fig1 shows a simplified schematic block diagram for a mechanical system for treating epilepsy and other neurological disorders by modifying ion concentration in brain fluid . in fig1 fluid from a patient &# 39 ; s brain 10 ( the fluid is not shown ) is extracted from the brain ( preferably from 1 of the brain ventricles ) 10 , by a pump 14 . extra - cellular fluid can be extracted by exerting a relatively negative pressure on a small - diameter flexible conduit ( i . e . a catheter or capillary tube 12 ) one end of which is coupled to the pump and which provides the negative pressure . the other end of the flexible conduit is inserted into the brain ventricle . extra - cellular brain fluid is drawn through an appropriately - sized capillary tube or catheter 12 to the pump 14 , which in the preferred embodiment was a positive displacement computer - controlled pump 14 . in the preferred embodiment , the pump 14 ( which may be computer controlled ) reads and executes stored program instructions that cause the pump to pump the extracted fluid according to the program and its parameters . in many applications , ion - adjusted fluid will be pumped in an “ open loop ” fashion , i . e . according to some predetermined schedule in the pump &# 39 ; s stored program . open - loop delivery methods can be based upon either the volume of modified extra - cellular brain fluid to be delivered per unit time or some other parameter . the pump 14 forces extracted extra - cellular brain fluid through an ion concentration adjustment mechanism 16 . ion concentrations in the extracted brain fluid are modified in the ion concentration adjustment mechanism 16 . the ion concentration of the fluid can be adjusted by methodologies well known in the art including , but not limited to , appropriate ion exchange mechanisms ; filtration , or chemical treatment . the ion concentration adjustment mechanism 16 changes the ion concentration in brain fluid such that when the fluid is returned to the brain , the brain fluid ion concentration , at least in localized regions , is modified . output from the ion concentration adjustment mechanism 16 is returned to the brain 10 through an appropriately sized capillary tube or catheter 18 . procedural steps of the method 200 of the invention are illustrated in fig2 . csf or extra - cellular brain fluid is extracted 210 and the ion - concentration of the fluid is adjusted 220 using an appropriate methodology . some techniques for modifying ion concentration would include filtering or various chemical treatment processes . after the ion concentration is adjusted , the modified ion - content fluid is re - injected into the patient &# 39 ; s brain 230 . at some point in the process , the flow rate of brain fluid from and / or into the patient &# 39 ; s brain is measured 240 . while this step is shown in fig2 as being after re - injection of the brain fluid 230 , alternate methodologies would certainly include deleting this step in its entirety and simply letting the pump run “ open loop ” doing whatever the program instructions dictate . still other embodiments would include calculating or measuring the extracted fluid 210 volume as well as the delivered fluid volume . inasmuch as brain fluid is incompressible , both the extracted and re - injected or delivered fluid volumes should be equivalent , except for any fluid lost during the ion - concentration adjustment . still other embodiments might measure the ion concentration in the brain fluid and , depending upon the measured ion concentration , adjust the fluid delivery rate or the ion - concentration adjustment , or both . in an optimum system , a closed - loop feedback system would include a system that measures ion concentration ( or other electrical characteristic ) and uses this information to control fluid extraction , delivery or ion content so as to achieve the optimum electrical potential difference between the inside and outside of brain cells , imbalances of which might cause epilepsy or other neurological disorders . various embodiments of the invention include localized delivery of ion - modulated brain fluid as well as dispersed delivery mechanism , such as a leaky catheter . by replacing the brain fluid at a modified ion concentration , it is possible to change the electrical potential difference between intra - cellular and extra - cellular brain fluid . in the preferred embodiment , changing the electrical potential difference across the nerve cell membrane in the epilepsy generating brain structure can significantly affect the occurrence of epileptic seizures . once a diagnosis of epilepsy is first made or the disease is established , changing the ion concentration in the extra - cellular fluid to increase the potential difference from − 70 millivolts to − 80 or more millivolts will locally hyper - polarize the brain cells and therefore , can substantially inhibit seizures . in one of the alternate embodiments , an electrical probe 20 inserted into a localized region of the brain 10 might be read by the computer that controls the pump 14 so as to provide closed - loop feedback so as to even more closely control ion concentrations and therefore more closely control epileptic seizures . a probe inserted into the brain fluid in the brain might measure the ion concentration by the conductivity or resistance of the fluid . in such an embodiment , it is preferable to measure ion concentration after the ion - adjusted fluid has been returned to the patient &# 39 ; s brain . the modified resulting membrane potential can be calculated using the well - known goldman equation . in another alternate embodiment , ion concentrations of extra - cellular fluid might be adjusted according to measured electrical activity of nerve cells in specific brain structures involved in the generation of the epileptic seizures . in such an embodiment , the electrical activity of brain cells , can be continuously adjusted by injecting more or less modified brain fluid in such a way to avoid seizures . such a closed - loop system could be used to carefully control , in real time , the rate at which ion adjusted fluid is delivered to the brain or to change the ion concentration changes effected by the ion concentration adjustment mechanism 16 . a control signal 22 from the computer - controlled pump 14 might be used to change the ion concentration in fluid that is output to the brain 10 . in yet another embodiment , it might be possible to alter electrical potential differences across cell membranes simply by adding or administering a predetermined liquid or other substance to brain fluid so as to change the electrical potential across brain cells . those skilled in the art will recognize that changing the ion concentration of extra - cellular brain fluid could have other beneficial effects in the treatment of other neurological disorders by adjusting the degree of communication between brain cells . this degree of communication depends on the level of the membrane potential . hyper - polarized or inhibited cells increase the threshold for cell communication , while hypo - polarized or excited cells decrease the threshold for cell communication . in instances where neurological disorders can be controlled by modulating the communication between brain cells the invention would find the applicability in treating these other disorders .