Systems and methods are described for the monitoring of patient motion via the detection of changes in capacitance, as measured using a capacitance position sensing electrode array. The changes in capacitance may be processed to determine a corresponding positional offset, for example, using a calibration data set relating capacitance to offset for each electrode of the array. The detected positional offset may be employed to provide feedback to a surgeon or operator of a medical device, or directly to the medical device for the control thereof. A medical procedure may be interrupted when the positional offset is detected to exceed a threshold. Alternatively, the detected positional offset may be employed to manually or automatically reconfigure a medical device to compensate for the detected change in position. Various configurations of capacitive position sensing devices are disclosed, including embodiment in incorporating capacitive sensing electrodes with a mask or other support structure.