a total of 1031 patients. Only 8 aneurysms were first diagnosed on follow-ups (0.78%). Careful review showed that some of these aneurysms reported on follow-up are of questionable validity. Initial digital subtraction angiography and follow-up imaging after a negative initial CTA showed no statistically significant benefits. CONCLUSIONS: In patients meeting the strict imaging criteria of pSAH, initial negative CTA is reliable in excluding aneurysms. A critical review of the literature through meta-analysis shows no foundation for multiple follow-up studies in patients with pSAH.

Cost-effectiveness of angiographic imaging in isolated perimesencephalic subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: The purpose of this study is to perform a comprehensive cost-effectiveness analysis of all possible permutations of computed tomographic angiography (CTA) and digital subtraction angiography imaging strategies for both initial diagnosis and follow-up imaging in patients with perimesencephalic subarachnoid hemorrhage on noncontrast CT. METHODS: Each possible imaging strategy was evaluated in a decision tree created with TreeAge Pro Suite 2014, with parameters derived from a meta-analysis of 40 studies and literature values. Base case and sensitivity analyses were performed to assess the cost-effectiveness of each strategy. A Monte Carlo simulation was conducted with distributional variables to evaluate the robustness of the optimal strategy. RESULTS: The base case scenario showed performing initial CTA with no follow-up angiographic studies in patients with perimesencephalic subarachnoid hemorrhage to be the most cost-effective strategy ($5422/quality adjusted life year). Using a willingness-to-pay threshold of $50 000/quality adjusted life year, the most cost-effective strategy based on net monetary benefit is CTA with no follow-up when the sensitivity of initial CTA is >97.9%, and CTA with CTA follow-up otherwise. The Monte Carlo simulation reported CTA with no follow-up to be the optimal strategy at willingness-to-pay of $50 000 in 99.99% of the iterations. Digital subtraction angiography, whether at initial diagnosis or as part of follow-up imaging, is never the optimal strategy in our model. CONCLUSIONS: CTA without follow-up imaging is the optimal strategy for evaluation of patients with perimesencephalic subarachnoid hemorrhage when modern CT scanners and a strict definition of perimesencephalic subarachnoid hemorrhage are used. Digital subtraction angiography and follow-up imaging are not optimal as they carry complications and associated costs.

Loeys-Dietz syndrome: cardiovascular, neuroradiological and musculoskeletal imaging findings.

Loeys-Dietz syndrome (LDS) is an increasingly recognized autosomal-dominant connective tissue disorder with distinctive radiological manifestations, including arterial tortuosity/aneurysms, craniofacial malformations and skeletal abnormalities. LDS exhibits a more aggressive course than similar disorders, such as Marfan or the vascular subtype of Ehlers-Danlos syndrome, with morbidity and mortality typically resulting from complications of aortic/arterial dissections. Early diagnosis, short-interval follow-up imaging and prophylactic surgical intervention are essential in preventing catastrophic cardiovascular complications. This review focuses on the cardiovascular, neuroradiological and musculoskeletal imaging findings in this disorder and recommendations for follow-up imaging.

Cost-effectiveness of Magnetic Resonance Imaging in Cervical Clearance of Obtunded Blunt Trauma After a Normal Computed Tomographic Finding.

Importance: Magnetic resonance imaging (MRI) continues to be performed for cervical clearance of obtunded blunt trauma, despite poor evidence regarding its utility after a normal computed tomographic (CT) finding. Objective: To evaluate the utility and cost-effectiveness of MRI vs no follow-up after a normal cervical CT finding in patients with obtunded blunt trauma. Design, Setting and Participants: This cost-effectiveness analysis evaluated an average patient aged 40 years with blunt trauma from an institutional practice. The analysis used a Markov decision model over a lifetime horizon from a societal perspective with variables from systematic reviews and meta-analyses and reimbursement rates from the Centers for Medicare & Medicaid Services, National Spinal Cord Injury Database, and other large published studies. Data were collected from the most recent literature available. Interventions: No follow-up vs MRI follow-up after a normal cervical CT finding. Results: In the base case of a 40-year-old patient, the cost of MRI follow-up was $14 185 with a health benefit of 24.02 quality-adjusted life-years (QALY); the cost of no follow-up was $1059 with a health benefit of 24.11 QALY, and thus no follow-up was the dominant strategy. Probabilistic sensitivity analysis showed no follow-up to be the better strategy in all 10 000 iterations. No follow-up was the better strategy when the negative predictive value of the initial CT was relatively high (>98%) or the risk of an injury treated with a cervical collar turning into a permanent neurologic deficit was higher than 25% or when the risk of a missed injury turning into a neurologic deficit was less than 58%. The sensitivity and specificity of MRI were varied simultaneously in a 2-way sensitivity analysis, and no follow-up remained the optimal strategy. Conclusions and Relevance: Magnetic resonance imaging had a lower health benefit and a higher cost compared with no follow-up after a normal CT finding in patients with obtunded blunt trauma to the cervical spine, a finding that does not support the use of MRI in this group of patients. The conclusion is robust in sensitivity analyses varying key variables in the model. More literature on these key variables is needed before MRI can be considered to be beneficial in the evaluation of obtunded blunt trauma.

