Challenging Steroid Shift in Neuronavigation - A clinical study proposal

Abstract The intraoperative orientation for neurosurgeons is routinely aided by tools such as neuronavigation. For this purpose, imaging data of the head are referenced to the patient's fixed head with the aid of electromagnetically or optically recorded surface points. However, a certain susceptibility for inaccuracy remains. Steroids such as dexamethasone are routinely given to reduce perifocal edema. Clinical improvement as well as reduction of edema can be observed radiologically just hours after steroid application – also making it a preoperative potential source of metric inaccuracy. The effect of steroids on tissue and tumoral shift on neuronavigation has not been quantified to date. While there are several reasons for navigation inacurracy, this type of shift is often forgotten and not accounted for, but could be easily corrected. We propose the need to perform an additional preoperative cranial MRI (cMRI) shortly before the biopsy/resection in patients who have received steroids due to perifocal cerebral edema to (1) quantify and (2) compensate for steroid induced tumor shift and thereby improve inaccuracies of neuronavigation.