Accuracy and pitfalls of multidetector-row computed tomography in detecting spinal dural arteriovenous fistulas

Interactive spinal computed tomography angiography-guided spinal digital subtraction angiography and embolization for thoracolumbar epidural arteriovenous fistulas: illustrative case

BACKGROUND

Spinal digital subtraction angiography (sDSA) is the gold standard for examining spinal arteriovenous fistulas; however, thorough sDSA evaluations of spinal arteriovenous fistulas require a long procedure, which may increase the radiation exposure time.

OBSERVATIONS

A 72-year-old man presented with progressive myelopathy due to a spinal epidural arteriovenous fistula. Spinal computed tomography angiography (sCTA) showed an epidural arteriovenous fistula fed by the left L3 segmental artery. To prepare for sDSA, the sCTA images were modified to mark the segmental artery bifurcations from T5 to L5 with multicolored markers. These modified sCTA images were loaded onto the multiwindow DSA display. The sCTA images were interactively modulated during sDSA. This sCTA-guided sDSA identified 18 segmental arteries within 47 minutes. The total radiation exposure was 1,292 mGy. Subsequently, transarterial embolization resolved the epidural arteriovenous fistula with clinical improvement.

LESSONS

Three-dimensional sCTA can provide detailed anatomical information before sDSA. Modified sCTA images with segmental artery bifurcation marking can provide interactive guidance on multipanel DSA displays. sCTA-guided sDSA is useful for accurate catheterization and reduction of procedure time.

ACR Appropriateness Criteria® Myelopathy: 2021 Update

Myelopathy is a clinical diagnosis with localization of the neurological findings to the spinal cord, rather than the brain or the peripheral nervous system, and then to a particular segment of the spinal cord. Myelopathy can be the result of primary intrinsic disorders of the spinal cord or from secondary conditions, which result in extrinsic compression of the spinal cord. While the causes of myelopathy may be multiple, the acuity of presentation and symptom onset frame a practical approach to the differential diagnosis. Imaging plays a crucial role in the evaluation of myelopathy with MRI the preferred modality. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Asymptomatic spinal dural arteriovenous fistula: case series and systematic review

OBJECTIVE

Spinal dural arteriovenous fistulas (SDAVFs) commonly present with symptoms of myelopathy due to venous congestion in the spinal cord; asymptomatic SDAVFs are rarely encountered. To elucidate the clinical characteristics of asymptomatic SDAVFs, the authors present 5 new cases of asymptomatic SDAVF and report the results of their systematical review of the associated literature.

METHODS

Five databases were systematically searched for all relevant English-language articles on SDAVFs published from 1990 to 2018. The clinical features and imaging findings of asymptomatic SDAVFs were collected and compared with those of symptomatic SDAVFs.

RESULTS

Twenty cases, including the 5 cases from the authors' experience, were found. Asymptomatic SDAVFs were more prevalent in the cervical region (35.0%); cervical lesions account for only 2% of all symptomatic SDAVFs. The affected perimedullary veins tended to drain more cranially (50.0%) than caudally (10.0%). Four cases of asymptomatic SDAVF became symptomatic, 1 case spontaneously disappeared, and the remaining 15 cases were unchanged or surgically treated.

CONCLUSIONS

The higher prevalence of asymptomatic SDAVFs in the cervical spine might be a distinct feature of asymptomatic SDAVFs. Given that venous congestion is the pathophysiology of a symptomatic SDAVF, abundant collateral venous pathways and unique flow dynamics of the CSF in the cervical spine might prevent asymptomatic cervical SDAVFs from becoming symptomatic. In cases in which venous congestion is avoidable, not all asymptomatic SDAVFs will become symptomatic.

Impact of non-contrast enhanced volumetric MRI-based feeder localization in the treatment of spinal dural arteriovenous fistula

BACKGROUND

The preoperative localization of the feeder of spinal dural arteriovenous fistula (SDAVF) could simplify the diagnostic spinal angiographic procedure. Localization by non-contrast-enhanced MRI-based techniques is an attractive option. However, the usefulness of such an approach for evaluation of SDAVF has not yet been reported.

