Idiopathic intracranial hypertension
Description
- Raised intracranial pressure with normal CSF constituents, no mass lesion, no hydrocephalus, no venous thrombosis
- A diagnosis of exclusion; "idiopathic" only after MRV is clear
- Pseudotumour cerebri is the umbrella term: primary (IIH) vs secondary (an identifiable cause - drug, endocrine, venous)
Classic phenotype
- Obese woman of reproductive age with recent weight gain
- Headache - daily, morning-predominant, worse lying flat, on coughing and straining
- Transient visual obscurations - seconds of greying, often on standing or bending
- Pulsatile tinnitus
- Horizontal diplopia from CN VI palsy (false localising)
- Papilloedema - bilateral disc swelling on fundoscopy
- Back and neck pain, radicular pain
- Visual acuity is preserved until late - the visual field is what is lost
Fulminant IIH
- Severe visual loss developing over days to <4 weeks
- A surgical emergency - acetazolamide alone is inadequate
Epidemiology
- Overall incidence ~1-3 per 100,000/yr
- ~20 per 100,000/yr in women aged 20-44 with obesity
- F:M ~8-9:1
- >90% have obesity; risk rises steeply with BMI and with recent weight gain (even from a normal baseline)
- Incidence tracking obesity prevalence - rising substantially
- Men are a minority but have worse visual outcomes; consider obstructive sleep apnoea in every male case
- Paediatric IIH: pre-pubertal cases have no sex or weight predominance
Aetiopathogenesis
- Mechanism incompletely understood; leading model:
- Obesity -> inc intra-abdominal pressure -> inc central venous pressure -> dec CSF absorption at arachnoid granulations
- Plus altered glucocorticoid and androgen metabolism in adipose tissue (raised 11beta-HSD1 activity), and altered CSF dynamics
- Transverse sinus stenosis present in most - both consequence and perpetuator: raised ICP compresses the sinus -> further outflow resistance -> self-reinforcing loop
- This is why venous stenting can work, and why a stenosis alone does not prove venous disease is the cause
Secondary causes (pseudotumour cerebri) - the exam list
Drugs
- Tetracyclines - tetracycline, minocycline, doxycycline
- Nitrofurantoin, sulphonamides
- Excess vitamin A and retinoids (isotretinoin, all-trans retinoic acid)
- Thyroxine, growth hormone
- Tamoxifen
- Corticosteroids - particularly withdrawal
- Lithium, ciclosporin
Endocrine and systemic
- Addison disease, Cushing syndrome, hypoparathyroidism, thyroid disease
- Anaemia (iron deficiency), polycythaemia
- Obstructive sleep apnoea, chronic hypercapnia
- Renal failure
- Down syndrome, Turner syndrome
- Autoimmune - SLE, Sjogren syndrome, Behcet
Venous
- Cerebral venous sinus thrombosis (must be excluded, not classified as secondary IIH), jugular obstruction, SVC syndrome, dural AV fistula, right heart failure
Diagnosis
Modified Dandy / Friedman criteria - all required
1. Symptoms and signs of raised ICP only (headache, papilloedema, VI palsy) - no other focal signs
2. Normal neurological examination except CN VI palsy and papilloedema
3. Neuroimaging normal - no mass, hydrocephalus, structural or meningeal lesion, and normal MR venography
4. Normal CSF composition
5. Elevated CSF opening pressure: >=25 cmH2O in adults (>=28 cmH2O in children; >=25 if the child is sedated or obese)
- Diagnosis without papilloedema requires either a CN VI palsy, or >=3 supportive MRI signs
MRI signs supporting raised ICP
- Empty sella
- Flattening of the posterior globe
- Distension of the perioptic subarachnoid space +/- optic nerve tortuosity
- Transverse sinus stenosis (on MRV)
- Meningocele/encephalocele, slit-like ventricles
Order of investigation
1. MRI brain + MR venography - MRV is not optional; CVST is the principal mimic
2. Lumbar puncture with opening pressure, after imaging
- Lateral decubitus, legs extended, relaxed; a tense or flexed patient gives a falsely high reading
- Send cell count, protein, glucose, culture, cytology
3. Bloods: FBE (anaemia), UEC, TFT, morning cortisol/short Synacthen if clinically indicated, ESR, autoimmune screen
4. Drug history reviewed explicitly against the list above
5. Sleep study if snoring, witnessed apnoea, male, or refractory
Ophthalmic assessment - the monitoring that matters
- Automated perimetry (Humphrey 24-2/30-2) at diagnosis and serially - the primary outcome measure
- Earliest: enlarged blind spot -> inferonasal step -> generalised constriction
- OCT retinal nerve fibre layer - quantifies swelling; a falling RNFL with worsening fields means atrophy, not improvement
- Visual acuity and colour vision (preserved until late - do not use as the trigger to escalate)
- Fundus photography, Frisen grade
Management
Two aims, and they are separate: preserve vision and control headache. Treatments that help one may not help the other.
