Efficacy of MR Angiography in the Detection and Characterization of Occlusive Disease in the Vertebrobasilar System

Severe Bilateral Vertebral Arterial Disease Masquerading as Vertigo

Vertebral artery stenosis (VAS), manifesting as vertebrobasilar insufficiency (VBI), results from the narrowing of the vertebral artery's lumen because of diverse vascular pathological processes, leading to various clinical presentations. We present the case of a 71-year-old male who experienced vertigo for almost two years and was ultimately diagnosed with severe bilateral VAS. Despite initial management for vertigo, the patient's symptoms persisted, prompting a referral to a cardiologist. Several assessments were performed, including an MRI of the brain, which ruled out acute intracerebral hemorrhage or infarction. After some visits to the cardiologist's office, the patient was referred to a neurologist who conducted a magnetic resonance angiography (MRA) of the neck, which showed an occlusion of the left vertebral artery at the origin and a patent right vertebral artery. Because of worsening symptoms of vertigo and the results of the MRA, the patient underwent invasive angiography that confirmed the occlusion of the left vertebral artery and also revealed severe stenosis of the right vertebral artery. This case report discusses an unusual presentation of VAS with vertigo as the primary symptom, emphasizing the importance of recognizing seemingly minor symptoms as manifestations of the underlying vascular pathology that requires careful evaluation. Furthermore, this case emphasizes the limitation of relying solely on noninvasive imaging for diagnosis as, in this instance, noninvasive imaging failed to detect the severe stenosis of the right vertebral artery, which was revealed by invasive angiography. Finally, this case report underscores the significance of collaboration across several disciplines, such as cardiology, neurology, and radiology, as well as endovascular medicine in diagnosing and managing atypical manifestations of complex conditions.

A review of the diagnosis and management of vertebral basilar (posterior) circulation disease

We have reviewed the English literature published in the last 70 years on Diseases of the Vertebral Basilar Circulation, or Posterior Circulation Disease (PCD). We have found that errors have been made in the conduct and interpretation of these studies that have led to incorrect approaches to the management of PCD. Because of the difficulty in evaluating the PC, the management of PCD has been incorrectly applied from anterior circulation disease (ACD) experience to PCD. PCD is a common form of stroke affecting 20-40% patients with stroke. Yet, the evidence is strong that the Anterior Circulation (AC) and Posterior Circulations (PC) differ in their pathology, in their clinical presentations, in the rapidity of development of symptoms, in optimal imaging methods, and in available treatments. There appears to be two categories of patients who present with PCD. The first, acute basilar artery occlusion has a more rapid onset. The diagnosis must be made quickly and if imaging proves a diagnosis of Basilar Artery Occlusion (BAO), the treatment of choice is Interventional removal of the basilar artery thrombosis or embolus. The second category of PCD and the most commonly seen PCD disease process presents with non-specific symptoms and early warnings of PCD that now can be related to ischemic events in the entire PC vessels. These warning symptoms and signs occur much earlier than those in the AC. IA angiography is still the gold standard of diagnosis and is superior in definition to MR and CT angiography which are commonly used as a convenient screening imaging tool to evaluate PCD but are both inferior to IA angiography in definition for lesions below 3-4 mm. In at least two reported studies 7T MR angiography appears superior to other imaging modalities and will become the gold standard of imaging of PCD in the future. Medical treatments applied to the ACD have not been proven of value in specific forms of PCD. Interventional therapy was promising but of unproven value in Randomized Controlled Trials (RCT) except for the treatment of Basilar Artery Occlusion (BAO). Surgical revascularization has been proved to be highly successful in patients, who are refractory to medical therapy. These studies have been ignored by the scientific community basically because of an incorrect interpretation of the flawed EC-IC Bypass Trial in 1985 as applying to all stroke patients. Moreover, the EC-IC Bypass Study did not include PCD patients in their study population, but the study results were extrapolated to patients with PCD without any scientific basis. This experience led clinicians to an incorrect bias that surgical treatments are of no value in PCD. Thus, incorrectly, surgical treatments of PCD have not been considered among the therapeutic possibilities for PCD. QMRA is a new quantitative MR technique that measures specific blood flow in extra and intracranial vessels. QMRA has been used to select those patients who may benefit from medical, or interventional, or surgical treatment for PCD based on flow determinations with a high success rate. QMRA accurately predicts the flows in many large and small vessels in the PC and AC and clearly indicates that both circulations are intimately related. From medical and surgical studies, the longer one waits for surgical treatment the higher the risk of a poor outcome results. This observation becomes obvious when the rapidity of development of PCD is compared with ACD. Recent advances in endovascular therapy in the treatment of acute basilar thrombosis is a clear sign that early diagnosis and treatment of PCD will reduce the morbidity and mortality of these diseases. In this review it is evident that there are multiple medical and surgical treatments for PCD depending upon the location of the lesion(s) and the collateral circulation demonstrated. It is clear that the AC and PC have significant differences. With the exception of the large population studies from Oxford England, the reported studies on the management of PCD in the literature represent small selected subsets of the universe of PC diseases, the information from which is not generalizable to the universe of PCD patients. At this point in the history of PCD, there are not large enough databases of similar patients to provide a basis for valid randomized studies, with the exception of the surgical studies. Thus, a high index of suspicion of the early warning symptoms of PCD should lead to a rapid individual clinical assessment of patients selecting those with PCD. Medical, interventional, and/or surgical treatments should be chosen based on knowledge presented in this review. Recording the results in a national Registry on a continuing basis will provide the data that may help advance the management of PCD based on larger data bases of well documented patient information to guide the selection of future therapies for PCD treatments. It is also clear that the management of patients within the complex of diseases that comprise PCD should be performed in centers with expertise in the imaging, medical, interventional and surgical approaches to diseases of the PCD.

