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Abstract
Idiopathic intracranial hypertension (IIH) is characterized by headache, papilledema, visual field changes and tinnitus with elevated cerebral spinal fluid opening pressures on lumbar puncture. Left untreated, this condition can lead to permanent visual loss. Previous treatment modalities include medical management, therapeutic lumbar puncture and optic nerve sheath fenestration. They have proved to be effective but carry high rates of symptom recurrence or procedural complications. Focal dural venous sinus stenoses have been identified in many patients with IIH, leading to development of treatment through venous sinus angioplasty and stenting. A review of the literature was performed which identified patients with IIH treated with venous sinus stenting. The procedural data and outcomes are presented. A total of 143 patients with IIH (87% women, mean age 41.4 years, mean body mass index 31.6 kg/m2) treated with venous sinus stenting were included in the analysis. Symptoms at initial presentation included headache (90%), papilledema (89%), visual changes (62%) and pulsatile tinnitus (48%). There was a technical success rate of 99% for the stent placement procedure with a total of nine complications (6%). At follow-up (mean 22.3 months), 88% of patients experienced improvement in headache, 97% demonstrated improvement or resolution of papilledema, 87% experienced improvement or resolution of visual symptoms and 93% had resolution of pulsatile tinnitus. In patients with IIH with focal venous sinus stenosis, endovascular stent placement across the stenotic sinus region represents an effective treatment strategy with a high technical success rate and decreased rate of complications compared with treatment modalities currently used.
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Introduction
Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a condition characterized by visual symptoms, intractable headache and tinnitus with elevated cerebral spinal fluid (CSF) opening pressures on lumbar puncture.1 ,2 Papilledema may be present in up to 95% of cases and, as the disease progresses, optic atrophy can lead to permanent visual loss.2 ,3 IIH is often a progressive disease process but may have periods of stability or even improvement followed by worsening of symptoms, so long-term follow-up is recommended.4 The original diagnostic criteria for IIH were developed by Walter Dandy in 1937,5 and he was the first to postulate a syndrome of increased volume of either blood or CSF as the cause of this condition. Dandy's original diagnostic criteria have been modified over time as our understanding of the disease has evolved. The current most widely accepted criteria include: (1) signs and symptoms referable only to elevated intracranial pressure (ICP); (2) CSF opening pressure of >25 cm H2O; (3) normal CSF composition; and (4) no evidence for mass lesion or other structural cause using modern imaging techniques.6 IIH has a prevalence of 0.9–1.07/100 000 in North America; however, when the criteria are modified to include only overweight women aged 20–44 years, the prevalence rises to 15–19/100 000.7
Pathophysiology
The pathophysiology of IIH is controversial and a matter of ongoing debate. However, intracranial venous hypertension leading to decreased CSF reabsorption has been implicated as a potential final common pathway in IIH.8–11 Many theories have been proposed for the underlying mechanism behind decreased CSF reabsorption and intracranial venous hypertension, from structural abnormalities within arachnoid granulations to dural venous sinus stenosis, or a combination of both.1 ,8 ,10 Recent studies have focused on the prevalence of focal venous sinus stenoses in patients with IIH, commonly in the transverse or upper sigmoid sinus. Focal stenosis has been demonstrated in 30–93% of patients using advanced imaging techniques.1 ,10 Furthermore, focal stenosis in the same sinus territory was only demonstrated in 6.8% of asymptomatic control subjects.10 These findings have shed new light on a potential pathophysiologic mechanism behind IIH, but have raised questions as to whether the focal stenosis is causing the increased ICP, or if the stenosis is itself a sequel of increased ICP. A positive feedback mechanism has been proposed which states that, no matter what is the initial cause of focal stenosis, venous hypertension proximal to the stenotic area leads to further increased ICP causing continued or worsening stenosis, and so forth.12 This theory leads to the belief that treatment of the focal stenosis is a viable option to break the feedback cycle and resolve the increased ICP.
