Overview
- Definition: Elevation of intracranial pressure (ICP) without an identifiable cause.
- Demographics: Primarily affects obese young women of childbearing age.
- Prevalence: Ranges from 0.5–2 per 100,000, increasing with the global rise in obesity.
Clinical Features
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Main Symptoms:
- Headache: Frequently migrainous in phenotype; may persist after ICP normalization.
- Visual Alterations: Papilledema-induced visual loss, transient visual obscurations (TVOs), diplopia.
Visual Features of IIH
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Transient Visual Obscurations (TVOs):
- Episodic visual clouding or loss (<1 minute).
- Associated with postural changes and raised ICP-induced optic nerve ischemia.
- Useful indicator of raised ICP.
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Diplopia:
- Horizontal binocular diplopia due to sixth nerve palsy.
- Third and fourth nerve palsies are rare.
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Visual Field Loss:
- Common early sign: Enlarged blind spot, nasal defects, arcuate defects.
- Visual acuity may remain unaffected in mild disease.
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Papilledema:
- Bilateral optic disc swelling due to raised ICP.
- Can result in optic atrophy and permanent visual loss if untreated.