A system and method for applying stimulation to a target stimulation site within a patient, while avoiding undesirable eye movement side effects of the stimulation, are provided. The method includes determining whether eye movement, sensed by internal or external electrodes, is a side effect of a conveyed electrical stimulus. If the eye movement is a side effect, the electrical current distribution of the stimulus is modified in order to steer a locus of the electrical stimulus from one tissue region of the patient to another different tissue region of the patient, thereby mitigating the eye movement side effects. For example, the locus of the electrical stimulus may be steered away from the oculomotor nerve. Eye movement side effects of DBS treatment may include apraxia of lid opening, downward movement and adduction of only one eyeball, and/or continuous deviation of both eyeballs.
Methods and apparatus for using sensors with a deep brain stimulation system