What Is the Best Surgical Intervention for Patients With Idiopathic Intracranial Hypertension?

Acetazolamide and weight loss are the standard first-line treatment for patients with idiopathic intracranial hypertension (IIH).

Point Counter-Point Section Editors: Andrew G. Lee, MD Gregory P. Van Stavern, MD What Is the Best Surgical Intervention for Patients With Idiopathic Intracranial Hypertension? Prem S. Subramanian, MD, PhD, Roger E. Turbin, MD, FACS, Marc J. Dinkin, MD, Andrew G. Lee, MD, Gregory P. Van Stavern, MD Introduction—Andrew Lee, MD and Gregory Van Stavern, MD Acetazolamide and weight loss are the standard first-line treatment for patients with idiopathic intracranial hypertension (IIH). However, a substantial number of patients fail to respond and require more aggressive treatment. Three primary interventional options exist: cerebrospinal fluid (CSF) diversion (generally with ventriculoperitoneal shunt placement), optic nerve sheath fenestration (ONSF), and more recently, venous sinus stenting. There is no high-quality evidence favoring one procedure over the other, and this remains an area of great uncertainty for clinical decision making. Three experts debate this issue. Prem Subramanian, MD, PhD Cerebrospinal fluid diversion is the preferred intervention Severe IIH can be treated effectively by CSF diversion procedures (ventriculoperitoneal [VP] or lumboperitoneal [LP] shunting) that will lower intracranial pressure in a controlled manner and lead to improvement in visual and other neurological symptoms such as headache. The concept of CSF diversion has been present for decades, with subtemporal decompression being among the earlier treatments for IIH. Surgical technical refinements and development of medical devices have led to a predictable, quick, and often durable intervention for patients with IIH and vision loss with or without intractable headache. Before the development and easy availability of stereotactic intraoperative navigation, LP shunts were favored because of the ease of placement relative to VP shunts. Although some research groups and institutions continue to favor LP shunts and report their effectiveness in patients who have failed Sue-Anschutz Rodgers University of Colorado Eye Center (PS), University of Colorado School of Medicine, Aurora, Colorado; Institute of Ophthalmology and Visual Science (RET), Rutgers New Jersey Medical School, Newark, New Jersey; Departments of Ophthalmology and Neurology (MD), Weill Cornell Medicine, NY Presbyterian Hospital, New York, New York; Blanton Eye Institute (AGL), Houston Methodist Hospital, Houston Texas; and Department of Ophthalmology and Visual Sciences (GPVS), Washington University in St. Louis School of Medicine, St Louis, Missouri. The authors report no conflicts of interest. Address correspondence to Gregory P. Van Stavern, MD, Department of Ophthalmology and Visual Sciences, Washington University in St. Louis School of Medicine, St Louis MO 63110; E-mail: [e-mail] Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 medical therapy,1 most neurosurgeons today will perform VP shunting for IIH patients. The combination of highquality preoperative imaging and intraoperative navigation permits accurate placement of the proximal shunt catheter, and the distal end of the shunt may be placed in the pleural cavity or even the internal jugular vein instead of the peritoneal cavity if contraindications such as prior abdominal surgery or pregnancy might limit catheter function and CSF drainage. Most surgeons also will place a valved shunt rather than a free-flowing device to lessen the risk of postoperative intracranial hypotension from shunt overdrainage. Shunt valves may be adjustable (by use of an external magnet) or have a fixed lower limit for drainage. There is not a direct relationship between the absolute shunt setting and the resulting intracranial pressure, and many devices are available on the market. Outcomes of CSF diversion in IIH should be evaluated by their ability to alleviate the primary problems that our patients experience, namely, headache as well as papilledema and resultant visual field and/or visual acuity loss. Both VP and LP shunts appear to be effective in treating symptoms, although LP shunts may have a higher revision rate than VP shunts.2 McGirt et al3 reported on the shortand long-term outcomes of patients with LP or VP shunts and their effect on headache. They noted that 95% of patients had acute relief of headache symptoms; although a significant percentage had later headache recurrence, more recent evidence suggests that IIH patients have a pressure independent aspect to headache that requires a separate therapeutic approach.4 CSF diversion also has proven benefit in patient in whom vision loss 261 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point occurs after ONSF, supporting its safety and efficacy in treating vision threatening conditions.5 In a series of 17 patients who underwent VP shunt placement over a 6year period, improvement in visual acuity of both eyes was noted and was statistically significant.6 Notably, 5 subjects underwent ONSF and had persistent papilledema and visual loss before VP shunting.6 Automated perimetry performance, a more global measure of optic nerve function than visual acuity, was shown to improve by 5.63 ± 1.19 dB after VP shunting in a series of 15 patients over 7 years; retinal nerve fiber layer thickness and Frisén papilledema grade also improved.7 In a retrospective analysis of IIH patients who required surgical intervention, Fonseca et al8 found that automated visual field mean deviation improved by the same amount in patients who underwent ONSF or CSF diversion. Papilledema improvement or resolution also was not statistically different between the 2 surgical groups. All surgical treatments for IIH have been reported to have increasing rates of failure with passage of time, and CSF diversion is no different. However, repair of distal shunt obstruction, a more common source of failure than an intracranial or shunt valve problem, may carry lower risk than repeat ONSF or dural venous sinus stenting. Therefore, CSF diversion should be considered as a primary surgical intervention for IIH patients who have failed maximal medical therapy and have persistent symptoms of headache and/or vision loss. Roger E. Turbin, MD, FACS Optic nerve sheath fenestration is the preferred intervention ONSF is a safe, effective, no brainer.. The simple phrase broaches each of the most important concepts. ONSF provides a safe unilateral or bilateral, rapid, visionpreserving procedure of short duration, which does not interfere with other concurrent therapies. Its titration (unilateral vs bilateral) also provides time for subsequent less invasive adjuvant therapy to become effective. Most importantly, it is literally a “no brainer,” preventing the wellknown complications of CSF diversion experienced with CSF shunts (lumboperitoneal shunt [LPS], ventriculoperitoneal shunt [VPS], or ventriculoatrial shunt [VAS]). Both CSF