How should benign (idiopathic) intracranial hypertension be diagnosed and treated?

Management of Benign (Idiopathic) Intracranial Hypertension

All patients with suspected IIH require urgent MRI brain within 24 hours (or CT if MRI unavailable) with mandatory venography to exclude secondary causes, followed by lumbar puncture with opening pressure measurement ≥25 cm H₂O in lateral decubitus position to confirm diagnosis. 1, 2

Diagnostic Workup

Immediate Imaging Requirements

• Obtain MRI brain within 24 hours as first-line imaging to exclude hydrocephalus, mass lesions, structural abnormalities, and abnormal meningeal enhancement 2
• If MRI unavailable within 24 hours, perform urgent CT brain followed by MRI when available 2
• CT or MR venography is mandatory within 24 hours to exclude cerebral sinus thrombosis 2

Key Neuroimaging Findings Supporting IIH

• Empty or partially empty sella 1
• Posterior globe flattening (56% sensitivity, 100% specificity) 2
• Enlarged optic nerve sheath (mean 4.3 mm vs 3.2 mm in controls) 2
• Increased tortuosity of optic nerve (68% sensitivity, 83% specificity) 2
• Intraocular protrusion of optic nerve head (40% sensitivity, 100% specificity) 2
• Bilateral transverse sinus stenosis 1

Lumbar Puncture Requirements

• Opening pressure must be ≥25 cm H₂O measured in lateral decubitus position with legs extended, patient relaxed and breathing normally 2
• Measure after pressure stabilizes to avoid false readings 2
• CSF composition must be normal 1
• If initial pressure is borderline, arrange repeat lumbar puncture at 2 weeks as pressure may fluctuate 2

Essential Baseline Visual Assessment

• Document visual acuity bilaterally 2
• Perform pupil examination 2
• Formal visual field testing is mandatory (not just confrontational testing) 3
• Dilated fundal examination to grade papilledema severity 2, 3
• Serial optic nerve head photographs or OCT imaging 2

Patient Characterization

• Calculate BMI (typical IIH: female, reproductive age, BMI ≥30 kg/m²) 2
• Document weight and recent weight gain (5-15% gain in preceding year is common) 1, 2
• Assess for atypical features requiring deeper investigation (male, prepubertal, normal weight) 2

Treatment Strategy: Three Core Principles

1. Protect Vision (Highest Priority)

For Imminent or Severe Visual Loss (Fulminant IIH)

Urgent surgical intervention is required when there is declining visual function or severe visual loss at presentation. 1, 3, 4

• Ventriculoperitoneal (VP) shunt is the preferred CSF diversion procedure due to lower revision rates per patient 1, 4
• Use neuronavigation for VP shunt placement 1
• Consider adjustable valves with antigravity or antisiphon devices to reduce low-pressure headache risk 1
• Lumboperitoneal shunt is an alternative option 1
• Temporizing lumbar drain can protect vision while planning definitive surgery 1, 3, 4
• Counsel UK patients to inform Driver and Vehicle Licensing Agency after VP shunt placement 1

For Mild to Moderate Visual Loss

Acetazolamide is first-line medical therapy for symptomatic patients or those with evidence of visual loss 4, 5

Critical Exception: Avoid acetazolamide in patients with kidney stones 3

• Use topiramate instead as first-line therapy in patients with kidney stone history, despite its 1.5% kidney stone risk 3
• Topiramate provides dual benefits: intracranial pressure reduction and appetite suppression leading to weight loss 3
• Titrate slowly to therapeutic dose 3
• Warn patients about depression, cognitive slowing, and teratogenic effects 3
• Consider zonisamide if topiramate side effects are excessive 3

Monitoring Schedule Based on Severity

• Severe papilledema: monitor every 1-3 months 3
• Moderate papilledema with visual symptoms: follow-up within 1-3 months 4
• Adjust frequency based on papilledema grade and visual field status 4

2. Treat the Underlying Disease (Disease-Modifying)

Weight loss is the ONLY disease-modifying treatment for IIH and must be implemented in all overweight patients regardless of other interventions. 1, 3, 4

• Target 5-10% weight loss through structured weight management program 3, 4, 5
• Implement low-salt diet 3, 4
• 5-15% weight loss may achieve disease remission 1, 4
• Refer to community or hospital-based weight management program 1
• Consider bariatric surgery for sustained weight loss when conservative measures fail, though more prospective evidence is needed 1
• Continue weight loss efforts even after surgical intervention, as surgery does not address underlying disease 1, 4

3. Minimize Headache Morbidity

• Document headache features, frequency, and severity using validated disability scores (e.g., HIT-6) 2
• Headache phenotype is highly variable and may mimic primary headache disorders 1, 2
• One-third to one-half of patients fail to achieve headache improvement despite treatment 4
• Address medication overuse if present 1

Treatment Duration and Monitoring

IIH treatment is outcome-driven, not time-limited. 4

• 34% of patients experience treatment failure at 1 year; 45% at 3 years 4
• Continue treatment as long as papilledema persists 4
• Serial visual field testing and optic disc assessment guide therapy continuation, escalation, or tapering 4
• Never stop treatment based solely on symptom improvement without objective evidence of papilledema resolution and stable visual fields 4
• Following venous sinus stenting, long-term antithrombotic therapy required for >6 months 4
• CSF shunt patients require lifelong monitoring 4

Critical Pitfalls to Avoid

• Do not use steroids as primary treatment - they worsen IIH and promote weight gain 4
• Do not rely on CT alone - many IIH patients have normal CT scans; MRI is essential 2
• Do not perform lumbar puncture with improper technique (sitting position, legs flexed, Valsalva) - this causes false readings 2
• Do not assume normal imaging excludes IIH - subtle findings are common and diagnostically important 6
• Do not delay surgical intervention when vision is declining - irreversible visual loss can occur 1, 3

Special Populations

Pregnancy

• Multidisciplinary communication required throughout pregnancy, peridelivery, and postpartum 4
• Use acetazolamide with caution after clear risk-benefit assessment 4

Pediatric Patients

• In non-obese prepubertal children, particularly consider cerebral venous sinus thrombosis as secondary cause 2
• MRI provides superior soft tissue contrast and is particularly valuable in pediatric patients 2