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Update on the pathophysiology and management of idiopathic intracranial hypertension

Valérie Biousse1,2, Beau B Bruce1,2, Nancy J Newman1,2,3
1Department of Ophthalmology, Emory University, Atlanta, Georgia, USA
2Department of Neurology, Emory University, Atlanta, Georgia, USA
3Department of Neurological Surgery, Emory University, Atlanta, Georgia, USA
Correspondence to
Dr V Biousse, Neuro-Ophthalmology Unit, Emory Eye Center, 1365-B Clifton Road NE, Atlanta, GA 30322, USA

Abstract
Idiopathic intracranial hypertension is a disease of unknown aetiology, typically affecting young obese women, producing a syndrome of increased intracranial pressure without identifiable cause. Despite a large number of hypotheses and publications over the past decade, the aetiology is still unknown. Vitamin A metabolism, adipose tissue as an actively secreting endocrine tissue and cerebral venous abnormalities are areas of active study regarding the pathophysiology of idiopathic intracranial hypertension. There continues to be no evidence based consensus or formal guidelines regarding management and treatment of the disease. Treatment studies show that the diagnostic lumbar puncture is a valuable intervention beyond its diagnostic importance, and that weight management is critical. However, many questions remain regarding the efficacy of acetazolamide, CSF shunting procedures and cerebral transverse venous sinus stenting.

Acetazolamide has been used for the treatment of sufferers of glaucoma. When used to treat glaucoma, acetazolamide inhibits production of HCO3-. In health, it is the production of HCO3- which draws Na+ into the eye; water follows by osmosis to form the aqueous humour. In glaucoma treatment, the goal is often to reduce the intraocular pressure and acetazolamide does this by reducing production of aqueous humour.[3]

Off-label uses include acetazolamide as a conjunction drug to merely assist patients with central sleep apnea by lowering blood pH and encouraging respiration.

Acetazolamide forces the kidneys to excrete bicarbonate, the conjugate base of carbonic acid. By increasing the amount of bicarbonate excreted in the urine, the blood becomes more acidic.[12] Acidifying the blood stimulates ventilation, which increases the amount of oxygen in the blood.[13][14] At high altitudes, climbers hyperventilate in response to lower oxygen levels. The hyperventilation results in reduced carbon dioxide (an acid) and a respiratory alkalosis. The normal physiologic response to a respiratory alkalosis is for the kidneys to increase excretion of bicarbonate (a base) to compensate for the loss of carbon dioxide. This kidney response takes a few days, however acetazolamide in a sense accelerates this process by leading to a more rapid renal bicarbonate loss (metabolic acidosis).