Decubitus CT Myelography for Detecting Subtle CSF Leaks in Spontaneous Intracranial Hypotension

[Spinal Presentation of Spontaneous Intracranial Hypotension]

Spontaneous intracranial hypotension (SIH), which generally presents as orthostatic headache, is increasingly being identified due to improved imaging technologies and heightened awareness. Many prior studies have reported the characteristic brain MRI findings of SIH. However, recently, focus has shifted to spinal MRI, as SIH is believed to be caused by leakage of cerebrospinal fluid from the spinal dural sac. Advanced techniques such as ultrafast CT myelography and digital subtraction myelography have emerged as useful technique to identify the site of cerebrospinal fluid leakage. In this review, we discuss the diagnosis, spinal MRI findings, imaging techniques, and treatment of SIH.

Temporal Characteristics of CSF-Venous Fistulas on Dynamic Decubitus CT Myelography: A Retrospective Multi-Institution Cohort Study

BACKGROUND AND PURPOSE

CSF-venous fistula can be diagnosed with dynamic decubitus CT myelography. This study aimed to analyze the temporal characteristics of CSF-venous fistula visualization on multiphase decubitus CT myelography.

MATERIALS AND METHODS

A retrospective, multisite study was conducted on patients diagnosed with CSF-venous fistula at 2 institutions between June 2017 and February 2023. Both institutions perform decubitus CT myelography with imaging immediately following injection and usually with at least 1 delayed scan. The conspicuity of CSF-venous fistula was assessed on each phase of imaging.

RESULTS

Forty-eight patients with CSF-venous fistula were analyzed. CSF-venous fistulas were better visualized on the early pass in 25/48 cases (52.1%), the delayed pass in 6/48 cases (12.5%) and were seen equally on both passes in 15/48 cases (31.3%). Of 25 cases in which the CSF-venous fistula was better visualized on the early pass, 21/25 (84%) fistulas were still at least partially visible on a delayed pass. Of 6 cases in which the CSF-venous fistula was better visualized on a delayed pass, 4/6 (67%) were partially visible on the earlier pass. Six of 48 (12.5%) CSF-venous fistulas were visible only on a single pass. Of these, 4/6 (66.7%) were seen only on the first pass, and 2/6 (33.3%) were seen only on a delayed pass. One fistula was found with one pass only, and one fistula was discovered upon contralateral decubitus imaging without a dedicated second injection.

CONCLUSIONS

A dynamic decubitus CT myelography imaging protocol that includes an early and delayed phase, likely increases the sensitivity for CSF-venous fistula detection. Further studies are needed to ascertain the optimal timing and technique for CSF-venous fistula visualization on dynamic decubitus CT myelography and its impact on patient outcomes.

Lateral Decubitus Dynamic CT Myelography with Real-Time Bolus Tracking (dCTM-BT) for Evaluation of CSF-Venous Fistulas: Diagnostic Yield Stratified by Brain Imaging Findings

BACKGROUND AND PURPOSE

CSF-venous fistulas (CVFs) associated with spontaneous intracranial hypotension (SIH) may have a transient appearance, relative to contrast arrival, which may influence the diagnostic performance of lateral decubitus CT myelography (CTM). We developed a dynamic CTM protocol using real-time bolus-tracking (dCTM-BT) to improve the temporal resolution and standardize the timing of CTM acquisitions post-intrathecal contrast administration. The purpose of our study was to evaluate the feasibility of the dCTM-BT technique and evaluate its diagnostic yield for CVF detection, stratified by brain MRI SIH findings.

MATERIALS AND METHODS

Patients with suspected SIH without extradural fluid collection on spine MRI who underwent dCTM-BT were retrospectively reviewed. CT bolus monitoring was performed at the upper thoracic level. Following the visualization of dense intrathecal contrast, at least 3 CTM acquisitions of the spine were obtained and reviewed by 2 neuroradiologists. The Bern SIH score was calculated on the brain MRI. The diagnostic yield for CVF detection was evaluated, stratified by Bern score categories and a receiver operating characteristic (ROC) analysis.

RESULTS

Out of 48 patients, 23 (48%) had a CVF on dCTM-BT, located at T1-5 (n = 4), T6-12 (n = 18), L1 (n = 1), with 70% on the right. CVF was identified in 22/22 (100%) of patients who had a high Bern score, 1/7 (14%) of those who had an intermediate score, and 0/19 (0%) of those who had a low score. The area under the ROC curve was 0.99 (95% CI, 0.98-1.00). The optimal cutoff was a Bern score of ≥5 (96% sensitivity, 100% specificity).

