Diagnostic Value of Orbital Ultrasound and Orbital Magnetic Resonsance Imaging in Idiopathic Intracranial Hypertension

Background: The optic nerve sheath is anatomically continuous with the dura mater and has a trabeculated arachnoid space through which cerebrospinal fluid (CSF) slowly percolates. Optic nerve sheath diameter (ONSD) measurements may help to estimate the degree of intracranial hypertension in patients with papilledema. Objectives: To evaluate the usefulness of orbital ultrasonography (OUS) and orbital MRI in the assessment of cerebrospinal fluid pressure elevation in patients with idiopathic intracranial hypertension. Methods: Twenty female subjects with IIH and 20 normal controls age and sex matched were included. Measurements of ONSD were done using OUS. The operator was blinded to the clinical background or data. Two readings were recorded in each eye and an average was calculated. MRI brain and orbit was also performed and optic sheath/optic nerve (OSON) ratio was calculated. Results: The ONSD was higher in patients than controls when measured by OUS on both right and left sides (p=0.007 and 0.001 respectively). No correlation existed between the ONSD measured by OUS and CSF pressure. The most significant abnormalities on orbital MRI were increased OS-ON ratio 2.5 and empty sella in 80%, followed by small cortical veins and slit like ventricles in 70%. Conclusion: ONSD measurements via OUS and OSON ratio via orbital MRI can reflect elevation of ICP in IIH patients, but cannot replace LP. No significant relation between the abnormalities detected by MRI Brain and orbit and the ONSD by OUS, opening pressure, or the field of vision.