Increased brain water self-diffusion in patients with idiopathic intracranial hypertension

PURPOSE: To investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension. METHODS: A motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers. RESULTS: A significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10^-9 m²/s) than in the control group (mean, 0.75 x 10^-9 m²/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter. CONCLUSION: Measurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.