CONCLUSIONS

dCTM-BT is feasible and has excellent diagnostic performance for CVF identification/localization. The Bern score is strongly associated with CVF detection and may help inform who will benefit from dCTM-BT.

Diagnostic Performance of Decubitus Photon-Counting Detector CT Myelography for the Detection of CSF-Venous Fistulas

BACKGROUND AND PURPOSE

CSF-venous fistulas are a common cause of spontaneous intracranial hypotension. Lateral decubitus digital subtraction myelography and CT myelography are the diagnostic imaging standards to identify these fistulas. Photon-counting CT myelography has technological advantages that might improve CSF-venous fistula detection, though no large studies have yet assessed its diagnostic performance. We sought to determine the diagnostic yield of photon-counting detector CT myelography for detection of CSF-venous fistulas in patients with spontaneous intracranial hypotension.

MATERIALS AND METHODS

We retrospectively searched our database for all decubitus photon-counting detector CT myelograms performed at our institution since the introduction of the technique in our practice. Per our institutional workflow, all patients had prior contrast-enhanced brain MR imaging and spine MR imaging showing no extradural CSF. Two neuroradiologists reviewed preprocedural brain MRIs, assessing previously described findings of intracranial hypotension (Bern score). Additionally, 2 different neuroradiologists assessed each myelogram for a definitive or equivocal CSF-venous fistula. The yield of photon-counting detector CT myelography was calculated and stratified by the Bern score using low-, intermediate-, and high-probability tiers.

RESULTS

Fifty-seven consecutive photon-counting detector CT myelograms in 57 patients were included. A single CSF-venous fistula was definitively present in 38/57 patients. After we stratified by the Bern score, a definitive fistula was seen in 56.0%, 73.3%, and 76.5% of patients with low-, intermediate-, and high-probability brain MR imaging, respectively.

CONCLUSIONS

Decubitus photon-counting detector CT myelography has an excellent diagnostic performance for the detection of CSF-venous fistulas. The yield for patients with intermediate- and high-probability Bern scores is at least as high as previously reported yields of decubitus digital subtraction myelography and CT myelography using energy-integrating detector scanners. The yield for patients with low-probability Bern scores appears to be greater compared with other modalities. Due to the retrospective nature of this study, future prospective work will be needed to compare the sensitivity of photon-counting detector CT myelography with other modalities.

Direct comparison of digital subtraction myelography versus CT myelography in lateral decubitus position: evaluation of diagnostic yield for cerebrospinal fluid-venous fistulas

BACKGROUND

Cerebrospinal fluid (CSF)-venous fistulas (CVFs) are increasingly identified as a cause of spontaneous intracranial hypotension (SIH). Lateral decubitus digital subtraction myelography (LD-DSM) and CT myelography (LD-CTM) are mainly used for detection, but the most sensitive method is yet unknown.

OBJECTIVE

To compare LD-DSM with LD-CTM for diagnostic yield of CVFs.

METHODS

Patients with SIH diagnosed with a CVF between January 2021 and December 2022 in which the area of CVF(s) was covered by both diagnostic modalities were included. LD-CTM immediately followed LD-DSM without repositioning the spinal needle, and the second half of the contrast agent was injected at the CT scanner. Patients were awake or mildly sedated. Retrospectively, two neuroradiologists evaluated data independently and blinded for the presence of CVF.

RESULTS

Twenty patients underwent a total of 27 combined LD-DSM/LD-CTM examinations (4/20 with follow-up and 3/20 with bilateral examinations). Both raters identified significantly more CVFs with LD-CTM than with LD-DSM (rater 1: 39 vs 9, P<0.001; rater 2: 42 vs 12, P<0.001). Inter-rater agreement was substantial for LD-DSM (κ=0.732) and LD-CTM (κ=0.655). The results remained significant after considering the senior rating for cases of disagreement (39 vs 10; P<0.001), and no CVF detected on LD-DSM was missed on LD-CTM.

CONCLUSION

In this study, LD-CTM has a higher diagnostic yield for the detection of CVFs than LD-DSM and should supplement LD-DSM, but further studies are needed. LD-CTM can be easily acquired in awake or mildly sedated patients with the second half of contrast injected just before CT scanning, or it may be considered as a stand-alone investigation.

A Novel Patient-Positioning Device for Dynamic CT Myelography

We describe a novel patient-positioning device for dynamic CT myelography. Dynamic CT myelography requires angling the patient's spine to distribute dense contrast along the dependent thecal sac. The proposed device is constructed of a low-density reinforced polymer frame and can be raised or lowered to various heights with a hand-operated mechanism, allowing precise adjustment of the spinal angle and control of the contrast bolus, increasing the safety, reproducibility, and sensitivity of dynamic CT myelography.

