What are the diagnostic features and management of Idiopathic Intracranial Hypertension (IIH)?

Idiopathic Intracranial Hypertension: Diagnostic Features and Management

Idiopathic Intracranial Hypertension (IIH) is characterized by elevated intracranial pressure without identifiable cause, requiring diagnosis based on modified Dandy criteria with CSF opening pressure ≥25 cm H₂O, normal neuroimaging, normal CSF composition, and normal neurological examination except for papilledema and possible sixth nerve palsy. 1

Clinical Presentation and Classification

Patient Demographics

• Typical IIH: Female, reproductive age, BMI >30 kg/m² 2
• Atypical IIH: Male, non-reproductive age, or BMI <30 kg/m² (requires more thorough investigation) 2
• Fulminant IIH: Rapid decline in visual function within 4 weeks of diagnosis 2
• IIH without papilledema: Meets all criteria except papilledema 2
• IIH in ocular remission: Previously diagnosed IIH with resolved papilledema 2

Common Symptoms

• Headache (90%)
• Visual disturbances (62%)
• Papilledema (89%)
• Pulsatile tinnitus (48%) 3

Diagnostic Criteria and Evaluation

Required Diagnostic Steps:

1. Neuroimaging:

   • Urgent MRI brain within 24 hours (or CT if MRI unavailable)
   • CT or MR venography to exclude cerebral sinus thrombosis
   • No evidence of hydrocephalus, mass, structural or vascular lesion 2

2. Lumbar Puncture:

   • Opening pressure ≥25 cm H₂O measured in lateral decubitus position
   • Normal CSF composition (glucose, protein, cell count) 1

3. Neurological Examination:

   • Normal except for possible papilledema and sixth nerve palsy
   • Other cranial nerve involvement suggests alternative diagnosis 2

4. Ophthalmological Assessment:

   • Visual acuity
   • Visual fields
   • Fundus examination for papilledema 1

Management Approach

Primary Treatment: Weight Loss

• Only disease-modifying therapy for typical IIH
• All patients with BMI >30 kg/m² should receive weight management counseling
• Up to 15% weight loss may be required for disease remission 2, 1
• Referral to structured weight management program recommended 2

Pharmacological Treatment

• First-line: Acetazolamide

  • Initial dose: 250-500 mg twice daily
  • Can be increased to 2-4 g daily based on tolerance 1
  • Demonstrated efficacy in the IIHTT study for visual outcomes 4

• Alternative: Topiramate

  • Benefits: weight loss promotion, migraine control, carbonic anhydrase inhibition
  • Contraindicated in pregnancy due to fetal abnormality risk 1

Surgical Interventions (for medically refractory cases)

Indicated when:

• Medical therapy fails
• Visual function deteriorates
• Persistent headaches despite medical management 1

Surgical Options:

1. Venous Sinus Stenting (VSS):

   • Best results for headache resolution (72.1%) and visual outcomes
   • Low complication rate (2.3%) and failure rate (11.3%)
   • Considered when pressure gradient ≥8 mmHg in venous sinus 5, 1

2. CSF Diversion Techniques:

   • Improves papilledema (78.9%), visual fields (66.8%), and headaches (69.8%)
   • Higher complication rate (9.4%) and failure rate (43.4%) 5

3. Optic Nerve Sheath Fenestration (ONSF):

   • Improves papilledema (90.5%), visual fields (65.2%), and headaches (49.3%)
   • Low complication rate (2.2%) and failure rate (9.4%) 5

Monitoring and Follow-up

• Regular ophthalmological monitoring for visual acuity, fields, and fundus examination
• Consider diagnostic LP if significant visual deterioration occurs
• Follow-up schedule:
  • Early review: 24-48 hours post-intervention
  • Intermediate follow-up: 10-14 days or 3-6 weeks
  • Late follow-up: 3-6 months 1

Special Considerations

• Pregnancy: Multidisciplinary approach required; acetazolamide generally avoided
• Non-obese patients: Investigate for secondary causes of intracranial hypertension
• Atypical presentations: Require more thorough investigation 2, 1

Prognosis

With accurate diagnosis and timely treatment, prognosis is generally good, particularly for vision preservation. Early intervention is crucial to prevent permanent visual loss 1.