Spontaneous intracranial hypotension due to CSF-venous fistula: Evaluation of renal accumulation of contrast following decubitus myelography and maintained decubitus CT to improve fistula localization.

PURPOSE: Presented here is a strategy of sequential lateral decubitus digital subtraction myelography (LDDSM) followed closely by lateral decubitus CT (LDCT) to facilitate cerebrospinal fluid (CSF)-venous fistula (CVF) localization. MATERIALS AND METHODS: This is a retrospective analysis of patients referred to our institution for evaluation of CSF leak. Patients with Type 1 and Type 2 leaks, and those not displaying MR brain stigmata of intracranial hypotension were excluded. All patients underwent consecutive LDDSM and LDCT. If the CVF was not localized on the first LDDSM-LDCT pair the patient returned for contralateral examinations. Images were reviewed for CVF and for accumulation of contrast within the renal pelvises expressed as a renal pelvis contrast score (RPCS) in Hounsfield units (HU). RESULTS: Twenty-two patients were included in this study. In 21 of 22 patients (95%) a CVF was identified yielding an RPCS for the LDDSM-LDCT pair ipsilateral to the CVF ranging from 71 to 423 with an average of 146 HU. An RPCS of the negative side LDDSM-LDCT pair contralateral to a CVF was available in 8 patients and averaged 51 HU. In 4 patients the initial bilateral LDDSM-LDCT pairs did not reveal the location of the CVF however in 3 of these 4 cases the CVF was revealed on a third LDDSM repeated ipsilateral to the higher RPCS. CONCLUSION: The strategy of sequential LDDSM-LDCT coupled with evaluation of renal accumulation of contrast agent appears to improve the rate of CVF localization and warrants further evaluation.

The presence of pachymeningeal hyperintensity on non-contrast flair imaging in patients with spontaneous intracranial hypotension.

PURPOSE: Traditionally, in the work-up of patients for spontaneous intracranial hypotension, T1 post-contrast imaging is performed in order to assess for pachymeningeal enhancement. The aim of this study is to assess whether pachymeningeal hyperintensity can be identified on a non-contrast FLAIR sequence in these patients as a surrogate sign for pachymeningeal enhancement. METHODS: The patient cohort was identified from a prospectively maintained database of patients with a clinical diagnosis of intracranial hypotension. Patients who had both a post-contrast T1 sequence brain as well as non-contrast FLAR sequence of the brain were reviewed. Imaging was retrospectively reviewed by three independent neuroradiologists. Each study was assessed for the presence or absence of pachymeningeal hyperintensity on the FLAIR sequence. RESULTS: From January 2010 to July 2022, 177 patients were diagnosed with spontaneous intracranial hypotension. In total, 121 were excluded as post-contrast imaging was not performed during their work-up. Twenty-four were excluded as the FLAIR sequence was performed after administration of contrast. Six were excluded as there was no pachymeningeal thickening present on T1 post-contrast imaging, although there were other signs of intracranial hypotension. The study group therefore consisted of 26 patients. Pachymeningeal thickening was correctly identified on the non-contrast FLAIR sequence in all patients (100%). CONCLUSION: Where present, diffuse pachymeningeal hyperintensity can be accurately identified on a non-contrast FLAIR sequence in patients with spontaneous intracranial hypotension. This potentially obviates the need for gadolinium base contrast agents in the work-up of these patients.

Minimally invasive surgery for spinal cerebrospinal fluid-venous fistula ligation: patient series.

