Morphometric and volumetric MRI changes in idiopathic intracranial hypertension

Abstract

We aimed at validating established imaging features of idiopathic intracranial hypertension (IIH) by using state-of-the-art MR imaging together with advanced post-processing techniques and correlated imaging findings to clinical scores. Twenty-five IIH patients as well as age-, sex- and body mass index (BMI)-matched controls underwent high-resolution T1w and T2w MR imaging in a 1.5 T scanner, followed by assessment of optic nerve sheaths, pituitary gland, ventricles and Meckel's cave. Imaging findings were correlated with cerebrospinal fluid (CSF) opening pressures and clinical symptom scores of visual disturbances (visual field defects or enlarged blind spot), headache, tinnitus (pulsatile and non-pulsatile) and vertigo. CSF as well as ventricle volumes were determined by using an automated MRI volumetry algorithm. So-called 'empty sella' and optic nerve sheath distension were identified as reliable imaging signs in IIH. Posterior globe flattening turned out as a highly specific but not very sensitive sign. No abnormalities of the lateral ventricles were observed. These morphometric results could be confirmed using MR volumetry (VBM). Clinical symptoms did not correlate with an increase in lumbar opening pressure. Our study results indicate that lateral ventricle size is not affected in IIH. In contrast, abnormalities of the pituitary gland and optic nerve sheath were reliable diagnostic signs for IIH.