Venous Sinus Stenting With the River Stent in IIH

Inclusion Criteria: Subjects must meet all of the following criteria to be eligible for participation in the study: 1. Subject is \> 18 year-old and has given informed consent. 2. Diagnosis of IIH per Modified Dandy Criteria. 3. CSF opening pressure is \> 25 cm H2O. 4. Radiological examination (magnetic resonance venography (MRV) or computed tomographic venography (CTV)) shows bilateral transverse-sigmoid venous sinus stenosis (\> 50%) or unilateral stenosis of the dominant sinus with contralateral hypoplastic sinus. 5. Presence of IIH clinical symptoms (6. OR 7.) 6. Headaches: Score \> 59 (severe impact) on the HIT-6 scale, refractory to medical therapy (e.g. acetazolamide 1000 mg twice daily, topiramate 100 mg twice daily, or other headache medication) for ≥ 4 weeks, or treatment intolerance OR 7. Visual field loss: defined by perimetric mean deviation (PMD) between -6 dB and -30 dB in one or both eyes (with papilledema Grade \>1) despite at least 2 weeks of medical therapy with acetazolamide 1000 mg twice daily, or if the visual field deteriorates by more than 2 dB during treatment, or treatment intolerance. 8. In the absence of this study, the subject would have been offered a surgical intervention by Optic Nerve Sheath Fenestration (ONSF), Cerebro Spinal Fluid (CSF) shunting procedure, or venous sinus stenting with an off-label device. 9. Catheter manometry shows a pressure gradient \> 8 mm Hg across the transverse sigmoid sinus stenosis. 10. Venographic evidence of sinus stenosis (\> 50%) Exclusion Criteria: Subject must be excluded from participation in this study if any of the following criteria are met 1. Subjects presenting with de novo papilledema and severe visual field(VF) deficit (VF loss \> -15db) that requires immediate surgical treatment without prior attempt of medical therapy. 2. Currently has or plans to have an implanted CSF shunt. 3. History of previously implanted intra-cranial sinus stent. 4. Transverse-sigmoid sinus vessel size \<5 mm or \>10 mm. 5. Creatinine \> 1.5 mg/dl and/or creatinine clearance \< 60 mL/min (except if patients is already on hemodialysis). 6. Allergic to imaging contrast media (iodine or gadolinium) despite premedication. 7. Allergic to nitinol or nickel. 8. Contra-indication to general anesthesia. 9. Contra-indication to aspirin, clopidogrel or other anticoagulant. 10. Hypercoagulable state (Factor V Leiden, Protein C or S deficiency, Anticardiolipin antibodies, Lupus anticoagulant, B2-glycoprotein-1 antibodies, or Hyperhomocysteinemia). 11. Currently requiring full anti-coagulation for other medical reasons, such as atrial fibrillation (AF), artificial valves, deep vein thrombosis pulmonary embolism, etc. 12. History of stroke or transient ischemic attack (TIA). 13. History of AF or other risks of stroke. 14. History of deep vein thrombosis or pulmonary embolism. 15. History of severe chronic obstructive pulmonary disease or other severe respiratory disease. 16. History of severe carotid atherosclerotic disease. 17. History of heart failure, dilated cardiomyopathy, or congenital heart conditions, etc. that are at high thrombogenic risk. 18. History of uncontrolled diabetes. 19. Use (oral) of tetracycline derivative, retinoid or vitamin A during the last 3 months. 20. Cerebral vascular lesions (arteriovenous malformation (AVM), arteriovenous fistula, aneurysms, significant stenosis of extra- or intra-cranial vessels other than the targeted venous sinus stenosis,intracranial artery dissection, etc.). 21. Patient has visions loss due to other disease (e.g. cataract, macular degeneration, glaucoma, etc.). 22. Inability to provide reliable and reproducible visual field examinations (\>15% false positive errors and/or failure to maintain fixation for eye monitoring). 23. For female subject of child bearing potential, pregnant or not willing to use contraception for 12 months. 24. Presence of a physical, mental or social condition that could prevent adequate one-year follow-up (homelessness, drug dependency, anticipation of moving far away, life threatening disease, terminal illness). 25. Anatomical anomaly of the venous sinus which would prevent safe catheterization and stenting (e.g multi-channel sinus) 26. Currently enrolled in a premarket investigational study. Enrollment in a post market study that does not impact the River™ Stent procedure or device is allowed.