BACKGROUND: Cerebrospinal fluid-venous fistulas (CVFs) may cause cerebrospinal fluid leaks resulting in spontaneous intracranial hypotension (SIH). Surgical treatment of CVFs aims to eliminate abnormal fistulous connections between the subarachnoid space and the epidural venous plexus at the level of the nerve root sleeve. The authors propose a percutaneous minimally invasive technique for surgical ligation of CVF as an alternative to the traditional open approach using a tubular retractor system. OBSERVATIONS: Minimally invasive surgical (MIS) ligation of spinal CVF was performed in 5 patients for 6 CVFs. The definite disconnection of the CVF was achieved in all patients by clipping and additional silk tie ligation of the fistula. None of the patients experienced surgical complications or required transition to an open procedure. One patient underwent 2 MIS procedures for 2 separate CVFs. Postoperative clinical follow-up and cranial magnetic resonance imaging confirmed resolution of symptoms and radiographic SIH stigmata. LESSONS: MIS ligation of CVFs is safe and efficient. It represents an elegant and less invasive procedure, reducing the risk of wound infections and time to recovery. However, preparedness for open ligation is warranted within the same surgical setting in cases of complications and difficult accessibility.

Digital Subtraction Myelography is Associated with Less Radiation Dose than CT-based Techniques.

PURPOSE: Both CT myelogram (CTM) and digital-subtraction myelogram (DSM) can be used to evaluate patients for possible cerebrospinal fluid (CSF) leaks. DSM is a relatively new technique. No data exists on the radiation dose associated with this procedure, and how it compares with CTM. MATERIALS AND METHODS: All patients who underwent DSM for spontaneous intracranial hypotension (SIH) refractory to blood patching from Dec 2016 - Sept 2019 were retrospectively assessed. DSM dose factors were then recorded (cumulative fluoroscopy time, total kerma area product (KAP, mGy.cm2), cumulative air kerma (mGy), as well as CTM dose factors (included CTDIvol (mGy) and dose-length product (DLP, mGy.cm). These indices were then used to calculate the effective dose for both procedures using standardized conversion factors. RESULTS: 61 DSMs were performed in 42 patients, 33 of which also underwent CTM. The median effective dose was 6.6 mSv per DSM study (range: 1.2 - 17.7). On a per-patient basis (i.e. those patients who underwent more than one DSM (as the initial one was negative), the median total effective dose was 13 mSv for their total DSM imaging (range: 2.6 -31.7). For the CTM, the median effective dose was 19.7 mSv (range: 3.2 - 82.4 mSv). CONCLUSION: The radiation dose with DSM appears to be significantly lower than that of CTM (p = 0.0005), when looking at CTM doses both from our institution and in the published literature.

Spontaneous spinal CSF-venous fistulas associated with venous/venolymphatic vascular malformations: report of 3 cases.

Spontaneous CSF-venous fistulas may be present in up to one-fourth of patients with spontaneous intracranial hypotension. This is a recently discovered type of CSF leak, and much remains unknown about these fistulas. Spinal CSF-venous fistulas are usually seen in coexistence with a spinal meningeal diverticulum, suggesting the presence of an underlying structural dural weakness at the proximal portion of the fistula. The authors now report the presence of soft-tissue venous/venolymphatic malformations associated with spontaneous spinal CSF-venous fistulas in 2 patients with spontaneous intracranial hypotension, suggesting a role for distal venous pathology. In a third patient with spontaneous intracranial hypotension and a venolymphatic malformation, such a CSF-venous fistula is strongly suspected.

Lateral decubitus digital subtraction myelography to identify spinal CSF-venous fistulas in spontaneous intracranial hypotension.

OBJECTIVE: Spontaneous spinal CSF-venous fistulas are a distinct type of spinal CSF leak recently described in patients with spontaneous intracranial hypotension (SIH). Using digital subtraction myelography (DSM) with the patient in the prone position, the authors have been able to demonstrate such fistulas in about one-fifth of patients with SIH in whom conventional spinal imaging (MRI or CT myelography) showed no evidence for a CSF leak (i.e., the presence of extradural CSF). The authors compared findings of DSM with patients in the lateral decubitus position versus the prone position and now report a significantly increased yield of identifying spinal CSF-venous fistulas with this modification of their imaging protocol. METHODS: The population consisted of 23 patients with SIH who underwent DSM in the lateral decubitus position and 26 patients with SIH who underwent DSM in the prone position. None of the patients had evidence of a CSF leak on conventional spinal imaging. RESULTS: A CSF-venous fistula was demonstrated in 17 (74%) of the 23 patients who underwent DSM in the lateral decubitus position compared to 4 (15%) of the 26 patients who underwent DSM in the prone position (p < 0.0001). The mean age of these 16 women and 5 men was 52.5 years (range 36-66 years). CONCLUSIONS: Among SIH patients in whom conventional spinal imaging showed no evidence of a CSF leak, DSM in the lateral decubitus position demonstrated a CSF-venous fistula in about three-fourths of patients compared to only 15% of patients when the DSM was performed in the prone position, an approximately five-fold increase in the detection rate. Spinal CSF-venous fistulas are not rare among patients with SIH.

