Assessing the Structural Footprint of Minimally Invasive Brain Cannulation on Cerebral White Matter: A Cadaveric Model.

BACKGROUND:  All brain surgery requires some degree of iatrogenic trauma to healthy tissue. Minimally invasive approaches to brain tumors offer the potential of decreasing this trauma compared with conventional approaches. However, there are no validated radiologic models to examine axonal damage after minimally invasive entry into the brain.

OBJECTIVE:  To present a cadaveric model of brain cannulation using fractional anisotropy measurements obtained from diffusion tensor magnetic resonance imaging (MRI). Two different methods of access are compared.

METHODS:  Freshly harvested unfixed cadaveric brains were cannulated using both direct and indirect (i.e., dilation followed by cannulation) methods. Specimens were subjected to 68-direction diffusion tensor imaging scans and proton-density imaging. Fractional anisotropy (FA) data from a region of interest surrounding the entry zone was extracted from scans using imaging software and analyzed.

RESULTS:  FA values were significantly higher following indirect cannulation (less invasive method) than they were following direct cannulation. FA values for undisturbed brain were significantly higher than in either of the cannulated groups, suggesting an inverse relationship between FA values and brain injury.

CONCLUSION:  Axonal damage following brain cannulation can potentially be evaluated by FA analysis in a cadaveric model. These data may lead to an MRI-based model of iatrogenic brain injury following tumor surgery. Future studies will focus on histologic analysis and clinical validation in live tissues.