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Idiopathic intracranial hypertension

Boyter, Elizabeth, MPA, PA-C

Journal of the American Academy of PAs: May 2019 - Volume 32 - Issue 5 - p 30–35
doi: 10.1097/01.JAA.0000554732.85914.91
CME: Neurology
Free
CME

ABSTRACT Idiopathic intracranial hypertension is a rare disorder of elevated intracranial pressure with normal cerebrospinal fluid composition and without intracranial pathology. This condition primarily affects obese women of childbearing age and frequently causes headaches, vision loss, diplopia, tinnitus, and nausea. The incidence of idiopathic intracranial hypertension is rising along with obesity rates. Primary care and ED clinicians must recognize the signs and symptoms of idiopathic intracranial hypertension and intervene promptly to control symptoms and to preserve vision. This article reviews the clinical presentation and management of patients with idiopathic intracranial hypertension.

Elizabeth Boyter practices neurology with Laureate Medical Group at Northside in Atlanta, Ga. The author has disclosed no potential conflicts of interest, financial or otherwise.

Earn Category I CME Credit by reading both CME articles in this issue, reviewing the post-test, then taking the online test at http://cme.aapa.org. Successful completion is defined as a cumulative score of at least 70% correct. This material has been reviewed and is approved for 1 hour of clinical Category I (Preapproved) CME credit by the AAPA. The term of approval is for 1 year from the publication date of May 2019.

Box 1

Box 1

Idiopathic intracranial hypertension occurs in 1 to 2 per 100,000 people per year.1 About 90% of patients with this condition are female, and 94% are obese.2 Obese women ages 15 to 44 years are at high risk for idiopathic intracranial hypertension, with a higher incidence rate of 19 to 21 per 100,000.3,4 Obese women in their 20s are most susceptible. In 1980, 12.7% of US adults were obese, and in 2012, that number approached 35%.5 The incidence of idiopathic intracranial hypertension reflects this rise in obesity, doubling between 1990 and 2014.5

Males account for 8% to 10% of patients with idiopathic intracranial hypertension. At presentation, they are more likely to be older and less likely to be obese.3,6,7 Men with idiopathic intracranial hypertension experience fewer headaches, but are twice as likely as women to experience severe vision loss.6,7 Idiopathic intracranial hypertension also has been reported in children as young as age 4 months old and adults up to age 88 years.3

Most cases are self-limited, but the condition may recur and become chronic, requiring follow-up care for years.4,6 Healthcare providers must be prepared to identify the signs and symptoms of increased intracranial pressure (ICP) and take action to control disabling headaches and avoid significant vision loss.

Box 2

Box 2

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PATHOPHYSIOLOGY

The cause of idiopathic intracranial hypertension remains unknown, but it has been closely correlated with obesity. Recent weight gain, even in patients who are not obese, is a significant risk factor for developing idiopathic intracranial hypertension. Weight gain often triggers recurrent symptoms in patients with idiopathic intracranial hypertension.2,3,6,8,9 A higher BMI is associated with worse visual outcomes; for every 10-unit increase in BMI, the odds of severe vision loss increases by 1.4 times.2,10 As obesity increases in the general population, reports of idiopathic intracranial hypertension in children and males are growing in number.11 Obesity, rather than sex or age, may be the primary causative factor.11

The medical literature offers several theories to explain the pathogenesis of increased ICP that causes symptoms of idiopathic intracranial hypertension in obese patients. For example, central obesity may increase intra-abdominal, pleural, cardiac filling, and central venous pressures, and ICP may rise as a result. However, this theory does not explain the sex disparity in idiopathic intracranial hypertension or explain why the condition occurs in patients who are not overweight or obese. Furthermore, pregnancy does not confer a higher risk of idiopathic intracranial hypertension.3 Cerebrospinal fluid (CSF) homeostasis may be disturbed by reduced CSF absorption, increased CSF secretion, or abnormal water and sodium metabolism related to endocrinologically active adipose tissue.1-3

ICP may rise because of cerebral venous outflow abnormalities, such as dural venous hypertension and dural venous sinus stenosis (Figure 1). Whether venous sinus stenosis is a cause or a consequence of intracranial hypertension is controversial, and studies suggest it may be both.3,12 A positive feedback mechanism may fuel both venous sinus stenosis and intracranial hypertension. Under the stress of elevated ICP, the walls of the transverse sinuses may remodel, triggering fibrosis and stenosis. The stenosis aggravates venous hypertension, which reduces CSF absorption. As a result, ICP continues to rise and venous stenosis worsens.1