Spontaneous Intracranial Hypotension: A Review and Introduction of an Algorithm For Management.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is a condition of low cerebrospinal fluid volume and pressure caused by a leak of cerebrospinal fluid through a dural defect. Diagnosis and management can be difficult, often requiring coordination between multiple disciplines for myelography, blood patching, and possible surgical repair. Patients should be monitored closely, because they can deteriorate into a coma or even death. There are no widely accepted guidelines for the management of SIH. METHODS AND CONCLUSIONS: We review the existing SIH literature, illustrate management challenges via a case review, and propose an algorithm developed by neurosurgeons, radiologists, and anesthesiologists intended to simplify and streamline the management of SIH.

The accuracy and utility of contrast-enhanced MR angiography for localization of spinal dural arteriovenous fistulas: the Toronto experience.

OBJECTIVES: The purpose of this study was to determine the accuracy and utility of contrast-enhanced MR angiography (CE-MRA) in spinal dural arteriovenous fistulas (SDAVF). METHODS: A retrospective analysis from 1999-2012 identified 70 patients clinically suspected of harboring a SDAVF. Each patient underwent consecutive conventional MR-imaging, CE-MRA, and digital subtraction angiography (DSA). The presence or absence of serpentine flow voids, T2-weighted hyperintensity, and cord enhancement were evaluated, as well as location of the fistula as predicted by CE-MRA. DSA was used as the reference standard. RESULTS: Of the 70 cases, 53 were determined to be a SDAVF, 10 cases were shown to be other forms of vascular malformation, and 7 were DSA-negative. On MRI, all reported cases of SDAVF showed serpentine flow voids (100 %). T2-weighted hyperintensity was seen in 48 of 50 cases (96 %), extending to the conus in 41 of 48 cases (85 %). Cord enhancement was seen in 38 of 41 cases (93 %). CE-MRA correctly localized the SDAVF in 43 of the 53 cases (81 %). CONCLUSIONS: CE-MRA is a useful non-invasive examination for the detection and localization of SDAVF. CE-MRA facilitates but does not replace DSA as confirmation of location, fistula type, and arterial detail, which are required before treatment. KEY POINTS: • CE-MRA correctly localized the site of the SDAVF in over 80 % of cases. • CE-MRA facilitates diagnostic DSA and expedites the diagnostic process. • CE-MRA does not replace diagnostic DSA in SDAVF cases as confirmative test. • CE-MRA provides better understanding of missed or mislocalized SDAVF cases.

Optic chiasm involvement on MRI with ethambutol-induced bitemporal hemianopia.

While ethambutol optic neuropathy usually causes central or cecocentral scotomas, bitemporal visual field defects also have been reported. The pathogenesis of the bitemporal hemianopia has not been established. This article describes magnetic resonance imaging abnormalities involving the optic chiasm in a patient with bitemporal visual field loss. To our knowledge, these neuroimaging findings have not been previously described in association with ethambutol therapy.

Vessel wall MRI to differentiate between reversible cerebral vasoconstriction syndrome and central nervous system vasculitis: preliminary results.

