Idiopathic Intracranial Hypertension
(Pseudotumor Cerebri)
Part I. Patient Information
Michael Wall, M.D.
The University of Iowa
Department of Neurology and
Department of Ophthalmology and Visual Sciences
Note: This is part one in a pair of article on the subject. Part I is intended for patients and the lay audience. Part II is written for Physicians.
Introduction
Idiopathic Intracranial Hypertension is a condition of high pressure in the fluid around the brain. It is also known as pseudotumor cerebri because there are some of the signs and symptoms of a brain tumor without a brain tumor being present (pseudo meaning false).
The results of a long-term prospective study are found inWall M, George D. Idiopathic Intracranial Hypertension. Brain 1991;114A(1):155-180, and a recent review can be found at this link: Wall M. Idiopathic intracranial hypertension. Neurol Clin. 2010;28(3):593-617.
The space around the brain is filled with a water-like fluid. (Fig 1.) If there is too much of this fluid present, (for example, if not enough being absorbed, Fig. 2), the pressure around the brain rises. This is because the space containing the fluid cannot expand. It is this high pressure that produces the symptoms of idiopathic intracranial hypertension (idiopathic means unknown cause; intracranial means inside the head; hypertension means the fluid is under high pressure).
Figure 1: The cerebrospinal fluid circulation. (click image to enlarge)
Figure 2: Meninges and Superficial Cerebral Veins. (click image to enlarge)
Figure 3: Age at diagnosis of IIH
What causes idiopathic intracranial hypertension?
Although we do not know what causes IIH, we have many clues. The condition occurs mostly in women in the childbearing years. The symptoms often start or worsen during a period of weight gain. The disease is rare in thin men. This has led some researchers to look for hormonal changes within the body. To date no consistent changes in hormones have been found.
Although no associated conditions besides recent weight gain are usually found, many conditions have been linked to high intracranial pressure. Any disorder that blocks the flow of spinal fluid between the brain and its route to the blood, the jugular vein, can cause raised pressure. For example, scarring cells next to the brain that absorb the spinal fluid (the arachnoid granulations) can cause raised pressure. Similarly, blood clots in the veins draining the brain can cause increased intracranial pressure (a disorder called venous sinus thrombosis). Withdrawal of corticosteroids, high doses of vitamin A or excessive intake of foods containing considerable vitamin A (such as liver), use of body building-type steroids and possibly certain drugs such as tetracycline and lithium can cause raised intracranial pressure. These conditions can mimic IIH.
What are the typical symptoms of IIH?
The symptoms most commonly reported by IIH patients followed by their frequency are:
- headache (94%)
- transient visual obscurations or blurring (68%)
- pulse synchronous tinnitus or "wooshing noise" in the ear (58%)
- pain behind the eye (44%)
- double vision (38%)
- visual loss (30%)
- pain with eye movement (22%)
Headache
Headache is present in nearly all patients with IIH and is the usual symptom for which patients seek medical attention. The headaches of the IIH patient are usually severe and daily; they are are often throbbing. They are different from previous headaches, may awaken the patient and usually last hours. Nausea is common and vomiting less so. The headache is often the worst head pain ever experienced. Although uncommon, the presence of pain behind the eyeball that is worsened movements of the eyes can occur.
Transient visual obscurations
Visual obscurations are episodes of transient blurred vision that usually last less than 30 seconds and are followed by full recovery of vision. Visual obscurations occur in about 3/4 of IIH patients. The attacks may be involve one or both eyes. They are not correlated with the degree of intracranial hypertension or with the extent of optic nerve swelling. Visual obscurations do not appear to be associated with poor visual outcome.
Pulsatile intracranial noises
Pulsatile intracranial noises or pulse-synchronous tinnitus is common in IIH. The sound is often unilateral. In patients with intracranial hypertension, compression of the jugular vein on the side of sound abolishes it. It is likely due to turbulence and narrowing of the transverse venous sinus (See Figure 4), known to occur with increased intracranial pressure.
Figure 4 : This figure shows is a magnetic resonance venogram showing veins draining the brain.
The arrow points to a narrow transverse venous sinus likely responsible for pulsatile tinnitus.
Visual loss
The most serious problem patients have is vision loss. (Figure 5, 6) About 5% of patients go blind in at least one eye. These are usually patients who do not return for follow-up evaluation or seek attention very late in their course.
A further scientific discussion can be found with this article: Wall M, George D. Idiopathic intracranial hypertension. A prospective study of 50 patients. Brain. 1991 Feb;114 ( Pt 1A):155-80. PubMed PMID: 1998880).
Figure 5: A typical visual field defect present using Goldmann perimetry in an IIH patient. Notice the large blind spot (black filled area) and the lower left indentation (an inferior nasal nerve fiber bundle defect).
Figure 6: A similar inferior nasal nerve fiber bundle defect in an IIH patient found with automated perimeter (Humphrey perimeter). These defects may resolve fully with treatment.
