In vivo, noncontact, real-time, optical and spectroscopic assessment of the immediate local physiological response to spinal cord injury in a rat model

We report a small study to test a methodology for real-time probing of chemical and physical changes in spinal cords in the immediate aftermath of a localized contusive injury. Raman spectroscopy, optical profilimetry and scanning NIR autofluorescence images were obtained simultaneously in vivo, within a 3 x 7 mm field, on spinal cords that had been surgically exposed between T9 and T10. The collected data was used alone and/or combined in a unique algorithm. A total of six rats were studied in two N=3 groups i.e. Injured and Control. A single 830 nm laser (100 mu m round spot) was either 1) spatially scanned across the cord or 2) held at a specified location relative to the injury for a longer period of time to improve signal to noise in the Raman spectra. Line scans reveal photobleaching effects and surface profiles possibly allowing identification of the anterior median longitudinal artery. Analysis of the Raman spectra suggest that the tissues were equally hypoxic for both the control and injured animals i.e. a possible artifact of anesthesia and surgery. On the other hand, only injured cords display Raman features possibly indicating that extensive, localized protein phosphorylation occurs in minutes following spinal cord trauma.