gms | German Medical Science

Objective: Intraoperative MRI (iMRI) has been introduced as a promising method for resection guidance and control in an increasing number of centers around the world. While most series report results from highly selected patient cohorts, routine iMRI surgery is performed at our institution for all intracranial gliomas to enhance radicality.

Method: All consecutive supratentorial gliomas treated at our institution, except for stereotactic and open biopsies, were scheduled for iMRI surgery and included into our database from 01/2011 until 09/2012. Prior to surgery, the aspired extend of resection (EOR) was prospectively defined by the operating surgeon on neuronavigation images. Volumetric analysis of EOR was performed on pre-, intra- and postoperative imaging. According to the predefined extent of surgery, success rates under routine iMRI guidance are analyzed with regards to post-iMRI resections and WHO subgroups. Postoperative neurologic deficits are documented to recognize possible downsides of extended surgery.

Results: A total of 160 cases were included into our database (11 WHO°I, 24 WHO°II, 25 WHO°III, 100 WHO°IV), mean age was 51y (range 19–80y), male to female ratio almost 2:1. Across all WHO grades, EOR was 90.1% + 14.9% after the first iMRI. Followed by additional tumor resection, a final EOR of 99.6% + 1.8% based on the predefined target resection volume was achieved (WHO°I: 94.0% + 12.0% and 100%; WHO°II: 84.5% + 18.4% and 99.6% + 1.2%; WHO°III: 82.5% + 22.0% and 99.1% + 3.6%; WHO°IV 92.8% + 10.9% and 99.6% + 1.3% for volume after iMRI and final EOR, respectively). In routine use, additional resection after iMRI was performed in 69% of all cases (WHO°I: 27%, WHO°II: 79%, WHO°III: 80%, WHO°IV: 69%). New permanent neurologic deficits were observed in 7.5% (12/160) of all patients postoperatively, 22.5% (36/160) of patients had transient neurologic deficits that ceased within four months after surgery.

Conclusions: Routine iMRI guidance shows unprecedented precision in resection guidance. Aspired EOR can be reached with almost 100% accuracy in an unselected and prospectively documented patient cohort. Increased incidence of additional post-iMRI resections in routine use contributes to safety and radicality: A defensive resection strategy in combination with precise localization of residual tumor warrants complete and safe tumor removal across all WHO grades. At the same time, increase in EOR did not translate into higher postoperative morbidity compared to literature.