8 The purpose of this article is to discuss the procedural technique of decubitus CTM and when to perform it in a patient with SIH so that radiologists of various backgrounds can implement it in their practices.Patient Selection Second, DSM is not performed at all institutions, and last, general anesthesia may be required. First, familiarity with digital subtraction imaging is a requisite for DSM and may be challenging to implement if the operator does not have traditional interventional or neurointerventional training. There are many barriers to the DSM technique. Kaiser Permanente Medical Center has explored many of the aforementioned myelographic techniques and found decubitus CTM to be a useful and relatively simple method to perform in most clinical practices and perhaps easier than DSM. There is a learning curve in some of these techniques, which may be challenging to perform and prevent radiologists from accurately diagnosing CSF-venous fistulas in daily practice.
3 While both decubitus CTM and DSM can identify CSF-venous fistulas, there are no reported studies that have compared the sensitivities and specificities of detection. In 1 study, a CSF-venous fistula was detected in 17 of 23 patients on decubitus DSM compared with 4 of 26 patients who underwent prone DSM. 11 DSM has also used a similar advantage with the decubitus technique. Because of this phenomenon, CSF-venous fistulas have been diagnosed on decubitus CTM and missed on prone or supine CTM. The decubitus position permits contrast to flow into a CSF-venous fistula on the dependent side of the thecal sac via gravity. 3 - 11 Of these techniques, decubitus CTM and DSM are the most frequently described in the literature to identify CSF-venous fistulas. Various diagnostics techniques have been reported to identify CSF-venous fistulas, which include conventional fluoroscopy and CT myelography (CTM), digital subtraction myelography (DSM), MR imaging myelography, and decubitus myelography in the aforementioned modalities. 3 In our experience and in the published literature, CSF-venous fistulas are under-recognized and are mostly discussed at only a few quaternary SIH academic centers in the United States. 2 While the incidence of CSF-venous fistulas was originally thought to be rare, they may be present in a quarter of patients with SIH.
1 CSF-venous fistulas are 1 of the 3 types of CSF leaks, while CSF leaks from dural tears and ruptured meningeal diverticula are the remaining types. A spinal CSF-venous fistula is an abnormal connection that usually occurs between a meningeal diverticulum and a paraspinal vein that results in continuous shunting of CSF fluid and spontaneous intracranial hypotension (SIH).
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