Idiopathic intracranial hypertension

What IIH is

Idiopathic intracranial hypertension (IIH) is raised pressure of the cerebrospinal fluid around the brain without a tumour, clot or other structural cause. “Idiopathic” means the cause is not fully understood, though it is strongly associated with weight gain and is most common in women of childbearing age.

The headache is typically daily and can be worse in the morning or when lying down, the opposite of a CSF leak. Its real danger is to the eyes: sustained pressure on the optic nerves can damage vision permanently if it is left untreated.

Why the eyes come first

Because sight is at stake, anyone with suspected IIH needs an eye examination to check for papilloedema (swelling of the optic nerve) and formal visual-field testing. Protecting vision, not just easing headache, drives the treatment plan.

• Pulsatile tinnitus: a whooshing sound in time with the pulse
• Brief grey-outs of vision, often linked to posture
• Double vision from pressure on the nerve that moves the eye
• Headache that is constant rather than coming in distinct attacks

How it is managed

Treatment combines lowering the pressure, often with medication such as acetazolamide and, where relevant, supported weight loss, with close monitoring of vision. A small number of people with rapidly threatened sight need surgical options. For many, sustained weight management is the most effective long-term lever.