Idiopathic intracranial hypertension

Background

aka. pseudotumor cerebri

Definition

• Increase in intracranial pressure without an identifiable cause
• Defined as elevated opening pressure > 25cm H2O on lumbar puncture without identifiable intracranial structural pathology

Pathophysiology

• Most likely from elevated venous pressure causing decreased CSF resorption

Risk Factors

• Obese female of child-bearing age
• Hypervitaminosis A
• Tetracycline antibiotics
• Isotretinoin
• Oral contraceptive pills
• Phenytoin
• Pregnancy
• Glucocorticoid use or withdrawal

Clinical Manifestations

• History
  • Diffuse, steady or throbbing headache that is worse in the morning
  • Visual obscurations: bilateral dimming of vision lasting seconds
  • Blurred vision, scotomas, and diplopia
  • Pulsatile tinnitus, dizziness, and neck pain
• Signs & Symptoms
  • Papilledema
  • Strabismus from CN VI palsy

Differential Diagnosis

• Primary or idiopathic: includes obesity, recent weight gain, polycystic ovarian syndrome, and thin children
• Secondary
  • Cerebral venous abnormalities
    • Cerebral venous sinus thrombosis
    • Bilateral jugular vein thrombosis or surgical ligation
    • Otitis media or mastoid infection
    • Right heart failure
    • Superior vena cava syndrome
    • Arteriovenous fistula
    • Decreased CSF absorption from prior infection or subarachnoid hemorrhage
  • Medications and other exposures
    • Antibiotics: tetracycline, minocycline, doxycycline, nalidixic acid, sulfa drugs
    • Vitamin A and retinoids: hypervitaminosis A, isotretinoin, all-trans retinoic acid, excessive liver ingestion
    • Hormones: human growth hormone, thyroxine (in children), leuprorelin acetate, levonorgestrel, anabolic steroids
    • Withdrawal from chronic corticosteroids
    • Lithium
    • Chlordecone
  • Medical conditions
    • Endocrine disorders: Addison disease, hypoparathyroidism, hypothyroidism
    • Hypercapnia: sleep apnea, Pickwickian syndrome, COPD
    • Infections: otitis media, Lyme disease, HIV, sinusitis, VZV, pharyngitis from group B streptococci, other febrile illnesses
    • Anemia
    • Renal failure
    • Systemic lupus erythematosus
    • Sarcoidosis
    • Turner syndrome
    • Down syndrome

Investigations

• Imaging
  • MRI brain may show small ventricles, partially empty sella turcica, widening of the optic nerve sleeves, optic nerve buckling, or flattening of the optic globes, or may be normal
• Other
  • Lumbar puncture with opening pressure for diagnosis
  • Visual field testing is crucial

Diagnosis

Modified Dandy criteria1

• Papilledema, with all of the following:
  • Normal neurologic examination except for cranial nerve abnormalities
  • Neuroimaging showing
    • Typical patients (female and obese): normal brain parenchyma without evidence of hydrocephalus, mass, or structural lesion, and no abnormal meningeal enhancement on MRI (with and without gadolinium)
    • Others: MRI (with and without gadolinium) plus MRV
    • If MRI unavailable, then CT with contrast
  • Normal CSF
  • Elevated lumbar puncture opening pressure ≥250 mm in adults or ≥280 mm in children
• No papilledema:
  • All of the above criteria are met, plus there is unilateral or bilateral abducens nerve palsy
• No papilledema, and no abducens nervy palsy:
  • Cannot be diagnosed, but can be suggested if all of the above criteria are met, plus at least 3 of the following are seen on neuroimaging:
    • Empty sella
    • Flattening of the posterior aspect of the globe
    • Distention of the perioptic subarachnoid space with or without a tortuous optic nerve
    • Transverse venous sinus stenosis

Management

Acute

• Discontinue offending medication, if any
• LP for decompression, including repeated
• May need surgical intervention if sight is threatened or treatment with medication fails

Chronic

• Medication
  • Acetazolamide 250-500 mg p.o. twice daily, and titrated up
  • Topiramate
  • Corticosteroids
• Repeat LPs, often every 1-3 months despite medications
• Remove causative factors, including counselling on weight loss
• Refer to Ophthalmology and Neurology