Spontaneous intracranial hypotension: updates from diagnosis to treatment.

Spontaneous intracranial hypotension (SIH) is caused by spinal cerebrospinal fluid (CSF) leaks, which result in continued loss of CSF volume and multiple debilitating clinical manifestations. The estimated annual incidence of SIH is 5/100,000. Diagnostic methods have evolved in recent years due to improved understanding of pathophysiology and implementation of advanced myelographic techniques. Here, we synthesize recent updates and contextualize them in an algorithm for diagnosis and treatment of SIH, highlighting basic principles and points of practice variability or continued debate. This discussion includes finer points of SIH diagnosis, CSF leak classification systems, less common types and variants of CSF leaks, brain MRI Bern scoring, potential SIH complications, key technical considerations, and positioning strategies for different types of dynamic myelography. The roles of conservative measures, non-targeted or targeted blood patches, surgery, and recently developed endovascular techniques are presented.

CSF-Venous Fistulas: Anatomy and Diagnostic Imaging.

CSF-venous fistulas (CVFs), first described in 2014, are an important cause of spontaneous intracranial hypotension. CVFs can be challenging to detect on conventional anatomic imaging because, unlike other types of spinal CSF leak, they do not typically result in pooling of fluid in the epidural space, and imaging signs of CVF may be subtle. Specialized myelographic techniques have been developed to help with CVF identification, but these techniques are not yet widely disseminated. This article reviews the current understanding of CVFs, emphasizing correlations between venous anatomy and imaging findings as well as potential mechanisms for pathogenesis, and describes current imaging techniques used for CVF diagnosis and localization. These techniques are broadly classified into fluoroscopy-based methods, including digital subtraction myelography and dynamic myelography, and cross-sectional methods, including decubitus CT myelography and MR myelography with intrathecal injection of gadolinium. Knowledge of these various options, including their relative advantages and disadvantages, is critical in the care of patients with spontaneous intracranial hypotension. Investigation is ongoing, and continued advances in knowledge about CVFs as well as in optimal imaging detection are anticipated.

CSF-Venous Fistula.

PURPOSE OF REVIEW: To provide an update on recent developments in the understanding, diagnosis, and treatment of CSF-venous fistula (CVF). RECENT FINDING: CVF is a recently recognized cause of spontaneous intracranial hypotension (SIH), an important secondary headache, in which an aberrant connection is formed between the spinal subarachnoid space and an adjacent spinal epidural vein permitting unregulated loss of CSF into the circulatory system. CVFs often occur without a concurrent epidural fluid collection; therefore, CVF should be considered as a potential etiology for patients with SIH symptomatology but without an identifiable CSF leak. Imaging plays a critical role in the detection and localization of CVFs, with a number of imaging techniques and provocative maneuvers described in the literature to facilitate their localization for targeted and definitive treatment. Increasing awareness and improving the localization of CVFs can allow for improved outcomes in the SIH patient population. Future prospective studies are needed to determine the diagnostic performance of currently available imaging techniques as well as their ability to inform workup and guide treatment decisions.

CSF-venous fistulas associated with traumatic spinal pseudomeningoceles.

CSF-venous fistulas (CVFs) are a common cause of spontaneous intracranial hypotension. These fistulas usually occur without any preceding major trauma, surgery, or other iatrogenic cause. Occasionally, patients have a history of minor trauma, though such cases are usually still considered spontaneous. Little is known about predisposing factors that cause patients to develop spontaneous CVFs. Most patients with CVFs have multiple meningeal diverticula on spine imaging, and fistulas usually arise in association with a diverticulum. In the vast majority of cases, the culprit diverticulum from which the CVF arises is atraumatic in origin, presumably on the spectrum of normal variation in spinal anatomy. Here, we present two cases of CVFs that arose in association with posttraumatic pseudomeningoceles. To our knowledge, this phenomenon has not yet been reported, and it potentially represents a novel etiology for CVFs that furthers understanding of their pathogenesis.

Spinal Cerebrospinal Fluid Leak Localization with Digital Subtraction Myelography: Tips, Tricks, and Pitfalls.

Cerebrospinal fluid (CSF) leak can cause spontaneous intracranial hypotension (SIH) which can lead to neurologic symptoms, such as orthostatic headache. Over time, imaging techniques for detecting and localizing CSF leaks have improved. These techniques include computed tomography (CT) myelography, dynamic CT myelography, cone-beam CT, MRI, MR myelography, and digital subtraction myelography (DSM). DSM provides the highest sensitivity for identifying leak sites and has comparable radiation exposure to CT myelography. The introduction of the lateral decubitus DSM has proven invaluable in localizing leaks when other imaging tests have been inconclusive.

