Definition and Overview
Idiopathic intracranial hypertension (IIH) is a disease in which intracranial pressure rises without an obvious structural cause, such as tumor, hydrocephalus, or venous sinus thrombosis. It is also called pseudotumor cerebri because intracranial pressure rises even though there is no tumor, causing symptoms similar to a tumor. If left untreated, papilledema can lead to permanent vision loss.
Epidemiology
It occurs more frequently in obese women of childbearing age. Obesity and weight gain are major risk factors, and some medications have also been reported as triggers. It can also occur in men and children, but less frequently.
symptoms
Chronic headaches are the most common symptom and often persist to the point that they interfere with daily life. It may be accompanied by pulsatile tinnitus, where sounds are heard in time with the heartbeat, transient visual blurring where vision becomes blurred for a few seconds, and double vision due to abducens nerve paralysis. Damage to visual function first appears as a defect in peripheral vision, and as it progresses, it leads to permanent vision loss.
diagnosis
Diagnosis is based on revised diagnostic criteria incorporating the following factors:
- Papilloedema: A fundus examination confirms swelling of the optic nerve head.
- Brain imaging: There must be no tumor, hydrocephalus, venous sinus thrombosis, etc. that could explain the increased intracranial pressure on MRI.
- Lumbar puncture: Cerebrospinal fluid opening pressure exceeds 25 cmH2O for adults.
- Cerebrospinal fluid composition: cell number and protein are normal.
Visual field testing is essential for diagnosis and follow-up, and quantitatively evaluates the degree of damage to visual function.
treatment
Weight loss is the key to fundamental treatment. Acetazolamide, a carbonic anhydrase inhibitor, is used to lower intracranial pressure. In a randomized controlled trial (IIHTT) targeting patients with mild vision loss, the group that received acetazolamide and weight loss had greater improvement in visual field.
In severely ill patients with rapidly progressing visual impairment, surgical treatments such as optic nerve sheath decompression, cerebrospinal fluid shunt, and venous sinus stent insertion are considered.
Clinical implications
Idiopathic intracranial hypertension should be suspected when chronic headache is accompanied by pulsatile tinnitus and transient visual blur, and papilledema is confirmed on fundus examination. Since preserving visual function is the top goal of treatment, early diagnosis and regular visual field tracking are important.