Synonyms: pseudotumour cerebri, benign intracranial hypertension

Raised intracranial pressure in the absence of a mass lesion or of hydrocephalus. It is often idiopathic. The condition appears to be due to impaired cerebrospinal fluid (CSF) absorption from the subarachnoid space across the arachnoid villi into the dural sinuses. Prompt recognition and treatment are needed to prevent potentially permanent visual loss.¹

Epidemiology

• It most frequently occurs in obese women of childbearing age.¹
• Incidence is 1 per 100,000 general population and idiopathic intracranial hypertension occurs in 10-20/100,000 obese women.²

Risk factors

• It mostly occurs in young obese females in their third or fourth decade.
• There is an increased risk in women with menstrual irregularity.
• Female to male ratio is between 3:1 to 8:1.
• Up to 90% of patients are overweight.
• In women it may coincide with recent weight gain, fluid retention, the first trimester of pregnancy and the postpartum period.

Causes

Known associations include:

• Endocrine: adrenal insufficiency, Cushing's syndrome, hypoparathyroidism, hypothyroidism and hyperthyroidism³
• Medication: cimetidine, corticosteroids, danazol, isotretinoin, levothyroxine, lithium, minocycline, nalidixic acid, nitrofurantoin, tamoxifen, tetracycline, ciclosporin, levonorgestrel implant, pancreatin, recombinant and natural human growth hormone, vitamin A in infants
• Miscellaneous: polycythaemia vera, iron deficiency anaemia, chronic renal failure, systemic lupus erythematosus

Presentation

• Headache tends to be the first symptom: generalised throbbing is worst first thing in the morning and last thing at night, and relieved on standing (consistent with raised intracranial pressure). It is also aggravated by straining, coughing or a change in position. In many cases the headache may be mild, nonspecific and have been present for many weeks or months.
• Gradual visual field defects; moderate or gross bilateral papilloedema without significant focal intracranial signs. Transient reduction of vision ('greying out') on bending or stooping, halo or short episode of visual Catherine wheel flashes, persistent blurring, scotoma or horizontal diplopia may also occur.
• Nausea, vomiting, drowsiness.
• Less commonly: diplopia due to VI cranial nerve palsy.

Differential diagnosis

• Other causes of headache, including cerebral tumours and malignant hypertension
• Other causes of papilloedema
• Other causes of visual disturbance

Investigations

Primarily to exclude any other possible cause of raised intracranial pressure.

• CT or MRI scanning: the ventricles, in contrast to hydrocephalus, are normal or reduced in size.
• Visual field charting: enlarged blind spot and peripheral field construction.
• Lumbar puncture, if not contra-indicated by clinical features and pressure measurement. Monitor intracranial pressure if in doubt as to the diagnosis.

Management

Management is initially medical with weight reduction if obese, and diuretic therapy. Cerebrospinal fluid diversion surgery may be required (e.g. for visual disturbance). Surgical options include lumbar-peritoneal of ventriculoperitoneal shunting, optic nerve sheath fenestration, or both.⁴

• The aim of treatment is the relief of symptoms of raised intracranial pressure and the prevention of progressive optic nerve damage.
• Weight reduction is advisable if obese.
• Treatment of underlying condition; stopping any causative medication.
• The intracranial pressure may be controlled by serial lumbar puncture.
• For acute treatment, prednisolone to relieve headache and papilloedema.
• In mild chronic disease, acetazolamide or other diuretics are effective at lowering the intracranial pressure.
• Surgery should be considered if all other interventions fail:
  • Lumboperitoneal or ventriculoperitoneal shunting to relieve CSF pressure.
  • Optic nerve decompression if visual problems persist in spite of treatment.⁵

Prognosis

• Response to treatment is generally good but recurrent attacks occur in up to one third of patients.
• Relapse and remission of symptoms is common.
• Permanent visual loss occurs in up to 50% and significant disability in 10%.

Document references

1. Friedman DI; Idiopathic intracranial hypertension. Curr Pain Headache Rep. 2007 Feb;11(1):62-8. [abstract]
2. Digre KB; Not so benign intracranial hypertension. BMJ. 2003 Mar 22;326(7390):613-4.
3. Merkenschlager A, Ehrt O, Muller-Felber W, et al; Reversible benign intracranial hypertension in a child with hyperthyroidism. J Pediatr Endocrinol Metab. 2008 Nov;21(11):1099-101. [abstract]
4. Acheson JF; Idiopathic intracranial hypertension and visual function. Br Med Bull. 2006;79-80:233-44. Epub 2007 Jan 22. [abstract]
5. Kessler LA, Novelli PM, Reigel DH; Surgical treatment of benign intracranial hypertension--subtemporal decompression revisited. Surg Neurol. 1998 Jul;50(1):73-6. [abstract]

Internet and further reading

• Gans MS; Idiopathic Intracranial Hypertension, eMedicine, Aug 2009.
• Intracranial Hypertension Research Foundation

Acknowledgements