Incremental diagnostic yield and clinical outcomes of lateral decubitus CT myelogram immediately following negative lateral decubitus digital subtraction myelogram

INTRODUCTION

Spontaneous intracranial hypotension (SIH) caused by a spinal cerebrospinal fluid (CSF) leak classically presents with orthostatic headache. Digital subtraction myelography (DSM) has a well-established diagnostic yield in the absence of extradural spinal collection. At our institution, DSM is followed by lateral decubitus CT myelogram (LDCTM) in the same decubitus position to increase diagnostic yield of the combined study. We evaluated the incremental diagnostic yield of LDCTM following negative DSM and reviewed patient outcomes.

METHODS

Retrospective review of consecutive DSMs with subsequent LDCTM from April 2019 to March 2021 was performed. Combined reports were reviewed, and studies with positive DSMs were excluded. Of the exams with negative DSM, only studies with LDCTM reports identifying potential leak site were included. Interventions and follow-up clinical notes were reviewed to assess symptoms improvement following treatment.

RESULTS

Of the 83 patients with negative DSMs, 11 (13.2%) had positive leak findings on LDCTMs, and 21 (25.3%) were equivocal. Of 11 positive LDCTMs, 6 leaks were nerve sheath tears (NSTs) and 5 were CSF-venous fistulas (CVFs). 10/11 (90.9%) had intervention and follow-up, with 9/10 (90%) having positive clinical outcome. Of the 21 equivocal LDCTM patients (19 CVFs and 2 NSTs), 15 (71.4%) had interventions and follow-up, with 3/15 (20.0%) with positive clinical outcomes.

CONCLUSION

LDCTM following negative DSM has an incremental diagnostic yield up to 38.6%, with up to 14.5% of positive patient outcomes following treatment. LDCTM should be considered after DSM to maximize diagnostic yield of the combined exam.

Resisted Inspiration Improves Visualization of CSF-Venous Fistulas in Spontaneous Intracranial Hypotension

BACKGROUND AND PURPOSE

CSF-venous fistulas are an important cause of spontaneous intracranial hypotension but are challenging to detect. A newly described technique known as resisted inspiration has been found to augment the CSF-venous pressure gradient and was hypothesized to be of potential use in CSF-venous fistula detection but has not yet been investigated in patients with spontaneous intracranial hypotension. The purpose of this investigation was to determine whether resisted inspiration results in improved visibility of CSF-venous fistulas on CT myelography in patients with spontaneous intracranial hypotension.

MATERIALS AND METHODS

A retrospective cohort of patients underwent CT myelography from November 2022 to January 2023. Patients with an observed or suspected CSF-venous fistula identified during CT myelography using standard maximum suspended inspiration were immediately rescanned using resisted inspiration and the Valsalva maneuver. The visibility of the CSF-venous fistula among these 3 respiratory phases was compared, and changes in venous drainage patterns between phases were assessed.

RESULTS

Eight patients with confirmed CSF-venous fistulas who underwent CT myelography using the 3-phase respiratory protocol were included. Visibility of the CSF-venous fistula was greatest during resisted inspiration in 5/8 (63%) of cases. Visibility was optimal with the Valsalva maneuver and maximum suspended inspiration in 1 case each, and it was equivalent in all respiratory phases in 1 case. In 2/8 (25%) cases, the pattern of venous drainage shifted between respiratory phases.

CONCLUSIONS

In patients with spontaneous intracranial hypotension, resisted inspiration improved visualization of CSF-venous fistulas in most, but not all, cases. Further investigation is needed to determine the impact of this technique on the overall diagnostic yield of myelography in this condition.

Utility of Photon-Counting Detector CT Myelography for the Detection of CSF-Venous Fistulas

CSF-venous fistulas are an increasingly recognized type of CSF leak that can be particularly challenging to detect, even with recently improved imaging techniques. Currently, most institutions use decubitus digital subtraction myelography or dynamic CT myelography to localize CSF-venous fistulas. Photon-counting detector CT is a relatively recent advancement that has many theoretical benefits, including excellent spatial resolution, high temporal resolution, and spectral imaging capabilities. We describe 6 cases of CSF-venous fistulas detected on decubitus photon-counting detector CT myelography. In 5 of these cases, the CSF-venous fistula was previously occult on decubitus digital subtraction myelography or decubitus dynamic CT myelography using an energy-integrating detector system. All 6 cases exemplify the potential benefits of photon-counting detector CT myelography in identifying CSF-venous fistulas. We suggest that further implementation of this imaging technique will likely be valuable to improve the detection of fistulas that might otherwise be missed with currently used techniques.

