26.1 Goals

1. 
   

   Review the literature that informs current understanding of the pathogenesis of intracranial hypertension.

   
   
2. 
   

   Critically analyze the literature on the treatment options for intracranial hypertension.

   
   
3. 
   

   Review the literature that evaluates outcomes of treatment of intracranial hypertension with venous sinus stenting.

26.2 Case Example

26.2.2 Treatment Plan

Treatment options were discussed in depth with the patient, including optic nerve sheath fenestration (ONSF), cerebrospinal fluid (CSF) diversion, and venography with potential venous sinus stenting. She elected to pursue venography and possible venous sinus stenting. Venography was performed under light conscious sedation. This confirmed a hypoplastic left transverse sinus with focal narrowing at the transverse-sigmoid junction (Fig. 26.2a) as well as a dominant right transverse sinus with focal narrowing at the transverse-sigmoid junction (Fig. 26.2b). Venous pressure manometry was performed showing a pressure of 21 mm Hg in the superior sagittal sinus, 21 mm Hg in the right transverse sinus, 14 mm Hg in the left transverse sinus, 7 mm Hg in the left sigmoid sinus, and 9 mm Hg in the right sigmoid sinus. Given the pressure gradient of 12 mm Hg in the dominant transverse sinus, the patient was offered transverse sinus stenting, and she elected to proceed. She was placed on 325 mg of aspirin and 75 mg of clopidogrel for 7 days and subsequently underwent uneventful placement of a stent within the right transverse sigmoid junction (Fig. 26.3).

26.3 Case Summary

1. 
   

   What are the criteria for diagnosis of idiopathic intracranial hypertension?

   
   

   While multiple classification and diagnostic schemes have been proposed for intracranial hypertension, ^{1 , 2 , 3} the most widely cited and adopted criteria for the diagnosis of idiopathic intracranial hypertension are the modified Dandy criteria, proposed by Smith in 1985 (▶ Table 26.1). ⁴ These criteria include signs and symptoms of increased intracranial pressure (such as papilledema and headache) in the setting of CSF pressure of greater than 200 mm of water relative to the level of the left atrium in a patient that is alert and oriented with no localizing neurological findings (except possible cranial nerve VI palsy). In addition, there can be no evidence of abnormalities within the ventricular system and no other obvious source of increased intracranial pressure. For CSF pressures of 200 to 250 mm H₂0, at least one of the following is also required: pulse synchronous tinnitus, cranial nerve VI palsy, Frisen grade II papilledema, MRV with transverse sinus stenosis/collapse, partially empty sella or optic nerve sheath with filled out CSF spaces on magnetic resonance imaging (MRI), echography for drusen negative. This patient meets the modified Dandy criteria for the diagnosis of idiopathic intracranial hypertension.

   
   
2. 
   

   What are the treatment options for idiopathic intracranial hypertension?

   
   
   
   
   1. 
      

      Diet and exercise/weight loss:

      
      

      In the absence of fulminant papilledema or progressive visual changes, treatment options begin with diet and lifestyle modification. In 1974, Newborg demonstrated a complete reversal of papilledema in all of nine patients with a very low-calorie (400-1000 calories per day) and low-sodium (less than 100 mg/d) diet with accompanying fluid restriction. ⁵ More recent studies have shown improvements with less draconian diets, with some studies showing reversal of symptoms in patients who are able to lose 5 to 10% of total body weight. ⁶

      
      
   2. 
      

      Carbonic anhydrase inhibitors:

      
      

      The Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) was the first randomized, controlled trial examining the use of acetazolamide and weight loss for treatment of vision loss related to idiopathic intracranial hypertension. Patients were randomized to weight loss and placebo or weight loss and acetazolamide with a primary outcome measure of perimetric mean deviation (PMD). Secondary outcomes included safety, quality of life, change in Frisen scale papilledema grade, weight loss, and headache disability.

      
      

      The study was able to demonstrate significant improvements in visual field, CSF opening pressure, papilledema, and quality of life in the acetazolamide and weight-loss groups when compared to the placebo and weight-loss groups. The study did not find a significant improvement in headache severity.

      
      
   3. 
      

