Evaluation of Spontaneous Intracranial Hypotension Probabilistic Brain MRI Scoring Systems in Normal Patients.

Background and purpose: Probabilistic brain MRI scoring systems have been introduced to stratify the likelihood of identifying a CSF leak at myelography in spontaneous intracranial hypotension (SIH). The Bern scoring system by Dobrocky et al. is now well recognized, with a scoring system by Benson et al. introduced more recently (referred to as the "Mayo" score in this study). Neither of these scoring systems have been thoroughly evaluated in patients without SIH. The goal of this study was to evaluate these scoring systems in patients without SIH to understand the specificity of these MRI findings.

Materials and methods: We retrospectively reviewed normal brain MRIs performed in patients without clinically suspected SIH. Each examination was reviewed by one of four board-certified neuroradiologists with extensive experience in SIH, and all criteria of both scoring systems were evaluated and recorded.

Results: 90 patients were included. Bern score was low probability in 78% and intermediate probability in 22%. Mayo score was low probability in 100%. Relatively high rates of positivity were seen in three specific Bern score parameters, including prepontine cistern effacement 5.0 mm or less (53%), decreased mammilopontine distance 6.5 mm or less (40%), and suprasellar cistern effacement 4.0 mm or less (28%). All intermediate probability Bern scores were due to suprasellar cistern effacement plus either or both prepontine cistern effacement and decreased mammilopontine distance. All other parameters of both scoring systems were either never or very rarely positive.

Conclusions: All intermediate probability Bern scores were due to decreased CSF cistern measurements, which had relatively high positivity rates in our non-SIH patient cohort. Due to substantial overlap with normals, these measurements are not specific indicators of "brain sag", a hallmark imaging finding for SIH, and are not specific for SIH when the only "positive" brain MRI finding(s). The Mayo score is likely more specific for SIH with low probability scores in all patients in our cohort.

Abbreviations: SIH, spontaneous intracranial hypotension; DSM, digital subtraction myelography; CTM, CT myelography; PC-CTM, photon counting CT myelography; CVF, CSF-venous fistula; ICC, intraclass correlation coefficient.