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 primary imaging modality, followed by MR venography, lumbar puncture with opening pressure measurement, and confirmation that the patient meets all diagnostic criteria including papilledema, normal neurological exam, normal brain imaging, normal CSF composition, and elevated opening pressure. 1, 2

Diagnostic Criteria

• Papilledema must be present (though in rare cases may be absent) 3
• Normal neurological examination (except possible sixth nerve palsy) 4, 2
• Normal brain parenchyma on imaging (absence of mass, hydrocephalus, or abnormal meningeal enhancement) 4, 2
• Normal cerebrospinal fluid composition 2, 3
• Elevated lumbar puncture opening pressure:

  • 280 mm CSF in children 4

  • 250 mm CSF if the child is not sedated and not obese 4

Step-by-Step Diagnostic Approach

Step 1: Initial Clinical Assessment

• Evaluate for common symptoms:
  • Headache (most common symptom, present in 76.2% of patients) 5
  • Visual disturbances including transient obscurations 1
  • Papilledema on fundoscopic examination 3
• Identify risk factors:
  • Obesity (especially in females of childbearing age) 3
  • Recent medication use (tetracyclines, vitamin A, retinoids, steroids, growth hormone, thyroxine, lithium) 4, 1
  • Endocrine disorders (Addison disease, hypoparathyroidism) 4, 3

Step 2: Neuroimaging

• MRI of the head and orbits is the most useful imaging modality 4
  • Provides higher resolution of intracranial and intraorbital structures 4
  • Can detect characteristic findings of IIH:
    • Posterior globe flattening (56% sensitivity, 100% specificity) 4
    • Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity) 4
    • Horizontal tortuosity of the optic nerve (68% sensitivity, 83% specificity) 4
    • Enlarged optic nerve sheath (mean 4.3 mm vs 3.2 mm in controls) 4
    • Partially empty sella 4, 3
    • Smaller pituitary gland size (mean 3.63 mm vs 5.05 mm in controls) 4

Step 3: Venous Imaging

• MR venography (MRV) of the head is essential to:
  • Demonstrate narrowing of the distal transverse sinuses (supportive of IIH diagnosis) 4
  • Exclude cerebral venous sinus thrombosis (a cause of secondary pseudotumor cerebri) 4, 2
• CT venography (CTV) may be used as an alternative to MRV 4

Step 4: Lumbar Puncture

• Measure opening pressure (diagnostic criterion)

  • 280 mm CSF in children 4

  • 250 mm CSF in non-sedated, non-obese children 4

• Analyze CSF composition (must be normal) 2, 3
  • Cell count
  • Protein
  • Glucose

Step 5: Rule Out Secondary Causes

• Medications: tetracyclines, vitamin A, retinoids, steroids, growth hormone, thyroxine, lithium 4, 1
• Endocrine disorders: Addison disease, hypoparathyroidism 4, 3
• Cerebral venous abnormalities: thrombosis, stenosis 2, 3

Common Pitfalls and Caveats

• Avoid the term "benign intracranial hypertension" as untreated papilledema can lead to progressive irreversible visual loss and optic atrophy 6, 7
• Do not rely solely on clinical findings to diagnose IIH, as they can be non-specific 2
• In prepubertal children, boys and girls are equally affected, unlike the female predominance in postpubertal cases 4
• Abnormal intracranial pressure can persist for extended periods, even in asymptomatic patients, requiring careful follow-up 8
• Secondary forms of pseudotumor cerebri must be thoroughly investigated, especially in non-obese patients 2, 5
• Visual field testing is essential to monitor for progressive visual loss, which can occur despite adequate treatment 6