Optic nerve sheath diameter ultrasonography and invasive cisternal pressure monitoring for risk stratification and surgical selection in idiopathic intracranial hypertension

Abstract

Objective: Accurate risk stratification in idiopathic intracranial hypertension (IIH) remains challenging, and surgical selection criteria lack standardization. The aim of this study was to evaluate a multidisciplinary diagnostic algorithm combining optic nerve sheath diameter (ONSD) measurement on ultrasonography and 48-hour invasive intracranial pressure (ICP) monitoring to classify patients with IIH by risk of vision loss and to guide individualized management.

Methods: The prospective study consecutively enrolled patients with suspicion of IIH treated with medical therapy, but with minimal response, from January 2021 to December 2024 at a single center. Exclusion criteria included secondary causes of intracranial hypertension or significant transverse sinus stenosis. The diagnostic protocol consisted of baseline measurement of ONSD; 48-hour cisternal pressure monitoring via external lumbar drainage, including a 24-hour CSF subtraction phase; and subsequent repeat of ONSD measurement. Patients were stratified into three groups (no IIH, IIH CSF subtraction nonresponders, and IIH CSF subtraction responders) based on the opening pressure, change in mean cisternal pressure (Δp), and ONSD change. Borderline cases were included in the pressure waveform analysis using mean absolute error and Dynamic Time Warping relative to a normative curve. Area under the curve (AUC) analysis was performed to determine optimal cutoff values for ONSD and Δp.

Results: Thirty-one patients (24 female, mean age 38.7 years, mean BMI 30.2) met inclusion criteria. ONSD and Δp were significantly associated with IIH diagnosis (p = 0.004 and p = 0.031, respectively). AUC analysis identified optimal cutoffs of 5.6 mm for ONSD (AUC 0.98, 92.5% sensitivity, 100% specificity) and 3.0 cm H2O for Δp (AUC 0.93, 81.7% sensitivity, 100% specificity). At the 3-month follow-up, IIH CSF subtraction responders (with shunting) had normalization of ONSD and visual field improvement in most cases, while the IIH CSF subtraction nonresponders remained stable on medical therapy.

Conclusions: The integration of ultrasonography-determined ONSD with invasive cisternal pressure monitoring and CSF subtraction provided an objective and reproducible approach for diagnosing IIH and stratifying patients by risk of vision loss. The proposed ONSD and Δp thresholds could support standardized surgical decision-making and reduce variability in IIH management. Multicenter validation and long-term follow-up are warranted.

Keywords: cerebrospinal fluid shunts; idiopathic intracranial hypertension; intracranial pressure monitoring; optic nerve sheath diameter ultrasound; risk stratification.