The Correlation between Intraoperative Microelectrode Recording and 3-Tesla MRI in Patients Undergoing ANT-DBS for Refractory Epilepsy.

BACKGROUND: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus) (ANT) has been suggested as a treatment option in refractory epilepsy. The targeting of ANT is especially challenging due to its poor visualization in commonly used MRI sequences, lack of easily observable symptom relief during surgery and high degree of anatomical variation between individuals.

OBJECTIVES: To study whether intraoperative microelectrode recording (MER), a method widely used in movement disorder surgery, provides clinically relevant information during the ANT-DBS implantation procedure.

METHODS: A total of 186 MER samples from 5 patients and 10 thalami obtained from ANT-DBS surgery for refractory epilepsy were analyzed with respect to the signal characteristics and location in 3-tesla (3T) MRI STIR (short T1 inversion recovery) images. The location of each MER sample was calculated relative to visible borders of the ANT after correction of the sample locations according to the position of the final DBS electrode in postoperative CT-MRI fusion images.

RESULTS: We found that the lateral aspect of the ANT lacked spiking activity consistent with the presence of white matter. The spike frequency in samples correlating with location at the ANT showed significantly lower spike frequency compared to samples correlating with location at the ventral anterior nucleus (median 3.0 and 7.0 spikes/2 s; p < 0.05), but spike bursts were morphologically similar in appearance. Trajectories entering the dorsomedial nucleus according to 3T MRI STIR images showed a yet different firing pattern with more low-amplitude regular activity.

CONCLUSIONS: Our data suggest that MER provides clinically relevant information during implantation surgery by demonstrating both nucleus-specific neuronal firing patterns and white matter laminae between different nuclear groups.