What is idiopathic intracranial hypertension (IIH) in obese women of childbearing age?

What is Pseudotumor Cerebri (Idiopathic Intracranial Hypertension)?

Pseudotumor cerebri, also known as idiopathic intracranial hypertension (IIH), is a syndrome of elevated intracranial pressure without an identifiable structural cause that most commonly affects obese women of childbearing age and can lead to permanent vision loss if untreated. 1, 2

Definition and Terminology

• Pseudotumor cerebri and idiopathic intracranial hypertension are interchangeable terms referring to the same clinical condition 2
• Primary pseudotumor cerebri syndrome (PTCS) is specifically known as idiopathic intracranial hypertension 1, 2
• This is a diagnosis of exclusion—other causes of increased intracranial pressure must be ruled out before confirming IIH 3

Who Gets This Condition?

The typical patient is an obese woman of childbearing age, but important exceptions exist 1, 4:

• Most commonly affects overweight females of childbearing age 1, 2
• Can also occur in obese males and prepubertal thin girls and boys 1, 2
• In prepubertal children, boys and girls are equally affected, unlike the female predominance seen after puberty 1
• The incidence is rising in parallel with the obesity epidemic 1, 2

Clinical Presentation

Patients typically present with severe headaches and visual disturbances, though the symptom profile can be highly variable 1, 5:

• Headache is the most common presenting symptom—progressively more severe and frequent, with a phenotype that may mimic other primary headache disorders 5
• Transient visual obscurations (unilateral or bilateral darkening of vision lasting seconds) are characteristic 5
• Pulsatile tinnitus (whooshing sound synchronous with pulse) 5
• Visual blurring 5
• Papilledema is the hallmark finding and should be documented 5
• Sixth nerve palsy may be present, but involvement of other cranial nerves should prompt consideration of alternative diagnoses 1, 5

Important caveat: None of these symptoms are pathognomonic for IIH—they can occur in other conditions, making diagnosis challenging 5

Pathophysiology

The exact cause remains unclear, but proposed mechanisms include 1, 2:

• Impaired cerebrospinal fluid (CSF) homeostasis 2
• Altered venous hemodynamics 2
• Reduced cerebral drainage through the internal jugular vein 2
• Increased intracranial CSF volume accumulating in the subarachnoid space 2

Diagnostic Criteria

To diagnose IIH, you must demonstrate elevated intracranial pressure while excluding structural causes 1, 2:

• Papilledema (typically present but not always required) 2
• Normal neurological examination (except possible sixth nerve palsy) 1, 2
• Normal brain parenchyma on imaging—no mass, hydrocephalus, or abnormal meningeal enhancement 1, 2
• Normal cerebrospinal fluid composition 1, 2
• Elevated lumbar puncture opening pressure: ≥25 cm H₂O (≥250 mm H₂O) measured in the lateral decubitus position 5
  • In children: >280 mm CSF (or >250 mm CSF if not sedated and not obese) 1, 2

Critical measurement technique: The patient must be in lateral decubitus position, relaxed, with legs extended and breathing normally, with measurement taken after pressure stabilizes 5

Imaging Findings

MRI is the preferred imaging modality and may show secondary signs of increased intracranial pressure 1:

• Empty sella 1, 2
• Dilated optic sheaths (mean size 4.3 mm in IIH versus 3.2 mm in controls) 5, 2
• Tortuous or enhancing optic nerves 1, 2
• Flattening of the posterior aspects of the globes (56% sensitivity, 100% specificity) 5, 2
• Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity) 5
• Transverse sinus stenosis 2
• Smaller pituitary gland size (mean 3.63 mm in IIH versus 5.05 mm in controls) 5

MRI provides superior soft tissue contrast compared to CT and is particularly valuable in pediatric patients 5

Secondary Causes to Exclude

Secondary pseudotumor cerebri can result from 1, 2:

• Cerebral venous abnormalities such as thrombosis (CT or MR venography is mandatory within 24 hours) 1, 5
• Medications: vitamin A, retinoids, tetracyclines, steroids, growth hormone, thyroxine, lithium 1, 2
• Endocrine disorders: Addison disease, hypoparathyroidism 1, 2

In non-obese prepubertal children, cerebral venous sinus thrombosis should be particularly considered, making venography especially important in this population 5

Most Serious Consequence

The most serious long-term consequence is permanent vision loss from untreated papilledema leading to optic atrophy 6, 3. This makes ophthalmologic monitoring essential in all IIH patients 7, 6.