Middle Cerebral Artery Stroke in a Neonate With a Congenital Hypercoagulable Condition Following Repair of an H-type Tracheoesophageal Fistula

We report a case of middle cerebral artery stroke with heterozygosity for 2 separate hypercoagulable conditions following repair of an H-type tracheoesophageal fistula (TEF) in an infant. Neonatal stroke is rare, occurring in 1 in 4000 births annually in the United States. Stroke after pediatric surgery occurs in approximately 0.05% of patients. Etiologies of stroke in neonates include cardiac, hematologic, vascular, traumatic, metabolic, pharmacologic, infectious, and hypoxemic insults. Thrombophilia has been described in 42% to 78% of neonates with neonatal stroke. Stroke after repair of an H-type TEF has not been reported as a postoperative complication. Manipulation of the carotid artery during this operation is presumed to have contributed to a thromboembolic event in this infant with a hypercoagulable state. Whereas preoperative workup may not be indicated due to the low prevalence of neonatal stroke, workup for a congenital hypercoaguable condition may be considered in infants with stroke as a postoperative complication. This report provides a concise review of the etiology and treatment of stroke and hypercoagulable states in neonates as well as presents the case of a previously undescribed complication of repair of an H-type TEF.

Hyperdense basilar artery sign diagnoses acute posterior circulation stroke and predicts short-term outcome

INTRODUCTION

It is well established that the hyperdense middle cerebral artery sign is a specific marker for early ischemia in anterior circulation. However, little is known about the hyperdense basilar artery sign (HDBA) in posterior circulation. Our aim was to determine whether the HDBA sign has utility in early diagnosis of acute posterior circulation stroke and prediction of short-term outcome.

METHODS

Three-blinded readers examined unenhanced computed tomography scans for the HDBA sign, and materials were classified into two groups according to this sign. Vascular risk factors, admission and discharge National Institute of Health Stroke Scale (NIHSS) scores, short-term outcome, and radiological findings between the two groups were compared.

RESULTS

One hundred and twenty-six cases of acute posterior circulation stroke (PCS) were included in the study. No statistically significant differences were found in risk factors of ischemic stroke, except atrial fibrillation (P=0.025). Admission and discharge NIHSS scores for the positive HDBA group were significantly higher than scores for the negative HDBA group (P=0.001, 0.002, respectively). The infarction territory for the positive HDBA group was mainly multi-region in nature (51.6%, P<0.001), while the negative HDBA group showed mainly middle territory infarction. Significant independent predictors of short-term outcome included the HDBA sign (P<0.001) and admission NIHSS scores (P<0.001).

CONCLUSION

Approximately half of the HDBA patients showed multi-region infarction and a serious neurological symptom. Based on our results, this sign might not only be helpful in early diagnosis of acute PCS but also be able to correlate with a poor short-term outcome.