BACKGROUND AND PURPOSE: Prospective differentiation between reversible cerebral vasoconstriction syndrome and central nervous system vasculitis can be challenging. We hypothesized that high-resolution vessel wall MRI would demonstrate arterial wall enhancement in central nervous system vasculitis but not in reversible cerebral vasoconstriction syndrome. METHODS: We identified all patients with multifocal segmental narrowing of large intracranial arteries who had high-resolution vessel wall MRI and follow-up angiography at our institute over a 4-year period and performed a detailed chart review. RESULTS: Three patients lacked arterial wall enhancement, and these all had reversal of arterial narrowing within 3 months. Four patients demonstrated arterial wall enhancement, and these had persistent or progressive arterial narrowing at a median follow-up of 17 months (range, 6-36 months) with final diagnoses of central nervous system vasculitis (3) and cocaine vasculopathy (1). CONCLUSIONS: Preliminary results suggest that high-resolution contrast-enhanced vessel wall MRI may enable differentiation between reversible cerebral vasoconstriction syndrome and central nervous system vasculitis.

Imaging of the intracranial venous system.

BACKGROUND: Evaluation of the intracranial venous system has historically been performed with conventional catheter-based digital subtraction angiography (DSA). The continued importance of DSA can not be overstated in light of its inherent option of endovascular intervention and thrombolysis for cerebral venous thrombosis. DSA is, however, an invasive procedure with associated risks, including radiation exposure, and adverse effects of iodinated contrast medium. DSA also suffers from the limitations of 2-dimensional planar imaging. For these reasons, noninvasive imaging techniques are playing a greater role in evaluation of the intracranial venous system. REVIEW SUMMARY: This review provides an overview of the current noninvasive methods and their applications and limitations, with examples of their use in a variety of disease processes. Computed tomography venography (CTV) is discussed as well as the various types of cerebral magnetic resonance venography (MRV). CONCLUSION: When available, MR supplemented with the technique of triggered gadolinium-enhanced MRV is the method of choice for the diagnosis of dural sinus thrombosis as well as most other pathologic entities affecting the intracranial venous system.

The dural venous sinuses: normal intraluminal architecture defined on contrast-enhanced MR venography.

INTRODUCTION: Our objective was to define the appearance and distribution of normally occurring intraluminal structures within the dural venous sinuses on contrast-enhanced MR venography (CE-MRV). METHODS: Informed consent was obtained from all subjects participating in the study, and the study protocol was approved by the institutional review board of the University Health Network. A group of 56 patients underwent CE-MRV. Intraluminal structures were categorized as an arachnoid granulation (AG) or trabeculation (Willis cord). Willis cords within the transverse and sigmoid sinuses as well as AGs 4 mm or more in size were recorded. RESULTS: In 20 of the 56 patients (36%), 29 AGs measuring 4 mm or more were identified within the dural sinuses. All AGs were spherical or ovoid and occurred at sites where a cortical vein joined a dural sinus. Nearly all AGs (28 of 29, 97%) displayed an eccentric internal vein. Willis cords were seen within the superior sagittal sinus in all patients. Willis cords were less prevalent in the remaining dural sinuses. A minimum of one Willis cord was seen in 58 of the 112 transverse sinuses (52%). These cords were 1-2 mm in maximal thickness, uniformly smooth, and commonly partitioned the sinus. Willis cords and AGs (of any size) were not encountered within the sigmoid sinuses or jugular veins. CONCLUSION: CE-MRV elucidates structures normally found within the dural sinuses. These consist of AGs and Willis cords. This report confirms and establishes new criteria for identification of these normally occurring intraluminal structures providing a basis for their differentiation from pathologic entities.

High-resolution imaging of the intracranial arterial and venous systems following a single contrast injection.

