Benign Intracranial Hypertension

 

• Pathophysiology

  • Impaired absorption of CSF from sub-arachnoid space leads to ↑ICP.
  • Aka benign intracranial hypertension, pseudotumor cerebri.

• Signs and symptoms

  Generalised throbbing headache:

  • Worse in the morning and last thing at night.
  • Exacerbated by lying, bending, coughing.

  Visual:

  • Symptoms: blurred vision, field loss ('grey out') on bending, flashes.
  • Signs: papilloedema, enlarged blind spot, absent venous pulsation on fundoscopy.

  Others:

  • Nausea and vomiting.
  • Seizures
  • Cranial nerve 6 palsy leading to diplopia.

• Risk factors

  • Demographic and lifestyle: female, obese, age 20-40.
  • Drugs: tetracycline, minocycline, nitrofurantoin, vitamin A, isotretinoin.

• DDx: Raised intracranial pressure

  • Idiopathic intracranial hypertension.
  • Space-occupying lesion (primary or mets).
  • Haemorrhage: subdural, extradural, sub-arachnoid, intra-cerebral.
  • Cerebral venous thrombosis.
  • Cerebral oedema.
  • Malignant hypertension.

• Investigations

  • CT or MRI: rule out mass, hydrocephalus, or other cause of ↑ICP. Ideally include CT/MR venography to rule out cerebral venous thrombosis.
  • LP: opening pressure >25 cm H20 is diagnostic, 20-25 is borderline.

• Management

  • Weight loss.
  • Acetazolamide: carbonic anhydrase inhibitor that reduces CSF production.
  • Ventriculoperitoneal (VP) shunt or optic nerve sheath fenestration if visual function declining.

• Complications and prognosis

  • Relapse is common.
  • Permanent blindness from cranial nerve 2 damage. Affects 10% of patients in at least one eye.