Spontaneous Intracranial Hypotension: A Systematic Imaging Approach for CSF Leak Localization and Management Based on MRI and Digital Subtraction Myelography

Abstract

BACKGROUND AND PURPOSE:Localization of the culprit CSF leak in patients with spontaneous intracranial hypotension can be difficult and is inconsistently achieved. We present a high yield systematic imaging strategy using brain and spine MRI combined with digital subtraction myelography for CSF leak localization. MATERIALS AND METHODS:During a 2-year period, patients with spontaneous intracranial hypotension at our institution underwent MR imaging to determine the presence or absence of a spinal longitudinal extradural collection. Digital subtraction myelography was then performed in patients positive for spinal longitudinal extradural CSF collection primarily in the prone position and in patients negative for spinal longitudinal extradural CSF collection in the lateral decubitus positions. RESULTS: Thirty-one consecutive patients with spontaneous intracranial hypotension were included. The site of CSF leakage was definitively located in 27 (87%). Of these, 21 were positive for spinal longitudinal extradural CSF collection and categorized as having a ventral (type 1, fifteen [48%]) or lateral dural tear (type 2; four [13%]). Ten patients were negative for spinal longitudinal extradural CSF collection and were categorized as having a CSF-venous fistula (type 3, seven [23%]) or distal nerve root sleeve leak (type 4, one [3%]). The locations of leakage of 2 patients positive for spinal longitudinal extradural CSF collection remain undefined due to resolution of spontaneous intracranial hypotension before repeat digital subtraction myelography. In 2 (7%) patients negative for spinal longitudinal extradural CSF collection, the site of leakage could not be localized. Nine of 21 (43%) patients positive for spinal longitudinal extradural CSF collection were treated successfully with an epidural blood patch, and 12 required an operation. Of the 10 patients negative for spinal longitudinal extradural CSF collection (8 localized), none were effectively treated with an epidural blood patch, and all have undergone (n ϭ 7) or are awaiting (n ϭ 1) an operation. CONCLUSIONS: Patients positive for spinal longitudinal extradural CSF collection are best positioned prone for digital subtraction myelography and may warrant additional attempts at a directed epidural blood patch. Patients negative for spinal longitudinal extradural CSF collection are best evaluated in the decubitus positions to reveal a CSF-venous fistula, common in this population. Patients with CSF-venous fistula may forgo further epidural blood patch treatment and go on to surgical repair. ABBREVIATIONS: CVF ϭ CSF-venous fistula; DSM ϭ digital subtraction myelography; EBP ϭ epidural blood patch; SIH ϭ spontaneous intracranial hypotension; SLEC ϭ spinal longitudinal extradural CSF collection; SLEC-N ϭ negative for spinal longitudinal extradural CSF collection; SLEC-P ϭ positive for spinal longitudinal extradural CSF collection Indicates open access to non-subscribers at www.ajnr.org http://dx.

Hydrocephalus and CSF Disorders

“…In patients being considered for a possible diagnosis of SIH imaging of the entire spine with high-resolution T2-weighted sagittal sequences is mandatory. While many SIH patients present with spinal longitudinal extradural collections (SLECs) some do not [26]. These SLECs have a typical appearance and are seen exclusively in SIH patients with dural mechanical tears along the thecal sac.…”

“…Conversely, patients with more laterally placed CSF leakage beyond the epidural compartment either from a CSF-venous fistula (CVF) or from a distal root sleeve tear do not display SLECs. The presence or absence of a SLEC on MRI is used to proscribe for the prone versus lateral decubitus positioning of the subsequent dynamic myelography [26,27]. Digital subtraction myelography (DSM) and ultrafast CT myelography [28] are techniques of dynamic myelography which allow for imaging of gravity dependent contrast media as it descends within the thecal sac from site of injection within the lumbar spine into the cervical spinal canal.…”

“…recently there has been a paucity of reliable knowledge disseminated about this syndrome. SIH has only recently been recognized as a syndrome that requires an organized approach by knowledgeable experienced neuroradiologists [26,29,30].…”

Lateral Decubitus Digital Subtraction Myelography: Tips, Tricks, and Pitfalls

“…The spine MR imaging is used to assess extradural fluid collections, and the brain MR imaging is used to look for manifestations of CSF hypotension and to further stratify the pretest probability. 4,5 At Mayo Clinic, patients are first evaluated in our CSF dynamics clinic by neurologists who specialize in headache disorders and intracranial hypotension, and if there is no extradural fluid collection in the spine MR imaging, we generally proceed with a conventional CT myelography with early and delayed images. If CT myelography findings are negative, lateral decubitus DSM is performed to look for CSF-venous fistulas or other slower CSF leaks.…”

“…1 Although prone DSM has been used for several years to identify the exact focus of a CSF leak in patients with suspected fast ventral leaks in the setting of spinal extradural fluid collections, 2 the technique of lateral decubitus positioning has been introduced more recently to detect subtle CSF-venous fistulas and different types of leaks. 3,4 At Mayo Clinic, we implemented this technique into our practice in 2018, and the advantages of DSM to identify CSFvenous fistulas compared with other techniques such as conventional, dynamic CT and positive pressure MR myelograms quickly became apparent, with continuously increasing demand from the patients and referring clinicians to increase availability. As we have performed an increasing number of these procedures, we have encountered and refined numerous small but easily implemented procedural steps that can make the difference between a diagnostic and nondiagnostic examination.…”