Systems for locating an optimal site within a brain of a patient for deep brain stimulation include a main cannula having an internal lumen, a guiding cannula having a bent distal end portion configured to pass through the lumen of the main cannula and guide a microelectrode into the brain, a depth adjustment mechanism configured to adjust an insertion depth of the guiding cannula, and a longitudinal angle adjustment device configured to adjust a longitudinal angle of the guiding cannula. The depth adjustment mechanism and longitudinal angle adjustment device adjust a position of the guiding cannula such that the microelectrode locates the optimal site for the deep brain stimulation.