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Woman presents with transient visual obscurations
Both eyes had optic disc edema and enlarged blind spots.
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A 32-year-old woman with a medical history of hypertension and obesity and an ocular history of myopia presented to the comprehensive ophthalmology clinic for recurrent, transient bilateral vision loss over a 4-month period. The vision loss was occurring four to five times per day and lasting 2 to 3 minutes with complete spontaneous resolution. The visual symptoms were associated with postural changes and headaches.
Examination
On initial examination, best corrected visual acuity was 20/25- in the right eye and 20/20 in the left eye. Color vision was intact bilaterally. Confrontational visual fields were full in the right eye with an inferotemporal deficit in the left eye. Both pupils were equal in size and reactive to light without afferent pupillary defect. Extraocular movements were full bilaterally. IOPs were normal. Slit lamp examination was unremarkable. Dilated funduscopic examination showed Frisen grade 3 to 4 optic nerve edema bilaterally (Figure 1).
Additional history
Source: James Constans, MD, Laurel N. Vuong, MD
The patient denied experiencing pulsatile tinnitus or diplopia, but did endorse a 30-lb weight gain over the preceding 6 months. She had no history of recent ingestion of vitamin A supplementation, minocycline, tetracycline, corticosteroids or oral contraceptives.
Automated perimetry testing showed enlarged blind spots bilaterally with an early inferior nasal step in the left eye (Figure 2). OCT measurements of the retinal nerve fiber layer confirmed optic disc edema but were not reliable due to algorithm failure secondary to the extensive swelling. Ganglion cell analysis was diffusely thin in both eyes. OCTs of the maculae were normal.
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Optic disc edema
The bilateral optic disc edema along with the enlarged blind spots and nasal defect were concerning for elevated intracranial pressure. Idiopathic intracranial hypertension was suspected given the patient’s body habitus and recent weight gain; however, an intracranial tumor or venous sinus thrombosis could not be ruled out. An MRI/MRV of the head obtained that same day showed partially empty sella, posterior flattening of both globes and narrowing of the right transverse sinus. There was no evidence of an intracranial mass or venous sinus thrombosis (Figure 3). A lumbar puncture revealed an opening pressure of 36 cm H2O. She was started on high-dose oral acetazolamide and followed closely. Despite increasing acetazolamide to as much as 3 g daily, papilledema remained unchanged and there was slight progression in peripheral visual field loss. At this point, a neurosurgery consult was obtained for surgical management.
A diagnostic cerebral arteriogram with venous sinus pressure sampling was performed, demonstrating a large flow gradient of 19 mm Hg across the right transverse sinus, implicating the stenotic region as the likely etiology for the patient’s elevated intracranial pressure. She was brought back to the angiography suite for interval stent placement at the region of stenosis with subsequent improvement of the flow gradient. (Figure 4).
Discussion
Idiopathic intracranial hypertension (IIH) represents a condition in which elevated intracranial pressure, in the absence of an intracranial mass or lesion, results in varying degrees of vision loss, diplopia, headaches and tinnitus. The overall reported incidence of IIH is approximately one to three patients per 100,000; however, this incidence climbs dramatically to 19 to 21 per 100,000 among young overweight females, which is the population most commonly associated with the condition.
Left untreated, visual loss can progress and become permanent. First-line therapies include weight loss and lifestyle modification for patients with preserved vision and oral carbonic anhydrase inhibitors for those with non-visual symptoms and early vision loss. Surgical intervention is usually reserved for refractory cases or patients presenting with severe vision loss during the initial evaluation. Various surgical approaches have been described, including cerebral spinal fluid (CSF) diversion and optic nerve sheath fenestration (ONSF), with varying risk profiles and rates of success. In recent years, dural venous sinus stenosis has been implicated as a potential etiology for IIH and has brought with it the emergence of venous sinus stenting as an additional treatment modality. Comparisons between these various treatment approaches have been examined extensively in the current medical literature.
McGirt and colleagues examined the long-term outcomes of CSF diversion through creation of lumboperitoneal (LP) and ventriculoperitoneal/ventriculoatrial (VP/VAT) shunts. The study included 42 patients carrying a diagnosis of IIH over a 30-year period, requiring 115 shunt procedures (79 LP, 36 VP/VAT). Ninety-five percent of patients reported improvement in headache symptoms at 1 month postoperatively; however, 19% and 48% reported severe recurrence in headache despite proper shunt function at 12 months and 36 months, respectively. Further analysis revealed both a lack of preoperative papilledema and long-term presence of symptoms for more than 2 years as independent risk factors for developing future recurrence in headache symptoms after treatment (5- and 2.5-fold increase in relative risk, respectively). Finally, 75% of all shunts demonstrated failure in function by 24 months postoperatively, primarily due to obstruction (48%), requiring repeat operative intervention. Additional reported complications included over-drainage (14%), distal catheter migration (5%), infection (3.5%) and CSF leak (3%).