Conventional treatment
Current treatment strategies for IIH are multimodal. Medical treatment including carbonic anydrase-inhibiting diuretics and therapeutic lumbar punctures are the mainstay of treatment and are often effective in patients without severe papilledema and/or progressive visual symptoms. However, two studies have demonstrated that, after 6–10 years of follow-up, between 38.4% and 45% of patients experienced delayed worsening or recurrence of visual symptoms despite optimal medical management.4 ,13 In overweight patients, aggressive weight loss and in some cases gastric bypass procedures have been reported to be effective in reducing ICP and improving visual symptoms.14
In the presence of progressive refractory visual symptoms, CSF diversion and/or optic nerve sheath fenestration (ONSF) are indicated to prevent further visual deterioration. Procedural treatment strategies such as shunting or ONSF have led to resolution of visual symptoms in 45% of patients (shunting) and up to 80% of patients (ONSF).15 These procedures are certainly not free of risk, and shunt failure after 1 year can be as high as 75% for lumboperitoneal shunts and 50% for ventriculoperitoneal shunts.16 Despite the reported 80% improvement in visual symptoms after ONSF, it has been shown that this procedure can carry a 40% complication rate and recurrence of initial visual symptoms in up to 33% of patients.1 ,17–19
With advances in endovascular techniques, venous sinus angioplasty and stenting has emerged as a potentially efficacious treatment strategy for IIH in patients with known focal sinus stenosis. We have conducted a systematic review of the pertinent literature to assess the current status of venous sinus angioplasty and stenting for the treatment of IIH.
Methods
Using PubMed, we performed a search of the English language literature with several combinations of the keywords ‘Idiopathic Intracranial Hypertension’, ‘Pseudotumor Cerebri’, ‘Benign Intracranial Hypertension’, ‘Endovascular’, ‘Stent’ and ‘Venous Sinus Stenting’ to identify studies dated after 1970 in which cases of IIH were treated with placement of a venous sinus stent. We identified seven case reports and eight case series (total of 143 patients) which met our inclusion criteria.1 ,2 ,10 ,11 ,20–30 Studies were excluded for likely consecutive inclusion of the same patient(s), inadequate information or irrelevant data. A review protocol was not used in this study. The included studies are listed in table 1.
Characteristics of patients with idiopathic intracranial hypertension treated with sinus angioplasty and stent placement (N=143)
Patient data were pooled and the results were calculated from the large cohort. Due to inhomogeneity of data presentation among included studies, means, percentages and ranges were calculated for a smaller subset of patients with adequate data for analysis. Patients without adequate data were excluded from that particular analysis to avoid diluting the result. In cases where the information was presented nominally, such as body mass index (BMI) >30 kg/m2 in 47 patients, these 47 patients were given a BMI value of 30 kg/m2 causing potential underestimation of the actual average BMI. Follow-up symptomatology data were not fully reported in all studies, and thus symptom resolution analysis was carried out only on patients with adequate data.
Results
A total of 143 total cases of IIH (125 (87%) women) treated with venous sinus stenting were included in this analysis. The average age was 41.4 years (range 10–64). BMI was determined in 111 patients, and the average was 31.6 kg/m2 (range 22–73 kg/m2). Symptoms at initial presentation, prior to the stent procedure, included headache in 128/143 (90%), visual changes in 79/128 (62%), documented papilledema in 114/128 (89%) and pulsatile tinnitus in 41/86 (48%). Opening CSF pressures at the time of presentation were recorded in 86 patients with an average of 35.2 cm H2O (range 22–73 cm H2O). A large number of patients (n=128) underwent determination of the pressure gradient across their sinus stenosis prior to stent placement and the mean pressure gradient was 21.8 mm Hg (range 4–160 mm Hg). Location of the stenotic sinus was not reported in enough studies to be relevant to this analysis; however, stent placement (left, right or bilateral) was recorded in 116/143 patients. It is unlikely that stents were placed either on the unaffected side or in the less stenotic of two locations, so stent placement probably represents the true location of the initial greatest sinus stenosis. Eighty of the 116 stents (69%) were placed in the right transverse or sigmoid sinuses, 31 (27%) in the left transverse or sigmoid sinuses and 5 (4%) were placed bilaterally. Endovascular stents were placed in 142 of the 143 patients (99%), with one patient requiring open surgical stent placement after failed endovascular attempt. There were three major complications (subdural hematoma requiring surgical decompression) and six minor complications (two patients with transient hearing loss, one femoral pseudoaneurysm, one minor retroperitoneal hematoma, one urinary tract infection and one syncopal episode). No patients died during or immediately after the procedure, so the overall life-threatening complication rate was 3/143 (2%). When minor complications are included, the rate becomes 9/143 (6%). Post-stent pressure gradients were recorded in 115 patients with a mean value of 2.8 mm Hg (range 0–23 mm Hg).