      Bariatric surgery:

      
      

      Given the success of weight loss in ameliorating symptoms of intracranial hypertension it is unsurprising that bariatric surgery has been suggested as an invasive treatment option for refractory intracranial hypertension. In a study of 24 morbidly obese females (mean BMI47) with headaches and elevated opening pressure on lumbar puncture who underwent gastric surgery, 18 of the 19 patients not lost to follow-up at 1 year demonstrated resolution of headache. Only 12 of the patients had papilledema preop-eratively and this improved following surgery. Two patients later regained weight with return of symptoms. ⁷ A meta-analysis comparing bariatric surgery and nonsurgical weight loss for treatment of symptoms of intracranial hypertension including a total of 65 patients undergoing surgery and 277 without surgery showed that 100% of the patients with papilledema in the surgical group improved and 90.2% had a reduction in headaches, whereas nonsurgical weight loss led to a reduction in papilledema in 66.7% and an improvement in headache symptoms in 23.2%. ⁸

      
      
   4. 
      

      Optic nerve sheath fenestration (ONSF):

      
      

      Multiple retrospective case series speak to the utility of ONSF in arresting visual deterioration in intracranial hypertension. ^{9 , 10 , 11 , 12} In one representative study, 54% of eyes had stabilization of visual acuity following ONSF, with 22% showing improvement and visual deterioration in 24% of operated eyes. ¹¹ These results are in alignment with other studies. ¹⁰ Although there is a broad agreement on the utility of ONSF for stabilization of visual loss, it seems to be less effective for ameliorating headaches than other surgical interventions. One systematic review found that only 36% of patients had improvement in headaches with ONSF compared to 62.5% with ventriculoperitoneal shunting, 75.2% with lumboperitoneal shunting, and 82.9% with venous stenting. ¹³ Complications can be seen in up to 40% and, although mostly minor disorders of ocular motility, approximately 5% were central retinal artery occlusion with subsequent loss of vision. ¹⁴

      
      
   5. 
      

      CSF diversion:

      
      

      CSF diversion has been the most widely adopted invasive intervention for intracranial hypertension. Shunting for intracranial hypertension increased 350% between 1988 and 2002. ¹⁵ Despite its widespread use there are no randomized, controlled trials to guide treatment; and evidence, similar to the other interventions discussed, remains largely limited to retrospective case series. While CSF diversion is generally effective at arresting vision loss or improving vision, its effect on headaches is more variable. Sinclair et al showed that, while visual acuity improved at 6 and 12 months following CSF diversion, 68% of patients had persistent headaches at 6 months and 79% at 2 years. ¹⁶

      
      

      CSF diversion generally is performed using either ventriculoperitoneal (VP) or lumboperitoneal (LP) shunts. There are multiple other possible configurations, such as ventriculoatrial and ventriculopleural, but these remain less commonly utilized or reserved for second-line procedures. Some studies have shown that LP shunts have a 2.5-fold risk of requiring revision. ¹⁷

      
      
   6. 
      

      Subtemporal decompression:

      
      

      Although initially used by Dandy as the treatment of choice for idiopathic intracranial hypertension, subtemporal decompression has largely fallen out of favor as a first-line surgical treatment for intracranial hypertension. In a retrospective study of eight patients undergoing subtemporal decompression for intracranial hypertension, Kessler et al demonstrated arrest of deterioration in visual fields in all eight patients, although five subsequently required CSF diversion for intractable headaches. ¹⁸

      
      
   7. 
      

      Venous sinus stenting:

      
      

      Recognition that dural sinus thrombosis can cause symptoms of intracranial hypertension dates back to at least 1951. ¹⁹ It was not until 2001, however, that Higgins reported the first use of a venous stent for treatment of intracranial hypertension. ²⁰ Multiple case series have since demonstrated the efficacy of venous sinus stenting in treating select cases of intracranial hypertensjon ^{21 , 22 , 23 , 24 , 25 , 26}

      
      

      Meta-analysis comparing CSF diversion and venous sinus stenting in medically refractory intracranial hypertension demonstrated that, among patients undergoing venous sinus stenting, 78% experienced improvement in vision, 83% showed improvement in headache, and 97% showed improvement in papilledema. These numbers compare favorably to ONSF (59% improvement in vision, 44% improvement in headache, and 80% improvement in papilledema) and CSF diversion (54% improvement in vision, 80% improvement in vision, and 70% improvement in papilledema). ²⁷

   
   
3. 
   

   What factors would you consider in making treatment recommendations?

   
   
   
   
   1. 
      

      Presence and characteristics of venous stenosis on MRV: Farb et al found that 90% of patients with intracranial hypertension have stenosis of the venous sinuses. They furthermore differentiated between two distinct types of stenosis: intrinsic and extrinsic. Intrinsic stenosis manifests as “marginated,” well-demarcated filling defects within the sinus—likely reflecting arachnoid granulation. Extrinsic stenosis are smooth, tapered areas of narrowing thought to reflect external compression (e.g., from swollen brain parenchyma). ²⁸

      
      

      While both extrinsic and intrinsic stenoses have responded to stenting, some authors have found that clinical recurrence has a predilection for extrinsic stenosis with many of these occurring in the setting of stenosis proximal to the stent. ²⁹ Other authors have noted a greater mean improvement in opening pressure following venous stenting in patients with intrinsic stenosis compared to extrinsic stenosis.

