Clinical safety of intracranial EEG electrodes in MRI at 1.5 T and 3 T: a single-center experience and literature review.

PURPOSE: Intracranial electroencephalography (EEG) can be a critical part of presurgical evaluation for drug resistant epilepsy. With the increasing use of intracranial EEG, the safety of these electrodes in the magnetic resonance imaging (MRI) environment remains a concern, particularly at higher field strengths. However, no studies have reported the MRI safety experience of intracranial electrodes at 3 T. We report an MRI safety review of patients with intracranial electrodes at 1.5 and 3 T. METHODS: One hundred and sixty-five consecutive admissions for intracranial EEG monitoring were reviewed. A total of 184 MRI scans were performed on 135 patients over 140 admissions. These included 118 structural MRI studies at 1.5 T and 66 functional MRI studies at 3 T. The magnetic resonance (MR) protocols avoided the use of high specific energy absorption rate sequences that could result in electrode heating. The intracranial implantations included 114 depth, 15 subdural, and 11 combined subdural and depth electrodes. Medical records were reviewed for patient-reported complications and radiologic complications related to these studies. Pre-implantation, post-implantation, and post-explantation imaging studies were reviewed for potential complications. RESULTS: No adverse events or complications were seen during or after MRI scanning at 1.5 or 3 T apart from those attributed to electrode implantation. There was also no clinical or imaging evidence of worsening of pre-existing implantation-related complications after MR imaging. CONCLUSION: No clinical or radiographic complications are seen when performing MRI scans at 1.5 or 3 T on patients with implanted intracranial EEG electrodes while avoiding high specific energy absorption rate sequences.

Ventriculoperitoneal shunt knot: a rare cause of bowel obstruction and ischemia.

Small-bowel obstruction caused by knotting of a peritoneal shunt catheter is an extremely rare and severe complication of a ventriculoperitoneal (VP) shunt. In the 1-week-old female infant reported here who had a VP shunt, inability to remove the peritoneal catheter was followed by small-bowel obstruction and necrosis due to intestinal strangulation in a tight loop of the catheter. An uncomplicated primary resection of the necrotic segment was followed by placement of a temporary ventriculoatrial shunt. The authors suggest that when withdrawal of the peritoneal part of a VP shunt meets with resistance, an intraoperative radiograph should be obtained to assess the position of the remaining catheter. If knotting is observed, an attempt to straighten the catheter with a guide wire is worthwhile. Should this fail, immediate laparoscopy or laparotomy is indicated.