What are the steps to diagnose pseudotumor cerebri (idiopathic intracranial hypertension)?

Diagnosing Pseudotumor Cerebri (Idiopathic Intracranial Hypertension)

The diagnosis of pseudotumor cerebri requires MRI of the head and orbits as the initial imaging modality, followed by MR venography, lumbar puncture with opening pressure measurement, and confirmation that all diagnostic criteria are met. 1, 2

Diagnostic Criteria

Pseudotumor cerebri (idiopathic intracranial hypertension) is diagnosed when all of the following criteria are met:

• Papilledema on ophthalmologic examination 1, 2
• Normal neurological examination (except possible sixth nerve palsy) 1, 2
• Normal brain parenchyma on neuroimaging (absence of mass, hydrocephalus, or abnormal meningeal enhancement) 1, 2
• Normal cerebrospinal fluid composition 1, 2
• Elevated lumbar puncture opening pressure:

  • 280 mm CSF in children 3, 2

  • 250 mm CSF if the child is not sedated and not obese 3, 2

Diagnostic Algorithm

Step 1: Initial Clinical Evaluation

• Look for characteristic symptoms:
  • Headache (most common symptom, present in 76.2% of pediatric cases) 4
  • Visual disturbances (transient obscuration of vision) 3, 5
  • Nausea and vomiting 3
• Identify risk factors:
  • Obesity (most common in overweight females of childbearing age) 5, 6
  • Medications (tetracyclines, vitamin A, retinoids, steroids, growth hormone, thyroxine, lithium) 1, 5
  • Endocrine disorders (Addison disease, hypoparathyroidism) 3, 5

Step 2: Neuroimaging

• MRI of the head and orbits (with and without contrast) is the preferred initial imaging modality 3, 1, 2

  • Look for secondary signs of increased intracranial pressure:
    • Empty or partially empty sella (reduced pituitary gland size) 3, 5
    • Posterior globe flattening (56% sensitivity, 100% specificity) 3
    • Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity) 3
    • Horizontal tortuosity of the optic nerve (68% sensitivity, 83% specificity) 3
    • Enlarged optic nerve sheath (mean 4.3 mm vs 3.2 mm in controls) 3
    • Transverse sinus stenosis 5

• MR venography (MRV) or CT venography (CTV) must be performed to:

  • Evaluate cerebral venous sinuses 3, 2
  • Exclude cerebral venous sinus thrombosis (a cause of secondary pseudotumor cerebri) 3, 2

Step 3: Lumbar Puncture

• Measure opening pressure in lateral decubitus position 1, 2
• Analyze CSF composition to ensure it is normal 1, 2
• Note: Pressure waves up to 70 mm Hg can occur in some patients 7

Step 4: Ophthalmologic Examination

• Document presence of papilledema 1, 2
• Perform formal visual field testing to assess for visual deficits 6
• Monitor for optic atrophy (a late finding indicating permanent damage) 6, 7

Differential Diagnosis Considerations

• Rule out secondary causes of increased intracranial pressure:
  • Space-occupying lesions 3
  • Hydrocephalus 3
  • Cerebral venous abnormalities including thrombosis 2, 5
  • Medication-induced pseudotumor cerebri 5, 4
  • Endocrine disorders 2, 5

Pitfalls and Caveats

• The term "benign intracranial hypertension" should be avoided as untreated pseudotumor cerebri can lead to permanent visual loss 6, 8
• In the absence of papilledema, diagnosis can still be made based on neuroimaging findings and elevated opening pressure 3
• Abnormalities in intracranial pressure and CSF outflow can persist even in asymptomatic patients 7
• Non-obese patients and prepubertal children require more thorough investigation for secondary causes 2, 4
• Despite adequate treatment, children can rarely experience permanent loss of visual field and acuity 4