Fig. 1

Brain CT (2009) and preoperative brain MRI (2013), fused with postoperative CT. Preoperative MRI (b–f) did not show evidence of cortical developmental malformations, corpus callosum defects, or any other inborn brain structure anomalies. The maturation of the brain including myelination is normal. Comparison of an axial CT from 2009 (a) and MRI T2 from 2013 (b) shows enlargement of the lateral ventricles, indicating some supratentorial volume loss over time. A mid-sagittal T1 (2D TSE) image from 2011 (c) shows normal configuration and no certain volume loss of the brain stem or cerebellum, and the preoperative MRI series (2013) did not disclose convincing signs of infratentorial volume loss (not shown due to more distorted images). Images d–f show preoperative T1-3D MPRAGE* (2013) fused with postoperative CT images (2015), showing the position of the DBS electrodes visualized as red dots (image fusion performed using software from NordicICE, NordicNeuroLab, Bergen, Norway). Images d and e show the electrodes in the posterior third and most ventral part of the internal globus pallidum. Image f shows the right electrode tip touching upon the optic tract (orange arrow) (*3D T1 MPRAGE was used for fusion with postoperative CT instead of T2 (which better visualizes the basal ganglia), because the cochlea implants inflicted heavy susceptibility artifacts on the T2 images with pronounced focal signal loss, as well as distortion. Also, the CT alignment/co-registration with the large (whole head) field of view 3D T1 MPRAGE series was accurate, whereas the CT alignment with the (reduced field of view) T2 images was not.)