Idiopathic Intracranial Hypertension

Aka: Idiopathic Intracranial Hypertension, Pseudotumor Cerebri, Benign Intracranial Hypertension

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II. Epidemiology

  1. Incidence
    1. General Population: 0.9 per 100,000
    2. Women aged 15 to 44 years: 3.5 per 100,000
    3. Obese women aged 20 to 44 years: 19.3 per 100,000
    4. Pseudotumor may occur in children and must be kept in differential in refractory new Headache
      1. (2015) Pediatr Emer Care 31:6-9 [PubMed]
  2. Rare (similar Incidence to other rare neurologic syndromes)
    1. Amyotrophic Lateral Sclerosis
    2. Guillain Barre Syndrome
    3. Muscular Dystrophy

III. Pathophysiology

  1. Intracranial Hypertension due to dysregulated CSF dynamics (mechanism not defined)
  2. Cerebrospinal Fluid
  3. Cerebral Ventricle

IV. Causes

  1. See Increased Intracranial Pressure Causes
  2. See Headache Causes

V. Symptoms

  1. See Headache History
  2. Headache
    1. Location
      1. Retro-orbital or frontal Headache
    2. Provocative
      1. Eye movement worsens Headache
    3. Timing
      1. Chronic Daily Headache
      2. Often insidious onset developing over weeks
      3. Worse on awakening
    4. Characteristics
      1. Throbbing Headache
    5. Associated Symptoms
      1. Nausea and Vomiting
  3. Transient Decreased Visual Acuity (75%)
    1. Monocular or Binocular Acute Vision Loss
    2. Lasts for only a few seconds
    3. Transient Optic Nerve ischemia
      1. Optic Disc edema may be present on fundoscopic exam
    4. Permanent visual changes occur uncommonly
      1. Profound Vision Loss or blindness (severe cases, may occur in 5-10%)
      2. Increased blind spot may occur with prolonged Papilledema (10% of cases)
        1. Blurred Vision or Tunnel Vision
        2. Dark spot in temporal Visual Field
    5. Other visual changes
      1. Photophobia
      2. Diplopia
  4. Pulsatile Tinnitus (50-60%)
    1. Unilateral or bilateral "whooshing" sound
    2. Palliative:
      1. Lumbar Puncture
      2. Jugular venous compression
  5. Musculoskeletal symptoms
    1. Neck Pain or neck stiffness
    2. Back pain
    3. Arthralgias (Shoulder, wrist, knee)
  6. Neurologic Symptoms and Psychiatric Symptoms
    1. Cranial Nerve 6 Palsy (binocular Diplopia)
    2. Paresthesias
    3. Radicular pain
    4. Facial palsy
    5. Impaired concentration or memory
    6. Major Depression

VI. Signs

  1. See Headache Exam
  2. Ophthalmoscopy (Fundoscopy)
    1. Decreased venous pulsations
    2. Papilledema
      1. Not predictive of visual outcome
  3. Visual Field Defects
    1. Best detected by perimetry (Visual Field testing)
    2. Blind spot enlargement
    3. Inferonasal visual loss
    4. Visual Field constriction (tunnel Vision)
      1. Central Vision Loss is a late finding
  4. Decreased Ocular Motility
    1. Cranial Nerve 6 Palsy

VII. Diagnostics: Lumbar Puncture

  1. Opening Pressure consistent with Pseudotumor Cerebri (Idiopathic Intracranial Hypertension)
    1. Obese Children > 280 mm of water (28 cm water)
    2. Non-obese Patient > 250 mm of water (25 cm water)
    3. Non-diagnostic: 200 to 250 mm of water (20 to 25 cm water)
  2. Opening Pressure falsely elevated by:
    1. Sitting position
    2. Prone position (fluoroscopy)
    3. Painful tap
    4. Anxiety
      1. Consider pretreating LP with Benzodiazepine
  3. Send CSF for spinal fluid analysis
    1. CSF Glucose
    2. CSF Protein
    3. CSF Cell Count
    4. CSF Cultures (Bacteria, fungi, Tuberculosis)
    5. CSF Cytology

VIII. Imaging

  1. Orbital Ultrasound
    1. Optic Nerve Sheath Diameter (ONSD) >5mm is consistent with Increased Intracranial Pressure
      1. ONSD >6mm has a Test Sensitivity 74%, Test Specificity 68% for Pseudotumor Cerebri
      2. Optic Disc elevation > 0.6 mm has a Test Sensitivity 100%, Test Specificity 83% for pseudotumor
      3. Korsbæk (2022) Cephalalgia 42(11-12):1116-26 +PMID: 35469442 [PubMed]
  2. CT Head
    1. Consider in the Emergency Department evaluation of Intracranial Hemorrhage (e.g. acute Thunderclap Headache, Trauma)
    2. Consider CT Venography (CTV Head) to evaluate for Cerebral Venous Thrombosis
  3. Head MRI (preferred over CT Head)
    1. Negative MRI does not exclude Idiopathic Intracranial Hypertension (but does evaluate for other causes)
    2. Ventricles may be decreased in size (slit-like) or may be normal
    3. Empty Sella Sign
      1. Test Sensitivity: 48 to 74%
      2. Test Specificity: 84 to 94%
    4. Posterior Globe Flattening
      1. Test Sensitivity: 46 to 65%
      2. Test Specificity: 85 to 98%
    5. Optic Nerve Tortuosity
      1. Test Sensitivity: 26 to 48%
      2. Test Specificity: 82 to 92%
    6. Transverse Sinus Stenosis
      1. Test Sensitivity: 65 to 94%
      2. Test Specificity: 92 to 97%
    7. References
      1. Kwee (2019) Eur J Radiol 116: 106-15 +PMID: 31153551 [PubMed]

