Sonographic measurement of optic nerve diameter as a non-invasive method of predicting raised intracranial pressure in patients with preeclampsia

Abstract

Background: Optic Nerve diameter (OND) is a surrogate marker for raised intracranial pressure. It is an established fact that obstetric patients with preeclampsia do have increased optic nerve diameter compared with normotensives patients. High resolution B-mode Ocular Ultrasonography is increasingly advocated as a valuable diagnostic tool for evaluating the optic nerve diameter due to its noninvasive nature, low cost, portability, dynamic real-time assessment and rapid performance. This study aims to determine the clinical usefulness of optic nerve diameter findings obtained with B-mode ultrasound in preeclamptic patients.

Methodology: This double-blinded, analytical cross-sectional study was carried out at the Department of Radiology, University of Medical Sciences Teaching Hospital Complex, (UNIMEDTHC), Ondo State, Nigeria and consisted of 95 preeclamptic and 95 normotensives aged matched pregnant women. The optic nerve diameter was measured by the radiologist using a high frequency linear ultrasound probe (7.5-12MHz). Fundoscopy was done by an ophthalmologist who was blinded to the optic nerve diameter measurements.

Results: The optic nerve diameter was higher in preeclamptic compared to controls with a mean of 6.72 ± 0.83mm and 4.30 ± 0.69mm respectively with p value <0.05. Positive fundoscopy findings was found in 35 preeclamptic patients. The OND, from ROC curve, that predicts raised intracranial pressure using fundoscopy as gold standard was a mean equal or >5.6mm.

Conclusion: Ocular ultrasound is an effective screening tool for prediction of the presence of raised intracranial pressure in preeclamptic.