Spoor and colleagues examined the long-term effectiveness of ONSF in treating IIH. Seventy-five patients were followed by serial perimetry testing, with 68% demonstrating improvement/stabilization of visual function compared with 32% demonstrating progressive visual field loss over time. ONSF is not without risk, with Plotnik and colleagues reporting an overall complication rate of 40% among a series involving 38 patients. These were stratified by severity, with reported minor complications including transient ocular motility disorder (29%), pupillary dysfunction (11%) and transient outer retina ischemia (2.6%). Major complications included branch and central retinal artery occlusions, with frequency of 2.6% and 5.2%, respectively.
Ducruet and colleagues reported on the long-term patency of venous sinus stents in 23 patients with a mean 23 months of follow-up. All stents remained objectively patent at final follow-up, with 17% demonstrating mild-moderate in-stent stenosis, not flow limiting, compared with 21% with severe stenosis and flow limitation. Five patients (21%) required subsequent placement of LP/VP shunt for persistent symptoms. Starke and colleagues examined the complication rates of venous sinus stenting among 185 patients requiring 221 stenting procedures (26 requiring bilateral stent placement, 10 requiring repeat stenting). Complication rates were reported to be 5.4% overall, including transient hearing loss, retroperitoneal hematoma, urinary tract infection and syncope. Femoral pseudoaneurysm formation occurred in two patients, one of which required further femoral artery stent placement. Notably, three patients (1.6%) developed subdural hemorrhages in the postoperative period requiring emergent surgical intervention.
Feldon performed a meta-analysis comparing the visual outcomes of ONSF, LP/VP shunts and venous sinus stenting in the setting of IIH. Eighty percent of eyes (66% of eyes with chronic IIH) demonstrated improvement in vision after ONSF compared with 11% with worsened vision; 38.7% and 45.4% of patients who underwent VP and LP shunts demonstrated visual improvement, respectively, with further analysis revealing rates of progressive vision loss of 0% with the former and 5% with the latter. Patients undergoing venous sinus stenting demonstrated visual improvement in 47.1% of cases and further decrease in vision in 6% of cases. Improvement/resolution of papilledema was reported in 54.8% of VP shunt cases compared with 38.6% of LP shunts and 52.9% of venous sinus stenting. Furthermore, improved/resolved headache was demonstrated in 6.5% of patients after VP shunt placement, 45.4% after LP shunt placement and 47.1% after venous sinus stenting.
Follow-up
Ongoing ophthalmic follow-up has demonstrated gradual and measured improvement of the patient’s papilledema (Figure 5), visual fields and symptoms. Her most recent appointment surpassed the 1-year mark after her stenting procedure. Imaging at that time revealed near-resolution of previous retinal nerve fiber thickening in both eyes down to 131 µm and 124 µm, with complete reversal and recovery of the previous ganglion cell layer thinning. Repeat perimetry was also performed, demonstrating improvement in the size of the initial blind spot enlargement with resolution of the previously identified early nasal steps (Figure 6). Her exam demonstrated no clinically significant disc edema, and she reported no further headaches or visual obscurations.
Idiopathic intracranial hypertension is a well-described entity with clear diagnostic and therapeutic approaches outlined in the medical literature. Traditional surgical approaches have historically included CSF diversion procedures and optic nerve sheath fenestration; however, these procedures carry a moderate burden of morbidity given their complications rates and potential need for further or repeat surgical interventions. Following the implication of dural venous sinus stenosis as a potential etiology for IIH, venous sinus stenting has provided an additional treatment modality, with early literature demonstrating comparable visual outcomes and symptomatic relief with a potentially more favorable risk profile. Additional stipulations, such as required postoperative anticoagulation, must be considered before performing these stenting procedures and may reduce the number of eligible patients. Because of the procedure’s relative infancy compared with the other surgical approaches listed above, future studies investigating the true long-term outcomes of venous stenting will prove invaluable in drawing full comparative conclusions.
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- For more information:
- James Constans, MD, and Laurel N. Vuong, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Aubrey R. Tirpack, MD, and Astrid C. Werner, MD. They can be reached at the New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.