Systems, apparatus, and methods for treating medication refractory epilepsy are disclosed. In one embodiment, a method of treating epilepsy is disclosed comprising detecting, using a first electrode array coupled to a first endovascular carrier, an electrophysiological signal of a subject. The method further comprises analyzing the electrophysiological signal using a neuromodulation unit electrically coupled to the first electrode array and stimulating an intracorporeal target of the subject using a second electrode array coupled to a second endovascular carrier implanted within a part of a bodily vessel superior to a base of the skull of the subject.