Additional Diagnostic Value of Cone Beam CT Myelography Performed After Digital Subtraction Myelography for Detecting CSF-venous Fistulas.

Background and purpose: CSF-venous fistulas are a common cause of spontaneous intracranial hypotension. The diagnosis and precise localization of these fistulas hinges on specialized myelographic techniques, which mainly include decubitus digital subtraction myelography and decubitus CT myelography (using either energy integrating or photon counting detector CT). A previous case series showed that cone beam CT myelography, performed as an adjunctive tool with digital subtraction myelography, increased the detection of CSF-venous fistulas. Here, we sought to determine the additive yield of cone beam CT myelography for CSF-venous fistula detection in a consecutive series of patients with spontaneous intracranial hypotension who underwent concurrent decubitus digital subtraction myelography and cone beam CT myelography.

Materials and methods: We retrospectively searched our institutional database for all consecutive patients who underwent decubitus digital subtraction myelography with adjunctive cone beam CT myelography between 8/5/2021 and 8/5/2024. We excluded any patients harboring extradural CSF on spine imaging, not meeting International Classification of Headache Disorders (3^rd edition) criteria for spontaneous intracranial hypotension, or not having undergone technically successful cone beam CT myelography in combination with digital subtraction myelography. All myelographic images were independently reviewed by two neuroradiologists. We calculated the diagnostic yield of both myelographic tests for localizing a CSF-venous fistula.

Results: We identified 100 patients who underwent decubitus digital subtraction myelography with adjunctive cone beam CT. We excluded 15 patients based on above criteria. 59/85 patients had a single definitive CSF-venous fistula. Among positive cases, the fistula was visible on digital subtraction myelography in 38/59 patients and visible on cone beam CT myelography in 59/59 patients. In 26/85 patients, no definitive fistula was identified on either modality.

Conclusions: Cone beam CT myelography increased the diagnostic yield for CSF-venous fistula detection and may be a useful addition to digital subtraction myelography.

Abbreviations: CB-CTM = cone beam CT myelography; CVF = CSF-venous fistula; DSM = digital subtraction myelography; EID-CTM = energy integrating detector CT myelography; PCD CTM = photon counting detector CT myelography; SIH = spontaneous intracranial hypotension.