PO-26 | Optic nerve sheath ultrasound in idiopatic intracranial hypertension: early findings

Francesca Cotichelli,^1,2 Davide Mascarella1,^1,2 Valentina Favoni,¹ Gaia Patanè,^1,2 Francesco Severi,^1,2 Francesca Verna,^1,2 Giulia Pierangeli,^1,2 Sabina Cevoli¹ | ¹IRCCS Istituto delle Scienze Neurologiche di Bologna; ²DIBINEM, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum, Bologna, Italy

Background: Idiopathic intracranial hypertension (IIH) is a neurological disorder marked by elevated intracranial pressure (ICP) without significant abnormalities on neuroimaging, except for MRI signs consistent with raised ICP. Previous studies have shown that patients with IIH have an increased optic nerve sheath diameter (ONSD), which tends to decrease after lumbar puncture. However, there is limited data on the reliability of ophthalmologic parameters for diagnosis and follow-up of these patients. This study aims to further support the diagnostic value of sonographically assessed ONSD by comparing measurements between IIH patients and healthy controls. The second objective is to demonstrate a reduction in ONSD after therapeutic lumbar puncture in IIH patients sustaining its role in longitudinal monitoring.

Methods: We prospectively enrolled adult patients with a confirmed diagnosis of IIH, alongside neurologically healthy control subjects. All participants underwent bilateral ONSD assessment through transorbital ultrasound. In the IIH group, measurements were obtained immediately before and within 24 hours after a therapeutic lumbar puncture. For each eye, the ONSD was calculated as the mean of three successive measurements. Demographic and clinical variables - including body mass index (BMI), presence of papilledema, and cerebrospinal fluid (CSF) opening pressure - were systematically collected and analyzed.

Results: At the time of this interim analysis, data from seven female patients with IIH (mean age 35.0 ± 12.6 years) and seven control subjects had been analyzed (mean age 27.2 ± 0.98). The mean baseline ONSD in the right eye was significantly larger in IIH patients (6.29 ± 0.61 mm) compared to the control (5.01 mm ± 0.51). A similar trend was observed in the left eye (6.30 ± 0.36 mm in IIH vs. 5.06 ± 0.68 mm in the control). All IIH patients demonstrated elevated CSF opening pressures (mean 29.8 ± 2.1 cmH₂O). Collection of post-lumbar puncture ONSD data is ongoing and will be presented when complete.

Conclusion: Preliminary findings indicate that optic nerve sheath diameter, as assessed by transorbital ultrasound, is increased in patients with IIH relative to healthy individuals. This non-invasive technique may represent a valuable adjunct in both the diagnostic process and longitudinal monitoring of IIH. Ongoing data collection will further elucidate the dynamic response of ONSD to cerebrospinal fluid decompression.