How is the diagnosis of IIH made?
The diagnosis of IIH is made by identifying the typical symptoms of the disease along with documentation of a high spinal fluid pressure (measured during a spinal tap). The neurologic examination is normal except for the presence of swollen optic nerves called papilledema (seen by examining the back of the eye). (Figs. 7-12) Sometimes double vision occurs, caused by limitation of lateral eye movement. Lastly, neuroimaging procedures such as CT scans or MRI scanning are normal except for signs known to occur with increased pressure.
Figure 7: Normal optic nerve (central pinkish disk)
Figure 9: Grade I papilledema, Another example of an optic nerve with mild papilledema.
Figure 11: Grade IV papillededema. With more severe swelling in addition to a circumferential halo, the edema covers major blood vessels as they leave the optic disk (grade III) and vessels on the disk (grade IV). A subretinal hemorrhage is present at 7 o'clock.
Figure 12: Pseudopapilledema. A patient with an elevated optic nerve present since birth. There is no halo, no major vessel covering a small nerve with abnormal vessel branching and tortuosity.
What is the relationship between optic nerve swelling and visual loss?
Why do the optic nerves swell with increased intracranial pressure?
Idiopathic intracranial hypertension is a disorder of increased in the fluid filled spaces around the brain pressure of unknown cause. The increased pressure takes place in the subarachnoid space, a space between the brain / spinal cord complex and its coverings called the meninges (Figure 1, 2). When a spinal tap is done, the needle is placed in the subarachnoid space to measure the pressure. Well, the eye is an outgrowth of the brain and with this outgrowth, the subarachnoid space continues right up to the optic nerve head (optic disc, papilla) in the back of the eyeball. When the pressure increases in this space, fibers in the optic nerve are compressed. This makes it harder for the neurons to transport their proteins and organelles so there is a decrease or slow down in flow in optic nerve fibers. This buildup is seen as swelling or edema of the optic nerve head or papilla, hence the term papilledema. A more extensive discussion can be found here.
What is the danger of papilledema to vision?
When the optic nerve fibers are under pressure, their microcirculation or blood supply is also under pressure. This results in decreased blood flow to the optic nerve, damage to the nerve and resultant visual loss. Since all the optic nerve fibers are under pressure, a visual field examination is necessary to determine whether visual loss is taking place so that the appropriate treatment can be started.
Can vision loss be reversed?
Fortunately, visual loss can be reversed. However, much depends on how long the visual loss has been present. In some cases, full recovery takes place and in others partial recovery. Most patients with visual loss have some recovery with treatment.
What are the earliest signs of permanent vision loss?
The most common early sign of visual loss is inferior nasal loss found with visual field testing. However, other types of visual loss can occur. What is important is that it is rare for early visual loss to involve the central area of vision. And, early peripheral visual loss is seldom recognized by the patient. This is yet another reason why perimetry is very necessary in the evaluation and management of patients with idiopathic intracranial hypertension.
How is IIH treated?
Treatment for patient with IIH can be divided into medical treatment and surgical treatment. The cornerstone of medical treatment is weight loss. It does not appear to be the total number of pounds lost. Some patients are effectively treated by losing one pound every week or two for several months and then maintaining the weight loss. It has been shown that loss of 5-10% of body weight is often sufficient for optic disc edema to regress, symptoms resolve and vision improve.
Loss of fluid can also be obtained using diuretics (fluid pills). Diamox® (acetazolamide) is the most commonly used medication. It is relatively safe but nearly all patients have tingling of the fingers and toes. This tingling is a benign symptom and suggests the medication is working. Patients also experience that carbonated soft drinks taste metallic. Less commonly, kidney stones can occur and rarely other blood disorders. Another diuretic commonly used that appears to be effective in some patients is Lasix® (furosemide). More about Diamox.
While there is no evidence based treatment to guide medical therepy there is currently an ongoing National Eye Institute sponsored trial, the Idiopathic Intracranial Hypertension Treatment Trial. The trial has two aims. One is to determine if acetazolamide (Diamox) with a low sodium weight reduction diet is superior to placebo with the diet. The second aim is to investigate the cause of idopathic intracranial hypertension. Further information can be found at the NORDIC website .
The surgical treatments currently used are optic nerve sheath fenestration (making slits in the optic nerve sheath or covering) (Fig. 13) and CSF shunting procedures (running a tube from the spinal fluid space into the abdominal cavity or a vein). These procedures are used when patients do not respond adequately to medical therapy. Optic nerve sheath fenestration is done first by an incision into the orbit. The eyeball is moved to the side and the optic nerve sheath is exposed. Slits or a large hole are then placed in the optic nerve sheath and fluid drains out, thereby taking pressure off the optic nerve.
