Idiopathic intracranial hypertension
Headache due to raised intracranial pressure (ICP), especially in idiopathic intracranial hypertension (IIH), is primarily caused by impaired cerebrospinal fluid (CSF) absorption across arachnoid villi into the dural venous sinuses. This leads to elevated CSF pressure without a mass lesion or hydrocephalus.
Epidemiology
- Predominantly affects women of reproductive age (20–45 years)
- Obesity is a major risk factor
- Estimated incidence:
- ~20 per 100,000/year in obese women aged 20–44
Risk Factors
- Female sex
- Obesity and rapid weight gain
- Endocrine disorders:
- Polycystic ovary syndrome (PCOS) is more commonly associated than Cushing’s syndrome
- Medications associated with raised ICP:
- Tetracyclines (e.g. minocycline, doxycycline)
- Vitamin A and retinoids (e.g. isotretinoin)
- Growth hormone
- Lithium
- Withdrawal of long-term corticosteroids
- Oral contraceptive pills (association weak and not clearly causative)
Clinical Features
- Headache:
- Typically worse in the morning or with lying down
- Worsens with Valsalva, bending over, or coughing
- Sometimes described as diffuse and daily
- Transient visual obscurations (brief episodes of vision loss with position changes)
- Pulsatile tinnitus (“whooshing” sound in one or both ears)
- Diplopia from 6th cranial nerve palsy (abducens)
- Papilloedema (bilateral; hallmark of raised ICP)
- Visual field defects:
- Gradual peripheral vision loss (can progress to blindness if untreated)
- Other features:
- Nausea/vomiting
- Photophobia
- Back or neck pain
- Cognitive symptoms (rare, in severe cases)
classic triad:
| Feature | Description |
|---|---|
| Headache | – Diffuse, daily, pressure-like – Worse in the morning or lying down |
| Papilloedema | – Bilateral optic disc swelling – May cause transient visual obscurations and visual field defects |
| Pulsatile Tinnitus | – “Whooshing” sound in one or both ears – Synchronous with heartbeat |
Investigations
- Neuroimaging (required before LP):
- MRI brain with MRV preferred to rule out mass lesions or cerebral venous sinus thrombosis
- Lumbar puncture:
- Performed after normal neuroimaging
- Measure opening pressure in lateral decubitus position
- CSF analysis: normal composition
- Ophthalmologic assessment:
- Fundoscopy for papilloedema
- Visual fields (perimetry) and optic nerve head measurements (OCT)
Diagnostic Criteria (Modified Dandy Criteria)
- Symptoms of raised ICP (e.g. headache, transient visual obscurations)
- Signs of raised ICP (papilloedema or cranial nerve VI palsy)
- Normal neurological examination (except cranial nerve VI palsy)
- Normal neuroimaging (excluding mass, hydrocephalus, venous thrombosis)
- Elevated lumbar puncture opening pressure:
- 25 cm H₂O (non-obese)
- 28 cm H₂O (obese)
- Normal CSF composition
Complications
- Progressive vision loss (can lead to permanent blindness)
- Chronic, disabling headache
Management
Multidisciplinary approach involving:
- Neurology
- Ophthalmology
- Neurosurgery (in refractory cases)
First-line pharmacological treatment:
- Acetazolamide:
- Carbonic anhydrase inhibitor that reduces CSF production
- Initial dose: 250–500 mg BD; titrate to max tolerated (up to 1 g BD)
Adjunctive options:
- Furosemide (if acetazolamide not tolerated)
- Topiramate: may assist with headache and weight loss (off-label use)
Non-pharmacological:
- Weight reduction (5–10% loss may be sufficient for symptom resolution)
- Ceasing contributing medications
Interventional:
- Therapeutic lumbar punctures (temporary relief)
- CSF shunting (e.g. ventriculoperitoneal) for refractory cases
- Optic nerve sheath fenestration (in progressive visual loss)
Follow-Up
- Ophthalmic review every 1–3 months in active disease
- Serial visual fields and OCT to monitor progression