Pseudotumor cerebri: Increased pressure within the brain in the absence of a tumor. Pseudotumor cerebri can cause headache, ringing in the ears, double vision, loss of visual accuracy, and even complete blindness. It is most common in obese woman of childbearing age. Although its cause is usually not known, pseudotumor cerebri is sometimes linked to use of tetracycline, nalidixic acid, nitrofurantoin, phenytoin, lithium, or amiodarone, or overuse of vitamin A. Diagnosis is made via brain imaging and lumbar puncture. Drugs to reduce cerebrospinal fluid production or hyperosmotic drugs may be used to reduce fluid buildup. Excess cerebrospinal fluid may be removed with repeated spinal taps, shunting, or a type of surgery called optic nerve sheath fenestration that allows the excess fluid to escape. Steroids may be prescribed to reduce swelling of brain tissue. Also known as benign intracranial hypertension, idiopathic intracranial hypertension (IIH).