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Visual field loss is seen and classically early loss is enlargement of the blind spot and inferonasal loss. Symptoms can mimic a tumour .

About

• Often found in young obese females
• We produce 500 mls of CSF per day
• Also called Pseudotumour cerebri as it mimics a brain tumour
• Not always benign as can cause papilloedema and visual loss

Aetiology

• Unknown cause but classically affects overweight young females
• Always consider possibility of cerebral venous thrombosis

Associations

• Pregnancy and OCP, Thrombophilia
• Retinoids, Vitamin A, Tetracycline, minocycline
• Ketamine, Nitrous oxide

Clinical

• Headache worse when lying down and there on waking up 94%
  • Associated temporally with IIH
  • Relieved by reducing ICP (post LP)
  • Worse by states that increase ICP
• Nausea + Blurred vision and blind spot enlarged
• Transient visual changes: vision may darken at times
• Visual field loss is seen and classically early loss is the enlargement of the blind spot and inferonasal loss with Papilloedema
• Possible VIth nerve lesion - diplopia 18%
• Pulse-synchronous tinnitus 50%
• Neck and back pain may be recorded in 50%
• Ask about weight gain and new medications

Investigations

• FBC, U&E, LFT, CRP, ESR, ALP.
• Visual field testing perimetry: Visual field loss is seen and classically early loss is enlargement of the blind spot and inferonasal loss
• CT/V is usually normal and the ventricles normal or even smaller but the subarachnoid space may be wider. CTV to look at venous drainage if needed
• MRI/V: usually normal too but may be required if there is a concern to exclude tumour and cerebral venous thrombosis
• Supportive Neuroimaging findings
  • Empty sella, partially empty sella/decreased pituitary height
  • Increased tortuosity of optic nerve
  • Enlarged optic nerve sheath (perioptic subarachnoid space)
  • Flattened posterior globe/sclera
  • Intraocular protrusion of optic nerve head
  • Attenuation of the cerebrovenous sinuses including bilateral transverse sinus stenosis or stenosis of a dominant transverse sinus.
  • Excluded venous thrombosis
  • No evidence of hydrocephalus, mass, structural, vascular lesion and no abnormal meningeal enhancement
• LP: High opening pressure > 25 cm H₂O (may be > 30 cm) in the lateral position. Lumbar puncture and removal of CSF may help to relieve headache and symptoms
• CSF : normal constituents

Differential

• Venous sinus thrombosis
• Brain tumour
• Hydrocephalus

Management

• Urgency is primarily needed to exclude venous thrombosis which can result in stroke if left. Secondly to preserve rapidly deteriorating vision in those rare patients with the fulminant disease. Once CVT is excluded and if vision is static and fields are okay then it is ongoing management of ICP. Local fundoscopy in these cases is done by Eye clinic. The main principles of management are then
  • 1. to treat the underlying disease
  • 2. to protect the vision
  • 3. to minimise the headache morbidity

• Stopping suspected causative medications such as avoid excess Vitamin A, minocycline, isotretinoin, danazol, nitrofurantoin etc.
• Treatment with weight loss for those with a BMI > 30kg/m2 helps markedly and in some bariatric surgery is needed
• Medications
  • Carbonic anhydrase inhibitors (typically acetazolamide). Start with 500 mg of acetazolamide twice daily. May go up to 2-4 g per day
  • Loop diuretics may be considered
  • Topiramate which often causes some weight loss as a side effect, might have an added advantage over other agents
  • Steroids: Steroids were once used commonly but their long-term use to lower ICP is not recommended due to the risk of rebound IH on withdrawal
• Shunting: VPS and LPS are CSF pressure-lowering procedures that can be effective in selected patients with IIH who fail maximum medical therapy
• Those with acute fulminant papilloedema and visual loss usually require urgent surgical intervention to prevent further irreversible visual loss. The choice between optic nerve sheath fenestration (ONSF) and neurosurgical shunting procedures depends on local surgical expertise, institutional experience and resources, as well as the timing and severity of the patient's symptoms and signs. A lumbar drain during the acute hospitalization might be useful as a temporizing measure prior to definitive surgical intervention.

References

• Papilloedema: epidemiology, etiology, and clinical management 2015
• Idiopathic intracranial hypertension: consensus guidelines on management