MR findings after depth electrode implantation for medically refractory epilepsy.

PURPOSE To evaluate using MR imaging chronic changes in the brain parenchyma after electroencephalography depth electrode placement in patients with medically refractory epilepsy.

METHODS A retrospective review of MR scans in 57 patients who underwent stereotactic placement of 210 depth electrodes was performed. Scans were evaluated for evidence of gliosis, hemorrhage, or infection along the probe tracts.

RESULTS Signal abnormalities along the probe tracts were seen in 38 patients (67%). Of the 210 probe tracts evaluated on long-repetition-time images, 85 (41%) were associated with punctate hyperintensity and four (2%) with punctate hypointensity; 120 (57%) showed no MR changes to suggest prior electrode placement. One probe placement was complicated by a significant intraparenchymal hemorrhage.

CONCLUSIONS Depth electrode implantation for electroencephalography monitoring results in imperceptible or minimal chronic changes as detected by MR in almost all patients. The punctate hypersensitivity on long-repetition-time images is though to be caused by gliosis along the probe tracts. These signal changes should not be confused with the seizure focus. Significant hemorrhage or infection is a rare complication of probe placement. Incorporation of MR angiographic data with conventional spin-echo images at the time of stereotactic probe placement may further reduce the low incidence of probe-related hemorrhage.