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.

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.

Prone Dynamic CT Myelography in Spontaneous Intracranial Hypotension : Diagnostic Need and Radiation Doses.

BACKGROUND AND PURPOSE: The diagnostic work-up in patients with spontaneous intracranial hypotension (SIH) and spinal longitudinal extradural CSF collection (SLEC) on magnetic resonance imaging (MRI) comprises dynamic digital subtraction myelography (dDSM) in prone position for leak detection. Dynamic computed tomography (CT) myelography (dCT-M) in prone position follows if the leak is not unequivocally located. A drawback of dCT­M is a high radiation dose. This study evaluates the diagnostic needs of dCT-M examinations and measures to reduce radiation doses. METHODS: Frequency, leak sites, length and number of spiral acquisitions, DLP and effective doses of dCT­M were retrospectively recorded in patients with ventral dural tears. RESULTS: Of 42 patients with ventral dural tears, 8 underwent 11 dCT­M when the leak was not unequivocally shown on digital subtraction myelography. The median number of spiral acquisitions was 4 (range 3-7) and the mean effective radiation dose 30.6 mSv (range 13.1-62.16 mSv) mSv. Five of eight leaks were located in the upper thoracic spine (range C7/Th1-Th2/3). Bolus tracking of intrathecal contrast agent in dCT­M was used to limit the number and length of spiral acquisitions. DISCUSSION: A dCT­M in prone position to localize a ventral dural tear is needed in every fifth patient with a SLEC on MRI. It is typically needed when the leak is located in the upper thoracic spine and when patients have broad shoulders. Measures to reduce the radiation dose include bolus tracking or to repeat the DSM with adjusted positioning of patient.

Clinical and Imaging Outcomes of Surgically Repaired Cerebrospinal Fluid-Venous Fistulas Identified by Lateral Decubitus Digital Subtraction Myelography.

OBJECTIVE: To describe clinical and radiographic outcomes of surgical repair of cerebrospinal fluid-venous fistula (CVF), an increasingly recognized cause of spontaneous intracranial hypotension that is poorly responsive to epidural blood patch (EBP). METHODS: Retrospective review identified adult patients who had lateral decubitus digital subtraction myelography indicative of cerebrospinal fluid leak at Mayo Clinic between November 2018 and February 2020, with clearly localized CVF, followed by surgical treatment. Patients without available imaging before or after surgery were excluded. History of EBP and clinical response to EBP were evaluated along with surgical outcomes. RESULTS: Of 25 patients with CVF who met protocol criteria and were included in the data analysis, 22 (88%) received EBP, but clinical benefit lasting ≥4 weeks occurred in only 2 of 22 (9%). Headache was the most prominent preoperative feature among patients (24/25; 96%). Following surgery, 18 of 24 (75%) patients had complete headache improvement, 4 (17%) had partial improvement, and 2 (8%) had no improvement. Ten of 25 (40%) patients reported cognitive disturbance at baseline; at follow-up, 5 of 10 (50%) had complete improvement, 3 (30%) had partial improvement, and 2 (20%) had no improvement. On postoperative brain magnetic resonance imaging, 6 of 25 (24%) patients had complete resolution of findings by Bern score criteria, 18 (72%) showed partial improvement, and 1 (4%) patient showed no improvement. Adverse events were minor and included surgical site pain and paresthesias. CONCLUSIONS: Surgical repair of CVF resulted in improvements in headache and other symptoms, with few side effects.

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.

The importance of repeat digital subtraction myelography in the diagnosis of cryptogenic CSF-venous fistula causing spontaneous intracranial hypotension.

Spontaneous intracranial hypotension (SIH) is a rare disorder that occurs secondary to acquired cerebrospinal fluid (CSF) leaks in the spine. Treatment involves either an epidural blood patch or surgical ligation. Essential to the selecting the optimal management strategy is classifying the type of leak and accurate localization of its level. Hitherto, this has been achieved using conventional imaging methods such as static CT or MR myelography which are adequate for the demonstration of only high flow leaks. Digital subtraction myelography (DSM) is a novel technique which provides superior temporal and spatial resolution in the localization of more challenging slow flow leaks. However, DSM may also be initially non-diagnostic. We report a case of SIH in which repeat DSM revealed a type 3 CSF-venous fistula and demonstrate a possible mechanism of transient CSF leak block resulting in the initial false negative findings based on morphological changes in the culprit nerve sheath diverticulum-pseudomeningocoele complex. The patient underwent successful surgical ligation with clinicoradiological resolution of SIH.

