Background CSF-venous fistulas (CVF) are an important cause of spontaneous intracranial hypotension (SIH). While perineural cysts are thought to be strongly associated with CVF, it remains poorly understood what the prevalence of SIH is in patients with perineural cysts and if there is a difference in diagnostic utility based on spinal level.

Methods All cases of perineural cysts within the cervical, thoracic, and lumbar spine MRIs were identified from our single institution over a 9 year period (2016-2023). From the patients with perineural cysts, cases with brain MRIs with features consistent with SIH were identified and used a surrogate for SIH. Subsequently, overall proportion of SIH were determined as a function of total cases with perineural cysts based on spinal level. Differences in proportions were calculated using a chi-square test. Standard error of each proportion were also determined.

Results In total, 83,695 distinct patients with spinal MRIs were screened which identified 4,174 patients (4.97%) with perineural cysts. From these, there were 1,203 cervical, 622 thoracic, and 2,979 lumbosacral spine MRIs. In total, 18 patients (0.43%; Standard Error [SE]: 0.53% to 0.33%) had a brain MRI compatible with SIH. Patients with cervical perineural cysts had brain MRIs compatible with SIH in 3 cases (0.25%; SE: 0.39% to 0.11%). SIH on brain MRI was present in 11 patients (0.37%; SE: 0.48% to 0.26%) with perineural cysts present in the lumbosacral spine. In patients with perineural cysts in the thoracic spine, 16 (2.6%; SE: 3.2% to 2.0%) had brain MRI features compatible with SIH. Cysts were present within all spinal levels in 2 patients (0.05%; SE: 0.054% to 0.046%), and within the thoracolumbar spine in 8 cases (0.2%; SE: 0.27% to 0.13%). SIH was significantly more prevalent in patients with thoracic perineural cysts compared to those with cervical cysts (P < 0.0001), and compared to patients with lumbosacral perineural cysts (P < 0.0001).

Discussion These findings indicate that in patients with perineural cysts, concurrent SIH is present in 0.43% of patients, suggesting that in the vast majority of cases they are an incidental finding. However, concurrent SIH is present in approximately 2.6% of patients with thoracic perineural cysts, which is significantly higher compared to the cervical and lumbosacral spine.

Disclosures D. Schartz: None. N. Ellens: None. A. Kessler: None. S. Ellika: None. M. Bender: None.