Neuroimaging of Meckel's cave in normal and disease conditions.

Meckel's cave is a dural recess in the posteromedial portion of the middle cranial fossa that acts as a conduit for the trigeminal nerve between the prepontine cistern and the cavernous sinus, and houses the Gasserian ganglion and proximal rootlets of the trigeminal nerve. It serves as a major pathway in perineural spread of pathologies such as head and neck neoplasms, automatically upstaging tumours, and is a key structure to assess in cases of trigeminal neuralgia. The purpose of this pictorial review is threefold: (1) to review the normal anatomy of Meckel's cave; (2) to describe imaging findings that identify disease involving Meckel's cave; (3) to present case examples of trigeminal and non-trigeminal processes affecting Meckel's cave. TEACHING POINTS: • Meckel's cave contains the trigeminal nerve between prepontine cistern and cavernous sinus. • Assessment is essential for perineural spread of disease and trigeminal neuralgia. • Key imaging: neural enhancement, enlargement, perineural fat/CSF effacement, skull base foraminal changes.

Ectopic intracranial germinoma.

Intracranial ectopic germinomas are often associated with synchronous midline disease. Germinomas involving the corpus callosum are exceedingly rare. The reported imaging appearance is not as varied as one might expect and a review of the literature reveals a few common imaging features amongst most ectopic lesions, including cyst formation. We report a 24-year-old man with panhypopituitarism. Neuroimaging revealed three enhancing lesions involving the pituitary infundibulum, the pineal region, and a parenchymal lesion involving the genu of the corpus callosum. The described ectopic mass, a parenchymal lesion, was associated with small peripheral cysts. Stereotactic biopsy and histopathological evaluation revealed this mass to be a germinoma. Following chemotherapy and radiation therapy, there was near-total resolution of the intracranial disease. Preoperative imaging plays an important role, not only in delineating the extent of disease, but also in assisting in generating an appropriate differential diagnosis. Germinomas in the corpus callosum are exceedingly rare but should be considered in the differential of any young patient with a characteristic cystic and solid intra-axial mass.

Cost-effectiveness analysis of CTA and LP for evaluation of suspected SAH after negative non-contrast CT.

OBJECTIVES: Diagnostic workup of patients presenting with thunderclap headache and negative initial head CT remains a challenge, with most commonly employed strategies being lumbar puncture (LP) and CT angiography (CTA). The objective of this study was to determine the cost-effectiveness of these options. PATIENTS AND METHODS: A decision model was designed using clinical probabilities, costs, and utilities from published values in the literature. Base case analysis and Monte Carlo simulation were performed using the model to determine the cost-effectiveness of both options. RESULTS: CTA was associated with an expected cost of $747 and an expected utility of 0.798603029. In comparison, LP was associated with a cost of $504 and an expected utility of 0.799259526, making it the optimal strategy from both the cost and the utility perspectives. LP was also the more cost-effective strategy in all iterations in the Monte Carlo simulation. A sensitivity analysis showed that with the 2014 US Medicare reimbursement values, LP would remain the more cost-effective strategy unless its cost exceeded 4 times its current value. CONCLUSION: LP should remain the preferred strategy for evaluation of SAH in patients presenting with thunderclap headache and negative non-contrast head CT. CTA is not an effective replacement, from either a utility or cost perspective.

Cost-effectiveness Analysis of Follow-up Strategies for Thunderclap Headache Patients With Negative Noncontrast CT.

OBJECTIVES: Accurate diagnosis of acute subarachnoid hemorrhage (SAH) is critical in thunderclap headache patients due to high morbidity and mortality associated with missed aneurysmal bleeds. The objective of this study was to determine the utility of computed tomography angiography (CTA) in managing patients with acute, severe headaches and negative noncontrast CT and assess the cost-effectiveness of three different screening strategies-no follow up, CTA, and lumbar puncture (LP). METHODS: A modeling-based economic evaluation was performed with a time horizon of 1 year for thunderclap headache patients in the emergency department with negative noncontrast CT for SAH. Sensitivity analyses were performed to determine the effect of sensitivity of CT and the prevalence of SAH on cost-effectiveness. RESULTS: Lumbar puncture follow-up has the lowest cost and the highest utility in the mathematical model. The Monte Carlo simulation shows noncontrast CT with LP follow-up to be the most cost-effective strategy in 85.3% of all cases even at a $1 million/quality-adjusted life-years willingness-to-pay. Sensitivity analyses demonstrate that LP follow-up should be performed, except for when CT sensitivity exceeds 99.2% and the SAH prevalence is below 3.2%, where no follow-up may be considered. CONCLUSIONS: Although CTA is frequently used for evaluation of thunderclap headache patients, its utility is not clearly defined. LP follow-up is shown to be the most cost-effective strategy for evaluation of thunderclap headache patients in most clinical settings.

