Idiopathic Intracranial Hypertension
On this page
Direct answer
Idiopathic intracranial hypertension is raised intracranial pressure without a mass lesion, hydrocephalus or venous sinus thrombosis, most often in obese women of childbearing age. Diagnosis rests on papilloedema, a lumbar opening pressure of 25 cm of CSF or more in adults with normal CSF composition, and normal imaging apart from signs of raised pressure. Treatment is weight reduction and acetazolamide, with surgery reserved for progressive visual loss.
What you must remember
- Epidemiology: obese women of childbearing age; recent weight gain is a strong risk factor, and men and children are less commonly affected.
- Symptoms: daily headache often worse in the morning, transient visual obscurations and pulsatile tinnitus.
- Signs: bilateral papilloedema, an enlarged blind spot and sixth nerve palsy as a false localising sign.
- Diagnostic criterion: lumbar opening pressure of 25 cm of CSF or more in adults, with normal CSF composition and no other cause.
- Imaging: MRI with venography to exclude venous sinus thrombosis and mass; empty sella and optic nerve sheath distension support the diagnosis.
- Drug causes: tetracyclines, vitamin A and retinoids such as isotretinoin, and abrupt steroid withdrawal.
- Treatment: weight reduction and acetazolamide, with topiramate or furosemide as alternatives in some patients.
- Vision protection: serial perimetry and optical coherence tomography, with optic nerve sheath fenestration or CSF shunting for progressive loss.
Where the examiner tests the silent threat
Headache is the presenting complaint, but vision is the outcome that matters.
- Trap: treating the headache alone. Correct: visual loss is often silent until late, so perimetry and optical coherence tomography belong in follow-up.
- Trap: reading the sixth nerve palsy as a brainstem lesion. Correct: it is a false localising sign in this condition and does not mean a brainstem lesion.
- Trap: confusing papilloedema with pseudopapilloedema from optic disc drusen. Correct: the two can be distinguished by imaging.
- Trap: performing lumbar puncture before imaging. Correct: the lumbar puncture is diagnostic and sometimes therapeutic, but it must not precede imaging that excludes a mass lesion.
Frequently asked questions
What lumbar puncture pressure defines idiopathic intracranial hypertension in adults?
Idiopathic intracranial hypertension in adults requires a lumbar opening pressure of 25 cm of CSF or more, with normal CSF composition and no other cause identified. The measurement is taken with the patient lying relaxed, since anxiety and straining can raise the reading.
Why is acetazolamide used in idiopathic intracranial hypertension?
Acetazolamide is used in idiopathic intracranial hypertension because it inhibits carbonic anhydrase, reducing cerebrospinal fluid production and lowering intracranial pressure. It is combined with weight reduction, and its dose is adjusted according to response and side effects such as paraesthesia and renal stones.
Which tests protect vision in idiopathic intracranial hypertension?
Visual field testing by perimetry and optical coherence tomography of the retinal nerve fibre layer protect vision in idiopathic intracranial hypertension. Serial measurements detect progressive loss that the patient may not notice, and deterioration despite medical therapy prompts consideration of surgery.
Which drugs can cause idiopathic intracranial hypertension?
Tetracyclines, vitamin A and its derivatives such as isotretinoin, and abrupt steroid withdrawal are classic drug causes of idiopathic intracranial hypertension. A full drug history is taken in every case, and the offending drug is stopped where possible, since the pressure often settles after withdrawal.