Practical noninvasive neurovascular imaging of the neck arteries in patients with stroke, transient ischemic attack, and suspected arterial disease that may lead to ischemia, infarction, or flow abnormalities

Stroke is the third leading cause of death in the United States, killing nearly 157,000 people a year with an estimated society cost of dollar 58 billion in 2006. A large percentage of ischemic strokes is secondary to extracranial carotid and vertebral arterial disease. While digital subtraction angiography has traditionally been used for the initial evaluation of the degree of stenosis, noninvasive imaging has moved to the forefront in the extracranial arterial evaluation. The importance of understanding the imaging techniques, findings, interpretation, artifacts, and pitfalls is essential to appropriate patient management.

Imaging the vertebral artery

Although conventional intraarterial digital subtraction angiography remains the gold standard method for imaging the vertebral artery, noninvasive modalities such as ultrasound, multislice computed tomographic angiography and magnetic resonance angiography are constantly improving and are playing an increasingly important role in diagnosing vertebral artery pathology in clinical practice. This paper reviews the current state of vertebral artery imaging from an evidence-based perspective. Normal anatomy, normal variants and a number of pathological entities such as vertebral atherosclerosis, arterial dissection, arteriovenous fistula, subclavian steal syndrome and vertebrobasilar dolichoectasia are discussed.

Proximal Great Vessels of Aortic Arch: Comparison of Three-dimensional Gadolinium-enhanced MR Angiography and Digital Subtraction Angiography

PURPOSE

To prospectively compare dynamic three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography and digital subtraction angiography (DSA) for the detection of ostial stenosis of the craniocervical vessels.

MATERIALS AND METHODS

Thirty-three patients with carotid stenosis of more than 50% at sonography prospectively underwent both MR angiography and DSA. The overall quality of each DSA and MR angiographic study was analyzed. For each craniocervical vessel (brachiocephalic, common carotid, subclavian, and vertebral arteries) (n = 231), ostial stenosis was graded as follows: normal, mild (<50%), moderate to severe (>50%), or occlusion. MR angiographic and DSA results were compared by means of the Spearman rank correlation coefficient (Rs).

RESULTS

The overall diagnostic quality of MR angiography was excellent or adequate. Three studies were inadequate because of a poor signal-to-noise ratio (13 of 231 arteries) or a coverage error (five of 231 arteries). Findings at MR angiography and DSA agreed on the degree of stenosis (Rs = 0.82, P <.001). No cases of stenosis of more than 50% were missed at MR angiography. However, some discrepancies were noted between vertebral arteries and the other craniocervical vessels. The sensitivity and specificity for stenosis of more than 50% in other craniocervical vessels were 100% and 98%, respectively. The sensitivity and specificity for stenosis of more than 50% in the vertebral arteries were 100% and 85%, respectively. Findings at MR angiography tended to result in overestimation of the degree of ostial stenosis, especially in vertebral arteries (10 [15%] of 66 arteries).

CONCLUSION

MR angiography is useful to rule out ostial stenosis of the craniocervical vessels. MR angiography is an adequate diagnostic tool for ostial stenosis, except in the vertebral artery.

Atherosclerotic disease distribution in carotid and vertebrobasilar arteries: clinical experience in 100 patients undergoing fluoro-triggered 3D Gd-MRA

PURPOSE

To determine how often three-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA) shows disease outside of the standard two-dimensional time-of-flight magnetic resonance angiography (2D TOF-MRA) imaging volume.

MATERIALS AND METHODS

One hundred consecutive patients with known or suspected cerebrovascular disease were examined using fluoro-triggered 3D Gd-MRA with a 1.5 Tesla scanner. All vessel segments from the aortic arch to the circle of Willis were independently evaluated for the presence of occlusive disease, ulceration, aneurysm, and anatomic variations by two radiologists blinded to clinical information. Branch vessel and circle of Willis visibility were also assessed. Kappa statistics were calculated to determine interobserver agreement.

RESULTS

Interobserver agreement for the degree of stenosis was good to excellent (kappa = 0.83-1.0). Disagreement was more frequent in the cases of mild stenoses and was less frequent for stenoses > or = 50%. In 38% of the patients, 3D Gd-MRA demonstrated either ulcerated plaques in carotid arteries (N = 14) or stenosis > or = 50% in great vessel (N = 20) and/or vertebral artery (N = 38) origins, none of which can be readily evaluated on standard TOF-MRA.

CONCLUSION

Fluoro-triggered 3D Gd-MRA provides a comprehensive evaluation of the carotid arteries including all vessel segments from the aortic arch to the circle of Willis.