Screening for Pediatric Blunt Cerebrovascular Injury: Review of Literature and a Cost-Effectiveness Analysis.

BACKGROUND: Timely and accurate screening for pediatric blunt cerebrovascular injury (BCVI) is important in order to administer appropriate anticoagulation therapy thus preventing stroke. The recommended criteria for screening in children are not clear. We performed a systematic review of the literature for screening and management of BCVI in children and designed a cost-effectiveness analysis in order to determine the optimal strategy for managing pediatric BCVI from a societal perspective. METHODS: Comprehensive review of studies citing BCVI in pediatric patients was carried out with data extraction and compilation. An economic evaluation of 5 possible screening strategies was performed by designing a decision tree over a 1-year horizon using parameters derived from literature review. Base case calculations were made to compare cost effectiveness for each strategy. Monte Carlo simulation and extensive sensitivity analyses were performed to examine the robustness of the conclusion against key variables. RESULTS: Selective anticoagulation therapy in patients with high-risk factors was found to be the most cost-effective strategy and selective computed tomography angiography (CTA) in high-risk patients was the optimal imaging strategy. This conclusion was corroborated by a Monte Carlo simulation of 10,000 iterations. In all sensitivity analyses, selective anticoagulation and selective CTA continue to be the optimal strategy until the risk of anticoagulation complications rises above 3.9%. CONCLUSIONS: Our study demonstrated selective CTA to be the optimal imaging strategy in order to assess BCVI in children. Further studies are needed for more clearly defined screening criteria.

Imaging of lumbar spinal surgery complications.

UNLABELLED: Lumbar spine surgery for spinal stenosis is a frequently performed procedure and was the fastest growing type of surgery in the US from 1980 to 2000. With increasing surgical invasiveness, postoperative complications also tend to be higher. Cross-sectional imaging techniques (CT and MRI) are more sensitive than radiographs and play an increasingly important role in evaluation of patients with lumbar spine surgery. Their use in patients with metallic implants is somewhat limited by artefacts, which can obscure pathology and decrease accuracy and reader confidence. Metal artefact reduction techniques have been developed, which can significantly improve image quality and enable early detection of postoperative complications. Complications can occur throughout postoperative course. Early complications include hardware displacement, incidental durotomy, postoperative collections-most commonly seroma, and less likely haematoma and/or infection. Incidental durotomy with CSF leak causing intracranial hypotension has characteristic MR brain findings and diagnosis of occult leak sites have been improved with use of dynamic CT myelography. Haematomas, even when compressing the thecal sac, are usually asymptomatic. Early infection, with nonspecific MR findings, can be diagnosed accurately using dual radiotracer studies. Delayed complications include loosening, hardware failure, symptomatic new or recurrent disc herniation, peri-/epidural fibrosis, arachnoiditis, and radiculitis. TEACHING POINTS: • CT and MRI play an increasingly important role in evaluation of patients with lumbar spine surgery • Complications can occur throughout the postoperative course and early detection is critical • Artefact reduction techniques can improve image quality for early and improved detection of complications.

Value analysis of digital breast tomosynthesis for breast cancer screening in a commercially-insured US population.

PURPOSE: The objective of this study was to conduct a value analysis of digital breast tomosynthesis (DBT) for breast cancer screening among women enrolled in US commercial health insurance plans to assess the potential budget impact associated with the clinical benefits of DBT. METHODS: An economic model was developed to estimate the system-wide financial impact of DBT as a breast cancer screening modality within a hypothetical US managed care plan with one million members. Two scenarios were considered for women in the health plan who undergo annual screening mammography, ie, full field digital mammography (FFDM) and combined FFDM + DBT. The model focused on two main drivers of DBT value, ie, the capacity for DBT to reduce the number of women recalled for additional follow-up imaging and diagnostic services and the capacity of DBT to facilitate earlier diagnosis of cancer at less invasive stages where treatment costs are lower. Model inputs were derived from published sources and from analyses of the Truven Health MarketScan(®) Research Databases (2010-2012). Comparative clinical and economic outcomes were simulated for one year following screening and compared on an incremental basis. RESULTS: Base-case analysis results show that 4,523 women in the hypothetical million member health plan who are screened using DBT avoid the use of follow-up services. The overall benefit of DBT was calculated at $78.53 per woman screened. Adjusting for a hypothetical $50 incremental cost of the DBT examination, this translates to $28.53 savings per woman screened, or $0.20 savings per member per month across the plan population and an overall cost savings to the plan of $2.4 million per year. CONCLUSION: The results of this study demonstrate clinical and economic favorability of DBT for breast cancer screening among commercially-insured US women. Wider adoption of DBT mammography presents an opportunity to deliver value-based care in the US health care system.