diversion and venous stenting use mechanical devices which fail, the former extremely frequently with potential catastrophic effects and the latter incompletely defined because the techniques have only been studied since approximately 2003, and the stents, as such, remain in an active state of developmental evolution.9 We already cite at least an 8.7%–26% chance10,11 of stent adjacent stenosis (SAS), combined with other forms of hemodynamic stent failure cited up to 32.3%. The patients require long-term, occasionally indefinite, antiplatelet therapy. Regimens typically require initial double followed by single-agent long-term use in otherwise healthy individuals who may need additional procedures, which are complicated by antiplatelet therapy. Furthermore, the primary and follow-up neurosurgical and neurovascular care is an order of magnitude greater for shunting and venous stenting than ONSF. Yet, evidence-based head-to-head trial data to answer the surgical question remain lacking, leading to no clear consensus. I would also argue that small variations in the surgical question would lead to vastly different surgical considerations, leading one to conclude that each of the proposed procedures has a clear place in our surgical armamentarium, albeit roles are evolving. One must define 262 safety and efficacy, which are not necessarily straightforward. These concepts certainly ought to include visual efficacy, but what about headache control, avoidance of comorbidity, or even correction of comorbidity associated with obesity? Commonly cited retrospective studies have ignored many or all these factors and even our best prospective medical study led to disappointing results with respect to control of headaches in milder cases of IIH, despite beneficial outcomes on visual parameters and other factors affecting the quality of life.12 Unfortunately, the Surgical Idiopathic Intracranial Hypertension Treatment Trial (SIGHT)13 was terminated in August 2019 due to low enrollment of 7 of the proposed 180 participants. Certainly, there is utility in studying published complication rates, outcomes, durability studies, but the data remain inconclusive and not strictly comparable due to many sources of bias. Therefore, any conclusions we draw about headto-head comparisons remain limited and potentially flawed. Techniques in optic nerve sheath fenestration Modern improvements in operative technique have, in general, shortened operative time, leading to improving cost-effectiveness. The superior medial transcutaneous approach was described “as a new procedure” in 2001 by Patel and Pelton,14 and later elegantly validated by Jefferis et al in 2020,15 who emphasized that the previous metanalysis in 2015 by Satti comparing ONSF, CSF diversion techniques and venous stenting did not include the superior medial transcutaneous technique.16 The superior medial transcutaneous remains my procedure of choice since. One may occasionally experience, especially operating on older children with eczema, that some individuals seem to have very thick-appearing skin and subcutaneous tissues. These children (in which the anesthesiologist might have trouble placing an IV line at the beginning of the case) may also have intra-orbital fascial septa that are also atypically Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point robust. The retrobulbar retraction in these individuals sometimes results in the displacement of the optic nerve out of the field so that the surgery is like “chasing one’s tail,” increasing the retraction leading to more difficulty finding the nerve because the retraction tethers it out of the operative field. In these cases, I have resorted to sharp dissection of the septa, carefully moderating the retraction often using a third (Sen) retractor to distract and relatively fixate the globe in the axial direction. Alternatively, I have had to occasionally revert intraoperatively to a combined approach, taking off the medial rectus and isolating the nerve and then dissecting from preexisting superior medial dissection. Relevant anatomical factors There is wide variation at the level of the intraorbital optic nerve among patients in the anatomy of the dura and arachnoid, the dura sometimes dissecting in thickened multiple layers, or a thinned ballooning frail layer. The former may leave the surgeon occasionally questioning whether the underlying optic nerve with tightly adherent pia has even actually been reached. I now routinely tent up the dura with a grasping instrument such as a very fine alligator forceps from the myringotomy tray. The technique simplifies the dissection and allows more precise confirmation of full-thickness durotomy. I also converted to using an operating microscope in all cases and enjoy the longer working distance of the neurosurgical scopes, which allow beautiful digital video capability, high-power magnification, zoom function, and depth of field control. In addition, these microscopes provide increased degrees of freedom to rotate the operating head and longer working distance between the patient and lens, which prevents contamination of instruments that plagues my dissections with shorter focal length, less mobile, ophthalmic scopes. When using these nonophthalmic scopes, I also take care to avoid direct transpupillary illumination in the absence of ophthalmic filters.17 Tse et al offer a particularly useful discussion of the layered dissection, which I offer below for all surgeons’ review. Dr. Tse et al18 discuss that “as the dura is incised, arachnoid bulges slightly through the incision. The arachnoid and the edge of the dura are then regrasped together with the forceps, and the subarachnoid space is entered by snipping the arachnoid with the microscissors. Because CSF escapes once the arachnoid is cut, it is important to prevent the arachnoid from collapsing onto the pia. The arachnoid and dura should be excised without touching the pia. The dural edge of the window is examined with a microforceps. Two distinct cut edges should be seen: the arachnoid and the overlying dura. It is important that the arachnoid within the window is excised because an intact arachnoid is an effective barrier to CSF egress.” The authors’ argument about the dedicated dissection of the arachnoid is well taken, although it might contradict the Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 idea that ONSF via slit or multiple slit technique may also be effective. Effect Most authors report ONSF to be highly effective for visual preservation, reduction of papilledema, improvement in OCT parameters, preservation, and improvement in visual field. Dissimilar baseline presentations, author selection preference to ONSF, shunting or stenting, and lack of uniform assessment of the procedures plague the literature with bias, leading to failure of metanalysis to provide reasonable comparison. In the absence of head-to-head randomized clinical trial, in the short term, one could reasonably conclude that there is no obvious inferiority with respect to visual efficacy