FIGURE 1

FIGURE 1

Several other conditions may be associated with idiopathic intracranial hypertension, including hypervitaminosis A; use of retinoids; and exposure to exogenous growth hormone, tetracyclines, or fluoroquinolones.3 Idiopathic intracranial hypertension related to medications tends to be self-limited and often resolves when the medication is discontinued.6 Other conditions associated with idiopathic intracranial hypertension are Addison disease, hypoparathyroidism, severe anemia, systemic lupus erythematosus, Behçet disease, sleep apnea, uremia, and coagulation disorders.3 Polycystic ovarian syndrome is twice as prevalent among women with idiopathic intracranial hypertension (15.5%) as in the general population (8.7%).13 Treating these disorders should improve idiopathic intracranial hypertension.3

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CLINICAL MANIFESTATIONS

Patients with idiopathic intracranial hypertension present with symptoms of increased ICP. They may experience throbbing frontal or retro-orbital headaches, nausea, vomiting, tinnitus, and visual loss.1,6,12,14 Actions that increase ICP, including the Valsalva maneuver, bending forward, and lying supine, commonly aggravate these symptoms.14 Resuming an upright position often relieves them.

At diagnosis, 93% of patients with idiopathic intracranial hypertension complain of headache.11 Headache is one of the most common reasons for primary care visits and ranks among the top 10 disabling conditions worldwide, according to the World Health Organization.15 In women, headache ranks among the top five causes of disability.15 Patients with idiopathic intracranial hypertension often present with typical symptoms of migraine, such as photophobia, phonophobia, nausea, and vomiting. In fact, migraine frequently coexists with idiopathic intracranial hypertension.12 Increased ICP may exacerbate the primary headache disorder.

Patients with idiopathic intracranial hypertension often describe transient visual dimming, visual blackout, or “tunnel vision” occurring with postural changes.14,6,12 High CSF pressure compresses the optic nerves and causes ischemia, which may lead to optic disk edema or papilledema (Figures 2 and 3).12 With prolonged papilledema, optic nerve damage progresses, and the visual fields gradually constrict.6

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

Bedside fundoscopy is the first step in identifying unilateral or bilateral papilledema.11 Confrontational visual fields testing may detect restricted visual fields.14 Perimetry, or visual field testing performed by an ophthalmologist or neuro-ophthalmologist, involves flashing lights in different locations in the visual field. The patient responds when she or he sees the light.16,17

Perimetry identifies visual loss in about 95% of patients with idiopathic intracranial hypertension, but only one-third of patients recognize the loss.18 The most common visual field abnormalities are an enlarged blind spot and peripheral vision loss. Central vision loss is a late finding.6,11,14,16 About 25% of patients have some irreversible visual loss, and 5% to 10% may progress to blindness.6,18 Serial perimetry is essential to monitor the disease and guide treatment.6,11,14,18 Only about 6% of patients with idiopathic intracranial hypertension do not have papilledema.12 These patients do not experience typical transient vision disturbances and are not at risk for permanent visual loss.6

The cranial nerve examination is usually normal, but may reveal an ocular motility defect, such as a palsy involving cranial nerve VI that causes diplopia.6,14 Patients often hear pulsatile, “whooshing” tinnitus related to high-pressure, turbulent blood flow in the cerebral venous sinuses.11 Neck stiffness and back pain also are common complaints.14

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DIAGNOSIS

Idiopathic intracranial hypertension is a diagnosis of exclusion.19 If increased ICP is suspected, MRI and magnetic resonance venography of the brain are recommended to exclude secondary causes of increased ICP, including dural venous sinus thrombosis, mass lesion, aneurysm, subarachnoid hemorrhage, meningitis, subdural hematoma, and stroke. A few imaging findings suggest intracranial hypertension, but they are not diagnostic of idiopathic intracranial hypertension, nor does their absence exclude idiopathic intracranial hypertension. These findings include bilateral or unilateral dural venous sinus stenosis, flattening of the posterior sclera, an empty sella turcica, and distension of the optic nerve sheaths (Figure 4).6,12,14

FIGURE 4

FIGURE 4

If brain imaging does not reveal a structural cause for elevated ICP, the next step is high-volume lumbar puncture, which obtains 30 to 40 mL of CSF compared with 8 to 15 mL for a routine lumbar puncture.12,14,20 High-volume lumbar puncture aids in diagnosis and often provides temporary headache relief.6,12,14 The opening pressure must be documented accurately because it is critical to making a diagnosis. In patients with idiopathic intracranial hypertension, the opening pressure is elevated above the normal level of 20 to 25 cm H2O. CSF also is collected in sterile tubes to be sent for analysis. The CSF analysis includes a cell count with differential, protein, and glucose, which are usually normal. If clinically indicated, the CSF may be analyzed for cytology and bacterial, viral, fungal, and mycobacterial pathogens.14,20

The Modified Dandy Criteria can be used to aid providers in the diagnosis of intracranial hypertension.

