Sounds odd, but using the EEG as a therapeutic tool was something like the predecessor of BCI technology. The whole concept was en vogue in the 70s and early 80s and is generally referred to as biofeedback or "the third application of EEG" (after brain function research and medical diagnosis).
In EEG-based biofeedback, epileptic patients "practise" certain EEG patterns that are known to reduce the frequency of seizures. To do so, they sit in front of a screen, connected to an EEG. In this setting, they try actively to produce the desired patterns in the hope that, after a training of usually months, the pattern also can be produced willingly without the screen.
It is a strongly behaviourist approach which falls into the wider field of operant conditioning, the "reward" being the reduction in seizure frequency. With drug therapy having improved, this very demanding and time-consuming kind of therapy is rarely used nowadays. But the idea has a revival in BCIs, which also rely on active training of brain activity (not all of them, though).