among each of the procedures in patients who are not already in acute decline. I believe that there is likely a difference in response rates of headache across the procedures as well as to the lowering of ICP, with ONSF likely faring the worst in these categories. Many authors report small series with each of the surgical procedures being used over the others, and special situations such as coexistent systemic conditions and hypercoagulable states requiring long-term anticoagulation, for instance, strongly favoring one procedure over another. Similarly, the duration of ONSF efficacy is open to some debate, as is the mechanism and decision to create a window vs slits. I strongly favor the window procedure. Whether the second eye effect is truly an effect of unilateral ONSF and independent of the other cotreatments I believe is open to debate, although many authors cite an independent role. Efficacy and durability A recent retrospective review of 30 patients undergoing superior medial transcutaneous surgery between 2011 and 2017 by one surgeon describes outcomes and complications over a median follow-up of 14.5 months.19 The surgical description of a standardized window in this text is useful: the authors describe the creation of “2 relatively long, longitudinal, 5-mm incisions separated by 2 mm, with additional enlargement to 7 · 3 mm with a punch.” Bilateral ONSFs were undertaken in 27 (90%) of 30 patients. The data from 1 eye per patient were analyzed. The mean kinetic perimetry score in mean radial degrees of the I4e isopter improved from 27.3° to 35.7° (P = 0.04). After removing cases with optic atrophy, the median modified Frisén grade of papilledema improved from 2.5 to 1.0 (P = 0.007). A total of 5 of 30 (17%) patients had complications: 2 (7%) had recurrence/late failure (1 managed medically and 1 with CSF diversion surgery), 1 had transient cotton wool spots postoperatively, 1 had transient retinal hemorrhages, and 1 patient had a transiently oval pupil. No patients had repeat ONSF, but CSF diversion surgery was subsequently conducted in 4 of 30 (13%) patients. Authors concluded that ONSF via a superomedial eyelid skin crease approach is effective at improving visual function in patients with 263 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point IIH. The complication rates are low when compared with CSF diversion surgery and other surgical approaches for ONSF. None of the patients in this series had repeat ONSF surgery, but 13% patients went on to have CSF diversion surgery, the main indication being persistent headache. The IIH consensus guidance states that headache alone should not be an indication for CSF diversion surgery; this should only be performed in a multidisciplinary team setting where there is agreement that the patient has exhausted all other medical options. A larger meta-analysis reviewed the effects, complications, and reoperation rates in patient undergoing ONSF, CSF diversion, or venous sinus stenting for refractory IIH.16 One thousand one hundred fifty-three eyes in 712 patients underwent ONSF, although the superior medial transcutaneous approach was not represented, the latter likely having a significantly lower rate of diplopia due to avoidance or eye muscle disinsertion. Post procedure, there was improvement in vision in 59%, headache in 44%, and papilledema in 80%; 14.8% of patients required a repeat procedure with major and minor complication rates of 1.5% and 16.4%, respectively. The CSF diversion procedure analysis included 435 patients. Post procedure, there was improvement in vision in 54%, headache in 80%, and papilledema in 70%; 43% of patients required at least 1 additional surgery. The major and minor complication rates were 7.6% and 32.9%, respectively. The dural venous sinus stenting analysis included 136 patients. After intervention, there was improvement in vision in 78%, headache in 83%, and papilledema in 97% of patients. The major and minor complication rates were 2.9% and 4.4%, respectively. Fourteen additional procedures were performed with a repeat procedure rate of 10.3%. Three patients had contralateral stent placement, whereas 8 had ipsilateral stent placement within or adjacent to the original stent. Only 3 patients required conversion to CSF diversion or 2.2% of patients with stents. Authors concluded that patients with medically refractory IIH have traditionally undergone a CSF diversion procedure as the first intervention. This paradigm may need to be reexamined, given the high technical and clinical success and low complication rates with dural venous sinus stenting. There is also likely a selection bias toward the more severe cases undergoing ONSF as pointed out by Pineles and Volpe,20 who reported on a large group of 37 patients undergoing ONSF. Yet, they reported that ONSF provides “similar improvement or stability in visual function with less systemic complications and argue for earlier intervention using ONSF. Despite the early overwhelming efficacy supported by the literature for ONSF, my surgical experience leads me to posit that some reported ONSF failures may be related to incomplete dissection. Also, I transitioned from cutting slits when I was more apprehensive about the procedure early in my career to creating a wide window with the goal of at least 3–4 mm by 5–6 mm or larger if 264 anatomy permits. Furthermore, in designing the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT), I had the opportunity to review surgical videos of ONSF from the Ischemic Optic Neuropathy Decompression Trial (IONDT). I actually cringed when reviewing some of these videos because technique in the videos were far from refined and objectively would not have passed the surgical certification we designed for the SIGHT trial. Patient selection Farris et al proposed that an opening pressure (OP) of $50 cm H2O may be a prognostic factor of ONSF failure in patients with IIH. An illustrative consecutive case series21 describes 132 eyes in 66 patients who underwent superior nasal ONSF that spared rectus muscle disinsertion at a single institution. All patients underwent bilateral procedure primarily with a mean surgical time of 50 minutes (range 25–89 minutes) and no operative complications or postoperative diplopia or worsened acuity 1 week after surgery. Despite successful bilateral decompressions, 4 patients (6.1%) experienced progressive visual loss. Of the 4 patients who progressed despite decompression, 2 had opening pressures of 50 cm of H2O, and all 4 had presenting visual acuity of count fingers or worse in 1 or both eyes. In an earlier article, Farris’s group also retrospectively reviewed 174 patients undergoing ONSF between 1992 and 2014 by 2 surgeons and identified opening pressure of $50 cm H2O as a possible independent risk factor for potential poor ONSF outcome. In 40 patients who had an opening pressure of $50 cm H2O, 6 (15%) had progressive visual loss after uncomplicated ONSD, vs 6 (4.5%) of 134 patients with an opening pressure of ,50 cm H2O (P = 0.032). In patients whose OP was $50 cm H2O and whose vision were 20/200 or worse in at least 1 eye, the failure rate of ONSD was 50% (95% CI: 18.7–81.3). They conclude patients with IIH and an OP of $50 cm H2O had a 3-fold increased risk of failure of ONSD to prevent progressive visual loss, requiring a shunting procedure when compared with those with OP of ,50 cm H2O.21 Headache response Well-designed head-to-head comparative assessments of effect on headache do not exist. The IIHTT, the first, large, randomized study on the use of acetazolamide and weight loss for treatment of idiopathic intracranial hypertension–associated vision loss, noted positive effects of acetazolamide on quality of life primarily mediated by improvements in visual field, neck pain, pulsatile tinnitus, and dizziness/vertigo that outweighed the side effects of acetazolamide.22 Similarly, although many authors23,24 cite a significant improvement in headache after ONSF, retrospective and noncomparative studies do not provide high-quality comparison of efficacy on headache treatment. Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point Even the IIHTT failed to show statistical significance on headache control of acetazolamide and weight loss of over placebo and weight loss.12 Revision rates A recent English language meta-analysis was performed25 searching the Cochrane, Medline, and Embase databases of patients meeting modified Dandy criteria for PTC from 1985 to 2014. The patients were dissimilar, and therefore, it is difficult to draw conclusions across the surgical procedures, but I find revision rates and the cost data and interesting. The types of revisions were not well defined, that is, if LPS were revised to VPS, nor were the revision rates incorporated into the cost data. The study revealed a revision rate per patient (RRPR) of 4.3 in LPS, with 49 of 128 patients undergoing 211 revisions and 1 converting to bilateral ONSF. For VPS, 53 revisions of VPS were reported in 29 of 70 patients (41%), RPPR 1.83. In 155 patients undergoing venous stenting, 10 required re-stenting (6.5%). In the ONSF patients, 63 of 397 eyes (15.9%) deteriorated regarding visual acuity and fields after a seemingly successful initial procedure. In 44 of 63 cases (69.8%), a second fenestration (reoperation) was performed, but the article does not specify whether it was unilateral or contralateral and it did not review the transcutaneous superior medial approach, which was more recently described. Recent discussions support the efficacy of secondary and tertiary ONSF in select patients.26 Cost of procedure The cost of both primary venous stenting and shunting are an order of magnitude higher than ONSF and is further magnified by a multiplier based on the frequency of revisions. ONSF is significantly less expensive even considering the need for second eye treatment. Similarly, no attempt is made in the cost analysis to consider the costs of subsequent imaging for these cases. Kalyvas et al25 reported the approximate costs of interventions based on European National Health System data after calculations were broken down into hardware cost, length of stay, and operative cost. The overall cost per procedure in £ (pounds) were LPS 2716£ (nonprogrammable valve) vs 4,227£ (programmable valve), VPS (valve type not detailed) 4,698£, ONSF 873£, and venous stenting 4,690£. Gastric banding and laparoscopic Roux -En-Y gastric bypass are offered for comparison at 5,348£ and 9,608£, respectively. Menger et al27 studied the summed charges using a US nationwide inpatient sample of patients treated for IIH in an NIS database for the years 2005–2009. In 4,480 patients, the mean charge for the placement of a single primary VPS was $37,708 and $32,617 for the placement of a primary LPS. The average charge for VPS revision was $37,543 and $45,414 for VPS removal. The mean charge for LPS revision was $32,849, and for LPS removal, it was $58,973. The summed charges for revision of 92 VPS ($3,453,956) and for 6 VPS ($272,484) totaled $3,726,352 over 5 years for the study population. The summed charges for revision of 70 LPS ($2,229,430) and those for 53 LPS removals ($3,125,569) totaled $5,408,679 over 5 years for the study population. Ahmed et al28 performed a cost comparison of venous stenting performed between 2001 and 2012 to 110 in 86 adult patients with IIH to the cost for shunting for hydrocephalus in 110 pediatric between 2007 and 2009. There was no significant difference between the cost of inserting an initial venous stent ($13,863 ± 4,890) vs inserting an initial CSF shunt ($15,797 ± 5,442) (P = 0.6337) or between inserting an additional venous stent ($9,421 ± 69) vs revising a CSF shunt ($10,470 ± 1,245) (P = 0.4996). There were far fewer additional venous stent insertions per patient than there were subsequent CSF shunt revisions; 87% of stents placed required just 1 stent procedure, whereas only 45% of shunts required 1 shunt procedure. The main cause of the cost difference was the need for repeated revisions of the shunts, especially when they became infected—24 instances of a total 143 shunt procedures (16.8%) at an average cost of $84,729, approximately 5 times the cost of an initial shunt insertion. Marc Dinkin, MD Venous sinus stenting is the preferred intervention Introduction and theoretical underpinnings Since the first venous stent was placed for a patient with idiopathic intracranial hypertension (IIH) by Higgins in 2002, the evidence supporting this procedure as a treatment for the disease has grown considerably. The theoretical grounds for using a stent to treat IIH begins with the fact that a significant portion of CSF drainage occurs through arachnoid granulations into the superior sagittal sinus. It is Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 for this reason that conditions that block sinus drainage, such as venous sinus thrombosis, or sinus compression by a mass may result in syndromes that mimic IIH.29,30 Therefore, the observation made in 2003 that 27 of 29 (93%) patients with IIH harbored substantial bilateral stenosis at the junction of the transverse and sigmoid sinus,31 vs only 4 of 59 (6.7%) of normal controls suggested that such stenoses played a role in the pathophysiology of the disease. In fact, 2 forms of stenosis, intrinsic and extrinsic, have been described. The intrinsic type describes a focal anatomical 265 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point narrowing due to a septal band, swollen arachnoid granulation, or organized chronic thrombus, which does not reverse with normalization of intracranial pressure and is therefore not a direct result of high ICP.32 The extrinsic type refers to a tapered stenosis, which does reverse with reduction in ICP and therefore appears to be a result of intracranial hypertension itself compressing the vessel externally. In both types, however, significant pressure gradients across the observed stenosis are demonstrated, consistent with hemodynamic significance.33 In other words, even the extrinsic type resulting from high ICP leads to proximally