benign raised idiopathic intracranial hypertension

see also:

• headache
• raised intracranial pressure (ICP)

• aka pseudotumor cerebri
• aka idiopathic intracranial hypertension (IICH)
• a cause of chronic headache

• increasingly common

• most commonly occurs in overweight young women
• medications such as fluoroquinolones and tetracyclines; and vitamin A analogues such as isotretinoin (Roaccutane)

• chronic headaches
  • can be migraine-like and often occurs daily
  • headache may be worse on waking and worse with Valsavre type events such as coughing
• may have:
  • visual impairment
    • may be transient upon standing or bending
    • may have reduced peripheral vision
    • may have blurred vision with loss of acuity and colour sensitivity
  • pulsatile tinnitus worse on lying down
• may have papilloedema
• may have horizontal diplopia secondary to abducens nerve palsy
• may have dizziness
• some have upper cervical or radicular pain
• have double the normal cardiovascular risk, independent of obesity¹⁾
• some may develop thing of skull bone resulting in a CSF leak causing severe postural headaches

• slit-like ventricles
• empty sella syndrome (ESS)
• other radiologic features that are suggestive of this cause²⁾:
  • optic nerve sheath distension
  • posterior globe flattening
  • optic nerve tortuosity in vertical or horizontal planes
  • papilledema/optic nerve head protrusion
  • optic nerve head enhancement
  • Meckel cave enlargement
  • arachnoid pits (aberrant arachnoid granulations) / small meningoceles, typically within the temporal bone and sphenoid wing
  • enlarged oculomotor cistern
  • prominent perivascular spaces
  • transverse sinus stenosis
  • acquired cerebellar tonsillar ectopia
  • increased subcutaneous fat thickness in the scalp and neck (a slim patient is unlikely to develop idiopathic intracranial hypertension)

• confirmed with raised LP opening pressures > 25cm CSF (grey zone is 20-25cm CSF)³⁾

• cerebral venous sinus thrombosis
• iron deficiency anaemia
• see raised intracranial pressure (ICP) for other causes

• if papilloedema present:
  • emergent MRI, CT brain +/- CT venography
  • neurology consult
  • if CT brain / venography normal then confirm Dx by measuring CSF opening pressure via lumbar puncture (LP) manometry
• acetazolamide
  • inhibits carbonic anhydrase and therefore reduces CSF production
  • dosage is 250 mg twice a day, titrated according to benefits and tolerability to a maximum of 4 g per day
  • possible side effects, including diarrhoea, vomiting, low mood, paraesthesia, renal stones and teratogenicity.
  • often poorly tolerated and patients are frequently switched to topiramate
• topiramate
  • inhibits carbonic anhydrase and has the additional benefits of appetite suppression and migraine prevention although there is no randomised evidence of efficacy in IIH
  • starting dose of 25 mg once daily and increased by 25 mg every couple of weeks until achieving a maintenance dose of 50 mg twice a day
  • topiramate is teratogenic (3% risk of major malformations) and should be avoided in pregnancy and it reduces the effectiveness of the combined oral contraceptive pill (OCP)
  • rarely it can cause acute glaucoma and renal stones
• glucagon-like peptide-1 (GLP-1) peptide analogs (eg. Ozempic)
  • are being trialled in IIH as they reduce CSF secretion and can have anti-obesity effects
• consider migraine prevention medications
• weight loss
  • even modest weight reduction (5–10% of body weight) can significantly reduce intracranial pressure and improve symptoms⁴⁾
• warned not to take painkillers, especially opiates, on more than 2 or 3 days in a given week
• regular ophthalmology reviews
• surgical Mx if medical Mx fails or rapid vision loss
  • male patients, and those with severe papilloedema and reduced visual acuity at presentation, are more likely to fail medical therapy⁵⁾
  • V-P shunt
  • optic nerve sheath fenestration