This is when the pressure inside the cranial cavity (i.e., inside the skull) is too high. The brain sits inside the skull and is suspended in a bath of fluid called the CSF (cerebrospinal fluid). This fluid cushions the brain and keeps it buoyant inside this cramped space. This fluid is constantly being renewed and reabsorbed back into the body. If the drainage of CSF fluid is blocked for some reason, the pressure inside the skull will increase. This creates headaches, and if severe and long-lasting, can create long-term neurologic and visual changes that may be permanent. Pseudotumor cerebri (also called idiopathic intracranial hypertension) can occur for many reasons, such as a reaction to antibiotics, hormonal changes, or a temporary thrombosis of the draining veins inside the skull. We see it most often in younger women of child-bearing years who’ve gained a little weight recently. Initial diagnosis is often made by an eye doctor as the fluid pressure can transmit to the back of the eye and be seen as swelling of the optic nerve (papilledema) during a dilated eye exam. More definitive diagnosis is made with a spinal tap to measure the “opening pressure.” Treatment is first geared at finding the underlying cause. This may involve evaluation with a neurologist and an MRI of the head to look for vein thrombosis. If no obvious cause is found, treatment begins with the oral pill Diamox. This is a water pill that decreases the production of CSF fluid and can lower CSF pressure. Weight loss is also a key in treatment. Sometimes, only a 5 to 10 percent reduction in weight can produce a dramatic improvement in symptoms. If the high pressure continues, then a neurosurgeon may need to insert a surgical drain to remove the excess fluid away from the brain.