      
      

      Anatomical variation is the rule rather than the exception in the venous sinuses, with hypoplasia or focal stenosis of one side being a common and likely incidental finding. This has led most groups to perform venography to better characterize any potential stenosis seen on noninvasive imaging as well as manometry evaluate the physiologic significance of any abnormalities prior to proceeding with stent placement.

      
      
   2. 
      

      Venography and manometry:

      
      

      Venography, typically using a 0.027-inch microcatheter, allows not only for better anatomical characterization of problem areas but also for dynamic evaluation of flow characteristics. By connecting the microcatheter to a manometer with “0 mm Hg” pressure standardized to the midaxillary line, venous pressure can be assessed throughout the venous sinus system. General anesthesia has a significant and highly variable effect on venous manometry and should be avoided during manometry. ³⁰ While the practice of performing manometry to define a pressure gradient across an area of stenosis is ubiquitous, there is no evidence-based data to suggest that a particular threshold can accurately predict a positive clinical response. Values represented in the literature vary from 4 mm Hg ³¹ to 15 mm Hg ³² with many larger series using a cutoff of 8 mm Hg. ²⁰

      
      
   3. 
      

      Severity of papilledema and vision loss:

      
      

      There is little data to support any particular treatment algorithm. In general, most patients benefit from a trial of weight loss and diet—advancing to treatment with carbonic anhydrase inhibitors before consideration is given to more invasive treatment options. The exception are patients with moderate-to-severe visual loss and high-grade papilledema (often defined as mean deviation on automated perimetry greater than -5 dB). ³³ Acute vision loss in the setting of intracranial hypertension is unusual and is a surgical emergency. CSF diversion should be performed emergently, either with lumbar puncture as a temporizing measure or proceeding directly to shunt placement. CSF diversion should be performed emergently, with consideration given to high-volume lumbar puncture if shunting emergently is not feasible. ³⁴

      
      
   4. 
      

      Headaches:

      
      

      Headaches are often the chief complaint of patients with intracranial hypertension. The efficacy of different treatment modalities in ameliorating this disabling symptom varies widely. Small studies have shown improvement in headache severity and frequency with an aggressive (< 425 kcal/d) weight-loss regimen. ³⁵ ONSF has widely variable results in headache management. In a series of 86 patients, only 13% reported improvement in headache at follow-up. ³⁶ With ventriculoperitoneal shunting up to 95% of patients have significant improvement in headache symptoms at 1 month; however, severe headaches recur in 19% by 12 months and 48% at 36 months. ¹⁶ Venous stent placement compares favorably to other treatment modalities in alleviating headaches. Rates of symptomatic improvement in larger studies range from 69.2% ³⁷ to 93% ²⁰ with a meta-analysis highlighting improvement in 83%. ²⁶

   
   
4. 
   

   What would you recommend for this patient?

   
   

   This patient has failed conservative management with intractable headaches, vision changes, and papilledema despite attempts at weight loss and therapy with a carbonic anhydrase inhibitor. Her MRV suggested a possible venous stenosis on her dominant side with hypoplasia of the transverse sinus on the contralateral side.

   
   

   Bariatric surgery is reserved for appropriate, morbidly obese candidates. Although this patient is overweight, she is not morbidly obese. ONSF is unreliable in treating headaches and, with headaches being a dominating symptom in this patient, there are better interventional options. CSF diversion and venography with an eye toward venous stenting are both reasonable options. We tend to offer VP shunting over LP shunting simply because of the higher failure rate of LP shunts. After extensive discussion with the patient regarding the relative merits of CSF diversion and stenting, the patient elected to proceed with venous sinus stenting. She underwent venography with manometry under conscious sedation, which confirmed a venous stenosis on the right with an associated venous pressure gradient. She was then started on aspirin and clopidogrel and underwent venous stent placement 7 days later.

   
   
5. 
   

   What follow-up is needed for patients with intracranial hypertension?

   
   

   There is no particular accepted follow-up protocol. We perform a computed tomography (CT) venogram at 6 months and, if there is no evidence of new or recurrent stenosis, allow the patient to discontinue clopidogrel and maintain them on aspirin indefinitely.