Idiopathic intracranial hypertension, known as IIH or pseudotumor cerebri, is a neurological disorder characterized by elevated intracranial pressure in the absence of a tumor or other disease.
IIH affects about 100,000 Americans, the vast majority of whom are obese women in their childbearing years. As the epidemic of obesity has increased, so has the incidence of IIH. The rate of IIH prevalence in various ethnic and racial groups correlates directly to the rate of obesity in those groups. The mean age of diagnosis is about 30 years; however, it may occur in all age groups and in patients of all body types.
The cause of IIH is not known. Three theories exist as to why pressure is elevated in IIH:
- an excess of cerebrospinal fluid (CSF) production
- increased volume of blood or brain tissue
- obstruction of the veins that drain blood from the brain and thereby remove CSF
Signs and symptoms
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 and are often throbbing.
Pulsatile intracranial noises or pulse-synchronous tinnitus (ringing in the ears) are also common in IIH. The sound is often only experienced on one side.
Papilledema, which is optic disc swelling due to increased intracranial pressure, is the cardinal sign of IIH and is either directly or indirectly responsible for visual loss in IIH. The optic disc is the spot where the optic nerve enters the eyeball. Papilledema can cause transient visual obscurations, which are episodes of blurred vision that usually last less than 30 seconds and are followed by visual recovery to baseline. While these episodes are anxiety-provoking for the patient, they do not appear to be associated with poor visual outcome. If papilledema is left untreated it can lead to visual loss, first in the periphery, then progressively toward the center of vision. Longstanding papilledema leads to optic atrophy, in which the disc looks pale due to lack of blood flow and visual loss is advanced.
Increased pressure may also lead to compression of the cranial nerves, a group of nerves that arise from the brain stem and supply the face and neck. Most often the sixth cranial nerve, or abducens nerve, is involved and the patient may experience sixth cranial nerve palsy. The seventh cranial nerve, or facial nerve, is occasionally affected resulting in partial weakness of the muscles of facial expression on one or both sides of the face.
Diagnosing idiopathic intracranial hypertension
Diagnosis of IIH is based on history, physical examination, imaging tests and lumbar puncture. Neuroimaging, usually with computed tomography (CT/CAT) or magnetic resonance imaging (MRI), is used to rule out any tumor or disease. Small or slit-like ventricles, pituitary gland flattening and buckling of the optic nerves may, however, be seen on scans of IIH patients.
Lumbar puncture is performed to measure the opening pressure, as well as to obtain CSF to examine for abnormal cells, infections, antibody levels, glucose levels and protein levels. CSF of IIH patients should test normal. Opening CSF pressure should be measured with the patient in the lateral position and is almost always elevated in IIH patients.
An eye exam, including visual field testing, is also included in an exam to diagnose IIH. The eye exam will test for papilledema.
Treating idiopathic intracranial hypertension
Weight control is a long-term factor in the management of IIH. The loss of as little as 6 percent of body weight may lead to the termination of this disorder and may also significantly diminish the risk of its recurrence. The importance of weight loss as the only effective means of reducing papilledema, and with it the threat of progressive blindness, cannot be overemphasized. Patients are urged to enroll in an aggressive weight-loss program, ideally using a multidisciplinary approach that includes diet and exercise along with psychological and lifestyle counseling.
Medications such as acetazolamide (Diamox®), topiramate (Topomax®) and furosemide (Lasix®) have been used to treat IIH. They work to lower intracranial pressure by reducing the production of CSF. Various analgesic painkillers may be used to control IIH headaches, as well as a low dose antidepressant or anticonvulsant.
Lumbar puncture is sufficient to control the symptoms in some cases and can be repeated if necessary, but if this is needed repeatedly it is a clue that additional treatments may be required to control the symptoms and preserve vision. Repeated lumbar punctures present a danger of introducing spinal infections if done too often.
Surgical therapies are reserved for patients who fail medical therapy or have significant loss of peripheral or central vision. The most common surgical technique in current use is shunting the spinal fluid from the lumbar (low back) or ventricle (head) spaces to the abdominal cavity or the right atrium of the heart. This surgery is performed by a neurosurgeon.