OBJECTIVE

To study the impact of non-contrast MRI-based feeder localization, followed by targeted spinal angiography, in the evaluation of SDAVF before endovascular intervention.

MATERIALS AND METHODS

Prospectively collected data were analyzed and the level of the feeder was localized preoperatively. The procedural time for targeted spinal angiography was calculated and compared with that of a historical cohort, who underwent routine spinal angiographic examination before the study period. Follow-up MRI was carried out to assess the reliability of this model for detection of occasional metachronous lesions that might be missed with this approach.

RESULTS

Seven patients underwent targeted spinal angiography during the study. The feeder level was accurately identified in five patients and was localized to one vertebral level in six patients. The correlation between MRI and DSA was statistically significant. The number of spinal levels assessed was fewer and overall procedure time was significantly shorter compared to historical cohort (58 min vs 162 min, respectively; p<0.001). Intervention was coupled with targeted angiography in two patients. Follow-up MRI demonstrated flow voids in one patient, who had recurrent fistula at one vertebral level below the previously embolized feeder.

CONCLUSIONS

The non-contrast MRI-based localization technique can reliably detect the level of feeder and help in therapeutic planning of SDAVF. The localization techniques potentially shorten the angiographic procedure and may facilitate simultaneous endovascular definitive treatment. Inclusion of follow-up MRI may be useful for detection of synchronous or metachronous lesions if a targeted approach is adopted. Additionally, this helps to identify failed endovascular therapy.

Utility of 3D SPACE T2-weighted volumetric sequence in the localization of spinal dural arteriovenous fistula

OBJECTIVE The aim of this study was to investigate the utility of a heavily T2-weighted volumetric MRI sequence (3D sampling perfection with application-optimized contrasts using different flip-angle evolutions [SPACE]) in the feeder localization of spinal dural arteriovenous fistula (SDAVF). METHODS Patients who were diagnosed with SDAVF and who had 3D SPACE source images available for review were identified from a retrospective review of medical records. A total of 16 patients were identified, and MR images were analyzed separately by 2 blinded observers. The accuracy of the observation and interobserver agreement were measured by Kendall's tau and kappa statistics. RESULTS The site of fistula was accurately predicted by Observers 1 and 2 in 81% and 88% of cases, respectively, which improved to 94% when the level was considered within 1 vertebral level. The observer agreement with gold-standard angiography and interobserver agreement were found to be highly significant (p < 0.0001). CONCLUSIONS The 3D SPACE MRI sequence is valuable in the precise detection of the site of SDAVF. It may help to tailor digital subtraction angiography and thereby reduce the radiation exposure, contrast load, and study time.

Spinal intraarterial computed tomography angiography as an effective adjunct for spinal angiography

OBJECT

Spinal digital subtraction angiography (DSA) is indispensable for the precise diagnosis of spinal vascular lesions and the assessment of blood supply to the spinal cord. However, comprehensive spinal DSA covering multiple segments requires repetition of selective catheterization into small segmental arteries, which is time consuming, sometimes difficult, and hazardous. The authors investigated the usefulness of CT angiography with intraarterial contrast injection (IA-CTA) as a preliminary study preceding spinal DSA. With the advent of multidetector CT, it is feasible to obtain images of the spinal cord vasculature instantaneously overa number of segments.

METHODS

A total of 56 patients with lesions involving the spinal vasculature underwent IA-CTA with 64- or 320-row detector CT in advance of comprehensive spinal DSA. Contrast material was injected via a pigtail catheter placed at the aorta in proximity to the segments of interest. Scanning was repeated twice to obtain arterial- and venous-phase images to differentiate between the arterial and venous components. The spinal arteries were identified by paging the various multiplanar reconstruction images and tracing the vessels from the aorta. Spinal DSA was subsequently performed by guiding selective catheterization to the feeding segments in reference to the IA-CTA findings. Visualization of the segmental arteries, normal spinal arteries, and abnormal vessels during IA-CTA was investigated and compared with that obtained during spinal DSA.