Figure 13: Cut sections of a optic nerves (post-mortem) from a patient with papilledema. Note the large space, filled with the web-like strands of arachnoid between the nerve and the nerve sheath.With optic nerve sheath surgery, a hole is cut in the sheath of the nerve that allows fluid to leak and pressure to decrease.
from Sergott RC, Savino PJ, Bosley TM. Modified optic nerve sheath decompression provides long-term visual improvement for pseudotumor cerebri. Arch Ophthalmol 1988; 106:1391-1397.
The second surgical procedure, called CSF shunting, is done as follows. Tubing is placed in the spinal fluid space, (either the space entered during a lumbar puncture or space in or around the brainand tubing is then run to the abdomen or a vein. This lowers the pressure around the brain and optic nerve, thereby eliminating the symptoms of raised intracranial pressure. Unfortunately, these procedures are complicated by various problems, the most severe one being some patients have periodic occlusion of the tubing with recurrence of symptoms and sometimes vision loss. A repeat operation is then needed. An overview of treatment is summarized in figure 14.
Figure 14: Treatment strategies for IIH. Visual loss does not include enlargement of the blind spot unless it is compromising vision. optic nerve sheath fenestration is preferred to steroids. Downward arrows show the next step when vision worsens.
Management of the pregnant IIH patient
Pregnancy occurs in IIH as often as in the general population and in any trimester. Patients with IIH during pregnancy do not have an increased spontaneous abortion rate. Therapeutic abortion to limit progressive disease is not indicated. The pregnant patient with IIH should be treated as any other patient with IIH. Also, the pregnancy should be managed like any other. The major exception is caloric restriction because of its adverse effect of ketosis on the fetus. Weight gain can be limited to 20 pounds or the amount recomended by an obstretician.
Use of corticosteroids has not been associated with birth defects in humans. Acetazolamide may be used after 20 weeks gestation; use before 20 weeks has been associated with one case of sacrococcygeal teratoma. Glycerol and thiazide diuretics probably should not be used in the second half of pregnancy because of the risk of decrease in placental blood flow. There is no obstetric contraindication to surgery for those that require it.
How is visual loss prevented?
The best way to prevent visual loss is to test vision regularly with a visual field examination called perimetry. Patients should be followed frequently with tests of vision until the doctor is confident that there is no vision loss occurring. Vision testing should then be done once or twice a year or whenever new symptoms occur. Unfortunately, IIH is a life-long disease and tends to occur during periods of weight gain. The symptoms though are very treatable and, if treatment is started early enough, the vision loss is reversible.
Part II of this series is written for physicians. Continue to Part II.
Selected References
Corbett JJ, Nerad JA, Tse DT, Anderson RL. Results of optic nerve sheath fenestration for pseudotumor cerebri. The lateral orbitotomy approach. Arch Ophthalmol 1988;106:1391-1397.
Corbett JJ, Thompson HS. The rational management of idiopathic intracranial hypertension. Arch Neurol 1989;46:1049-1051.
Durcan FJ, Corbett JJ, Wall M. The incidence of pseudotumor cerebri. Population studies in Iowa and Louisiana. Arch Neurol 1988;45:875-877.
Friedman DI, Streeten DH. Idiopathic intracranial hypertension and orthostatic edema may share a common pathogenesis. Neurology 50:1099-1104, 1998.
Giuseffi V, Wall M, Siegel PZ, Rojas PB. Symptoms and disease associations in idiopathic intracranial hypertension (pseudotumor cerebri): a case-control study. Neurology 1991;41:239-244.
Gucer G, Vierenstein L. Long-term intracranial pressure recording in management of pseudotumor cerebri. J Neurosurg 1978;49:256-263.
Ireland B, Corbett JJ, Wallace RB. The search for causes of idiopathic intracranial hypertension. A preliminary case-control study. Arch Neurol 1990;47:315-320.
Lessell S. Pediatric pseudotumor cerebri (idiopathic intracranial hypertension). Surv Ophthalmol 1992;37:155-166.
Meador KJ, Swift TR. Tinnitus from intracranial hypertension. Neurology 1984;34:1258-1261.
Newborg B. Pseudotumor cerebri treated by rice reduction diet. Arch Intern Med 1974;133:802-807.
Sergott RC, Savino PJ, Bosley TM. Modified optic nerve sheath decompression provides long-term visual improvement for pseudotumor cerebri. Arch Ophthalmol 1988; 106:1391-1397.
Wall M, George D. Idiopathic intracranial hypertension. A prospective study of 50 patients. Brain 1991;114:155-180.
Wall M, George D. Visual loss in pseudotumor cerebri. Incidence and defects related to visual field strategy. Arch Neurol 1987;44:170-175.
Wall M. The headache profile of idiopathic intracranial hypertension. Cephalalgia 1990;10:331-335.
Wall, M. Idiopathic intracranial hypertension. Neurol Clin 9:73-95, 1991.
