Idiopathic Intracranial Hypertension
(Pseudotumor Cerebri)

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 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.

Figure 2. The superior saggital sinus and the site of cerebrospinal fluid absorbtion,
the cauliflower-like arachnoid granulations.

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. As a part of our research program, we are trying to find some hormonal changes in a newly discovered hormone.

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. Withdrawal of steroids, large doses of vitamin A or 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 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. The periodic compressions were thought to convert the laminar blood flow to turbulent.

Visual loss The most serious problem patients have is vision loss. (Figure 9, 10) About 5% of patients go blind in at least one eye. These are usually patients who do not return for follow-up evaluation.

Figure 9. At 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 10. 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 (done 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 3-8) Sometimes double vision occurs, caused by limitation of lateral eye movement. Lastly, neuroimaging procedures such as CT scans or MRI scanning are normal.

Figure 3. Normal optic nerve (central pinkish disk)

Figure 4. An optic nerve with mild swelling (papilledema).
Note the pathologic"C"-shaped halo of edema surrounding the optic disk (Grade I papilledema).

Figure 5. Grade I papilledema, Another example of an optic nerve with mild papilledema.

Figure 6. Grade II papilledema. The halo of edema now surrounds the optic disc.

Figure 7. 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 8. 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.

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 may be the loss of fluid accompanying weight loss that is the significant factor but this has not been proven.

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. 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).

The surgical treatments currently used are optic nerve sheath fenestration (making slits in the optic nerve sheath or covering) (Figure 11) and lumbar shunting procedures (running a tube from the spinal fluid space in the lower spine into the abdominal cavity). 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 11. 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.

The second surgical procedure, called lumbar-peritoneal shunting, is done as follows. Tubing is placed in the spinal fluid space, (the space entered during a lumbar puncture or spinal tap and tubing is then run to the abdomen. 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 12.

Figure 12. Treatment strategies for IIH.

How is visual loss prevented?

The best way to prevent visual loss is to test vision regularly. 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.

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Copyright 2002. International Perimetric Society