Intraoperative MRI in trans-sphenoidal surgery using frameless stereotaxis

Intraoperative magnetic resonance imaging (iMRI) has been used for pituitary surgery for approximately 20 years. The introduction of frameless stereotaxis allows efficient navigation for both the ENT and neurosurgeon. This allows flexibility in placement of the patients head to facilitate resection, efficient use of theater time and improves the safety profile of the operation. This is the first study to describe and investigate the use of frameless stereotaxis in conjunction with iMRI.Consecutive patients who underwent iMRI guided trans-sphenoidal debulking using frameless stereotaxis over a 3-year period, from January 2016 to June 2019, were included in this case series and reviewed retrospectively. The use of AxiEM (Medtronic, USA) tracker facilitated frameless stereotaxis in conjunction with iMRI for trans-sphenoidal debulking of sellar lesions based on the "twin-operating" model.The cohort of 47 patients had a mean age of 55 years with a slight female predilection. The average lesion size measured 20 mm (3-46 mm) in maximal diameter with objective evidence of visual deterioration being the most common indication to consider surgery. The use of iMRI identified two patients with suboptimal decompression facilitating further resection in the same anesthetic and one hemorrhagic complication requiring evacuation and hemostasis to reduce postoperative morbidity.This study describes the procedural nuances in the use of frameless stereotaxis for iMRI in transsphenoidal surgery to further reduce morbidity and improve outcomes, as well as improving theater utilization and reducing cost.