Responsive Neurostimulation of the Mesial Temporal White Matter in Bilateral Temporal Lobe Epilepsy

Abstract

BACKGROUND Responsive neuromodulation (RNS) is a treatment option for patients with medically refractory bilateral mesial temporal lobe epilepsy (MTLE). A paucity of data exists on the feasibility and clinical outcome of hippocampal-sparing bilateral RNS depth lead placements within the parahippocampal white matter or temporal stem. OBJECTIVE To evaluate seizure reduction outcomes with at least a 1-yr follow-up in individuals with bilateral MTLE undergoing hippocampus-sparing implantation of RNS depth leads. METHODS A retrospective analysis of prospectively collected data was performed on patients at our institution with bilateral MTLE who were implanted with RNS depth leads along the longitudinal extent of bitemporal parahippocampal white matter or temporal stem. Baseline and postoperative seizure frequency, previous surgical interventions, and postimplantation electrocorticography and stimulation data were analyzed. RESULTS Ten patients were included in the study (7 male, 3 female). Overall seizure frequency declined by a median 44.25% at 3.13 yr (standard deviation 3.31) postimplantation. Four patients (40%) achieved 50% responder rate at latest follow-up. Two of four patients with focal onset bilateral tonic-clonic seizures became completely seizure-free. Forty percent of patients were previously implanted with a vagus nerve stimulator, and 20% underwent a prior temporal lobectomy. All depth lead placements were confirmed as radiographically located in the parahippocampal white matter or temporal stem without hippocampus violation. There were no cases of lead malposition. CONCLUSION Extrahippocampal or temporal stem white matter targeting during RNS surgery for bitemporal MTLE is feasible and allows for electrographic seizure detection. Larger controlled studies with longer follow-up are needed to validate these preliminary findings.

Strategic targeting of the temporal lobe with orthogonal placement of responsive neurostimulation leads

“…However, this was not associated with a difference in outcome. This finding is consistent with other reports that have found RNS to be efficacious even if the contacts do not lie precisely within the SOZ or if the SOZ is not well defined 2,13,14 . There may still be value to approximating the target structures, as the volume of tissue activated by slightly off‐target leads may include the target structure or its input and output pathways.…”

“…This finding is consistent with other reports that have found RNS to be efficacious even if the contacts do not lie precisely within the SOZ or if the SOZ is not well defined. 2,13,14 There may still be value to approximating the target structures, as the volume of tissue activated by slightly off-target leads may include the target structure or its input and output pathways. A previous report found that seizure control correlates with proximity of stimulator contacts to the subiculum, which is adjacent to the EC.…”

Probabilistic comparison of gray and white matter coverage between depth and surface intracranial electrodes in epilepsy

“…A recent study on ictal mapping using SEEG has shown that a greater percentage of patients with good surgical outcomes had stimulation induced seizures compared to the poor outcome cohort 31 ; a finding that motivates the use of depth electrodes to interrogate seizure networks. The utility in quantifying white matter coverage may also be relevant in patients who are candidates for neuromodulation therapy to control their seizures using responsive neurostimulation, as recent evidence indicates that placement of leads and stimulation in the parahippocampal or temporal stem white matter may more effectively target the epileptic network in temporal lobe epilepsy (TLE) without sacrificing recording ability 32 .…”

Epileptogenic Zone Localization in Refractory Epilepsy by FDG-PET: The Comparison of SPM and SPM-CAT With Different Parameter Settings

“…Diagnosing refractory epilepsy remains a tedious task. While several researchers investigated refractory epilepsy to diagnose and reveal possible causes (3,4), the main cause remains unknown, and doctors are yet to determine why some patients are receptive to medicine and others not.…”