Limited benefit of intraoperative low-field magnetic resonance imaging in craniopharyngioma surgery

Objective: To investigate the benefit of intraopertive low- field magnetic resonance imaging (MRI) in craniopharyngioma surgery. Methods: We used a 0.2-T Magnetom Open scanner (Siemens Medical Solutions, Erlangen, Germany) that was located in a radiofrequency-shielded operating theater for intraoperative MRI. The head of the patient was placed in the fringe field of the scanner, so that standard microinstruments could be used. In transcranial surgery, a three-dimensional, gradient echo, T1-weighted, fast low-angle shot sequence was measured, thus allowing multiplanar reformatting. Results: A total of 21 surgical procedures in craniopharyngioma patients were investigated. In 10 patients, a bifrontal-translaminar approach was use; in 6 patients, the craniopharyngioma was removed via a transsphenoidal approach; and in 5 patients, intraoperative MRI was use to monitor cyst puncture and aspiration. In the craniotomy group, intraoperative imaging depicted a clear tumor reminant in one patient, which was subsequently removed. In another patient, an area of contrast enhancement was interpreted as artifact; however, postoperative follow-up at 3 months was suspicious for a minor remnant. Two of the patients with complete removable developed a recurrence during the follow up period. In the group of patients who underwent primary transsphenoidal surgery (n = 4), complete removal was estimated by the surgeon in three cases. Intraoperative imaging depicted a remaining tumor in one case, leading to further tumor removal, however, follow-up revealed further cysts. Conclusion: Intraoperative low-field MRI allows an ultraearly evaluation of the extent of tumor removal in craniopharyngioma surgery in most cases. Imaging showing an incomplete resection offers the chance for further tumor removal during the same operation. However, intraopertive low-field MRI depicting a complete resection does not exclude craniopharyngioma recurrence.