elevated venous pressures, and therefore, it can be expected to curb CSF drainage and elevate ICP even further. This in turn would lead to a positive feedback loop of higher ICP, further venous stenosis and so on, until the mechanical resistance of the vessel to further narrowing outweighed the external pressure. As such, both types have been the target for angioplasty and venous stent placement to eradicate the stenosis and the associated pressure gradient, thus allowing greater CSF drainage and breaking the vicious cycle. With this mechanistic framework in mind, venous stenting is appealing because it addresses an underlying contributor to the disease. Conversely, CSF shunting and ONSF treat the problem of IIH further downstream. Effect on intracranial pressure The theoretical appeal of venosus stenting is buttressed by its observed effect on intracranial pressure among studies that have compared pre- and poststent OP. Of 594 patients in whom a prestent lumbar puncture was performed, 195 underwent poststent LP, of which 183 (93%) were reported to have improvement in the opening pressure.11,33 Although the mean prestent opening pressure among the 461 patients in whom it was reported to be 35.3 cm of water, the mean poststent pressure among the 196 in whom it was checked to be 16 cm of water. Given that the poststent cohort was only a subset of the prestent group, the comparison is imperfect. However, our own study of 50 patients who underwent poststent LP at 3 months demonstrated an average reduction of 16.8 cm H2O (37 reduced to 20.2), despite an average decrease in acetazolamide dose from 950 mg to 300 mg and an average increase in body mass index (BMI) of 0.35 over the period.34 It should be noted that similar results were observed regardless of whether the stenosis was intrinsic or extrinsic. Similar results were reported by Lui et al35 who demonstrated a reduction to a mean OP of 22.1 cm H2O among 53 patients vs a mean prestent OP of 33.9 cm H2O among 83 patients. An even more impressive drop of 28.5 cm H2O was demonstrated by Wang et al36 in 8 patients. These results are encouraging, but because poststent LP was typically performed at least a month after stenting (owing to the dangers of LP while patients are on dual platelet therapy), a reduction in ICP fast enough to prevent optic nerve damage due to papilledema is not proven. This ques266 tion is addressed by Matloob et al26 who placed intraparenchymal monitors that demonstrated a reduction in spikes/hour of .33 cm H2O from 717 to 85 over the 24 hours immediately after stenting. Liu et al35 used right frontal bolts to assess ICP in real time following stenting and demonstrated an immediate reduction in OP in all 10 patients, yielding a drop in mean OP from 37.4 to 17 cm H2O. With a wealth of data supporting stenting’s timely effect on intracranial pressure, we turn to clinical outcomes next. More than 1,000 patients with IIH treated with venous stenting have been documented in the literature over the past 2 decades, with rates of improvement in both symptoms and signs comparable if not superior to that seen with alternative surgical procedures. In 2019, I reviewed outcomes for 808 patients in the literature, reflecting 30 studies with 4 or more patients and 12 case reports.37 The results, as I will summarize below, support venous stenting as an effective procedure for medically refractory IIH with safety parameters like shunting and fenestration. Effect on symptoms Among 678 noting headache at presentation, 498 (73.4%) reported improvement (298) or complete resolution (200) in their headaches. Although this leaves 26.6% with no effect on their headaches, such results are comparable to most therapeutic studies in IIH, owing to the multifactorial nature of headaches in these patients. In fact, even among patients with mild visual loss in the IIH Treatment trial, 69% of the those taking acetazolamide and 68% of those treated with weight loss and placebo still had headaches after 6 months.12 Of 229 patients noted to have pulsatile tinnitus, 195 (85.1%) experienced complete resolution. An analysis using the pulsatile tinnitus handicap score (THI) found complete resolution of PT in 28 of 29 patients immediately after stenting, with a reduction in mean THI score from 61.6 to 0.35, an outcome that reflects the fact that PT is a direct result of venous stenosis. Of 50 patients with diplopia, 47 (94%) were reported to have complete resolution after stenting. Finally, 84% (126 of 154) of patients complaining of transient visual obscurations reported complete resolution after stenting, a maker of improvement in papilledema. Papilledema and OCT In our review of 558 patients with papilledema in the literature,11,37 271 (49%) experienced complete resolution and an additional 107 (19%) experienced improvement. Importantly, we only found 28 cases where optic atrophy was present post stenting, the majority of which were present before the intervention. In Shield’s study, an impressive 29 of 29 (74.3%) experienced complete resolution of papilledema,38 whereas Su et al39 showed a reduction in papilledema in all 99 patients undergoing stenting. Looking Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point more specifically at the degree of improvement, we found that in our cohort of 48 eyes with papilledema, the Frisén grade improved from a mean of 2.37 to 0.56. A more quantitative look at disc edema can be obtained using optical coherence tomography (OCT) to assess pre- and poststent retinal nerve fiber layer (RNFL). Seven studies looked at pre- and poststent RNFL measurements among a total of 151 eyes. A metanalysis demonstrates a reduction from a mean thickness of 189.5 to 82.8 mm. Importantly, in our cohort, thinning of the RNFL to 70 mm or less was not observed in any patients in whom such atrophy was not already present before treatment. Visual fields No surgical procedure can be supported for patients with IIH with papilledema if it has not been shown to protect against loss of afferent visual function, the most serious long-term complication of suboptimally treated papilledema. Unfortunately, many studies only reported qualitative assessments, such that 95 of 129 (74%) patients experienced an improvement in visual acuity and 86 of 190 (45%) experienced an improvement in visual fields. Among 163 eyes for which mean deviation (MD) was reported preand poststenting, the average MD improved from 212.83 to 27.53 dB, and among our own cohort of 48 eyes, the MD improved from 210.1 to 4.67 dB.37 Failure and need for retreatment As with all surgical interventions for IIH, relapses may occur after venous stenting, owing mostly to the development of new stent-adjacent stenosis. Of 808 patients stented in the literature, 57 required a second stent or angioplasty and a further 17 required either a shunt or ONSF to address recurrences, for a total of 74 of 808 (9.2%) failures.11,37 True failure rates are likely higher because many of the studies in the analysis did not follow patients long term. In our initial