Volumetric Assessment of Optic Nerve Sheath and Hypophysis in Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE: Idiopathic intracranial hypertension is a headache syndrome characterized by increased CSF pressure. Compression of the hypophysis and distension of the optic nerve sheath are reliable imaging signs. The purpose of the study was to validate, in patients with idiopathic intracranial hypertension, MR imaging–based volumetric measurements of the optic nerve sheath and hypophysis as an objective observation method for more accurate diagnosis and posttreatment follow-up.

MATERIALS AND METHODS: Twenty-three patients with idiopathic intracranial hypertension as well as age-, sex-, and body mass index–matched controls underwent volumetric measurements of the optic nerve, optic nerve sheath, and hypophysis on high-resolution T2-weighted MR images by using a 7-cm surface coil, followed by correlation with CSF opening pressures and clinical symptom scores of visual disturbances and headache.

RESULTS: Mean values of optic nerve sheath (341.86 ± 163.69 mm³ versus 127.56 ± 53.17 mm³, P < .001) and hypophysis volumes (554.59 ± 142.82 mm³ versus 686.60 ± 137.84 mm³, P < .05) differed significantly between healthy and diseased subjects. No significant differences between mean optic nerve volumes were observed. Receiver operating characteristic analysis showed optic nerve sheath volumes of >201.30 mm³ (sensitivity, 86.96%; specificity, 91.30%) and hypophysis volumes of <611.21 mm³ (sensitivity, 78.26%; specificity, 69.57%) to be indicative of idiopathic intracranial hypertension diagnosis. In patients with idiopathic intracranial hypertension, no correlations were found between optic nerve sheath and hypophysis volumes and CSF opening pressures or clinical scores of visual disturbances and headache.

CONCLUSIONS: Semiautomated volumetric measurement of optic nerve sheath and hypophysis has the potential to more accurately diagnose and follow patients with idiopathic intracranial hypertension.