Conebeam CT as an Adjunct to Digital Subtraction Myelography for Detection of CSF-Venous Fistulas

Lateral decubitus digital subtraction myelography is an effective technique for precisely localizing CSF-venous fistulas, a common cause of spontaneous intracranial hypotension. However, despite an optimal imaging technique, digital subtraction myelography fails to identify some CSF-venous fistulas for a variety of reasons. Here, we describe a technique involving conebeam CT performed during intrathecal contrast injection as an adjunct to digital subtraction myelography, allowing identification of some otherwise-missed CSF-venous fistulas.

Surgical Ligation of Spinal CSF-Venous Fistulas after Transvenous Embolization in Patients with Spontaneous Intracranial Hypotension

A spinal CSF-venous fistula is an increasingly recognized type of CSF leak that causes spontaneous intracranial hypotension. The detection of these fistulas requires specialized imaging such as digital subtraction myelography or dynamic CT myelography, and several treatment options are available. A novel treatment for these CSF-venous fistulas consisting of transvenous embolization with the liquid embolic agent Onyx has been described recently, but some patients require further treatment if embolization fails. The purpose of this study was to evaluate the safety and effectiveness of surgery following transvenous embolization. In a series of 6 consecutive patients who underwent surgical ligation of the fistula after endovascular embolization, there were no surgical complications. Postoperatively, complete resolution of symptoms was reported by 5 of the 6 patients, and brain MR imaging findings of spontaneous intracranial hypotension resolved in all patients. This study suggests that surgical ligation of spontaneous spinal CSF-venous fistulas after endovascular embolization is effective and safe.

Lateral decubitus dynamic CT myelography for fast cerebrospinal fluid leak localization

Dynamic CT myelography is used to precisely localize fast spinal CSF leaks. The procedure is most commonly performed in the prone position, which successfully localizes most fast ventral leaks. We have recently encountered a small subset of patients in whom prone dynamic CT myelography is unsuccessful in localizing leaks. We sought to determine the added value of lateral decubitus dynamic CT myelography, which is occasionally attempted in our practice, in localizing the leak after failed prone dynamic CT myelography. We retrospectively identified 6 patients who underwent lateral decubitus dynamic CT myelography, which was performed in each case because their prone dynamic CT myelogram was unrevealing. Two neuroradiologists independently reviewed preprocedural spine MRI and all dynamic CT myelograms for each patient. Lateral decubitus positioning allowed for precise leak localization in all 6 patients. Five of six patients were noted to have dorsal and/or lateral epidural fluid collections on spine MRI. One patient had a single prominent diverticulum on spine MRI (larger than 6 mm), whereas the others had no prominent diverticula. Our study suggests that institutions performing dynamic CT myelography to localize fast leaks should consider a lateral decubitus study if performing the study in the prone position is unrevealing. Furthermore, the presence of dorsal and/or lateral epidural fluid collections on spine MRI may suggest that a lateral decubitus study is of higher yield and could be considered initially.

Same-Day Bilateral Decubitus CT Myelography for Detecting CSF-Venous Fistulas in Spontaneous Intracranial Hypotension

Lateral decubitus CT myelography is a sensitive technique for detecting CSF-venous fistulas in patients with spontaneous intracranial hypotension. It might be necessary to perform bilateral studies to locate a fistula. We report on the feasibility of obtaining diagnostic-quality bilateral decubitus CT myelography in a single session, avoiding the need to schedule separate examinations for the left and right sides on different days.

Diagnostic Yield of Intrathecal Gadolinium MR Myelography for CSF Leak Localization

PURPOSE

Intrathecal gadolinium magnetic resonance (MR) myelography can be used to localize various types of spinal cerebrospinal fluid (CSF) leaks; however, its diagnostic yield is not well known. We sought to determine the diagnostic yield of MR myelography in patients with spontaneous intracranial hypotension.

METHODS

A retrospective review was performed on all patients who had undergone intrathecal gadolinium MR myelography at our institution from 2002 to 2020 for suspected spinal CSF leak. The MR myelography images were reviewed for the presence or absence of a spinal CSF leak site. Images were also evaluated for the presence an extradural fluid collection.

RESULTS

A total of 97 patients were included in the final cohort. The average age was 52.6 years; 67.0% were female, 4 patients underwent 2 examinations each, yielding a total of 101 MR myelograms. The source of a spinal CSF leak was localized in 14 patients. The diagnostic yield for CSF leak localization on intrathecal gadolinium MR myelography was 14/101 (13.9%) per GdM examination and 14/97 (14.4%) per patient. Among the subset of patients without extradural fluid collections, the yield was 15.7% per examination. All detected leaks were either CSF-venous fistulas or distal nerve root sleeve tears.

