Pseudo-tumor cerebri can happen if pressure rises around your brain due to too much spinal fluid. This fluid surrounds your brain and spinal cord and protects them from injury. Your body constantly makes cerebrospinal fluid. Then it reabsorbs the fluid through your blood vessels to keep the same amount flowing around your brain and spinal cord. Sometimes your body makes too much cerebrospinal fluid. Or it doesn't reabsorb enough fluid. If either of these things happens, the amount of fluid surrounding your brain can rise. This can raise the pressure on your brain and cause swelling of the optic nerve, which sends messages from your eyes to your brain. Too much swelling of the optic nerve can cause permanent blindness so it has to be corrected to prevent damage.