Systematic Review of the predictive value of negative brain or low probability brain MRIs in patients with CSF venous fistulas.

Background: Since the discovery of the cerebrospinal fluid venous fistula, its diagnosis has become more frequent, especially in patients with brain MRIs positive for spontaneous intracranial hypotension (SIH). However, there is a need to understand the likelihood of diagnosis of a cerebrospinal fluid venous fistula in a patient with negative brain imaging.

Purpose: Our aim was to investigate the frequency of cerebrospinal fluid venous fistula in patients suspected of SIH who have negative neuroaxis MRIs.

Data Sources: All studies reporting on the incidence of cerebrospinal fluid venous fistula in patients with negative neuroaxis MRIs or low probability scores according to the Bern and Mayo score were searched on PubMed, EMBASE, Scopus, Web of Science and Cochrane.

Study Selection: Nine studies comprising of 898 patients suspected of SIH with 80 cerebrospinal fluid venous fistulas were included.

Data Analysis: Data were collected on patient demographics, number of patients found to have negative neuroaxis MRIs or low probability scores according to the Bern or Mayo scoring systems, type of imaging used, and number of patients diagnosed with cerebrospinal fluid venous fistula. Analysis was performed using the standard method for evaluating the negative predictive value of a diagnostic test.

Data Synthesis: There were 27 (10.7%) patients with a cerebrospinal fluid venous fistula of 252 patients found to have negative brain MRIs, 15 (18.3%) of 82 patients found to have low probability on the Bern score, and 38 (34.8%) of 109 patients found to have low probability on the Mayo score. The negative predictive value of a negative brain MRI was 0.89 (95%CI, 0.86-0.92), 0.81 (95% CI, 0.77-0.87) for the Bern score, and 0.65 (95% CI, 0.58-0.72) for the Mayo score.

Limitations: Our review was limited by heterogeneity of the reference standard and few studies in each subcategory.

Conclusions: This review demonstrated that a negative brain MRI is effective in predicting that a patient will not have a CVF, with a high NPV of 89%. However, a patient with a strong clinical suspicion for CSF leak should be considered for more invasive imaging.

Abbreviations: bMRI-- negative brain magnetic resonance imaging, CTM - computed tomography myelogram, CVF - cerebrospinal fluid venous fistula, dCTM-BT - lateral decubitus dynamic CTM protocol using real-time bolus-tracking, DSM - digital subtraction myelogram, NPV - negative predictive value, PC-CTM - photon-counting detector CT myelography.