Abstracts

Rationale: Deep brain stimulation (DBS) for epilepsy is a standard treatment for persons with drug-resistant epilepsy (DRE). Device programming protocols vary by institution, but have largely followed those established in pivotal trials. Selecting electrodes within the target and current increase are standard procedure, but changes of other parameters including frequency have not been systematically studied. We aimed to investigate how consistently DBS adjustments were performed at our institution and developed a programming algorithm to allow systematic evaluation of seizure reduction.

Methods: Retrospective chart review of all patients who received DBS for epilepsy between 2020-2024 to extract demographics, epilepsy type, seizure frequency, DBS settings initially and at follow-up, seizure outcomes, surgical complications and side-effects. Consistency of DBS programming was evaluated and subsequently a programming algorithm was developed.

Results: Ten patients (5 female) with a mean age of 33.2 yrs [21-57] received a DBS for DRE after an average epilepsy duration of 17.7 yrs [3-56] with a mean baseline seizure frequency of 19.7/month [0.5-52]. Six had focal epilepsy and 4 had a generalized epilepsy syndrome. Anterior nucleus of the thalamus was targeted in 4 patients, centromedian nucleus in 5, and the subthalmic nucleus/substantia nigra junction in 1 patient (Medtronics 9, Boston Scientific 1). Average follow-up was 19 months [2-49] during which patients had a mean of 5 programming visits [1-16], at intervals of 1-6 months. During these visits, stimulation current was increased initially in all patients, in 6 patients other parameters were variably adjusted, including decrease of OFF-time, turning cycling off, changing frequency, pulse width or montage, without systematic protocol (Table 1). Seizure frequency reduction of >90% was seen in 1 patient, of 50-89% in 2, of < 50% or no change in 6, and worsening in 1 person. No patient became seizure free.

Postoperative complications included skin infection (x1), pain at generator pocket (x1), transient right-sided weakness (x1) and delayed seroma around the generator (x1). Intermittent stimulation-induced side-effects were tingling and numbness in arms or legs in 3 patients, feeling “unwell” in 1, and worsened gait in 1. Depression deteriorated in 1 patient, new drop seizures developed in another.

Conclusions: Review of DBS programming at our institution showed remarkable variations regarding timing and nature of adjustment of parameters during follow-up, reflecting treatment of diverse epilepsies and lack of data-based guidelines. This makes correlations with seizure outcome difficult and creates challenges determining which parameters might be optimal for certain epilepsies. Therefore, a DBS programming algorithm was developed (Figure 1) allowing future comparisons with different settings and better understanding of parameter modifications and their effect on seizures.

Funding: No funding was received