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 intracranial hypotension complicated by diffuse cerebral edema and episodes of severely elevated intracranial pressure: illustrative case.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is a well-documented condition that typically follows a defined clinical course. Previously published studies describing the pathophysiology of SIH have demonstrated extensive evidence of low intracranial pressure (ICP) driving the clinical features of the condition. Through lumbar puncture and use of intracranial monitoring devices, however, both low and normal cerebrospinal fluid (CSF) pressures have been documented. This report outlined and discussed the unique finding of elevated ICP associated with clinical features of SIH. OBSERVATIONS: Here, the authors presented a case of a patient with spontaneous spinal CSF leak who developed tonsillar herniation, cerebral edema, and subsequent episodes of elevated ICP. Although more diverse presentations of SIH are being reported, the authors believed the case to be unique because SIH was accompanied by elevated ICP. LESSONS: This case adds to the growing body of literature surrounding SIH by demonstrating that patients can develop elevated CSF pressures associated with acute encephalopathy.

Diagnosis of a Cerebrospinal Fluid-Venous Fistula Associated with a Venous Malformation Using Digital Subtraction and Computed Tomography Myelography.

BACKGROUND: Spontaneous cerebrospinal fluid (CSF) leaks can be an intractable cause of orthostatic headaches but have several treatable causes. CSF-venous fistulas are an increasingly recognized cause of rapid CSF leaks. Although CSF-venous fistulas have been previously reported in the literature, their imaging appearance, associated anomalies, and treatment are incompletely understood. We present a case of a CSF-venous fistula draining to adjacent venous malformations with symptoms responding to surgical treatment. This is the first such case to our knowledge showing enhancement of venous malformations on computed tomography myelography. CASE DESCRIPTION: A 61-year-old woman with known soft tissue venous malformations presented with progressive hearing loss, headaches, and nausea. Brain magnetic resonance imaging performed at an outside institution showed findings of CSF hypotension. Her symptoms were refractory to a single-level blood patch. Digital subtraction and computed tomography myelography performed at our institution showed CSF-venous fistulas arising from thoracic nerve root sleeve diverticula and draining to paraspinal venous malformations. She was treated with surgical ligation of the fistula and associated nerve roots. At 3-month follow-up, she reported improvement in her headaches, and magnetic resonance imaging showed resolution of all brain abnormalities. CONCLUSIONS: CSF-venous fistulas are a relatively uncommon cause of spontaneous CSF leaks. Though difficult to diagnose, they can respond to surgical treatment as seen in this case. In our experience, decubitus digital subtraction myelography combined with computed tomography myelography is instrumental in making the diagnosis and fully characterizing any abnormalities associated with the fistula. This case also supports the suggested association between CSF-venous fistulas and venous malformations, which is worthy of continued study.

Association Between Klippel-Trenaunay Syndrome and Spontaneous Intracranial Hypotension: A Report of 4 Patients.

BACKGROUND: Klippel-Trenaunay syndrome (KTS) is associated with a wide variety of vascular and neurologic abnormalities, including venolymphatic malformations. A recent report postulated that patients with KTS may also be predisposed to spontaneous intracranial hypotension. We reviewed brain magnetic resonance imaging from 67 patients with KTS and unexpectedly noted findings of cerebrospinal fluid (CSF) hypotension in 4 of them. CASE DESCRIPTION: Patients included a 39-year-old woman with episodic orthostatic headaches, a 62-year-old woman with orthostatic headaches and light-headedness, a 14-year-old girl with a history of headaches for years, and an asymptomatic 20-year-old man. All 4 patients had known KTS, and all had brain magnetic resonance imaging done during their evaluation showing evidence of CSF hypotension. The first 2 patients also had spine imaging demonstrating paraspinal and/or epidural venolymphatic malformations. The second patient had a meningeal diverticulum and underwent surgical repair with intraoperative evidence of a CSF leak. CONCLUSIONS: Patients with KTS have an increased incidence of CSF hypotension. While it is possible that intrinsic dural weakness may be responsible for this association, we hypothesize that these patients are also predisposed to developing CSF venous fistulas. Paraspinal and epidural venolymphatic malformations have been described in multiple patients with CSF venous fistulas. Such malformations were present in 2 of our 4 patients who underwent spine imaging. Patients with KTS with orthostatic headaches may benefit from brain and spine magnetic resonance imaging to assess for evidence of CSF hypotension and venolymphatic malformations. Decubitus digital subtraction myelography may also have a role in these patients if CSF venous fistulas are suspected.

