Postoperative MRI examinations in patients treated by deep brain stimulation using a non-standard protocol

MRI in patients bearing deep brain stimulation (DBS) electrodes may induce cerebral lesions due to electrode heating. To avoid neurological deficits related to MRI, post-operative MRI protocol was installed in our institution. However, our protocol comprised a higher specific absorption rate (SAR) and different positioning of lead excess than the later released electrode manufacturer's guidelines. The objective was to evaluate the safety using this protocol.

Between January 2000 and May 2008, post-operative MRI was performed in all patients. In selected patients, additional MRI scans were performed with the implanted generator. MRI was acquired at 1.5 T with a RF transmit/receive head coil comprising a T2-weighted fast spin echo (FSE) and a T1-weighted inversion recovery FSE sequence. Local cranial SAR values measured up to 0.9 W/kg compared to the manufacturer's recommendation of 0.1 W/kg. Initial scans (1-7 days after surgery) were performed with externalized leads, long-term scans (>30 days after surgery) with a connected generator. New neurological deficits were assessed before and after MRI. Additional MRIs were compared to the initial postoperative MRI with emphasis on new lesions.

In 211 patients, 243 MRIs were performed, including 212 initial post-operative MRI. In 12% (n = 24), 31 additional MRI examinations for various clinical reasons were achieved. No patients demonstrated new neurological deficits during or after MRI acquisitions.

No complications were observed using this MRI protocol in DBS patients. Our results suggest that, within this setting, higher SAR values may be feasible for DBS patients than in the manufacturer's guidelines.