Cryptogenic Cerebrospinal Fluid Leaks in Spontaneous Intracranial Hypotension: Role of Dynamic CT Myelography

Abstract

Purpose To propose a modified dynamic CT myelographic technique to locate cerebrospinal fluid (CSF) leaks, also known as cryptogenic leaks, in patients with spontaneous intracranial hypotension (SIH) in whom previous imaging did not show the dural breach. Materials and Methods This retrospective analysis included 74 consecutive patients with SIH and a myelographically proven CSF leak who were evaluated between February 2013 and October 2017. In 14 patients, dynamic CT myelography in the prone or lateral position showed the exact leakage point after unsuccessful previous imaging. During image analysis, the first time point showing extrathecal contrast material was defined as the site of dural breach point. Results Mean population age was 44 years (range, 25-65 years [nine women; mean age, 44 years; age range, 25-65 years] [five men; mean age, 46 years; age range, 29-61 years]). All patients had previously undergone spine MRI, conventional dynamic myelography, and CT myelography. Subsequent dynamic CT myelography covered a mean range of seven vertebral levels. The leak was caused by a calcified microspur in 10 patients and by a dural tear at the axilla of a spinal nerve root in the remaining four. The mean volume CT dose index of dynamic CT myelography was 107 mGy (range, 12-246 mGy), and the mean dose-length product was 1347 mGy·cm (range, 550-3750 mGy·cm). Conclusion Dynamic CT myelography is a valuable adjunctive tool with which to identify the precise location of a dural tear when other examinations are unsuccessful. © RSNA, 2018 See also the editorial by Dillon in this issue.

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

“…Until recently, the cause of SIH had been unclear, and several etiologies had been postulated. 10 With evidence presented here as well as that provided by other authors, 1,2,5,11,[17][18][19] it now appears that these leaks are predominantly, if not exclusively, due to mechanical tears, CVFs, and leaking nerve root sleeves. For guidance of management and efficiency of discussion, we have categorized the CSF leaks we have encountered into 4 types based on the morphology and distance from the midline.…”

“…[1][2][3][4] The leakage of CSF causes variable symptoms, the most characteristic of which is a positional headache and is commonly associated with typical intracranial MR imaging findings or stigmata. [5][6][7][8][9][10] We have also noted, as have other authors, 2,[11][12][13] that while many patients with SIH present with a spinal longitudinal extradural CSF collection (SLEC), some do not. 5 These SLECs have a typical appearance (Fig 1) and, in our experience, are seen exclusively in patients with SIH with dural mechanical tears along the thecal sac.…”

“…These leaks are thought to arise from the base of the nerve root relating to a pre-existing thinned or dehiscent area of the dura. 11 In our experience, these lateral dural dehiscent lesions are more commonly seen in women (4 of 4 in our series) and appear to be more amenable to treatment with multiple EBPs and bedrest, possibly due to the nature of the tear and it not being held open by a disc protrusion or substantiated by continued flow as in a CVF. This lesion was seen in 4 of 31 patients (13%).…”

“…All patients with type 1 are SLEC-P on MR imaging with or without intracranial findings and show a typical ventral hole in the thecal sac on DSM or dynamic CT myelography. 5,11,20 The site of CSF leakage is occasionally seen associated with a calcific "microspur" at the site of a degenerated disc. 11,21 Unless imaged in a dynamic fashion so that the initial flow of contrast agent is captured as it travels down the spine, the site of leakage will be obscured by mixing of contrast in the intradural and extradural compartments above and below the hole.…”

“…Our observations regarding the association of SLECs with differing types of CSF leaks is similar to experiences of other authors. Dobrocky et al 11 19 have reported their success in using dynamic CT myelography and DSM to identify 22 cases of CVF. In that study, the authors also noted that CVFs "often occur without epidural leak."…”