Data on clinical follow-up time were available in 142 patients and the mean time of recorded follow-up was 22.3 months (range 1–136 months). Of 128 patients who presented with headache and had adequate clinical follow-up data, 112 (88%) experienced improvement in their headache symptoms or complete resolution after stent placement, 13 (10%) did not have any change in their headache symptoms and 3 (2%) had worsening of their headache after placement of the stent. Of the 113 patients who presented with papilledema and had clinical follow-up, 110 (97%) demonstrated improvement or resolution of their papilledema after placement of the sinus stent. Of 62 patients noted to have visual changes at presentation with adequate clinical follow-up, 54 (87%) experienced improvement or resolution of their presenting symptoms after stent placement. Of the eight with persistent visual symptoms, at least five were noted to have optic atrophy prior to stent placement. Only 41 patients who presented with pulsatile tinnitus had adequate follow-up data regarding this symptom, and it was noted that pulsatile tinnitus resolved in 38 patients (93%) after stent placement.
Discussion
IIH is a poorly understood cause of chronic headache with a predilection for overweight middle-aged women. Many patients have coexisting pulsatile tinnitus, papilledema and transient visual obscurations.1 ,2 Recent studies have demonstrated areas of focal stenosis within the dural venous sinus system in 30–93% of patients diagnosed with IIH.1 ,10 Focal venous sinus stenosis has been implicated as either the causative or contributory cause, and thus focused treatment of the stenotic sinus with a stent has emerged as a new potential treatment strategy. There have been numerous recent case reports and case series documenting the use of venous sinus stenting for the treatment of IIH, and we have reviewed and analyzed these reports to determine the potential efficacy of this potential treatment. As a whole, this combined cohort of 143 patients demonstrated consistent demographics with the commonly known patient presentation characteristics in IIH, the mean BMI of the cohort being consistent with the definition of obesity (31.6 kg/m2), mean age 41.4 years and 87% of patients being women. Headache and papilledema were very common presentations (90% and 89%, respectively), with visual changes in 62% and tinnitus in 48% of patients. Endovascular venous sinus stenting had a technical success rate of 99%, with only one reported patient failing the procedure (due to tortuous venous sinus anatomy) requiring stent placement via open approach.27 Placement of a stent had a large effect on venous sinus pressure gradients as the average gradient dropped approximately sevenfold from 21.8 mm Hg before stent placement to 2.8 mm Hg after placement of the stent. This procedure was highly effective clinically, resulting in improvement or resolution of headache in 88% of patients, improvement or resolution of papilledema in 97% of patients, restoration of normal vision in 87% of patients who presented with vision changes and resolution of pulsatile tinnitus in 93% at clinical follow-up. There was a 2% rate of subdural hematoma requiring operative intervention and an overall complication rate of 6% when minor complications were included. These rates are preferable to a reported 40% rate of complications with ONSF,15 frequent need for shunt revision (as many as 50–75% of cases16) and a high symptom recurrence rate (38.4–45%) despite optimal medical management.4 ,13 It is important to consider that these data apply to a selected population of patients with IIH who demonstrate focal stenosis of a main draining venous intracranial sinus.
Our analysis is limited by the retrospective nature of the studies analyzed and the lack of coordinated data reported in the studies considered. Only cases with specific documentation of a certain variable were included in the eventual analysis of that variable so that the true findings were not diluted. This caused a decreased power in the analysis of certain variables included in this report. Despite these inconsistencies, important variables such as headache, papilledema and pressure gradients were reported in large numbers of cases, demonstrating valuable treatment information.
Conclusion
In patients diagnosed with IIH who also present with a focal stenosis of the dural venous sinus system, endovascular stent placement across the stenotic region may represent an effective treatment strategy with a high technical success rate and an acceptably low rate of complications.
References
Footnotes
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Funding None.
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Competing interests None.
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Provenance and peer review Not commissioned; internally peer reviewed.