a positionally sensitive spinal cord stimulation apparatus and method using near - infrared reflectometry are provided for automatic adjustments of spinal cord stimulation . the system comprises an electrode assembly with an integrated optical fiber sensor for sensing spinal cord position . the integrated optical fiber sensor , comprising a set of optical elements for emitting light from a set of ir emitters and for collecting reflected light into a set of ir photodetectors , determines a set of measured optical intensities . as the spinal cord changes position , the angles of incidence for light from the ir emitter and the measured optical intensities change . electrode pulse characteristics are adjusted in real time , based on the set of measured optical intensities , to minimize changes in stimulation perceived by the patient during motion .