INTRAOPERATIVE BRAIN SHIFT AND DEFORMATION - A QUANTITATIVE-ANALYSIS OF CORTICAL DISPLACEMENT IN 28 CASES

OBJECTIVE: A quantitative analysis of intraoperative cortical shift an d deformation was performed to gain a better understanding of the natu re and extent of this problem and the resultant loss of spatial accura cy in surgical procedures coregistered to preoperative imaging studies . METHODS: Three-dimensional feature tracking and two-dimensional imag e analysis of the cortical surface were used to quantify the observed motion. Data acquisition was facilitated by a ceiling-mounted robotic platform, which provided a number of precision tracking capabilities. The patient's head position and the size and orientation of the cranio tomy were recorded at the start of surgery. Error analysis demonstrate d that the surface displacement measuring methodology was accurate to 1 to 2 mm. Statistical tests were performed to examine correlations be tween the amount of displacement and the type of surgery, the nature o f the cranial opening, the region of the brain involved, the duration of surgery, and the degree of invasiveness. RESULTS: The results showe d that a displacement of an average of 1 cm occurred, with the dominan t directional component being associated with gravity. The mean displa cement was determined to be independent of the size and orientation of the cranial opening. CONCLUSION: These data suggest that loss of spat ial registration with preoperative images is gravity-dominated and of sufficient extent that attention to errors resulting from misregistrat ion during the course of surgery is warranted.