Pressure builds around the brain in this disorder, yet no cause is found
Idiopathic intracranial hypertension raises the pressure around the brain with no tumour or other detectable reason; its older name was pseudotumor cerebri. Nearly everyone affected gets severe headaches, many hear a whooshing in time with their pulse, and the swelling it causes where the optic nerve meets the eye can threaten sight.
About 2 in every 100,000 people develop it each year, most often women between 20 and 50, who are affected roughly 20 times as often as men. Doctors first described it in 1897. Being overweight or gaining weight recently raises the risk, and the antibiotic tetracycline may set it off. Headache shows up in 92–94% of cases, typically throbbing, felt all over the head, worst in the morning and sharpened by coughing or sneezing. Between 64% and 87% of patients report pulsatile tinnitus, a rushing sound that keeps time with the heartbeat.
The pressure swells the optic disc, a sign called papilledema that appears in practically every case, though not everyone notices it. Those who do describe brief spells of dimmed vision. Left untreated for a long time, the swelling erodes sight from the edges inward. Squeezed cranial nerves add their own trouble, most often the sixth, which moves the eye outward, producing side-by-side double vision.
Why pressure climbs is unknown. The Monro–Kellie rule says skull pressure depends on the combined volume of brain tissue, spinal fluid and blood, so three explanations compete. Overproduction of fluid, the earliest idea, lacks experimental support. Extra volume is more plausible: scans and biopsies show waterlogged brain tissue, and phase contrast MRA work by Bateman and colleagues suggests blood flow runs high. Many patients also have narrowed transverse sinuses, possibly part of a loop in which pressure narrows the veins, which then drain fluid less well. Certain drugs, including high-dose vitamin A derivatives such as isotretinoin, can raise pressure, while the contraceptive pill is not linked. On July 1, 2022, the FDA flagged hormone-agonist drugs used for early puberty as a possible risk factor.
Diagnosis rests on ruling everything else out. Brain scans usually look normal, sometimes with a flattened pituitary, and a lumbar puncture finds high opening pressure with otherwise normal fluid. Walter Dandy set out criteria in 1937; Smith swapped in CT scanning in 1985, and Friedman and Jacobson in 2002 insisted the patient lie on one side, since sitting can inflate the reading. Treatment centres on protecting vision: most patients who lose around 6–10% of body weight go into remission, acetazolamide is often added, and a small minority need surgery.
Source: Idiopathic intracranial hypertension
