IIH (also known as pseudotumor cerebri) is a disorder of idiopathic raised intracranial pressure primarily affecting overweight women of childbearing age, with an incidence of 3-4 per 100,000.
Patients typically present with headaches (90%) that have nonspecific features of migraine or tension-type headache, and a minority (20%) experience symptomatic visual loss. Other common symptoms include pulse synchronous tinnitus (60%) or transient visual obscurations (10%), which are unilateral or bilateral blackouts of vision lasting for seconds.
Infrequently, patients are asymptomatic, with papilledema identified during a routine fundus examination. Papilledema due to raised intracranial pressure is the hallmark clinical feature and is present in over 90% of patients. The risk of permanent visual loss correlates with papilledema severity, and a subset of patients have a fulminant presentation with severe papilledema requiring aggressive management, including surgical interventions.
While the exact pathophysiology remains elusive, 90% of patients are overweight or obese. The incidence of IIH has increased since the early 1990s in parallel with the rise in obesity. Hormonal changes related to obesity may play a role, and changes in cerebral venous outflow due to the development of transverse venous sinus stenosis may also potentiate raised intracranial pressure.