Dural venous sinus stenting in idiopathic intracranial hypertension: let’s try to understand something more

Key point:

    • 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.

Modified Dandy criteria (from Smith)

1 Presence of signs and symptoms of increased intracranial pressure.
2 Absence of localizing findings on neurologic examination except those known to occur from increased intracranial pressure.
3 Absence of deformity, displacement, or obstruction of the ventricular system and otherwise normal neurodiagnostic studies, except for evidence of increased CSF pressure (>20 cmH2O). Abnormal neuroimaging, except for empty sella turcica, optic nerve sheath with filled out CSF spaces, and smooth‐walled non flow‐related venous sinus stenosis or collapse, should lead to another diagnosis.
4 Awake and alert patient.
5 No other cause of increased intracranial pressure present.

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 [1].

More recently, some studies have shown areas of focal stenosis in the venous sinuses in roughly 30–93% of patients diagnosed with IIH [2] and venous sinus stenting has matured as a promising treatment for IIH patients [3].

 

But how a sinus stenosis could cause the IIH?

 

Dural venous stenosis and Monro-Kellie doctrine

As demonstrated by some studies there is a correlation between the ICP and the intracranial venous pressure (IVP) and diameters of dural sinuses have a dynamic nature that depends on CSF pressure variations[4,5]. Recent studies proposed therefore to focus on the role of the IVP on the Monro-Kellie doctrine (MK 2.0), for different reasons:

  • Normal ICP is 5–15 mmHg, but is influenced by orthostatic position and is generally very similar to cerebral venous pressures (CVP).
  • The initial Monro-Kellie doctrine (MK 1.0) misses the dynamic reality of the ICP.
  • The Miller and Langfit equation (CPP = MAP – ICP), derived from the MK doctrine is not entirely true; according to the equation the ICP = MAP – CPP implying no venous involvement on the ICP, but it is well recognized that gentle pressure to the neck over the jugular veins causes an ICP rise.

Moreover, a recent article published by Mangalore et al. [6] analyzed morphologic changes of the brain in chronic venous hypertensive encephalopathy (IIH) and chronic hydrocephalic encephalopathy (NPH) (MK 3.0).

Monro-Kellie doctrines: MK1.0 – Role of acute increase of intracranial pressure by intracranial pathology resulting in compensatory volume changes of CSF and venous volumes to maintain intracranial pressure; MK2.0 – Role of acute increase of intracranial pressure by intra- or extra-cranial causes of increase in venous pressure resulting in raised intracranial pressure and causing cerebral perfusion pressure arterial changes and changes in cerebrospinal fluid volumes; MK3.0 – Role of chronic process of passive increase in venous pressure in idiopathic intracranial hypertension and mirror pathology of increased cerebrospinal fluid velocity in normal pressure hydrocephalus causing shear stress and strain on the brain.

 

What about results of venous sinus stenting?

 

In published systematic reviews and meta-analyses venous sinus stenting has been associated with significant symptomatic improvement:

Symptoms Improvement (%)
headache 78–83
papilledema 87–97
visual symptoms 74–85
tinnitus 95
Major complication rate (%) Minor complication rate (%)
1.6-2.9 1.6-4.4

 

How to select a patient with IIH for a dural venous stenting?

 

Fargen et al. [7] proposed recommendations for the selection and treatment of patients with IIH.

Recommendation for selection and treatment of patients with IIH

  • Many authors support using non-invasive venous imaging to detect sinus stenosis and determine candidacy for angiography. However, the high rate of venous sinus variability in normal patients suggests that the utility of non-invasive venous imaging is questionable. It is reasonable to use non-invasive venous imaging as a screening tool to determine candidacy for catheter angiography (Moderate).
  • Given that a proportion of patients that undergo angiography and manometry without pre-imaging studies or without a demonstrated stenosis on MRV or CTV are found to have significant pressure gradients, it is reasonable to suggest that IIH patients without previous imaging studies.
  • The available literature suggests that it is reasonable to perform diagnostic catheter angiography on patients who continue to have symptoms while on medical therapy or who are intolerant of medical therapy (Moderate).
  • It is reasonable to perform venography on patients with intracranial pressures greater than or equal to 25cm H2O (Moderate) and in select cases where pressures are below 25cm H2O (Weak).
  • There are no data to support BMI as a predictive factor for symptomatic venous sinus stenosis in IIH and therefore BMI should not be used to influence candidacy for diag- nostic catheter angiography (Weak).
  • Venous sinus manometry should be performed to assess candidacy for treatment prior to stenting (Strong).
  • A pressure gradient of 8 mm Hg or higher should be present when selecting candidacy for stenting (Moderate). A pres- sure gradient threshold of 4–7mm Hg may show benefit in select cases (Weak).
  • It is reasonable to perform selective catheter arteriography in conjunction with venography and manometry to evaluate venous anatomy and outflow patterns (Moderate).
  • Diagnostic venography and manometry should be performed with the patient awake (Moderate).
  • A large diameter microcatheter is recommended, or a smaller diameter catheter which is shown to be more accurate in the literature such as the Echelon 10 or Prowler Select Plus (Weak).
  • There are no data to suggest superiority or inferiority of different stent devices in venous sinus stenting (Weak).
  • There are no data to support a benefit to upfront bilateral transverse sinus stenting over unilateral stenting (Weak).
  • There are no data to suggest the use of multiple stents to reduce the risk of retreatment or treatment failure (Weak).
  • Antiplatelet agents should be administered prior to stenting and in the follow-up period for at least 3–6 months following stenting (Strong).
  • There are no data to support inferiority of single antiplatelet agents over dual antiplatelet agents, although thromboem- bolic complications have been reported with aspirin use only (Weak).
  • It is important to perform post-stenting manometry to confirm resolution of the pressure gradient after stenting to document procedural success (Strong).
  • There are limited data on the criteria for retreatment or for the optimal retreatment strategy. It is reasonable to repeat angiography and manometry on patients with recurrence of symptoms after resolution with stenting to evaluate for recurrent stenosis (Strong).

Subsequently, same Authors [8] 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.

Definition of pressure grandient

Gradient Calculation
CCP gradient SSS-ET
ET-TS pressure gradient ET-dominant TS
TS-SS pressure gradient dominant TS-SS
skull base pressure gradient dominant SS-IJV
cervical extracranial pressure gradient dominant IJV-CVP
Summative gradients
totat CP gradient SSS-dominant IJV
Overall pressure gradient SSS-CVP

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.

 

Reference

  1. 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 trialclinical profile at baseline. JAMA Neurol. 2014 Jun;71(6):693-701. doi: 10.1001/jamaneurol.2014.133.
  2. 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.
  3. 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.
  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.
  5. 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.
  6. 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.
  7. 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.
  8. Fargen KM, Garner RM, Kittel C, Wolfe SQ.[Epub ahead of print]. 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.

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