Predictors of Vertebral Artery Injury in Isolated C2 Fractures Based on Fracture Morphology Using CT Angiography.

STUDY DESIGN: Retrospective database analysis. OBJECTIVE: To determine C2 fracture patterns associated with vertebral artery injury (VAI) as assessed by computed tomography angiography. SUMMARY OF BACKGROUND DATA: The incidence of C2 fracture hospitalizations has increased significantly in the last decade. The vertebral arteries are susceptible to injury as each courses through the C2 transverse foramen. Early screening for VAI to institute antithrombotic treatment is critical to prevent ischemic neurological sequelae. Imaging-based fracture classification schemes to determine which patterns are predictors of VAI in isolated C2 fractures using computed tomography angiography have not been described. METHODS: Cervical spine computed tomographic (CT) scans at a level I trauma center were reviewed for isolated C2 fractures from 2004 to 2014 under institutional board review approval. Exclusion criteria included penetrating injury or additional cervical/occipital fractures. Fractures were classified using multiplanar CT scans into type I/II/IIa/III spondylolisthesis, type I/IIA/IIB/IIC/III dens, transverse foramen (displacement/comminution/intraforaminal fragments), and miscellaneous vertebral body fractures. Corresponding CT angiograms were assessed for VAI on the basis of the Denver grading criteria. Fisher exact test and Student t test were performed to determine predictors of VAI on the basis of fracture type. RESULTS: Sixty-seven patients met inclusion criteria. Fracture pattern analysis revealed that the majority were dens fractures (50.8%) and traumatic spondylolisthesis (41.8%); 29.9% had miscellaneous coronal/sagittal fractures and 22.4% were a combination.VAI was identified in 37.3% of patients with isolated C2 fractures, and 88% of patients had transverse foramen involvement. Fracture patterns significantly associated with VAI were type III dens and transverse foramen fractures with intraforaminal fragments, with or without comminution. CONCLUSION: The C2 fracture pattern most associated with VAI was comminuted transverse foramen fracture with intraforaminal fragments. Transverse foramen fracture alone was not found to be significant. These results help stratify patients with isolated C2 fractures who are at high VAI risk and should be further evaluated with computed tomography angiography. LEVEL OF EVIDENCE: 3.

Value of non-contrast sequences in magnetic resonance angiography of hepatic arterial vasculature.

OBJECTIVE: To evaluate value of adding non-contrast MR angiographic sequence (In-Flow Inversion Recovery [IFIR]) to standard fat-suppressed T1-weighted postcontrast sequence (3D spoiled gradient echo [3D-GRE]) for evaluating hepatic arterial anatomy. METHODS: Retrospective evaluation of 30 consecutive patients undergoing multiphase liver MRI. Individual vessels for IFIR/3D-GRE sequences were evaluated by two blinded readers using a four-point scale. Statistical analysis was performed using the Wilcoxon signed-rank test for vessel conspicuity between IFIR/3D-GRE sequences. RESULTS: IFIR alone diagnostically imaged 8.1% of vessels, 3D-GRE alone 25.8%, 55.8% by both 3D-GRE/IFIR, and 10.3% of vessels by neither. Two patients with variant vascular anatomy were visualized with both sequences. Addition of IFIR to 3D-GRE resulted in statistically significant increase in arterial visualization (p<0.001), 10% relative increase in identified vessels, and 3-5 mi increase in acquisition time for total scan time of 30-35 min. CONCLUSIONS: IFIR may be a useful adjunct to 3D-GRE in hepatic angiography without adding considerably to scan time. 10% more hepatic arteries were seen when combining information from IFIR/3D-GRE vs. 3D-GRE alone.

Teaching NeuroImages: perfusion imaging of cerebral hyperperfusion syndrome following revascularization.

A 69-year-old man developed acute-onset confusion and hypertension with systolic pressures in the 160s 1 day after carotid endarterectomy for right facial droop from left hemispheric lacunar infarcts. CT perfusion (figure, A-D) demonstrated findings consistent with cerebral hyperperfusion syndrome (CHS) following revascularization. CHS is caused by loss of autoregulation, hypertension, and ischemia-reperfusion injury resulting in increased regional blood flow and vascular congestion.(1) CHS following revascularization may present as ipsilateral headache, focal seizure, or neurologic deficit. Nonperfusion imaging may show intraparenchymal hemorrhage or edema. Labetalol and clonidine are used for aggressive blood pressure control until cerebral autoregulation is restored.(2.)