What is the diagnostic approach and initial treatment for idiopathic intracranial hypertension (IIH)?

Diagnostic Approach to Idiopathic Intracranial Hypertension (IIH)

The diagnosis of idiopathic intracranial hypertension requires urgent neuroimaging with MRI brain within 24 hours, followed by lumbar puncture showing elevated opening pressure with normal CSF composition, and the presence of papilledema in most cases. 1, 2

Clinical Presentation

• Headache is the most common presenting symptom, typically progressively more severe and frequent, with a variable phenotype that may mimic other primary headache disorders 2, 3
• Transient visual obscurations (unilateral or bilateral darkening of vision lasting seconds) are common 2
• Pulsatile tinnitus (whooshing sound in ears synchronous with pulse) is frequently reported 2, 4
• Visual blurring and horizontal diplopia may occur 2, 5
• Additional symptoms may include dizziness, neck pain, back pain, cognitive disturbances, and radicular pain 2
• Papilledema is the hallmark finding on examination 1, 6
• Sixth cranial nerve palsy may be present, but involvement of other cranial nerves suggests alternative diagnoses 1

Diagnostic Algorithm

Step 1: Neuroimaging

• Urgent MRI brain within 24 hours 1, 2
• If MRI unavailable within 24 hours, perform urgent CT brain with subsequent MRI 1
• CT or MR venography is mandatory to exclude cerebral sinus thrombosis 1, 2
• Neuroimaging should show:
  • No evidence of hydrocephalus, mass, structural or vascular lesion 1, 6
  • No abnormal meningeal enhancement 1
  • May show secondary signs of increased ICP (empty sella, dilated optic sheaths, tortuous optic nerves, flattening of posterior globe, transverse sinus stenosis) 6

Step 2: Lumbar Puncture

• Perform after normal neuroimaging 1
• Measure opening pressure in lateral decubitus position 1
• Diagnostic criteria:
  • Opening pressure >250 mm CSF in adults 6
  • Normal CSF composition 6

Step 3: Ophthalmologic Assessment

• Document visual acuity 1
• Perform pupil examination 1
• Conduct formal visual field assessment 1
• Dilated fundal examination to grade papilledema 1
• Consider formal documentation with serial photographs or OCT imaging 1

Step 4: Patient Categorization

• Typical IIH: Female, reproductive age, BMI ≥30 kg/m² 1, 6
• Atypical IIH: Not female, not of reproductive years, BMI <30 kg/m² 1
• Fulminant IIH: Vision at imminent risk 1

Initial Management Approach

1. Weight loss for all patients with BMI >30 kg/m² (disease-modifying therapy) 1

   • Counsel about weight management at earliest opportunity 1
   • Refer to community or hospital-based weight management program 1

2. Protect vision

   • For imminent risk of visual loss, consider surgical management 1
   • Regular ophthalmology assessments to monitor visual function 1

3. Manage headache symptoms

   • Medical therapy may include acetazolamide and topiramate 5

Common Pitfalls and Caveats

• Headache characteristics in IIH are highly variable and may mimic other primary headache disorders, making clinical diagnosis challenging 2
• IIH without papilledema is a rare subtype that meets all other criteria but lacks papilledema 2
• Secondary causes of intracranial hypertension must be excluded, including cerebral venous abnormalities, medications (vitamin A, retinoids, steroids), and endocrine disorders 6
• If other cranial nerves besides CN VI are involved, or other pathological findings are present, consider alternative diagnoses 1