Introduction: Deep Brain Stimulation (DBS) of the anterior nucleus (AN) of the thalamus has demonstrated the ability to diminish seizure frequency with long term follow up, most notably in the SANTE trial. However, these promising results also revealed notable adverse events and in some instances patients were not candidates for implantation because of regional vascular anatomy in the ventricle. We posit an alternate approach to targeting the AN and present imaging and neurophysiological data.
Methods: We retrospectively reviewed 2 DBS patient implanted bilaterally via a supraorbital route to anterior nucleus of the thalamus. One patient had refractory bitemporal epilepsy, while the other was bifrontal. Stereotactic targeting was analyzed for both a standard frontal transventricular approach and the supraorbital approach. Physiological data, including microelectrode recordings (MER) and local field potentials (LFP) were processed. Finally, MRI diffusion tensor imaging (DTI) data was processed in a probabilistic connectivity format.
Results: Both patients had undergone supraorbital DBS to the anterior nucleus of the thalamus without complication. Clinically significant improvement was noted in both patients, Engel II and III outcomes. One of the most interesting clinical findings was a substantial reduction of aura's, in addition to clinical seizure burden. In both patients, the standard transventricular route appeared tenuous because of ependymal veins and choroid plexus. The supraorbital route was free of any major vessels and the ventricular structures. Physiological data suggested showed bursting spike activity on MER and LFP, and a broad variation in frequency with the local field potential data in the AN. Probabilistic tractography demonstrated connectivity between the anterior nucleus of the thalamus and both the frontal lobe and the temporal lobe in the patient with bifrontal epilepsy, and connectivity between the anterior nucleus of the thalamus and temporal lobe in the bitemporal epilepsy patient.
Conclusions: MER and LFP data seem to demonstrate data that can be used to target the AN. Probabalistic DTI seems to demonstrate a variation in connectivity depending on the type of epilepsy, age, or other unknown pathophysiological mechanism. Larger clinical series are needed to further investigate these preliminary findings.
Patient Care: Better understanding of dbs for epilepsy
Learning Objectives: Lfp and dti