Brain shift is deformation of the brain that occurs during neurosurgery. It is caused by several factors indirectly related to surgery including gravity, head position, fluid drainage, use of hyperosmotic drugs, changes in intracranial pressure and swelling of brain tissue. It is also directly affected by the surgical intervention itself, i.e., by tissue retraction and tumor resection. Brain shift can range from a few millimeters to more than 25 mm and it has been shown to be patient specific and highly non-linear.
This figure shows MRI of a brain tumor A) before (dark region) and B) after near-complete resection with significant brain shift. Brain shift significantly usefulness of preoperative imaging for neuronavigation. Brain shift can occur far from the surgical site (blue arrows). More clinically relevant, it can cause significant deformation and displacement near margins of the resection cavity (red arrows), precisely where surgeons could most benefit from accurate image guidance.
We are investigating methods for measuring and compensating for brain shift continuously during neurosurgery. These include using intraoperative ultrasound to monitor brain shift and tracking surgical instruments so that we can construct a model of the resection cavity in real time.