PURPOSE: To generate two separate three-dimensional (3D) high spatial resolution images of the intracranial arterial and venous systems using a single contrast injection. MATERIALS AND METHODS: A 3D contrast-enhanced (CE) magnetic resonance angiography (MRA) acquisition was modified to create two separate k-space data sets to encode the arterial and venous enhancement signals individually after contrast agent injection. Following an automated detection of contrast arrival, the central k-space views corresponding to the arterial phase were acquired for the first eight seconds. A full elliptical-centric acquisition was then acquired for the venous phase and the missing views in the periphery of the first k-space data set were copied from the venous phase. A total of 18 patients underwent this study. Image quality, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were determined in both intracranial systems. RESULTS: Two 3D image sets were generated for the arterial and venous intracranial systems. Both sets have high quality images that are clinically diagnostic. SNR and CNR were high in both sets, so that all the major vessels were visible. CONCLUSION: This technique provides images with high spatial resolution for both arterial and venous intracranial systems using a single contrast injection.

Rapid expansion of a previously asymptomatic subependymoma. Case report.

This 39-year-old man presented with a 6-month history of occipital headaches. Magnetic resonance imaging revealed an irregularly shaped fourth ventricle mass. One month after his initial presentation, he was admitted to the hospital with significant tumor expansion and clinical deterioration. A posterior fossa craniectomy was performed and the mass was resected. Histopathological analysis of this tumor showed central necrosis with associated edema in an otherwise typical and benign-appearing subependymoma. To the authors' knowledge, this is the first reported case of rapid, nonhemorrhagic expansion associated with necrosis in a previously asymptomatic subependymoma.

Surveillance of intracranial aneurysms treated with detachable coils: a comparison of MRA techniques.

Two MRA techniques were evaluated for the follow-up of coiled intracranial aneurysms. Twenty-nine coiled aneurysms were evaluated for a total of 36 follow-up assessments using 3D time-of flight MRA (TOF MRA), an auto-triggered elliptic-centric-ordered three-dimensional gadolinium-enhanced MR angiogram (ATECO MRA), as well as a selective digital subtraction angiography (DSA), which served as the "gold standard". Confident visualization was seen in 36 (100%) of ATECO MRAs and in 32 (89%) of the TOF MRAs. Eleven residual aneurysm components (RACs) greater than 2 mm were described on DSA. Of these, nine were seen on ATECO MRA (sensitivity of 81% and specificity of 88%) and four were seen on TOF MRA (sensitivity of 40% and specificity of 90%). The two RACs not seen on ATECO MRA both measured 3 mm. The six RACs not seen on TOF MRA measured 3, 4 and 5 mm. ATECO MRA provides a non-invasive reliable angiogram for the surveillance of coiled aneurysms and is superior to TOF MRA for this purpose.

Mastoid effusion associated with dural sinus thrombosis.

We present a series of three patients with mastoid air cell effusions associated with adjacent lateral sinus thrombosis. In all of these cases, the findings support the hypothesis that the mastoid effusion is secondary to sinus thrombosis rather then the other way around. Also shown is the chronology and natural evolution of mastoid air cell effusion secondary to sinus thrombosis as seen on planar imaging.

Pulsatile motion effects on 3D magnetic resonance angiography: implications for evaluating carotid artery stenoses.

In-plane carotid artery motion during a 3D MR angiography (MRA) scan can significantly degrade the resulting image resolution. This study characterizes the effect of cardiac pulsatility on 3D contrast-enhanced (CE) MRA with elliptical centric acquisitions using a point-spread function (PSF) analysis. Internal carotid artery (ICA) motion was collected from volunteers and patients using both MR and ultrasound (US) scans. After measuring the carotid artery motion displacement, a simulation was performed which calculated the blurring effects for three different protocols: nongated and two different cardiac gating schemes. The motion sensitivity of each protocol was evaluated for different spatial resolutions. The selection of optimal imaging parameters for a given scan time was investigated. The final results showed that cardiac-gated acquisitions only over a limited region of k-space high spatial frequencies are more time-efficient than cardiac gating for the entire k-space, as it allows for higher resolutions to be achieved and for capturing the arterial phase with low spatial frequencies. Selecting the optimal gating parameters depends directly on the motion characteristics of each individual. Our initial clinical experience is presented, and the need for a real-time tool that characterizes motion behavior for each individual as a prescan protocol is discussed.