  • Symptoms and signs of increased ICP: headache, transient visual obscuration, pulse-synchronous tinnitus, papilledema, visual loss
  • No other neurologic abnormality (except unilateral or bilateral cranial nerve VI palsy) or impaired level of consciousness
  • Elevated ICP with normal CSF composition
  • Neuroimaging showing no secondary cause of intracranial hypertension
  • No other apparent cause of intracranial hypertension.6,14
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TREATMENT

The goals of treatment for patients with idiopathic intracranial hypertension are to alleviate symptoms and preserve vision.6,8 Refer the patient to a neurologist for ongoing management of headaches and other symptoms.6 Because the condition may lead to severe and permanent vision loss, the patient should be followed by an ophthalmologist or neuro-ophthalmologist to monitor papilledema and perform serial perimetry.1,12,14

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Weight loss

Educate patients about the effect of excess weight on idiopathic intracranial hypertension and the critical role of weight loss in controlling the condition.6 Weight loss is considered the cornerstone of management.2,6,9,12 Patients should receive counseling on regular exercise and diet modification.2

Some patients may be candidates for bariatric surgery. Compared with nonsurgical weight loss techniques, bariatric surgery produces greater weight loss and higher remission rates of the metabolic consequences of obesity.2 A 2017 systematic review appraised the effects of bariatric surgery and nonsurgical weight loss methods on signs and symptoms of idiopathic intracranial hypertension.2 Bariatric surgery provided superior outcomes: BMI dropped by 17.5 kg/m2, compared with 4.2 kg/m2 for patients who used nonsurgical weight loss techniques.2 Bariatric surgery reduced or resolved headache in 90.2% of patients, but only 23.2% of patients got headache relief from nonsurgical weight loss.2 Papilledema resolved in 100% of surgical patients and 66.7% of nonsurgical patients.2

The Idiopathic Intracranial Hypertension Weight Trial (IIH:WT) is in progress.21 This randomized controlled prospective trial will assess the effect of bariatric surgery compared with a community weight loss program for the long-term treatment of idiopathic intracranial hypertension in patients with BMIs over 35 kg/m2. The study will monitor ICP, idiopathic intracranial hypertension symptoms, headache, papilledema, visual function, quality of life, and cost-effectiveness over 5 years. The investigators aim to determine whether bariatric surgery provides superior sustained weight loss and idiopathic intracranial hypertension symptom relief.21

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Medications

Although weight loss is considered the cornerstone of treatment for idiopathic intracranial hypertension, medications also can help lower ICP. The carbonic anhydrase inhibitors acetazolamide and methazolamide may reduce CSF production and CSF pressure.8 Acetazolamide may improve idiopathic intracranial hypertension symptoms, visual field measurements, and papilledema. The usual starting dose of acetazolamide is 500 mg twice daily, titrating as needed and tolerated to 2 to 4 g/day.8 Patients taking acetazolamide often experience acral paresthesias. Monitor electrolytes periodically, as patients may experience a mild metabolic acidosis.8,12

The antiseizure medication topiramate also inhibits carbonic anhydrase. Like acetazolamide, topiramate may relieve some symptoms of idiopathic intracranial hypertension and improve vision impairment.8 Often used for migraine headache prophylaxis, topiramate 100 to 150 mg/day may provide dual benefit for patients with idiopathic intracranial hypertension who also suffer from migraines.12 In addition, topiramate may suppress the appetite and boost weight loss efforts.6,8,12 Adverse reactions, including cognitive slowing, memory impairment, alteration of taste, acral paresthesias, metabolic acidosis, acute angle-closure glaucoma (rare), and kidney stones, may limit the titration of topiramate.8,22 Topiramate use during pregnancy has been associated with an increased risk of birth defects such as oral clefts.23,24 Before prescribing topiramate to women of childbearing age, advise them to use effective birth control.24

A loop diuretic, such as furosemide, can be used in combination with acetazolamide to reduce CSF pressure and treat papilledema. Labwork should be drawn regularly to monitor renal function and electrolytes.8

