IDIOPATHIC INTRACRANIAL HT

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  • What is idiopathic intracranial hypertension & when does it occur?
    • Increased intracranial pressure without obvious or known cause.
    • Proposed etiologies include: CSF absorption abnormality, decreased venous drainage, or overall increased cerebral water content.
  • Typical clinical history
    • Young to middle-aged obese female, majority are African American, presents with recurrent headaches, papilledema, cranial nerve VI palsies, and/or visual field defects.
  • Best imaging modality: MR
  • Imaging findings
    • CT (non-contrast)
      • Important to rule out intracranial mass or other causes of papilledema.
      • May appear normal
      • Possibly enlarged bilateral optic nerves, empty sella (if sella is seen)
      • Less commonly slit like ventricles (10%)
    • MR
      • T1: (Partially) empty sella, tortuous optic nerves, posterior scleral flattening
      • T2: Enlarged, hyperintense signal around optic nerves (increased nerve sheath fluid); may demonstrate bulbous dilation of the nerve sheath behind the globes
    • MRV: Excludes dural sinus thrombosis / stenosis (secondary pseudotumor cerebri)
  • Imaging findings of differential diagnoses:
    • Optic neuritis (idiopathic or MS-related): enhancing, mildly enlarged optic nerves that demonstrate hyperintense T2 signal; usually unilateral
    • Optic nerve papillitis: optic neuritis focal to the retrobulbar optic nerve; usually unilateral
    • Empty sella, normal variant: normal optic nerve sheaths, intrasellar CSF (T1 hypointense, T2 hyperintense), flattened pituitary
    • Secondary pseudotumor cerebri: same imaging findings as idiopathic intracranial hypertension but also associated with the following:
      • Medications: lithium, OCPs, tetracycline, and steroids (use or cessation)
      • Medical conditions: venous sinus thrombosis, Lyme disease, lupus, renal disease, mononucleosis, or head injury
  • Complications/treatment
    • Ophthalmic emergency, may progress to optic neuropathy +/- constriction of the field of vision and loss of color vision; blindness in 10% of patients
    • Many spontaneously, completely regress
    • For persistent symptoms
      • Medical: diuretics or carbonic anhydrase inhibitors +/- weight loss
      • Procedural: repeat lumbar punctures, placement of a CSF drain, optic nerve sheath fenestration
   source : auntminnie.com

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