Pseudotumor cerebri (SOO-doe-too-mur SER-uh-bry) occurs when the pressure inside your skull (intracranial pressure) increases for no obvious reason. It's also called idiopathic intracranial hypertension. Symptoms mimic those of a brain tumor. The increased intracranial pressure can cause swelling of the optic nerve and result in vision loss. Medications often can reduce this pressure and the headache, but in some cases, surgery is necessary.