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Idiopathic Intracranial Hypertension

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Overview

Also known as pseudotumor cerebri, idiopathic intracranial hypertension (IIH) is classically seen in overweight women of childbearing potential and is a raised intracranial pressure (ICP) in the absence of a mass or hydrocephalus.

It is thought to be due to reduced cerebrospinal fluid (CSF) absorption.

Epidemiology

  • Most often seen in obese women of childbearing age
  • Prevalence is increasing with time and this is thought to be due to increasing obesity

Risk Factors

Presentation

  • IIH classically presents in an obese woman of childbearing potential with features of a raised ICP, usually a headache and papilloedema. Some features are:
    • Headaches – usually throbbing in nature and worse with lying down
    • Blurred vision
    • Papilloedema – seen as optic disc margin blurring
    • Enlarged blind spot
    • CN VI palsy may sometimes be present
    • A relative afferent pupillary defect may be present
    • Photophobia may be present
    • Tinnitus that comes on in sync with the pulse may be present

Differential Diagnoses

Any other case of raised ICP

  • Without investigations, any other cause of a raised ICP (e.g. tumours) cannot be ruled out clinically

Investigations

  • Visual field testing:
    • To assess visual field defects
  • Fundoscopy:
    • Shows papilloedema
  • Visual acuity:
    • Usually normal or minimally impaired
  • MRI brain:
    • To rule out mass lesions e.g. tumours
  • Lumbar puncture:
    • Once mass lesions are ruled out
    • Shows elevated opening pressure

Management

  • 1st-line: weight loss + manage underlying risk factors e.g. stop offending drugs
  • Offer acetazolamide or topiramate – these can help reduce ICP and protect vision
  • Consider repeated lumbar punctures
  • Consider surgery:
    • Optic nerve sheath fenestration – decompresses the optic nerve
    • CSF shunting
    • Intracranial venous sinus stenting

Monitoring and Patient Advice

Monitoring

  • Patients with mild-moderate vision loss are usually followed up every 2-6 weeks
  • Patients with more severe papilloedema and visual loss are followed up more closely

Patient Advice

  • Patients should be encouraged to lose weight and should be helped with this
  • Patients should also aim to reduce sodium in their diet
  • Patients should be safety-netted on symptoms and seek help if symptoms return

Complications and Prognosis

Complications

  • Irreversible vision loss – patients with severe vision loss and papilloedema should be considered for prompt surgery

Prognosis

  • IIH can be self-limiting or lifelong
  • IIH does not have any known or specific effect on mortality
  • Delay in identification and treatment is associated with a worse prognosis

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