RESULTS

In all 56 patients, spinal IA-CTA successfully enabled visualization of the spinal vessels, including the radicular arteries and the anterior spinal artery. Below the aortic arch, all segmental arteries were identified clearly. The segmental arteries, radiculomedullary arteries, spinal arteries, and abnormal vessels were traced from the aorta, which would be the target of selective catheterization. In 3 (6.8%) patients, IA-CTA revealed severe aortic atherosclerosis and occlusion of some segmental arteries. The information obtained was useful for directing selective catheterization studies. The findings of IA-CTA corresponded well with those of spinal DSA.

CONCLUSIONS

IA-CTA is a useful adjunct to spinal DSA for surveying the vasculature surrounding the spinal cord and for orienting selective catheterization. IA-CTA can complement spinal DSA, curtail unnecessary segmental injections, and thus reduce procedural complications.

Bone-Subtracted Spinal CT Angiography Using Nonrigid Registration for Better Visualization of Arterial Feeders in Spinal Arteriovenous Fistulas

BACKGROUND AND PURPOSE

Pretreatment diagnosis for the location of shunts and arterial feeders of spinal arteriovenous fistulas is crucial. This study aimed to evaluate the utility of subtracted CT angiography imaging by using nonrigid registration (R-CTA) in patients with spinal arteriovenous fistulas compared with conventional CTA imaging.

MATERIALS AND METHODS

The records of 15 consecutive subjects (mean age, 65 years; 2 women) who had undergone CTA and digital subtraction angiography for clinically suspected spinal arteriovenous fistula were reviewed. From CTA images obtained at the arterial and late arterial phases, warped images of the late arterial phase were obtained by using nonrigid registration that was adjusted to the arterial phase images. R-CTA images were then obtained by subtracting the warped images from the arterial phase images. The accuracies of using nonrigid registration and conventional spinal CTA and the time required for detecting arterial feeders in spinal arteriovenous fistulas were analyzed for each patient with DSA results as a standard reference. The difference between R-CTA and conventional spinal CTA was assessed by the Welch test and the McNemar χ(2) test.

RESULTS

R-CTA had a higher accuracy compared with conventional spinal CTA (80% versus 47%, P = .025). The time for interpretation was reduced in R-CTA compared with conventional spinal CTA (45.1 versus 97.1 seconds, P = .002).

CONCLUSIONS

Our subtracted CTA imaging by using nonrigid registration detects feeders of spinal arteriovenous fistulas more accurately and quickly than conventional CTA.

Intramedullary hemorrhage from a thoracolumbar dural arteriovenous fistula

BACKGROUND CONTEXT

Spinal dural arteriovenous fistulas (AVFs) are acquired lesions presenting typically with neurologic deficits secondary to chronic congestive myelopathy. The low-flow and low-volume nature of these lesions makes hemorrhage very unlikely, and intramedullary hemorrhage caused by thoracolumbar dural AVFs is exceedingly rare.

PURPOSE

The purpose of this study was to report a case of intramedullary hemorrhage caused by a thoracolumbar dural AVF.

STUDY DESIGN/SETTING

The study design included a case report and review of literature.

METHODS

A case of intramedullary hemorrhage from a thoracolumbar dural AVF was reported, and the literature regarding hemorrhagic presentations of dural AVF was reviewed.

RESULTS

A 66-year-old woman presented with a sudden onset of abdominal pain, paraplegia, sensory loss below the costal margins, and urinary retention. Magnetic resonance imaging scan showed intramedullary hemorrhage with abnormal flow voids raising suspicion of an intramedullary AV malformation. However, subsequent selective spinal angiography demonstrated a spinal dural AVF fed by the T7 intercostal artery and a varix within the draining vein. Complete obliteration of the dural AVF and the varix was achieved via embolization. As far as we are aware, there are only two other similar cases in the literature. Literature review revealed that presentation of thoracolumbar dural AVFs with hemorrhage is frequently associated with accelerated venous flow and the presence of a venous varix.

CONCLUSIONS

Although very unusual, a spinal dural AVF may present with intramedullary hemorrhage, and hemorrhage in such conditions may be associated with an accelerated venous flow and the presence of a venous varix.

Comparison of dynamic contrast-enhanced 3T MR and 64-row multidetector CT angiography for the localization of spinal dural arteriovenous fistulas

BACKGROUND AND PURPOSE

For the localization of spinal dural arteriovenous fistulas, it is not determined whether dynamic contrast-enhanced MRA is more reliable than multidetector CTA. The aim of this study was to compare the agreement between intra-arterial DSA, dynamic contrast-enhanced MRA at 3T, and 64-row multidetector CTA for the localization of spinal dural arteriovenous fistulas.