prospective study in which we followed patients for at least 2 years, 2 of 13 (15.4%) required an additional stent.40 As we expanded our study, we found a slightly better rate of 10 of 79 patients (13.9%) and found that higher opening pressures at diagnosis predicted a greater likelihood of recurrence.41 The need for retreatment was higher in the study by Garner et al42 of 81 patients with a total of 10 months of follow-up, with 21 of 81 (25.9%) requiring further surgical intervention. However, even this rate of failure is significantly lower than rates described in studies of CSF shunting. Greener et al,43 for example, found that by 3 years post shunt, only 52% of IIH patients still had a surviving shunt, and the median survival of the initial shunt was 23 months. Furthermore, causes of failure included infection, which can be associated with morbidity and mortality over and above the associated worsening of IIH, a complication that does not affect venous stents. Failure rates for ONSF also appear to be higher than those observed with venous stenting. Spoor and McHenry44 Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 reported a deterioration of vision in 24 of 75 (32%) of eyes or 20 of 50 (37%) patients treated with ONSF requiring a secondary procedure. In all fairness, ONSF is typically performed in patients with more severe papilledema, which might affect the failure rates. Nevertheless, the available data suggest that failure rates among those treated with stenting are comparable if not superior to those treated with CSF shunting or ONSF. Complications Venous stenting is not without a risk of complications. Contrast allergy in 0.25%, anaphylaxis in 0.13%, and femoral pseudoaneurysm in 0.89% have been found. In stent, thrombosis was reported in 8 of 769 patients, although 2 of these cases were in Higgin’s original cohort in which antiplatelet therapy was not started before the procedure.11 Subdural (SDH) or intracerebral hemorrhage was reported in 0.5%. Townshend et al45 recently reported a series of 6 major complications following venous stenting, culled from 811 procedures at 8 institutions for a rate of 0.74%. These included 5 cases in which the patient recovered without neurological sequelae: acute SDH, intraprocedural stent thrombosis, delayed in-stent thrombosis, subdural perforation by the microcatheter with transient mild contrast extravasation, and perforation of a cerebellar bridging vein resulting in subarachnoid and subdural hemorrhage. In a sixth case, however, a cerebellar hemorrhage occurred contralateral to the stent, resulting in hydrocephalus and death. This was attributed to either venous congestion related to changes in venous flow dynamics or due to the dramatic drop in ICP, which has been previously described. Ahmed et al46 also reported one death, resulting from malignant intracranial hypertension, which, one can surmise, may have resulted from compromised flow in the vein of Labbe due to obstruction by the stent. A third death was reported following cerebellar hemorrhage that the authors felt was due to rupture of a cerebellar vein by the guidewire.47 However, this case was unique in that a large 35-gage guidewire was used, which is designed for use in larger extracranial arteries. In total, we are aware of a total of 6 deaths of 1,626 patients undergoing venous stenting for IIH in the literature, a mortality rate of 0.37%. These risks of venous stenting should be explained to every patient consenting for the procedure but should be placed in context of the myriad risks that are inherent in CSF shunting. These include central nervous system infection and acute or delayed intraparenchymal hemorrhage, all of which can be fatal,48,49 as well as ectopic migration of the peritoneal tip to sites as disparate as the pulmonary artery (often with secondary thrombosis),50 mouth,51 urethra,52 or rectum.53 In one single-center series of 95 patients treated with VPS over an 8-year period,54 there were 5 severe complications, and one fatal, yielding a mortality rate of approximately 1%. Although I have not been able to find reports of death 267 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point related to ONSF, there is a risk of secondary blindness, due to arterial occlusion or orbital hemorrhage, estimated at 1%–2%,55 a complication not known to occur with shunting or stenting. Concluding statement In summary, there is now growing evidence for efficacy and safety of venous stenting in patients with IIH that are comparable and, in some ways, superior to alternative procedures such as shunting and ONSF. A lack of comparative prospective studies remains a shortcoming in the literature on venous stenting, but such data are lacking for all surgical procedures in IIH. Despite encouraging data, patients should be selected carefully for venous stenting, and further research should be aimed at maximizing its efficacy, longevity, and safety. Rebuttal—Dr. Subramanian Drs. Dinkin and Turbin have laid out the data that describe how either ONSF or dural venous sinus stenting (VSS) might be used to treat patients with IIH. I agree with them that both may have a role in treating our patients with IIH, and I discuss these procedures as well as CSF diversion with all my patients who have failed medical therapy. As my colleagues note, there are no prospective head-to-head data comparing all 3 procedures, and this comparative study is unlikely to be done. In this absence of data, I will detail why CSF diversion may still be the best choice in many of our patients. The adverse physiologic effects of IIH result from elevated intracranial pressure. Dr. Dinkin points out that distal transverse venous sinus narrowing is seen in the vast majority of IIH patients and remits with stenting, suggesting a primary role. However, reversal of such stenoses has been observed after CSF diversion, indicating extrinsic compression,56 and a systematic study of this potential phenomenon after CSF diversion has not been conducted. While some institutions have advocated for ensuring that the venous sinus stenosis remains present after temporary CSF pressure reduction to a normal level,57 this system has fallen out of favor, and it is possible that some patients would benefit equally from direct CSF pressure lowering. Both VSS and CSF diversion involve introduction of a foreign object into the body. However, a shunt and its tubing can be removed if concerns such as infection develop. Similarly, if over drainage should occur, the distal shunt catheter can be ligated in a minor procedure. For most patients, the shunt system is well-tolerated and can remain in place indefinitely. It requires no long-term medical prophylaxis, unlike a venous stent which is permanent, cannot be removed, and mandates ongoing antiplatelet medical therapy. Reported complications of VSS include intracranial hemorrhage and death; while these events are uncommon and occur in 2%–5% of patients,58,59 they are directly procedure-related and not incidental. ONSF has been described by Dr. Turbin