CONCLUSION

Intrathecal gadolinium MR myelography is capable of localizing CSF-venous fistulas and distal nerve root sleeve tears; however, our data show that it has a limited diagnostic yield. We suggest that other modalities may be a better first step before attempting intrathecal gadolinium MR myelography.

Spinal Compliance Curves: Preliminary Experience with a New Tool for Evaluating Suspected CSF Venous Fistulas on CT Myelography in Patients with Spontaneous Intracranial Hypotension

BACKGROUND AND PURPOSE

Craniospinal space compliance reflects the distensibility of the spinal and intracranial CSF spaces as a system. Craniospinal space compliance has been studied in intracranial pathologies, but data are limited in assessing it in spinal CSF leak. This study describes a method to estimate craniospinal space compliance using saline infusion during CT myelography and explores the use of craniospinal space compliance and pressure-volume curves in patients with suspected cerebrospinal-venous fistula.

MATERIALS AND METHODS

Patients with suspected cerebrospinal-venous fistula underwent dynamic CT myelography. During the procedure, 1- to 5-mL boluses of saline were infused, and incremental changes in CSF pressure were recorded. These data were used to plot craniospinal space compliance curves. We calculated 3 quantitative craniospinal space compliance parameters: overall compliance, compliance at opening pressure, and the pressure volume index. These variables were compared between patients with confirmed cerebrospinal-venous fistula and those with no confirmed source of CSF leak.

RESULTS

Thirty-four CT myelograms in 22 patients were analyzed. Eight of 22 (36.4%) patients had confirmed cerebrospinal-venous fistulas. Bolus infusion was well-tolerated with no complications and transient headache in 2/34 (5.8%). Patients with confirmed cerebrospinal-venous fistulas had higher compliance at opening pressure and overall compliance (2.6 versus 1.8 mL/cm H₂0, P < .01). There was no difference in the pressure volume index (77.5 versus 54.3 mL, P = .13) between groups.

CONCLUSIONS

A method of deriving craniospinal space compliance curves using saline intrathecal infusion is described. Preliminary analysis of craniospinal space compliance curves provides qualitative and quantitative information about pressure-volume dynamics and may serve as a diagnostic tool in patients with known or suspected cerebrospinal-venous fistulas.

A Novel Endovascular Therapy for CSF Hypotension Secondary to CSF-Venous Fistulas

We report a consecutive case series of patients who underwent transvenous embolization of the paraspinal vein, which was draining the CSF-venous fistula, for treatment of spontaneous intracranial hypotension. These are the first-ever reported cases of this treatment for CSF-venous fistulas. All patients underwent spinal venography following catheterization of the azygous vein and then selective catheterization of the paraspinal vein followed by embolization of the vein with Onyx. All patients had improvement of clinical and radiologic findings with 4 patients having complete resolution of headaches and 1 patient having 50% reduction in headache symptoms. Pachymeningeal enhancement resolved in 4 patients and improved but did not resolve in 1 patient. Brain sag resolved in 4 patients and improved but did not resolve in 1 patient. There were no cases of permanent neurologic complications. All patients were discharged home on the day of the procedure.

Decubitus CT Myelography for CSF-Venous Fistulas: A Procedural Approach

Decubitus CT myelography is a reported method to identify CSF-venous fistulas in patients with spontaneous intracranial hypotension. One of the main advantages of decubitus CT myelography in detecting CSF-venous fistulas is using gravity to dependently opacify the CSF-venous fistula, which can be missed on traditional myelographic techniques. Most of the CSF-venous fistulas in the literature have been identified in patients receiving general anesthesia and digital subtraction myelography, a technique that is not performed at all institutions. In this article, we discuss the decubitus CT myelography technique and how to implement it in daily practice.

Respiratory Phase Affects the Conspicuity of CSF-Venous Fistulas in Spontaneous Intracranial Hypotension

Spinal CSF-venous fistulas are a cause of spontaneous intracranial hypotension that can be difficult to detect on imaging. We describe how the respiratory phase affects the visibility of CSF-venous fistulas during myelography.

MR Myelography for the Detection of CSF-Venous Fistulas

CSF-venous fistula is an important treatable cause of spontaneous intracranial hypotension that is often difficult to detect using traditional imaging techniques. Herein, we describe the technical aspects and diagnostic performance of MR myelography when used for identifying CSF-venous fistulas. We report 3 cases in which the CSF-venous fistula was occult on CT myelography but readily detected using MR myelography.