A. Risk stratification drives the pathway
| Approach | |
|---|---|
| No/mild papilloedema, normal fields | Weight management, remove cause, monitor. Acetazolamide if headache troublesome |
| Moderate papilloedema, mild field loss | Acetazolamide + weight loss, close perimetry (every 4-6 weeks initially) |
| Progressive field loss despite treatment | Surgical referral - ONSF, CSF diversion, or venous stenting |
| Fulminant (rapid loss over days) | Emergency: admit, IV acetazolamide +/- steroid as a bridge, urgent surgery |
B. Weight management - the only disease-modifying treatment
- ~5-10% total body weight loss produces remission of papilloedema in most patients
- Structured programmes, dietitian, exercise
- Bariatric surgery outperforms a community weight management programme for both ICP and papilloedema (IIH:WT trial) - consider in refractory disease with BMI >=35
- GLP-1 receptor agonists - increasingly used; evidence emerging (exenatide reduces ICP)
- This conversation is difficult and is frequently avoided. It is the treatment with the largest effect size
C. Remove the cause
- Stop tetracyclines, retinoids, excess vitamin A, growth hormone; review thyroxine and lithium
- Treat anaemia, thyroid disease, adrenal disease
- Treat obstructive sleep apnoea - CPAP
D. Medical
- Acetazolamide - first-line; titrate as tolerated (trial doses up to 4 g/day, but most tolerate far less)
- Paraesthesia, dysgeusia, fatigue, metabolic acidosis, renal stones, hypokalaemia
- Avoid in sulfonamide allergy; caution in pregnancy (avoid first trimester) and severe renal impairment
- Topiramate - alternative; also reduces weight and treats headache
- Furosemide - adjunct
- Corticosteroids only as a short bridge in fulminant disease - rebound on withdrawal and weight gain make them harmful longer term
- Headache management in parallel - medication overuse headache is extremely common here and is often the real reason the headache persists after ICP normalises
E. Surgical
- Optic nerve sheath fenestration - best for vision, unreliable for headache
- CSF diversion (VP or LP shunt) - treats both, but high failure and revision rates; LP shunts block frequently
- Venous sinus stenting - where a significant trans-stenotic pressure gradient (typically >8 mmHg) is demonstrated on venography; requires dual antiplatelet therapy
- Repeat LPs - temporary only; not a management strategy
F. Practical
- Contraception counselling; IIH is not a contraindication to pregnancy - manage with weight stabilisation, close perimetry, acetazolamide avoided in the first trimester
- Driving: assess visual fields against licensing standards
- Education: this is a chronic condition requiring surveillance even after remission
Associations
- Obesity, recent weight gain, PCOS
- Obstructive sleep apnoea
- Anaemia (especially iron deficiency), chronic kidney disease
- Endocrine: Addison disease, Cushing syndrome, hypoparathyroidism, thyroid disease, growth hormone therapy
- Drugs: tetracyclines, retinoids and vitamin A excess, nitrofurantoin, sulphonamides, thyroxine, lithium, ciclosporin, tamoxifen, corticosteroid withdrawal
- Down syndrome, Turner syndrome
- SLE, Sjogren syndrome, Behcet
- Cerebral venous sinus thrombosis - overlaps clinically; transverse sinus stenosis found in most IIH
- Migraine and medication overuse headache - frequently coexist and confuse the picture
- Depression, anxiety, reduced quality of life independent of visual outcome
Natural history & complications
- Variable: remission, relapsing course, or chronic
- Remission commonly follows sustained weight loss; relapse commonly follows weight regain
- Papilloedema usually resolves over months once ICP is controlled
- Permanent visual loss in ~5-10%; severe loss in ~1-2%
- Higher risk: male sex, fulminant onset, severe papilloedema at presentation, anaemia, obstructive sleep apnoea, rapid weight gain, poor follow-up attendance
- Headache frequently persists after ICP normalises - a major source of disability, and usually migrainous or medication-overuse in character by then
Complications
- Irreversible optic atrophy and blindness - the outcome the whole management plan exists to prevent
- Chronic daily headache, medication overuse headache, analgesic dependence
- Diplopia from VI palsy
- Acetazolamide adverse effects: renal stones, acidosis, paraesthesia, rarely aplastic anaemia
- Shunt complications - blockage, infection, low-pressure headache, repeated revisions
- Depression, unemployment, reduced quality of life
- Improving disc appearance with worsening fields = evolving optic atrophy, not recovery. Fields and OCT, not fundoscopy, drive decisions
🔒
6 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access