1. Effects of Diving on Spinal Cord Injury-Associated Decompression Sickness Richard Sové Medical Biophysics University of Western Ontario Supervisors: Dr. Paula Foster, Dean Percy March 22 nd, 2011

2. Decompression Sickness (DCS) Dissolved gases in the blood at high pressure leaving solution during re-pressurization 1 – Causes damage to blood vessels and surrounding tissue 1 Approximately 9 million recreational divers in US alone 1 – 900 to 1000 treated for severe DCS per year 1 1 Newton, Am. Fam. Physician, 2001

3. Decompression Sickness (DCS) Type I : musculoskeletal pain, cutaneous and lymphatic manifestations, anorexia, fatigue 1 Type II : central nervous system dysfunction 1 – 40% of DCS cases 2 – Spinal cord injury-associated DCS (SCI-DCS) is most related to type II DCS 3 1 Francis, Diving Med. 2004 2 Vann, Undersea Hyperb. Med.1998 3 Greer, Diving Med. 2004

4. How does this happen? Dalton’s Law: “The partial pressure of a gas at a constant temperature is proportional to the solubility of the gas” At 1 ATA (at sea level): PO2 = 0.21 ATA and PN2 = 0.79 ATA At 4 ATA (30 m under water): PO2 = 0.84 ATA and PN2 = 3.16 ATA ATA – Absolute Total Atmospheres

5. Spinal Cord Pathology Haemorrhage 1 Differences in white and grey matter properties 1 Histology used ex vivo to study tissue pathology 1 1 Slucky, J Am Acad. Orthop. Surg. 1998

6. Problem Need to be able to assess treatment strategies for SCI-DCS Ex vivo histology most commonly used 1 - Impractical to sample the entire spinal cord Solution: Magnetic Resonance Imaging (MRI) - May be sensitive to haemorrhage 1 - May be able to detect differences in white and grey matter properties 1 1 Slucky, J Am Acad. Orthop. Surg. 1998

7. Objective Determine whether magnetic resonance imaging (MRI) can be used to identify regions of pathology associated with SCI-DCS

8. Hypotheses There will be a difference in the white matter to grey matter contrast-to-noise ratio (CNR) in the spinal cords of rats with SCI-DCS when compared to rats without the injury There will be differences in the number of signal voids in the spinal cords of rats with SCI- DCS when compared to rats without the injury

9. Methods SCI-DCS was induced in Adult male Wistar rats by simulating a 6.3 ATA dive Control: Adult male Wistar rats of similar age that did not dive Intact spinal columns of both groups were isolated and subjected to two MRI scans (9.4T); one long (~10 hours), and one short (~2 hours) CNR and number of signal voids were measured

10. CNR Measurement (Long Scan) Sagittal slice of control rat’s spinal cord from long scan Sagittal slice of injured rat’s spinal cord from long scan Grey Matter White Matter CNR = (GM-WM)/STD GM – Mean signal from grey matter WM – Averaged mean signal from white matter STD – Standard deviation of the background

11. CNR Measurement (Short Scan) Sagittal slice of control rat’s spinal cord from short scan Sagittal slice of treated rat’s spinal cord from short scan

12. Results n = 4 n = 3 n = 4 P > 0.05

13. Void Counting Axial slice of control rat’s spinal cord from long scan Axial slice of injured rat’s spinal cord from long scan

14. Results n = 5 P > 0.05 Spinal Cord Voids Number of Voids

15. Summary The lack in significance between short and long scan times indicate that the shorter scan time can be used to image the pathology No significant differences in CNR or number of voids, however there was a trend to lower CNR and more voids in the 6.3ATA group – Future experiments may show significance if a larger sample size is used

16. Acknowledgements Supervisor: Dr. Paula Foster Collaborators: Dr. Greg Deckaban Cdr. Kyle Peterson, USN Grad Students: Dean Percy Sonali Dechickera