MATERIALS AND METHODS

We enrolled 12 consecutive patients (11 men, 1 woman; age range, 46-83 years; mean, 65 years) who underwent preoperative dynamic contrast-enhanced MRA at 3T and 64-row multidetector CTA. The spinal dural arteriovenous fistula location was confirmed by intra-arterial DSA as the reference standard. Two reviewers independently evaluated the level of the artery feeding the spinal dural arteriovenous fistula on the basis of continuity between the feeder and abnormal spinal vessels on 3T dynamic contrast-enhanced MRA and 64-row multidetector CTA images. Interobserver and intermodality agreement was determined by calculation of the κ coefficient.

RESULTS

On DSA, the vessel feeding the spinal dural arteriovenous fistula was the intercostal artery (7 cases), the lumbar artery (3 cases), and the internal iliac artery or the ascending pharyngeal artery (1 case each). For the fistula level, interobserver agreement was excellent for 3T dynamic contrast-enhanced MRA (κ = 0.97; 95% CI, 0.92-1.00) and very good for 64-row multidetector CTA (κ = 0.84; 95% CI, 0.72-0.96). Intermodality agreement with DSA was good for 3T dynamic contrast-enhanced MRA (κ = 0.78; 95% CI, 0.49-1.00) and moderate for 64-row multidetector CTA (κ = 0.41; 95% CI, 0.020-0.84).

CONCLUSIONS

For the localization of spinal dural arteriovenous fistulas, 3T dynamic contrast-enhanced MRA may be more reliable than 64-row multidetector CTA.

The diagnosis of spinal dural arteriovenous fistulas

STUDY DESIGN

Retrospective consecutive case series.

OBJECTIVE

To review and analyze clinical presentations and radiological imaging of 326 consecutive patients with spinal dural arteriovenous fistula (SDAVF) from 2 institutions.

SUMMARY OF BACKGROUND DATA

The clinical presentations of SDAVF are nonspecific. Patients may be initially diagnosed with other spinal diseases. Magnetic resonance imaging (MRI) can reveal spinal cord changes associated with the disorder, but neurosurgeons often overlook these changes.

METHODS

From 1989 to 2009, 326 patients were diagnosed with SDAVF and treated at Qilu Hospital of Shandong University and the Xuanwu Hospital of the Capital University of Medical Sciences. We retrospectively reviewed the clinical records and radiological images of all patients, and collected and analyzed the related data.

RESULTS

Two hundred eighty-two males and 44 females (male/female ratio 6.4:1; mean age, 53.9 yr; SD, 12.1) were included in the study. Fistulas were located at the T7 spinal segment (41, 12.6%), but were more typically found at T5 to L5 (273, 82.5%). The most common initial symptoms were lower extremity weakness (234, 71.8%), sensory disturbance (229, 70.2%), and sphincter disturbance (87, 26.7%). These percentages increased to, 85.6%, 80.8%, and 52.5%, respectively, until patients were properly diagnosed. The mean diagnostic time to SDAVF was 19.9 months (SD, 25.2). Two major changes noted on magnetic resonance images were intramedullary T2-weighted signal hyperintensity (284, 87.1%) and perimedullary dilated vessels (251, 77%). Fistulas were often located outside of the vertebral segments of T2-weighted signal change (P = 0.005). Magnetic resonance angiography and computed tomography angiography of 33 (71.7%) patients revealed perimedullary dilated vessels and precisely located fistulas in 19 (41.3%) patients. Magnetic resonance angiography and computed tomography angiography studies of the perimedullary vessels also led to identification of a second fistula through angiography. Degenerative disc disease and myelitis were the most common misdiagnoses, and the patients were often treated incorrectly.

CONCLUSION

"Worsening" and "symptoms combination" are progression characteristics of SDAVF. Patients should undergo spinal magnetic resonance imaging when they are first suspected to have SDAVF. Magnetic resonance angiography and computed tomography angiography as noninvasive angiography are helpful for diagnosis.