AKA: Pseudotumor cerebri, benign intracranial hypertension
Definition: increased intracranial pressure of unknown cause that results in a variety of neurological symptoms, especially headache and visual problems
Symptoms of IIH (Pseudotumor)
Headache: 99% of patients with IIH seen by neurologists complain of headache. The headache is most often diffuse, worse in the morning, and worse with Valsalva maneuvers such as coughing, sneezing or straining.
Visual Symptoms: Transient visual difficulties are frequent and lasts 1-5 seconds. The episodes are described as a graying out of vision and can occur with standing up or bending over. Double vision when looking side to side is much more frequent than double vision when looking up or down.
Other Symptoms: Patients with IIH may also have dizziness, nausea, vomiting, and ringing in the ears (tinnitus).
The cause of IIH (pseudotumor) is unknown. Among the possibilities are decreased absorption of cerebrospinal fluid (CSF), thus the brain contains more spinal fluid. Another possibility is abnormal cerebral circulation resulting in increased brain water. The increased fluid within the brain tissue causes the pressure within the cranium (intracranial pressure) to increase.
The increased pressure affects structures within cranium, including the optic nerves and cause the complaints of vision reported by many.
Pseudotumor is more common in obesity, especially in overweight women. As the abdomen enlarges, the cardiac filling pressures increase. The elevated pressure in the heart decreases venous blood return from brain and causes an in increase in intracranial venous pressure.
Pseudotumor can affect persons of any age but is most common in the third decade of life. For unknown reasons children with pseudotumor are usually not obese.
On neurological examination, the doctor may find:
- Swelling of the optic nerves (papilledema; although rarely, the optic nerves normal
- Decreased vision; this is evaluated by vision test and test of visual fields
- Double vision (diplopia)
- Weakness of nerves that move the eyes
Risk Factors for Pseudotumor
Pseudotumor has been found to be more common when these following factors are present:
- Medications: antibiotics, steroids, lithium, oral contraceptives, phenytoin, vitamin A (>100,000 U/day)
- Diseases: anemia, chronic respiratory insufficiency, hypertension, multiple sclerosis, renal disease, sarcoidosis, Lupus
- Disorders of venous drainage: tumors affecting venous sinuses, sinus thrombosis, radical neck dissection surgery
Relation to Chiari I Malformation
MRI scans in 68 patients with IIH showed that 10% had Chiari I malformation (5 mm or more), 13% had tonsillar herniation of 2-4 mm (tonsillar ectopia). Spinal taps were performed to measure the intracranial pressure in 36 patients who had failed to improve following decompression surgery for the Chiari malformation. Of these, 42% had were found to have both Chiari and psuedotumor. Thus, pseudotumor is a cause of failure following posterior fossa decompression for Chiari.
The evaluation of a patient suspected of having IIH (pseudotumor) may include:
- Visual exam including evaluation of the optic nerves and visual fields
- MRI & MRV (venography) of the brain
- Lumbar puncture (spinal tap) to measure the intracranial pressure. (This can help relieve the symptoms as well.)
Weight loss is the most important treatment in persons that are obese. Just a 6% loss of weight can be effective in resolving the condition. Patients on medications that increase the chances of developing pseudotumor should consult with their doctor to determine if they can come off of the suspected medication. If any of the diseases noted above are present, they should be treated as best as possible.
Medications that are used in the treatment of pseudotumor include:
- acetazolamide (Diamox)
- furosemide (Lasix)
- course of steroids
The most common surgical treatment for pseudotumor is a cerebrospinal fluid shunt. Usually this is a shunt running from the spinal canal into the abdominal cavity and is called a lumbo-periotoneal shunt. Some patients may need a shunt from the cerebral ventricles to the peritoneum, a ventriculo-peritoneal shunt.
Optic nerve sheath fenestration is a surgical procedure performed by ophthalmologists that can reduce the pressure around the optic nerve. However, this treatment is usually reserved for severe cases where the risk to vision is high and a shunt is not effective.