P. Noonan
Department of Radiology
Scott and White Memorial Hospital
Temple, Texas

How did the recent article by Satti et al¹ pass muster? A review of the status of venous sinus stent placement in 2013² included more patients with stents than the so-called meta-analysis review in your October 2015 issue. Seven of the studies cited in the 2013 analysis had only 1 patient each and were not included in the 2015 analysis; stripped of those 7 single patient studies, the 2015 meta-analysis looks much like the 2013 review. Nevertheless, why choose to include in the meta-analysis a study with only 4 patients—or the studies with only 10, 12, 15, or 18 patients? The power in both the 2013 review and the current meta-analysis lies in the 52-patient study by Ahmed et al,³ in which CSF opening pressure, an essential criterion for the diagnosis of idiopathic intracranial hypertension (IIH), was not documented in either 11 or 9 patients depending on which meta-analysis one chooses to read. Likewise, the 2 studies with 15 patients each (Fields et al⁴ and Albuquerque et al⁵) did not record the CSF opening pressure for any of their included patients; and both the 4-patient study (Owler et al⁶) and the 18-patient study (Kumpe et al⁷) did not record CSF opening pressure in 1 and 4 patients, respectively. A study of 10 patients noted to be without recorded CSF opening pressures in the 2013 analysis (Bussière et al⁸) is noted in Table 4 of the 2015 meta-analysis as having an opening pressure range of 25–50 cm H₂0. What was the source of that post hoc information?

Given that an elevated CSF pressure is an essential diagnostic criterion of IIH, for which all of these patients were treated, it is therefore possible that as many as 56 of the patients included in the meta-analysis did not meet the criteria for diagnosis of the disease and should not be included in any study of IIH. Given that so little regard was shown for adherence to strict diagnostic criteria to establish the presence of IIH, it is no wonder that there is absolutely no mention of poststenting CSF opening pressure in any of the included studies, which is remarkable because failing to do so missed an opportunity to establish causality. The authors are correct in noting that future studies of operative techniques for this disease should include pre- and postintervention CSF studies, of which I would suggest that at a minimum these require documented CSF pressures in all patients.

Whether or no IIH actually existed, all patients in the meta-analysis studies underwent the stent-placement procedure and were subject to subsequent complications. Subdural hematoma, noted in passing as a major complication in the meta-analysis, is treated more rigorously in the 2013 review, which noted that all cases of recorded subdural hematomas were treated with open surgical decompression. Therefore, the possibility exists that at least some patients who did not meet the criteria for a diagnosis of IIH underwent an unnecessary procedure that caused a life-threatening complication requiring an emergent operation. Also treated in passing are the 8 patients in the meta-analyzed studies who underwent re-stenting for in-stent/peri-stent restenosis–events that are normally noted as complications in most studies of vascular stents but not so in the Satti article where they are neither listed as complications nor listed as “revisions” in Table 4. There is also the possibility that the 2.2% conversion rate to another treatment technique noted in the meta-analysis may not be accurate. A study from a dedicated multidisciplinary IIH treatment center that is not referenced in the meta-analysis (Goodwin et al⁹) reported that 3 of 18 (16.6%) patients failed venous sinus stent placement and ultimately required a shunt procedure. A conversion to a more invasive procedure as a result of treatment failure should be counted as a complication of the initial procedure.

The only conclusion that can be drawn is that there is a hint of a promise for this procedure in some patients in whom medically refractory IIH is correctly established. Without a controlled trial comparing venous sinus stent placement with either an accepted surgical technique or the best available medical therapy, conclusions cannot be drawn regarding which patients, if any, may benefit from venous sinus stent placement.

References

1. Satti SR, Leishangthem L, Chaudry MI. Meta-analysis of CSF diversion procedures and dural venous sinus stenting in the setting of medically refractory idiopathic intracranial hypertension. AJNR Am J Neuroradiol 2015;36:1899–904
2. Puffer RC, Mustafa W, Lanzino G. Venous sinus stenting for idiopathic intracranial hypertension: a review of the literature. J Neurointerv Surg 2013;5:483–86
3. Ahmed RM, Wilkinson M, Parker GD, et al. Transverse sinus stenting for idiopathic intracranial hypertension: a review of 52 patients and of model predictions. AJNR Am J Neuroradiol 2011;32:1408–14
4. Fields JD, Javedani PP, Falardeau J, et al. Dural venous sinus angioplasty and stenting for the treatment of idiopathic intracranial hypertension. J Neurointerv Surg 2013;5:62–68
5. Albuquerque FC, Dashti SR, Hu YC, et al. Intracranial venous sinus stenting for benign intracranial hypertension: clinical indications, technique, and preliminary results. World Neurosurg 2011;75:648–55
6. Owler BK, Parker G, Halmagyi GM, et al. Pseudotumor cerebri syndrome: venous sinus obstruction and its treatment with stent placement. J Neurosurg 2003;98:1045–55
7. Kumpe DA, Bennett JL, Seinfeld J, et al. Dural sinus stent placement for idiopathic intracranial hypertension. J Neurosurg 2012;116:538–48
8. Bussière M, Falero R, Nicolle D, et al. Unilateral transverse sinus stenting of patients with idiopathic intracranial hypertension. AJNR Am J Neuroradiol 2010;31:645–50
9. Goodwin CR, Elder BD, Ward A, et al. Risk factors for failed transverse sinus stenting in pseudotumor cerebri patients. Clin Neurol Neurosurg 2014;127:75–78

Reply

S.R. Satti
Department of Neurointerventional Surgery
Christiana Care Health System
Newark, Delaware

