Optic nerve sonographic examination to predict raised intracranial pressure in idiopathic intracranial hypertension: The cut-off points

Abstract

Purpose Monitoring of raised intracranial pressure (ICP) in patients with idiopathic intracranial hypertension (IIH) is required to prevent secondary optic nerve damage. Sonographic measurement of the optic nerve sheath diameter (ONSD) is a noninvasive method to evaluate intracranial hypertension. Different ONSD cut-off values have been reported probably due to ethnic variations. Our aim was to determine optic nerve sonographic examination cut-off points to predict raised ICP in IIH patients. Methods This case-control study was conducted on 99 IIH post-pubertal female patients (both probable and definite) and 35 age- and sex-matched healthy volunteers. Sonographic ONSD and optic nerve diameter (OND) were obtained 3 mm behind the posterior edge of the globe in a horizontal plane via a 7–13 MHz linear probe. Lumbar puncture was then carried out on the patients. Results The opening cerebrospinal fluid pressure documented in the patient group was 279.64 ± 65.97 mm H2O. A statistically significant difference was found between IIH patients and controls regarding ONSD. The best ONSD cut-off value indicating raised ICP was 6.05 mm with an area under the curve of 0.850 (95% confidence interval 0.805 to 0.894, 73.2% sensitivity and 91.4% specificity). Regarding OND/ONSD ratio, there was an insignificant difference between both groups. Conclusion Sonographic ONSD but not OND/ONSD ratio could offer a bedside adjunct or alternative indicator of elevated ICP in IIH patients. Ethnic differences, however, should be noted when using this parameter.