Idiopathic intracranial hypertension
Idiopathic intracranial hypertension (IIH) is elevated pressure within the cerebrospinal fluid of the brain, causing severe headaches and vision problems. The condition can be successfully treated, but has been known to recur. High pressure within cerebrospinal fluid or intracranial pressure sometimes has unknown origins (in which case, it is said to be idiopathic), although certain preconditions and triggers are suspected. Because the symptoms can mimic those of a brain tumor, the condition has also been labeled false brain tumor or pseudotumor cerebri.
Definition & Facts
Intracranial pressure can be acute, meaning it will resolve, or chronic, meaning it is an ongoing condition. Increased pressure within brain fluids can cause swelling of the optic nerve and damage - a condition called papilledema.
It is estimated that 100,000 Americans have idiopathic intracranial hypertension. More women than men are diagnosed with IIH, and age of onset is usually between 20 and 50. Only about five percent of those who are affected by this condition are men.
Symptoms & Complaints
Neurological tests may present as normal, but abnormal ocular symptoms may be present. An important optical symptom of papilledema is a spot of blindness found on a visual field test. Often peripheral vision loss is not immediately noted by patients unless tested. Abnormal pressure can also affect muscles controlling eye movement, resulting in double vision (diplopia). Other symptoms may include:
- Visual abnormalities upon movement.
- Tinnitus/intracranial noise.
- Arm pain and back pain.
- Stiff neck
- Pain in back of the eye.
- Memory loss
Obesity and IIH are strongly correlated. A body mass index of over 30 in a woman of childbearing age is considered a serious risk factor. If five to fifteen pounds has recently been gained, even if the BMI is below 30, risks rise. Weight seems not to be a factor in the five percent of men diagnosed, or for children under the age of 10.
In most cases, there is too much cerebrospinal fluid in the brain. Spaces that contain the fluid (subarachnoid space) cannot grow larger and so pressure rises.
If a patient with IIH is not overweight, there are certain other predisposing factors that may have a bearing upon an IIH diagnosis. These include:
- Certain antibiotics, particularly in children and corticosteroids or oral contraceptive pills in adults.
- Diseases such as sarcoidosis, kidney disease, or systemic lupus erythematosus.
Another possible cause is that the venous sinuses may be smaller than normal in people with idiopathic intracranial hypertension, which may obstruct normal cerebral overflow of cerebrospinal fluid.
Diagnosis & Tests
Subjective diagnosis of headache and ocular symptoms of intracranial pressure are the first indications of IIH, provided the patient is awake and alert.
Neurological examination usually shows no neurological abnormalities, such as unsteady gait or inability to move a limb. Sometimes the patient and the emergency room will dismiss important optic features of IIH, and diagnose the illness as a migraine, which may have similar symptoms.
A magnetic resonance imaging (MRI) scan and/or computed tomography (CT) scan often reveals no indication of venous obstruction or blockage of cerebral fluid or blood flow, and will rule out other causes for intracranial pressure.
A spinal tap or lumbar puncture is recommended. Local anesthetic numbs the lower back and a needle is guided into place to measure intracranial pressure. Some cerebrospinal fluid is removed for further lab tests.
Spinal fluid is tested for the presence of bacteria, syphilis markers or tumor markers in patients with cancer history. Blood tests may indicate specific causes for idiopathic intracranial hypertension, such as vascular disease or lupus erythematosus. A screening test for Lyme disease is performed for those in endemic disease areas.
Treatment & Therapy
The first consideration upon diagnosis of IIH is preserving vision through relief of optic nerve pressure. Optic nerve viability is monitored through tests for color vision and visual acuity. Obese patients are strongly advised about weight control and management.
Vision loss is a serious component of this disease. A short course of corticosteroids is advised if rapid vision loss or poor response to other therapies is indicated. Emergency surgical intervention will be performed if other methods fail.
Loss of vision field in one or both eyes can move quickly in spite of strong efforts to stop the disease. Timing of intervention is crucial, but there is debate about how rapidly intervention should occur.
Idiopathic intracranial pressure may become chronic. In this case, a spinal fluid shunt may be advised. This is a tiny tube inserted into the brain or spine to remove extra fluid. The success rate is reportedly higher than 80 percent.
Another successful treatment for chronic IIH is optic nerve sheath fenestration. The sheath surrounding the optic nerve is cut to let out excess fluid. According to specific studies, this procedure is more than 85 percent successful in resolving symptoms.
Prevention & Prophylaxis
Once pressures resolve in incidences of IIH, regular monitoring of vision through vision field tests is recommended. The ophthalmologist will assess the condition carefully to make sure no vision changes have occurred. Vision changes from IIH can result in permanent vision loss.