Low Frequency Electrical Stimulation of the Fornix in Intractable Mesial Temporal Lobe Epilepsy (MTLE)

Inclusion Criteria: * Participants are between the ages of 18 -65 years of age * Participants must have had a non-invasive video-EEG monitoring revealing seizure semiology and ictal EEG consistent with unilateral or bilateral MTLE * Participants must have tried and failed two trials of antiepileptic drugs (AEDs) * Participants may have lesional or non lesional hippocampi, as evidenced by brain MRI acquired within the previous two years * Participants are prescribed and taking 1-4 AEDs at the time of study entry * Study participants will have intractable (MTLE) with a seizure frequency of at least 1/month averaged over the preceding 6 months prior to enrollment, including maximum seizure-freedom periods of no more than 60 days. * Participants must have a platelet count greater than 125,000 per cubic millimeter and prothrombin time (PT) and activated partial thromboplastin time (aPTT) within normal limits at the visit prior to surgery Exclusion Criteria: * Progressive neurological or medical diseases, such as brain tumors or neurodegenerative disease or cancer * Non-compliance with antiepileptic medications as demonstrated by the medical record * Any conditions interfering with electrode implantation * Any non-epileptic seizures * Inability or unwillingness to complete neuropsychological tests or complete seizure diaries * Current drug or alcohol use or dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements * Pregnant, or planning to become pregnant\* * Participation in another research trial where the participant was treated with another investigational drug or device within 30 days prior to enrollment of study * Intelligence Quotient showing a general ability Quotient of less than 70. The score excludes the contribution of working memory and processing speed (which are areas of cognitive functioning that are vulnerable to numerous influences including seizures and fatigue and effects of AEDs) * Inability or unwillingness of individual to give written informed consent * Participants who have changes to their antiepileptic medications during the baseline phase (as they will need to repeat the baseline phase) * Subjects with history of status epilepticus within the preceding year * History of psychiatric illness necessitating hospitalizations * Subjects who have any of the following implanted devices: aneurysm clips, cardiac pacemaker or defibrillator, cochlear implant, spinal cord, DBS, or vagal nerve stimulator * Co-morbid conditions that would interfere with study stimulation activities or response to treatment, which may include: * Neoplasm with life expectancy \< 5 years * Severe chronic pulmonary disease * Local, systemic acute or chronic infectious illness * Life threatening cardiac arrhythmias * Severe collagen vascular disorder * Kidney failure or other major organ system failures