as being a “safe, effective no brainer,” and if that were the case, this debate would not be necessary. This procedure does require training and expertise, and it can be challenging to find the optic nerve and to gently retract the overlying 268 vascular complex to access the nerve sheath itself. The procedure is made much easier with the participation of one or 2 skilled assistants who may not always be available for urgent interventions. Like both CSF diversion and VSS, clinical case series and meta-analyses do show a high success rate for resolution of papilledema with a lesser rate of recovery of visual function. While this difference has been attributed to factors such as irreversible optic nerve damage before surgery, we must always consider that the surgery itself may damage the nerve. Experimental ONSF in rats showed histopathologic evidence for retinal ganglion cell and amacrine cell loss after surgery,60 and similar data are not available in humans. Known complications of ONSF as Dr. Turbin describes are fortunately uncommon, and unlike the adverse events seen with either VSS or CSF diversion, they directly impact vision, the very function we are trying to preserve in our patients with IIH. Neither CSF diversion nor VSS will result in immediate postoperative blindness as ONSF can. The need for additional surgery, either repeat ONSF or CSF diversion and/or VSS also exists, with clinical ONSF failure rates as high as 9.4% in one systematic review.326 Again, this rate impacts visual function directly, unlike the more broadly defined term of “shunt failure” that may describe headache recurrence and/or lack of CSF flow, both of which may be independent of visual function if headache is pressure independent. The difficulty of repeat ONSF, even with selection of a different surgical corridor, should not be underestimated (I state this as a surgeon who performs ONSF). A small case series looking at optic nerve sheath structure before and after ONSF demonstrated irregular and disorganized scar postoperatively, suggesting this tissue would be unable to allow continued CSF egress.61 Although it has been suggested that scarring of the arachnoid around the nerve at the fenestration site may insulate or buffer the lamina cribrosa from CSF pressure and thus be protective, this idea remains unproven. In conclusion, ONSF, VSS, and CSF diversion all have been shown to be effective in improving papilledema, with the latter 2 having greater efficacy for acute headache relief than ONSF. CSF diversion may be more widely available than either VSS or ONSF, since shunt placement is a core Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point neurosurgical skill that does not require any further specialized training. Although shunt failure can and does occur, I consider all surgical interventions for IIH to be temporizing, providing optic nerve protection from the elevated ICP while the underlying driver(s) of the IIH, typically obesity, are addressed and resolved. Rebuttal—Dr. Turbin ONSF is a highly effective procedure for preventing subsequent ipsilateral visual loss in most cases, independent of the cause of papilledema. Whether dependent or independent on concurrent therapy, the seemingly bilateral effect of unilateral surgery also provides a temporizing window to titrate to clinical response to a potential sequential contralateral ONSF or other surgical interventions. Few patients undergoing unilateral ONSF require ipsilateral revision, but the development of new surgical approaches allows potential ONSF same site revision from unoperated corridors. Some patients require contralateral surgery, and a few require shunting or venous stenting “rescue.” Revisions and multiple revisions of shunting procedures remain commonplace. The magnitude of complications in ONSF remain reasonably limited; the anesthesia choice defines the global potential complications, and the ONSF procedure typically results in minor complications in all but a few cases with rare, more serious, ocular complications to the operated eye (rare visual loss from optic neuropathy or retinal arterial or venous occlusion, double vision, ptosis, dellen formation, skin hypoesthesia, paralysis of accommodation, pupil abnormalities, globe perforation, retrobulbar hemorrhage, infection). Complications of shunting and venous stenting, in distinction, may be devastating beyond the risk of the anesthesia necessary. ONSF does not prevent nor interfere with subsequent surgical interventions nor additional imaging investigations and may be used as a “belt and suspenders approach coupled to temporary CSF diversion. In many cases, this prevents the need for the most aggressive permanent surgical procedures.” Although ONSF may always be used, venous stenting has not yet been defined as widely applicable to all cases and currently should meet certain venous hemodynamic measures in evolution, especially with respect to pressure gradients across a dynamic or fixed stenosis. Venous stenting requires the initial double antiplatelet agent for 3–6 months followed by single-agent antiplatelet therapy for years. ONSF patients may become medication free or limited to acetazolamide, similar agent, or headachespecific therapeutic, although the risks of long-term antiplatelet agents necessary in venous stenting must be balanced in the typically young individual of childbearing age. The use of antiplatelet agents increases potential complications of both revision and the selection of other available surgical procedures in cases of primary and secondary failure. Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Although most IIH patients in general require longterm ophthalmic follow-up, many patients stabilize and the disease becomes self-limited, especially after subsequent weight loss from lifestyle modification or bariatric procedure. Patients undergoing ONSF typically do not require surgery-directed specific monitoring. Those undergoing shunting techniques with modern magnetic programable valves require special management after MRI and remain prone to lifelong hardware infection. Patients occasionally may suffer unexpected valve resets during medical and nonmedical events. However, the iatrogenic complications of more aggressive interventions are not self-limited, converting a potentially self-limited temporary process into an iatrogenic situation that must be monitored forever. One must manage completely differently the CSF shunted patient or venous sinus stented patient who calls with a new headache as compared with the patient who had an ONSF patient and maybe on acetazolamide. Patients who have ONSF to preserve vision may achieve a “cure.” Yet, shunted patients who go on to lose significant weight after shunting through lifestyle modification or bariatric procedure may become shunt dependent for unclear reasons, including the syndrome of altered ventricular compliance. Although some patients who have ONSF may develop an arachnoid pseudocyst at the surgical site, only rarely do some of these patients develop body position sensitive orbital symptoms. On the other hand, the day-to day discomfort and body position accommodations in patients with shunts is commonplace and significant, with patients frequently complaining of body position–dependent changes that effect quality of life. Long-term monitoring of surgical devices may require commitment to repeated MRI or CT, leading to potential iatrogenic harm of contrast and radiation. Body habitus with high BMI may interfere with subsequent MRI, leaving only CT as an option, which has measurable deterministic and stochastic effects, especially important with repeated scanning in young patients of childbearing years. ONSF preserves vision without exposing patients to angiograms and brain surgery. Costs of primary surgical intervention and revisions have been reviewed and remain orders of magnitude lower for ONSF than for the more aggressive procedures. 