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.

False localizing signs of spinal CSF-venous fistulas in spontaneous intracranial hypotension: report of 2 cases.

A spinal CSF-venous fistula is one of three specific types of spinal CSF leak that can be seen in patients with spontaneous intracranial hypotension (SIH). They are best demonstrated on specialized imaging, such as digital subtraction myelography (DSM) or dynamic myelography, but often they are diagnosed on the basis of increased contrast density in the draining veins (the so-called hyperdense paraspinal vein sign) on early postmyelography CT scans. The authors report on 2 patients who underwent directed treatment (surgery in one patient and glue injection in the other) based on the hyperdense paraspinal vein sign, in whom the actual site of the fistula did not correspond to the level or laterality of the hyperdense paraspinal vein sign. The authors suggest consideration of DSM or dynamic myelography prior to undertaking treatment directed at these fistulas.

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.

Digital subtraction myelography in the investigation of post-dural puncture headache in 27 patients: technical note.

OBJECTIVE Post-dural puncture headaches are common, and the treatment of such headaches can be complex when they become chronic. Among patients with spontaneous spinal CSF leaks, digital subtraction myelography (DSM) can localize the exact site of the leak when an extradural CSF collection is present, and it can also demonstrate CSF-venous fistulas in those without an extradural CSF collection. The authors now report on the use of DSM in the management of patients with chronic post-dural puncture headaches. METHODS The patient population consisted of a consecutive group of 27 patients with recalcitrant post-dural puncture headache that had lasted from 2 to 150 months (mean 26 months). RESULTS The mean age of the 17 women and 10 men was 39.1 years (range 18-77 years). An extensive extradural CSF collection was present in 5 of the 27 patients, and DSM was able to localize the exact site of the dural defect in all 5 patients. Among the 22 patients who did not have an extradural CSF collection, DSM showed a CSF-venous fistula in 1 patient (5%). Three other patients had a small pseudomeningocele at the level of the dural puncture. Percutaneous glue injection or microsurgical repair resulted in resolution of symptoms in 8 of the 9 patients in whom an abnormality had been identified on imaging. CONCLUSIONS Digital subtraction myelography is able to precisely localize the dural puncture site in patients with a post-dural puncture headache and an extensive extradural CSF collection, and it may rarely detect a CSF-venous fistula in such patients without an extradural CSF collection.

Digital subtraction myelography for the identification of spontaneous spinal CSF-venous fistulas.

OBJECTIVE In most patients with spontaneous intracranial hypotension, a spinal CSF leak can be found, but occasionally, no leak can be demonstrated despite extensive spinal imaging. Failure to localize a CSF leak limits treatment options. The authors recently reported the discovery of CSF-venous fistulas in patients with spontaneous intracranial hypotension and now report on the use of digital subtraction myelography in patients with spontaneous intracranial hypotension but no CSF leak identifiable on conventional spinal imaging (i.e., non-digital subtraction myelography). METHODS The patient population consisted of 53 consecutive patients with spontaneous intracranial hypotension who underwent digital subtraction myelography but in whom no spinal CSF leak (i.e., presence of extradural CSF) was identifiable on conventional spinal imaging. RESULTS The mean age of the 33 women and 20 men was 53.4 years (range 29-71 years). A CSF-venous fistula was demonstrated in 10 (19%) of the 53 patients. A CSF-venous fistula was found in 9 (27%) of the 33 women and in 1 (5%) of the 20 men (p = 0.0697). One patient was treated successfully with percutaneous injection of fibrin sealant. Nine patients underwent surgery for the fistula. Surgery resulted in complete resolution of symptoms in 8 patients (follow-up 7-25 months), and in 1 patient, symptoms recurred after 4 months. CONCLUSIONS In this study, the authors found a CSF-venous fistula in approximately one-fifth of the patients with recalcitrant spontaneous intracranial hypotension but no CSF leak identifiable on conventional spinal imaging. The authors suggest that digital subtraction myelography be considered in this patient population.