The role of arachnoid granulations in idiopathic intracranial hypertension

Objectives Idiopathic intracranial hypertension (IIH) is a disease defined by elevated intracranial pressure (ICP) without an established etiology. Arachnoid granulations (AG) are conduits for CSF resorption from the subarachnoid space to the venous system. AG have been implicated to play a central role in maintaining CSF homeostasis. We tested the hypothesis that patients with fewer visible AG on MRI are more likely to present with IIH. Methods In this institutional review board (Institutional Review Board)-approved retrospective chart review study, 65 patients with a clinical diagnosis of idiopathic intracranial hypertension were compared to 144 control patients who met inclusion/exclusion criteria. Patients’ signs and symptoms pertaining to IIH were obtained through the electronic medical record Brain MR images were reviewed for the number and distribution of AGs indenting the dural venous sinuses. The presence of imaging and clinical findings associated with long standing increased ICP was noted. Propensity score method (with inverse probability weighting technique) was used to compare case and control groups. Results In the control group, the number of AG indenting the dural venous sinuses on MRI (NAG) was lower in women compared to men when matched for age (20–45 yo) and BMI (>30 kg/m2). The NAG was lower in 20–45 yo females in the IIH group as compared to the 20–45 yo females in the control group. This statistically significant difference persists when controlled for BMI. In contrast, the NAG in >45 yo females in the IIH group trended higher compared to the >45 yo females in the control group. Conclusion Our results suggest that alterations in arachnoid granulations could play a role in the development of IIH.