Cervical interlaminar epidural injections at high doses do not increase optic nerve sheath diameter on a long-term basis

Background: Cervical epidural injection (CEI) is widely performed on patients with pain originating from the cervical spine. Studies have shown a good relationship between the optic nerve sheath diameter (ONSD) and the intracranial pressure (ICP). Objective: The aim of this study was to evaluate the changes in the ONSD as a non-invasive surrogate marker of ICP after CEI. Study Design: Prospective observational study. Setting: Hospital and ambulatory pain clinic. Methods: Twenty patients undergoing CEI at the C5-6 level were enrolled in this observational study. The CEIs were performed using a total of 14 mL of mixture volume via the interlaminar approach in the right lateral decubitus position. The ONSD through ultrasonography was measured in the initial supine position (T0, baseline), 30 seconds after the completion of CEI (T0.5), at 30-second intervals for 5 minutes (T0.5~T5), and at one-minute intervals for 5 minutes (T6~T10). Results: The values of the baseline ONSD (T0) in both eyes were 4.1 ± 0.4 mm. The ONSD significantly increased from T1 to T10 (P < 0.05) compared with T0. The maximum value of the ONSD was measured as 5.1 ± 0.4 mm at T4, and the mean difference between the baseline ONSD and its maximum value was 1.0 mm, which represented about 27%. There was no increase in ICPrelated complications such as dizziness, headache, visual acuity, or retinal hemorrhage. Limitations: This was an observational study without a control group. All patients were presumed to have no intracranial pathology. Conclusion: The 14 mL CEI resulted in an increase in the ONSD by ultrasonography over time. The most critical increase in ONSD was observed 4 minutes after CEI, but this increase was not sustained. Further work is needed to confirm the effects of the speed and volume of the injection and of the position. Registration: Registered in the Clinical Research Information Service of the Korea National Institute of Health (https://cris.nih.go.kr/cris/index.jsp), registration number: KCT0001487.