1. RELATIONSHIP BETWEEN CRANIAL DEFECT AND PHYSIOLOGY OF CEREBROSPINAL FLUID: An experimental study in rabbits Dr. Ersin Erdogan Department of Neurosurgery Gulhane Military Medical School Ankara, TURKEY

2. Objective The aim of this study is to determine the effect of craniectomy on the flow kinetics of CSF, in vivo.

3. Introduction Decompressive craniectomy performed; Decompressive craniectomy performed; to reduce the increased intracranial pressure due to different etiological factors, to reduce the increased intracranial pressure due to different etiological factors, may cause clinical findings which called “Sinking skin flap or trephined syndrome” may cause clinical findings which called “Sinking skin flap or trephined syndrome” Mizumaki Y, Oka N, Itoh K, Endo S. A case of traumatic hydrocephalus after large craniectomy for acute subdural hematoma. No Shinkei Geka 2003;31:201-206

4. Introduction When cranioplasty had been applied to the cases of craniectomy, the objective and subjective improvements in clinical, cognitive and physiological findings were observed. When cranioplasty had been applied to the cases of craniectomy, the objective and subjective improvements in clinical, cognitive and physiological findings were observed. Erdogan E, Duz B, Kocaoglu M, Izci Y, Sirin S, Timurkaynak E. “The effect of cranioplasty on cerebral hemodynamics: evaluation with transcranial Doppler sonography.” Neurol India. 2003 Dec;51(4):479-81.

5. Material and Methods The experiments were conducted using eleven male New Zealand white rabbits weighing between 1500 and 1800 g The experiments were conducted using eleven male New Zealand white rabbits weighing between 1500 and 1800 g The rabbits were anesthetized with a combination of ketamine and xylazine The rabbits were anesthetized with a combination of ketamine and xylazine

6. cisternography with 300±50 microcurie/0.1 cc Tc-99m- diethylenetriamine pentaacetic acid (Tc-99m-DTPA) injected into the 4 th ventricle of the rabbits via insulin injector. Kusumi and Plouffe 1979

7. The rabbit was positioned laterally, with the lateral cranial surface facing the detector of the gamma camera Scanning

8. (Rabbit # 3) The control cisternography of the rabbit performed at the 3 rd month postoperatively. The reframed 1 hour follow-up image.

9. Scanning Dynamic data acquisition in every minute for a period of one hour was performed Dynamic data acquisition in every minute for a period of one hour was performed D ata were generated over the subsequent 60-minute at 60 second per frame in a dynamic mode after regions of interest were placed around the injection site. D ata were generated over the subsequent 60-minute at 60 second per frame in a dynamic mode after regions of interest were placed around the injection site.

10. Scanning The computer - generated time activity curve for region of interest by using commercially available software (Entegra). Using data clearance half time (t 1/2 ) for each region of interest was generated in seconds using an exponential fit. The computer - generated time activity curve for region of interest by using commercially available software (Entegra). Using data clearance half time (t 1/2 ) for each region of interest was generated in seconds using an exponential fit. The t 1/2 values of pharmaceutical agent for each study were calculated with the same method and the results were recorded. The t 1/2 values of pharmaceutical agent for each study were calculated with the same method and the results were recorded.

11. Surgery After the preoperative cisternography, all rabbits were anesthetized The scalp was shaved, prepped with Betadine, and a midline scalp incision was made. After the preoperative cisternography, all rabbits were anesthetized The scalp was shaved, prepped with Betadine, and a midline scalp incision was made. The periosteum was reflected laterally and a craniectomy was performed with microscopic magnification. The dura was exposed overlying right cerebral hemisphere and the scalp was then closed. The periosteum was reflected laterally and a craniectomy was performed with microscopic magnification. The dura was exposed overlying right cerebral hemisphere and the scalp was then closed. The mean width of cranial defect was 1/3 of hemicranium. The mean width of cranial defect was 1/3 of hemicranium.

12. Statistical analysis Differences in DTPA clearance t 1/2 before and after craniectomy were compared using the Wilcoxon Signed Ranks test. Differences in DTPA clearance t 1/2 before and after craniectomy were compared using the Wilcoxon Signed Ranks test.

13. Results Four rabbits died in the 7 th day of the experiment and a total of 5 rabbits died at the end of 3 rd month and they were excluded from this study. The t 1/2 values and median (mean; minimum-maximum) t 1/2 values obtained preoperatively, 24 th hour, 7 th day and 3 rd month postoperatively are summarized in Table. Four rabbits died in the 7 th day of the experiment and a total of 5 rabbits died at the end of 3 rd month and they were excluded from this study. The t 1/2 values and median (mean; minimum-maximum) t 1/2 values obtained preoperatively, 24 th hour, 7 th day and 3 rd month postoperatively are summarized in Table.

14. Statistically significant difference was not found between these results according to Wilcoxon Signed Ranks test.

15. The exponential fit applied-time/activity curve obtained from the region of interest drawn on the site of injection.

16. Conclusion There is no doubt that the physiology of CSF is being influenced by cranial defect. There is no doubt that the physiology of CSF is being influenced by cranial defect. The most important evidence of this situation is variations of CSF pressure. The most important evidence of this situation is variations of CSF pressure. This pathophysiological change of CSF due to cranial defect is not clear, but it could be related to overproduction or decreased absorption of CSF that may increase pressure. This pathophysiological change of CSF due to cranial defect is not clear, but it could be related to overproduction or decreased absorption of CSF that may increase pressure.

17. Conclusion Our study is the first experimental study, which investigated the physiology of CSF kinetics via cisternography by protecting in vivo conditions. Our study is the first experimental study, which investigated the physiology of CSF kinetics via cisternography by protecting in vivo conditions. Certainly, we stated that cranial defect do not cause statistically significant difference on the CSF kinetics. Certainly, we stated that cranial defect do not cause statistically significant difference on the CSF kinetics.