Controlling headaches is often challenging for patients with idiopathic intracranial hypertension. Headache abortive treatments, such as triptans and butalbital-APAP-caffeine, relieve pain but may elevate BP. Counsel patients about judicious use of analgesics to avoid the common problem of analgesic rebound headache.8,25 Preventive medications, including topiramate and beta-blockers, may reduce headache burden. In the emergency setting, severe headache may respond to a combination of IV antiemetics (such as promethazine) or dopamine receptor blockers (such as metoclopramide, prochlorperazine, or chlorpromazine); and ketorolac, diphenhydramine, and dexamethasone.25

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Lumbar puncture

This procedure may relieve escalating headache or symptoms of increased ICP.6,8 However, serial lumbar puncture is an undesirable long-term solution. CSF reforms within 6 hours. The procedure itself may be technically challenging in obese patients. CSF infection, CSF leak, and low-pressure headache are potential complications of lumbar puncture.8

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Surgery

In patients with refractory intractable headache or continued vision loss unresponsive to maximum medical therapy, surgical intervention is the next step.1,8,12 A patient may require surgery if she is unable to participate appropriately in care and follow-up because of noncompliance or impaired cognition.8

Current surgical options include optic nerve sheath fenestration, CSF diversion with ventriculoperitoneal (VP) or lumboperitoneal (LP) shunt, and venous sinus stenting.8 Optic nerve sheath fenestration is indicated for papilledema-related vision loss and is performed by an ophthalmologist or neuro-ophthalmologist.1,8,12,26 The procedure involves making a slit or rectangular window in the optic nerve sheath to decompress the nerve.26 The procedure improves or stabilizes visual acuity and visual fields and relieves papilledema.8,12,26 Optic nerve sheath fenestration makes little effect on overall ICP, but there is some evidence that it reduces headache.8,12 Patients undergoing optic nerve sheath fenestration may experience temporary diplopia or pupillary dysfunction. Transient or permanent vision loss may occur. The benefit of the procedure may wane over time, and patients may require repeat surgery.8

The most common surgical intervention for idiopathic intracranial hypertension is CSF diversion using VP or LP shunt. CSF diversion is indicated for patients who experience refractory headache or progressive vision loss despite maximal medical therapy.1,6,8,12 To implant a VP shunt, a neurosurgeon passes a catheter through the skull into a lateral ventricle and tunnels the catheter under the skin and into the peritoneal cavity.27 Less common than VP shunting, LP shunting involves inserting a catheter into the lumbar subarachnoid space, then threading it under the skin into the peritoneal cavity. In both types of shunt, a programmable or nonprogrammable one-way valve is used to control CSF flow.27

These procedures can stabilize or improve headache, papilledema, vision loss, and diplopia.8,12 Headache burden decreases in almost all patients soon after shunting, but nearly half of patients have recurrent severe headaches within 3 years.8 Shunts are associated with several common complications, including shunt infection, CSF leak, and abdominal or back pain.8 Shunts sometimes malfunction and often need revision.8

Patients with dural venous sinus stenosis who do not benefit from medical therapy may get relief from venous sinus stenting, a relatively new intervention for idiopathic intracranial hypertension.1,8,12 Stenting results in significant reductions in headache, visual symptoms, papilledema, and pulsatile tinnitus. Complications of the procedure include ipsilateral headache, intracranial hemorrhage, proximal stent stenosis, in-stent thrombosis, and stent migration.1,6,8,12 To prevent thrombosis, the patient must start antiplatelet therapy before the procedure and continue therapy for 3 to 6 months after stenting.1,12 If vision loss progresses, an alternative surgical procedure such as optic nerve sheath fenestration or CSF diversion may have to be delayed until after the patient has discontinued antiplatelet therapy. More studies are needed to determine the role of venous sinus stenting in managing patients with idiopathic intracranial hypertension.6,8

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CONCLUSION

Idiopathic intracranial hypertension is a diagnosis of exclusion, and the diagnosis is often difficult to make. Although idiopathic intracranial hypertension is most common among obese women in their 20s, it also may occur in children, males, and older adults. The US population of obese patients continues to increase, and with it, the burden of idiopathic intracranial hypertension. Clinicians should consider idiopathic intracranial hypertension in obese patients presenting with headache. Recognizing this serious disorder and promptly taking action may make a tremendous effect on a patient's vision and quality of life.

Despite adequate medical or surgical therapy for idiopathic intracranial hypertension, many patients continue to experience some degree of headache, elevated ICP, papilledema, or vision loss. The road to recovery may be long and frustrating, but patients can get better. Until they stabilize, patients require regular follow-up with their care team and monitoring for recurrent disease.

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REFERENCES

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Keywords:

idiopathic intracranial hypertension; obesity; headache; vision loss; tinnitus; increased intracranial pressure

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