Venous Sinus Stenting With the River Stent in IIH

Study objective: The objective of the study is to show that stenting the transverse-sigmoid sinus with the River stent is safe and has probable benefit to relieve clinical symptoms in subjects with idiopathic intracranial hypertension (IIH) Investigational product: Serenity River Stent System Study design: prospective, multicenter, single arm, open label clinical trial Subject population: IIH subjects with significant (\>50%) stenosis of the transverse-sigmoid sinuses and moderate to severe visual field loss or severe headaches that have failed medical therapy. In the absence of this trial, subjects would have been offered a surgical treatment of IIH such as sinus stenting with an off-label device, cerebrospinal fluid shunting, or optic nerve sheath fenestration by the treating physician. * For subjects with visual field loss: if moderate to severe visual field loss (mean deviation between -6db and -30 db) for at least 2 weeks despite escalation of acetazolamide to 1000 mg twice a day or if the visual field deteriorates by more than 2 db during treatment, or treatment intolerance. * For subjects with headaches: if they have severe headaches (HIT \> 59) for at least 4 weeks despite treatment with topiramate 100 mg twice a day or other headache medication, or treatment intolerance. Enrollment size and sites: 39 subjects will be enrolled in up to 10 US sites. Primary safety endpoint: Major Adverse Event at 12 months. The MAE is a composite of the following: moderate or severe stroke (NIHSS \> 3), neurological death, perforation or thrombosis of sinus or cerebral vein, device distal embolization, need for target lesion revascularization or need for alternate IIH surgical procedure such as cerebrospinal fluid shunting or optic nerve sheath fenestration. Primary probable benefit endpoint: a composite at 12 months of: * Absence of significant (\>50%) stenosis of the stented sinus on retrograde catheter venography and * Trans-stent pressure gradient \< 8 mm Hg and * Clinically relevant improvement in the main clinical outcome per specific inclusion criteria and stabilization or better of the other: * Headaches: if the specific inclusion criteria was headaches, improvement in the HIT- 6 scale by \> 4 points and improvement or stabilization of visual field. * Ophthalmic: if the specific inclusion criteria was visual field loss, improvement of visual field by \> 29% of the baseline value in the study eye, stabilization or improvement in the fellow eye, and improvement or stabilization of headaches. Study duration and follow-up: The subjects will be followed at 2 weeks, 3 months, 6 months and 12 months. At 12 months, clinical examination, lumbar puncture and retrograde catheter venography with manometry will be performed to evaluate the patency of the treated sinus and the absence of trans-stent pressure gradient. Subjects will be consented to be clinically followed annually for up to 5 years.