Stroke-free Survival and Its Determinants in Patients with Symptomatic Vertebrobasilar Stenosis: A Multicenter Study

OBJECTIVE

We sought to determine the long-term stroke-free survival of patients who present with ischemic events related to intracranial vertebrobasilar stenosis.

METHODS

A retrospective cohort of patients diagnosed with symptomatic vertebrobasilar stenosis on the basis of magnetic resonance angiography and/or conventional angiography was identified at four academic medical centers. Patients' clinical and follow-up information was obtained through hospitalization records, clinic visits, and telephone interviews. Kaplan-Meier analysis was performed to determine the rate of stroke-free survival for a 5-year period. Cox proportional hazards analysis was performed to determine the effect of demographic and clinical factors on stroke-free survival.

RESULTS

A total of 102 patients were included, whose mean age was 64 ± 12 years. Fifty-five (54%) of the patients were men. The mean follow-up period was 15 ± 15.9 months (range, 1–60 mo). During the follow-up period, 14 (14%) of the patients experienced recurrent stroke. The overall mortality rate was 21% (n = 21). Stroke-free survival, calculated by using the Kaplan-Meier curve, was 76% at 12 months (95% confidence interval [CI], 66–83%) and 48% at 5 years (95% CI, 27–65%). The risk of recurrent stroke was 10.9 per 100 patient-years, and the rate of recurrent stroke and/or death was 24.2 per 100 patient-years. Cox proportional hazards analysis revealed that increasing age (hazards ratio, 1.05; 95% CI, 1.00–1.09) decreased stroke-free survival. Treatment with either antiplatelet agents or warfarin (hazards ratio, 0.018; 95% CI, 0.003–0.11) had a protective effect on stroke-free survival after adjusting for age, sex, race, hypertension, diabetes mellitus, smoking, hyperlipidemia, and lesion location.

CONCLUSION

A low rate of stroke-free survival is observed in patients with symptomatic vertebrobasilar stenosis. Further studies are required to evaluate new medical and endovascular treatment options for this group of patients to improve long-term stroke-free survival.

Detection and characterization of intracranial aneurysms with MR angiography: comparison of volume-rendering and maximum-intensity-projection algorithms

OBJECTIVE

The purpose of this study was to compare volume rendering and maximum intensity projection as postprocessing techniques of MR angiography in the detection and characterization of intracranial aneurysms.

MATERIALS AND METHODS

Three-dimensional time-of-flight MR angiography studies performed in 82 patients were retrospectively evaluated by two independent reviewers who were unaware of digital subtraction angiography findings, the standard of reference. Panoramic maximum-intensity-projection and volume-rendered angiograms were produced from each data set to investigate the presence of underlying aneurysms. Each detected aneurysm was then interactively evaluated with subvolume maximum-intensity-projection and targeted volume-rendering algorithms to evaluate aneurysm morphology and size. Aneurysm detection and characterization were evaluated by means of the receiver operating characteristic analysis, and aneurysm size was evaluated using the limits-of-agreement method. Image quality, aneurysm neck depiction, and vascular delineation were also compared between maximum-intensity-projection and volume-rendered images. The time required for the generation and interpretation of maximum-intensity-projection and volume-rendered images was assessed.

RESULTS

Volume rendering tended to improve the diagnostic confidence (A(z) [area under the receiver operating characteristic curve] = 0.95 vs A(z) = 0.90 for maximum intensity projection) and yielded a considerable improvement in sensitivity (89% vs 71% for maximum intensity projection), particularly in the detection of small cerebral aneurysms. Regarding aneurysm morphology, volume rendering performed significantly better than maximum intensity projection in lobulation detection (p < 0.001) and slightly better in neck categorization (p > 0.238). Limits-of-agreement analysis showed a trend toward improved assessment of the aneurysm size by volume rendering (-0.31 +/- 1.62 mm vs -1.27 +/- 2.84 mm by maximum intensity projection). Overall image quality and vascular delineation of involved vessels on volume-rendered images were rated better than that obtained by maximum intensity projections (p < or = 0.007 and p < or = 0.001, respectively). Evaluation of time-of-flight MR angiography data sets was significantly facilitated with volume rendering (p < 0.001).

CONCLUSION

The volume-rendering technique facilitates the evaluation of cerebral time-of-flight MR angiography data sets and allows better detection and more reliable characterization of intracranial aneurysms than does maximum intensity projection.