To understand the relationship between the intracranial venous gradient and the idiopathic intracranial hypertension;
To understand the rationale behind the intracranial venous sinus stenting in patient with pseudotumor cerebri.
Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a syndrome characterized by increased intracranial pressure, with non-specific neurological symptoms and a normal neuroimaging, except for findings occurring with chronic increased intracranial pressure of any cause.
Diagnostic criteria have been identified by Dandy and Smith.
IIH occurs with a frequency of about 1 case per 100'000 population/year or 19.3 per 100'000/year in obese women aged 20 to 44 years.
Historical treatment strategies including weight loss, carbonic anhydrase inhibitors, and therapeutic lumbar punctures have a percentage of failure of 38–45% with eventual worsening or recurrence of symptoms within 6–10 years .
More recently, some studies have shown areas of focal stenosis in the venous sinuses in roughly 30–93% of patients diagnosed with IIH  and venous sinus stenting has matured as a promising treatment for IIH patients .
In published systematic reviews and meta-analyses venous sinus stenting has been associated with significant symptomatic improvement:
|Major complication rate (%)||Minor complication rate (%)|
Fargen et al.  proposed recommendations for the selection and treatment of patients with IIH.
Subsequently, same Authors  conducted a milestone study to determine the relationship between normal physiologic and pathologic venous sinus pressures in patients with IIH. They seek to describe venous pressures and gradients in a large series of patients with IIH during retrograde venography and manometry and provide insight into the relationship between patient factors such as gender, age, body mass index (BMI) and open pressure on lumbar puncture (OP on LP) with venous pressure measurements.
They reviewed a database of patients with IIH and they included in the study patients presented with clinical symptoms of IIH without evidence of intracranial mass lesion on imaging, a lumbar puncture (LP) opening pressure (OP) >20cm H2O in the lateral decubitus position, and either medically refractory symptoms or medication intolerance. Patients previously treated with venous sinus stenting or a CSF shunting procedure, with an indwelling shunt system, and patients with a known diagnosis of sinus thrombosis were excluded.
Any patient with a LP performed within 7 days before the venogram procedure was excluded given the known temporary effect of CSF diversion on venous pressure gradients [4,5]. Patients who had a LP within the 7 days after the venogram procedure were included.
All included patients underwent diagnostic catheter angiography and retrograde venography with venous manometry.
Under minimal conscious sedation, Authors recorded all pressure measurements of 104 patients and identified tree groups:
- Group A: all patients
- Group B: patients with at least 1 pathologic adjacent pressure gradient (≥8 mmHg) and potentially benefit from venous stenting
- Group C: patients with an OP of ≤20 cmH2O and all adjacent pressure gradients <4mmHg.
Comparing data of all groups Authors noticed that:
- Among all patients with IIH, OP on LP is strongly predictive of SSS pressures and of the presence of a pathologic pressure gradient.
- Higher OP is highly predictive of a pathologic pressure gradient (≥8 mmHg): 3/4 of patients had an OP of ≥35 cmH2O, but 1/4 of patients had a normal OP (≤24 cmH2O).
- There is not a clear pressure gradient threshold when selecting patients for venous sinus stenting: a pressure gradient of ≥8mmHg has been arbitrary selected by Ahmed et al. without studies validating it and without outcome studies supporting the magnitude of the gradient.
- A non-invasive venographic imaging, such as MR venography, it is not useful for stenting selection, because it has a very poor negative predictive value for a significant pressure gradient (west2018).
- In normal individuals SSS pressures should probably be less than 16–18mmHg with overall pressure gradients of <8 mmHg and total cranial gradients <5mmHg.
- Wall M, Kupersmith MJ, Kieburtz KD, Corbett JJ, Feldon SE, Friedman DI, Katz DM, Keltner JL, Schron EB, McDermott MP; NORDIC Idiopathic Intracranial Hypertension Study Group. The idiopathic intracranial hypertension treatment trial: clinical profile at baseline. JAMA Neurol. 2014 Jun;71(6):693-701. doi: 10.1001/jamaneurol.2014.133.
- Kumpe DA, Bennett JL, Seinfeld J, Pelak VS, Chawla A, Tierney M. Dural sinus stent placement for idiopathic intracranial hypertension. J Neurosurg. 2012 Mar;116(3):538-48. doi: 10.3171/2011.10.JNS101410. Epub 2011 Dec 9.
- Puffer RC, Mustafa W, Lanzino G. Venous sinus stenting for idiopathic intracranial hypertension: a review of the literature. J Neurointerv Surg. 2013 Sep 1;5(5):483-6. doi: 10.1136/neurintsurg-2012-010468. Epub 2012 Aug 4.
- Horev A, Hallevy H, Plakht Y, Shorer Z, Wirguin I, Shelef I. Changes in cerebral venous sinuses diameter after lumbar puncture in idiopathic intracranial hypertension: a prospective MRI study.
J Neuroimaging. 2013 Jul;23(3):375-8. doi: 10.1111/j.1552-6569.2012.00732.x. Epub 2012 Aug 22.
- Buell TJ, Raper DMS, Pomeraniec IJ, Ding D, Chen CJ, Taylor DG, Liu KC. Transient resolution of venous sinus stenosis after high-volume lumbar puncture in a patient with idiopathic intracranial hypertension. J Neurosurg. 2018 Jul;129(1):153-156. doi: 10.3171/2017.3.JNS163181. Epub 2017 Aug 25.
- Mangalore S, Rakshith S, Srinivasa R. Solving the Riddle of "Idiopathic" in Idiopathic Intracranial Hypertension and Normal Pressure Hydrocephalus: An Imaging Study of the Possible Mechanisms - Monro Kellie 3.0. Asian J Neurosurg. 2019 Apr-Jun;14(2):440-452. doi: 10.4103/ajns.AJNS_252_18.
Fargen KM, Liu K, Garner RM, Greeneway GP, Wolfe SQ, Crowley RW.Recommendations for the selection and treatment of patients with idiopathic intracranial hypertension for venous sinus stenting. J Neurointerv Surg. 2018 Dec;10(12):1203-1208. doi: 10.1136/neurintsurg-2018-014042. Epub 2018 Jul 20.
Fargen KM, Garner RM, Kittel C, Wolfe SQ.[Epub ahead of print]. A descriptive study of venous sinus pressures and gradients in patients with idiopathic intracranial hypertension. J Neurointerv Surg. 2019 Aug 31. pii: neurintsurg-2019-015251. doi: 10.1136/neurintsurg-2019-015251.