NORD gratefully acknowledges Bradley K. Farris, MD, Professor, Department of Ophthalmology, Adjunct Professor, Department of Neurology & Neurosurgery, University of Oklahoma School of Medicine; and James O’Brien, MD, Neuro-Ophthalmology Fellow, Department of Neurology & Neurosurgery, University of Oklahoma School of Medicine, for assistance in the preparation of this report.
Intracranial Hypertension (IH) is characterized by increased pressure inside the skull. Intracranial means inside the skull and hypertension means high fluid pressure. Intracranial hypertension means that the pressure of the fluid that surrounds the brain (cerebrospinal fluid or CSF) is too high. Elevated CSF pressure can cause two problems, severe headache and visual loss. If the elevated CSF pressure remains untreated, permanent visual loss or blindness may result. Pseudotumor cerebri and benign intracranial hypertension are both former names for IH, which are now considered inaccurate. These names do not adequately describe the disorder and downplay the seriousness of IH.
There are two categories of IH: primary intracranial hypertension and secondary intracranial hypertension. Primary intracranial hypertension, now known as idiopathic intracranial hypertension (IIH), occurs without known cause. This form is known to occur in young, overweight, females in their reproductive years (ages 20-45). However, IH can develop in both males and females of all ages and body types. Secondary intracranial hypertension has an identifiable, causative agent, including drugs (such as tetracycline, lithium, Vitamin A-derived oral acne medications or excessive ingestion of Vitamin A, and oral or intrathecal steroids, growth hormone treatments), sleep apnea and certain systemic diseases such as lupus, leukemia, kidney failure (uremia), meningitis and dural venous sinus thrombosis. There is an association of IH and Chiari type I malformation. Many other causes have been suggested in the medical literature but have not yet been confirmed as true causes. It is critical in these patients to rule out an intracranial space occupying mass by neuro-imaging (CT or MRI). Although many factors are known to trigger the disease, the mechanism by which IH occurs, in either primary or secondary forms, is not known. In many cases, either type of IH may be chronic.
The most common symptom is often an unbearably painful or frequent headache, sometimes associated with nausea and vomiting that is not relieved by medication. The headache often awakens the patient from sleep. Some patients are treated in the emergency room where a lumbar puncture (spinal tap) is done as a last resort, to temporarily ease the headache. Measurement of the opening pressure is encouraged during these procedures in order to assess for intracranial hypertension.
The diagnosis is also confirmed by detecting a high spinal CSF pressure reading, usually greater than 250 mmH2O or 25 cmH2O (200-250 mmH2O or 20-25 cmH2O is considered borderline high) and normal laboratory and imaging studies including CT scans and MRIs. There is generally a normal neurological examination as well, although abnormal findings may be detected on eye examination. The eye findings may be subtle, and not noted in an emergency room evaluation. It is not uncommon to misdiagnose a patient with IH as simply having a refractory migraine headache, and be treated as such. Unlike primary IH, secondary IH patients may have abnormal scans and laboratory tests.
The high CSF pressure may cause the optic nerves to swell (papilledema). The optic nerve connects the interior of each eye, the retina, to the vision centers of the brain. The optic nerve transmits impulses from the retina to these brain centers. The earliest sign of papilledema on a visual field test is known as an enlarged blind spot. Abnormal CSF pressure can also affect the eye muscles controlling eye movements producing double vision, but this is an infrequent event. (All patients with presumed IH should have a thorough eye examination including visual field tests by an ophthalmologist or neuro-ophthalmologist).
Other common symptoms include transient altered vision, particularly on movement or bending over, intracranial noise (pulse synchronous tinnitus), stiff neck, back and arm pain, pain behind the eye, exercise intolerance, and memory difficulties.
In the idiopathic or primary type (IIH), obesity is considered a factor in young women. However, only a small fraction of obese individuals develop IH, so other unknown causes are yet to be determined.
The many potential causes of secondary intracranial hypertension have been noted above. Note that in secondary IH, unlike IIH, obesity, gender, age and race are NOT risk factors, but may be present.
The mechanism by which IH occurs is not known, but several possibilities have been suggested. Most research supports the theory that there is resistance or obstruction to CSF outflow through the normal existing pathways in the brain, leading to relative over-production of CSF.
The incidence of IIH in the general population is thought to be about 1 per 100,000. In obese young females the incidence of IIH is about 20 per 100,000. IIH occurs in men and children as well, but with substantially lower frequency. Weight is not usually a factor in men and in children under 10 years of age.
The true incidence of secondary IH remains unknown because of the wide range of underlying causes and the lack of published surveys on the subject. Current statistics are not available on how many people have secondary intracranial hypertension.
Treatment should first and foremost involve lifestyle and dietary modifications in order to promote weight loss for those patients who are overweight or obese. This may even include consultation with a nutritionist or dietician.
Medical treatment consists of using drugs called carbonic anhydrase inhibitors to suppress the production of CSF. The most commonly used of the carbonic anhydrase inhibitors is acetazolamide. A large multicenter, randomized, controlled trial published in 2014 demonstrated that acetazolamide combined with dietary weight loss resulted in improved visual field function, nerve swelling, and quality of life measures, compared to the treatment of dietary changes alone. Carbonic anhydrase inhibitors inhibit the enzyme system needed to produce CSF and control the pressure (by controlling the volume) to some degree. These drugs do not work in all cases and can have potentially serious side effects. Acetazolamide should be avoided in early (1st trimester) pregnancy, and should be used with caution in later stages of pregnancy.
Topiramate is another, second-line, agent sometimes used to treat IH. While it has less potent carbonic anhydrase inhibition, it may be helpful in its capacity as a migraine headache medication. Other potential treatment options include methazolamide and furosemide, however these all of the above agents have not been evaluated as thoroughly as acetazolamide, and further study is needed to establish their utility. Corticosteroids, while used in the past to treat IH, are no longer recommended.
When medical treatment fails and vision is at risk, surgical intervention may be necessary. One of two types of surgery may be performed: optic nerve sheath fenestration, neurosurgical shunt Optic nerve fenestration is a procedure in which a small opening is made in the sheath around the optic nerve in an attempt to relieve swelling (papilledema). Optic nerve sheath fenestration has a high rate of success in protecting vision, but usually does not significantly reduce headaches. Implantation of neurosurgical shunts (internal tubes) is used to drain CSF into other areas of the body. These shunts protect vision and reduce headache, but typically have a higher complication rate than optic nerve sheath fenestration.
In addition to the above procedures, there is some evidence that venous sinus stenting procedures may be helpful for lowering intracranial pressure, improving headaches and stabilizing vision in select patients with narrowing or stenosis of these sinuses. This treatment modality may carry a relatively high risk of significant complications, however, and is not as well-studied. Further trials are necessary to establish its efficacy and safety.
The Intracranial Hypertension Research Foundation together with the Casey Eye Institute of the Oregon Health Sciences University maintain the IH Registry in which IH patients may voluntarily register. Registrants may participate (only with informed consent) in surveys and receive almost immediate news of clinical trials in which registrants may participate.
Because IH is a rare disorder affecting so few patients a central register is key to gathering epidemiological data and to notifying patients of a clinical trial of interest.
Interested persons can receive more information by contacting:
The Intracranial Hypertension Research Foundation
6517 Buena Vista Drive
Vancouver, WA 98661
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
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