269 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point Rebuttal—Dr. Dinkin My colleagues have made excellent points defending the use of CSF diversion and ONSF, respectively. There is clearly data in support of all 3 interventions, each with their particular benefits and complications. In my practice, even when a patient is referred for consideration of venous stenting, I review all the options with them, including CSF diversion, ONSF, and bariatric surgery, and try my best to convey the risks and benefits of each. Dr. Subramanian laid out the argument for CSF diversion well. A recent protocol involving frameless stereotactic ventricular catheter placement, and peritoneal catheter insertion laparoscopically reduced the 30-day revision rate from 22% to 6%.62 Yet even with this new system, a 6% rate of revision in just the first month is quite high. Lumboperitoneal shunts are particularly prone to failure, with a revision rate of 40%, and a high degree of repeat revisions (4.3/patient).25 The incidence of overdrainage has been reported as high as 30%, often leading to secondary Chiari malformations. In addition, some patients experience radicular pain from the LP catheter, a complication that I have witnessed to be debilitating. Although the failure rate of VPS is lower than LPS, it is still high, ranging from 18.7%65 to 41%26 in patients with IIH. It should be noted that in study of Brune et al of 32 patients undergoing VPS, although the percentage of patients who experienced failure was 6 of 32 (18.7%), there were actually 12 failures among them, yielding a rate of 37.5%.63 Furthermore, each failure was accompanied by complications that resulted in significant morbidity, including an iatrogenic enterotomy requiring intravenous antibiotics, 2 intracerebral hemorrhages (one with cerebral edema, reversible hemiparesis, and seizures), 1 patient with abdominal adhesions, a CSF–cutaneous fistula behind the ear and several bouts of meningitis (bacterial and fungal), and meningitis in 2 others. In the study by Huang et al, only 48% of VPS were still functioning without revision or replacement at 3 years.64 By contrast, the failure rate of venous stenting appears to range from 9% to 13% and is not associated with the morbidity of meningitis or the prolonged hospitalization sometimes seen with VPS. Furthermore, as with LPS, overdrainage can occur, resulting in low pressure headaches and tonsillar herniation. Although programmable shunts afford more control over ICP, they have their own issues. Repeated manipulations of the shunt valve can lead to a cycle of alternating high-pressure and low-pressure headaches and the burden of frequent neurosurgical visits. I agree with Dr. Turbin that ONSF can be quite effective in improving papilledema and saving vision in patients with high-grade papilledema and may even help the fellow eye.65,66 However, there are case reports of progressive vision loss despite ONSF.67 In the study by Goh et al of 29 eyes with progressive visual loss despite medical therapy, visual acuity only improved in 14% of patients, whereas visual fields did not improve or worsened in 52%.68 Four repeat surgeries had to be performed, in which one eye lost vision permanently. In the study by Herzau et al, 3 of 23 eyes that had papilledema with cotton wool spots and rapid vision loss at the time of surgery ended up with optic atrophy and severe vision loss even after ONSF,69 highlighting the fact that even ONSF may not be able to save vision in some cases of fulminant papilledema. In addition, the percentage of cases in which ONSF reduced headache was less than stenting or CSF diversion in a recent meta-analysis (49.3% vs 72.1% and 69.8%, respectively).25 Complications of ONSF are not uncommon and include pupillary dysfunction in up to 11%, diplopia in up to 35% (typically reversible), and irreversible vision loss from vascular complications such as central retinal artery occlusion, branch retinal artery occlusion, and outer retinal ischemia in up to 11%.70 Mauriello et al5 described 5 patients with progressive loss of vision after ONSF, one with intraorbital hemorrhage, another with infectious optic neuropathy and 3 with progressive vision loss that stabilized only after LPS. However, unlike with CSF diversion and venous stenting, death is almost unheard in ONSF. In a center with competent surgeons who perform ONSF regularly, therefore, I agree that it remains an excellent choice for the treatment of patients with medically refractory papilledema and severe vision loss. Unfortunately, in many institutions, orbital surgeons are not eager to perform ONSF or do not perform it commonly. In summary, I think there is a role for all 3 procedures in the surgical management of progressive IIH despite medical therapy. Conclusions—Drs. Lee and Van Stavern All 3 authors have done a wonderful job summarizing the evidence for and against each other various procedures. It is unfortunate that the SIGHT study was unable to recruit enough subjective continue because this would have provided much higher quality evidence guiding 270 management. It may be that certain patients respond better to one intervention over another. There may exist yet to be defined clinical predictors or biomarkers that would allow us to tailor treatment to each specific clinical scenario. Subramanian et al: J Neuro-Ophthalmol 2023; 43: 261-272 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Point Counter-Point However, until we have higher-quality evidence, the choice of intervention must be individualized. The decision should include clinical factors (visual field loss, degree of papilledema, prior medical therapy), the resources of the institution, individual patient risk for complications from each procedure, and the desires of an informed patient. REFERENCES setting of medically refractory idiopathic intracranial hypertension. AJNR Am J Neuroradiol. 2015;36:1899–1904. 17. Lai KE, Lao KC, Hildebrand PL, Farris BK. Superonasal Transconjunctival Optic Nerve Sheath Decompression: A Modified Surgical Technique without Extraocular Muscle Disinsertion. 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