IX. Diagnosis: Headache Attributable to Idiopathic Intracranial Hypertension (ICHD-3 Criteria)

  1. New or significantly worsened Headache AND
  2. Idiopathic Intracranial Hypertension diagnosed and CSF Pressure >25 cm (or >28 cm in obese children) AND
  3. At least one of the following
    1. Headache has developed or significantly worsened in temporal relation to IIH or led to its diagnosis
    2. Headache is accompanied by pulsatile Tinnitus or Papilledema
  4. Not better described by another ICHD-3 Diagnosis
  5. Reference: ICHD-3
    1. https://ichd-3.org/7-headache-attributed-to-non-vascular-intracranial-disorder/7-1-headache-attributed-to-increased-cerebrospinal-fluid-pressure/7-1-1-headache-attributed-to-idiopathic-intracranial-hypertension-iih/

X. Differential Diagnosis

  1. See Headache Causes
  2. Migraine Headache
  3. Chronic Daily Headache
  4. Rebound Headache (Analgesic overuse)
  5. Subarachnoid Hemorrhage

XI. Precautions

  1. Delayed diagnosis is common (often missed on initial clinical evaluations)

XII. Management: Acute Presentation

  1. Consultations
    1. Neurology Consultation
    2. Ophthalmology Consultation
  2. Hospital Admission Indications
    1. Papilledema (esp. moderate to severe)
    2. Elevated Intracranial Pressure
    3. Acute Decreased Visual Acuity
    4. Uncontrolled pain
    5. Unreliable follow-up
  3. Severe Papilledema (or severely Increased Intracranial Pressure, or acute severe Vision changes worse than 20/70)
    1. Acetazolamide 4 g every 24 hours IV
    2. May require surgical intervention (see below, Optic Nerve Sheath fenestration)
  4. Moderate Papilledema
    1. Acetazolamide 1 g every 24 hours IV
  5. No or minimal Papilledema (no Vision change, mild symptoms e.g. Headache, Nausea)
    1. May discharge home with follow-up with neurology and ophthalmology
    2. Follow medical management as below (transitioning to oral Diuretics)
  6. Other acute measures to consider
    1. Systemic Corticosteroids
    2. Mannitol 20%
    3. Therapeutic large volume Lumbar Puncture
      1. Removal of 20 to 25 ml of spinal fluid
    4. Surgical intervention (see below, Optic Nerve Sheath fenestration)

XIII. Management: Medical Maintenance

  1. Neurology Consultation
  2. Weight loss
  3. Dietary changes
    1. Low salt diet
    2. Low tyramine diet
  4. Precautions
    1. Avoid Medication Causes of Increased Intracranial Pressure
  5. Diuretics
    1. Acetazolamide (Diamox, preferred)
      1. Dose: 250 to 500 mg every 12 hours
      2. May titrate per effect up to maximum of 4000 mg/day
    2. Alternatives to the preferred Acetazolamide
      1. Furosemide (Lasix)
        1. Dose: 20 mg every 12 hours
        2. May titrate per effect up to maximum of 100 mg/day
      2. Topiramate
        1. Topiramate has carbonic anhydrase inhibitor activity
  6. Systemic Corticosteroids
    1. Reserved for acute severe cases or urgent management of Vision Loss
    2. Prednisone 1-2 mg/kg orally daily for 2-6 weeks (with taper)
  7. Headache Management
    1. Acute Treatment: NSAIDs
    2. Prophylaxis: Tricyclic Antidepressants
  8. Therapeutic large volume Lumbar Puncture
    1. Removal of 20 to 25 ml of spinal fluid

XIV. Management: Surgical

  1. Optic Nerve Sheath Decompression (fenestration)
    1. Indicated for associated Decreased Visual Acuity (not recommended for Headache alone)
    2. Window or fenestration cut in Optic Nerve sheath
    3. Acutely lowers CSF Pressure in subarachnoid space around the Optic Nerve
      1. Results in increased Blood Flow to the Optic Nerve
      2. Fenestration site scarring may also help limit Elevated ICP transmission to the Optic Nerve
  2. Cerebrospinal Fluid Shunt
    1. Lumboperitoneal shunt (preferred over Ventriculoperitoneal Shunt)
    2. Short term: Very effective
    3. Long term: Multiple revisions often required
    4. Complications
      1. Low pressure Headaches
      2. Tonsillar Herniation
      3. Lumbar Radiculopathy
      4. Shunt malfunction

XV. Management: Pregnancy

  1. Careful follow-up
    1. Frequent Neurology evaluation
    2. Frequent Ophthalmology evaluation
    3. Repeated Lumbar Puncture monitoring
  2. Intervention
    1. Acetazolamide (Diamox) after 20 weeks gestation
    2. Systemic Corticosteroids for Vision deterioration
    3. Optic Nerve Sheath Decompression
    4. Ventriculoperitoneal Shunt
  3. Contraindicated Agents
    1. Avoid Tricyclic Antidepressants
    2. Avoid Thiazide Diuretics

XVI. Complications

  1. Blindness

XVII. References

  1. Jundoria, Dave, Hoag and Lopez (2026) Crit Dec Emeg Med 40(5): 4-11
  2. Marcolini and Swaminathan (2024) Neurocritical Care: Idiopathic Intracranial Hypertension, EM:Rap, 8/19/2024
  3. Friedman (1999) Neurosurg Clin N Am 10(4):609-21 [PubMed]

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