L. Leishangthem
Department of Neurology
Albert Einstein Medical Center
Philadelphia, Pennsylvania

T. Sivapatham
Department of Neurointerventional Surgery
Christiana Care Health System
Newark, Delaware

I appreciate the thorough review and comments on our recent article, “Meta-Analysis of CSF Diversion Procedures and Dural Venous Sinus Stenting in the Setting of Medically Refractory Idiopathic Intracranial Hypertension,”¹ by Dr Noonan. I humbly concede that our meta-analysis of the dural venous sinus stent (DVSS) is not significantly different from the previously published meta-analysis on the topic of DVSS for idiopathic intracranial hypertension (IIH),² though another meta-analysis on DVSS was not the goal of the article. The DVSS portion of the article represented only one-third of the focus of the article. The goal of the article was to compare outcomes and complications of DVSS with traditional surgical approaches (CSF flow diversion and optic nerve sheath fenestration) on the basis of the best available published literature and to highlight that the “standard of care” for medically refractory IIH may not be superior to DVSS. To date, no large meta-analysis has been performed comparing surgical intervention with the DVSS in the setting of IIH. The purpose of this article was to challenge the assertion that surgery, rather than endovascular treatment, should be considered as the first-line standard of care for all patients with medically refractory IIH. Therefore, this article represents a significant and unique contribution to the literature.

The major limitation of the article was the retrospective nature and inconsistent data collection, which are inherent with meta-analysis study designs and are further complicated by comparison of different procedures by different operators focusing on different clinical parameters. This limitation was a considerable challenge, and direct comparison of baseline characteristics and follow-up was impossible.

One criticism raised by Dr Noonan was our approach to exclusion/inclusion of particular articles. This was largely driven by the numbers and was arbitrary. DVSS is a relatively new procedure compared with optic nerve sheath fenestration and CSF flow diversion; therefore, significantly less patient data were available. Data regarding DVSS were incomplete and inhomogeneous, given the current lack of standards (selection and follow-up). We chose to exclude any article deemed to have poor or incomplete data. Articles with a single patient were also excluded because they did not significantly add to the power of the study (7 articles with single patients are already well-described in the literature). Larger patient numbers were, in our opinion, worth the effort required to evaluate and standardize the data to help power the study. The 15-patient cohort from Albuquerque et al³ was included to help power the DVSS subset, despite not providing detailed pretreatment CSF opening pressures, given that the remainder of the data points were documented. Albuquerque et al did report, however, that elevated venous pressures were confirmed in all except 1 patient (18/19 patients).³ In reference to the comments regarding Table 4, venous sinus stenting, Bussière et al² did report CSF opening pressures as a range between 25 and 50 cm H₂O, which was provided in the body of the article under “Materials and Methods.” Strict inclusion criteria were not commonly adhered to in the surgical modalities.

Emergent evacuation of a subdural hematoma is not to be taken lightly and may be less common now, given improved catheter technology with use of flexible large-bore guiding catheters such as the Neuron Max catheter (Penumbra, Alameda, California). Subdural hematomas were reported in only 4/136 patients and resulted in no deaths in the DVSS group. Additionally, the major complication rate in this group was significantly lower than that in the surgical alternatives. I humbly contend that most neurointerventionalists would not consider re-stent placement as a complication, but rather a limitation. If we defined “repeat procedure” as a complication, the CSF flow-diversion group would appear even less appealing to physicians and patients because 154/435 patients required an astonishing additional 428 procedures. This was just during the average follow-up period of 41 months in largely young female patients, with an average age of 31.9 years (potentially, additional procedures might be needed for many more years).

Finally, I would agree with Dr Noonan that there is great promise for the DVSS in the setting of appropriately chosen patients with medically refractory IIH. I would propose incorporation of the following before any stent procedure:

1. A multidisciplinary approach (documenting truly medically refractory IIH)

2. CSF studies with elevated opening pressures

3. Careful imaging selection before venography (MR imaging and MRV with and without contrast)

4. Venography confirming stenosis and direct pressure measurements (gradient, ≥8 mm Hg) without sedation

5. Intervention by using a careful technique (a triaxial approach by using modern ultra-flexible guiding catheters) and the “conduit technique” to minimize the risk of dural sinus injury⁴ and dual antiplatelet therapy minimizes risk of in-stent thrombosis

6. Thorough long-term follow-up including clinical examination (symptoms, papilledema, funduscopic examination) and follow-up CSF pressures.

I sincerely hope this article proves to be a valuable contribution to the literature, ideally serving as a stepping stone to better understand the disease and potentially suggesting a new paradigm in the treatment of patients with medically refractory IIH.

References

1. Satti SR, Leishangthem L, Chaudry MI. Meta-analysis of CSF diversion procedures and dural venous sinus stenting in the setting of medically refractory idiopathic intracranial hypertension. AJNR Am J Neuroradiol 2015;36:1899–904
2. Bussière M, Falero R, Nicolle D, et al. Unilateral transverse sinus stenting of patients with idiopathic intracranial hypertension. AJNR Am J Neuroradiol 2010;31:645–50
3. Albuquerque FC, Dashti SR, Hu YC, et al. Intracranial venous sinus stenting for benign intracranial hypertension: clinical indications, technique, and preliminary results. World Neurosurg 2011;75:648–52; discussion 592–95
4. Turk A, Manzoor MU, Nyberg EM, et al. Initial experience with distal guide catheter placement in the treatment of cerebrovascular disease: clinical safety and efficacy. J Neurointerv Surg 2013;5:247–52