Abstracts

Rationale: High-frequency CM-DBS is an established therapy for pharmaco-resistant generalized epilepsy. High frequency stimulation (HFS) is preferentially used in DBS therapies. On the other hand, low-frequency stimulation (LFS) may be advantageous; it inherently requires less current and thus could potentially cause less tissue damage and deplete less the generator (IPG). Little is known about the long-term effects of DBS on epileptogenesis, especially using low-frequency stimulation. Epilepsy is a network disease, and DBS could potentially transiently or definitively modulate the abnormal circuitry. The purpose of this study was to assess the impact of low vs high frequency CM-DBS in patients with generalized epilepsy chronically treated.


Methods: Six (out of 12 planned) patients with generalized drug-resistant epilepsy (DRE) who underwent CM-DBS and had at least one year of follow up were included so far. All patients had daily seizures. All patients were submitted to bipolar stimulation CM-DBS; the cathode was located immediately below CM and the anode, immediately above it. Initial stimulation parameters were 300usec, 4-5V and frequency ranging from 130 Hz to 180 Hz. Impedance ranged from 1200-2600 Ohms. After at least one year of follow up, they were moved to 6-10Hz stimulation. Patients were then reevaluated after one month, three months, and six months under LFS. Antiseizure medications (ASM) remained stable.


Results: The median time between CM DBS surgery and frequency reduction was 6 years: the oldest patient was implanted in 2007 and the newest in 2021. All were reevaluated after one month, four after 3 months, and one after 6 months. After one month, four patients (66.6%) did not notice any difference, one presented with severe behavioral deterioration (16.6%) and was moved back to HFS with resolution of the symptoms, and one patient (16.6%) noticed that tonic clonic seizures became more prolonged. In all of them, parents reported a qualitative improvement in attention. After three months, three patients (75%) had unaltered seizure frequency, and the patient that initially had more prolonged tonic clonic seizures noticed improvement in both seizure frequency and duration. The patient evaluated after six months kept the same seizure frequency.


Conclusions: Moving patients with CM-DBS from HFS to LFS appears to be safe and allows for the continuation of the study. Longer follow-up data would be especially useful to overcome potential long-lasting aftereffects from the initial HFS that might bias the results.


Funding: No funding