gms | German Medical Science

Objective: In multi-drug-resistant epilepsy vagus nerve stimulation (VNS) is an efficacious additional treatment to reduce seizure frequency and -severity. A recently developed cardiac-based seizure detection (CBSD) algorithm triggers additional stimulation upon heart rate increases of at least 20% (Model AspireSR). Yet, long term sensitivity and specificity of the CBSD-algorithm remain unclear. We present a case series of 11 adult patients with epilepsy with AspireSR.

Methods: Individual VNS data and seizure diaries were reviewed. Open- and closed-loop VNS was active in all patients. We reviewed CBSD-settings, operating hours and battery status of the devices. Percentage of auto-stimulation was assessed in comparison to continuous but intermittent stimulation. If seizure diaries were available, we verified whether a high rate of auto-stimulation was present during the documented seizures.

Results: We reviewed 11 patients with a mean age of 28 years (± 18y). Mean duration since implantation was 43 months (± 13m). Mean operating time was 4908 hours (1766-8907h), CBSD-thresholds ranged between 30% and 70%. Battery status was 75% in all patients. No correlation between CBSD-thresholds and number of auto-stimulations was seen. Of 2,471,370 detected stimulations 100,448 (4.1%) were auto-stimulations according CSDB-algorithm. Proportion of auto-stimulation varied substantially. While 7 patients had a mean of 2.4% (± 2.2%), 4 patients had a significantly higher proportion of auto-stimulation 9.3% (± 3.2%). Seizure-frequency was higher in patients with more auto-stimulation, according to data from seizure diaries (eligible in 5 patients, only). Adverse events occurred in none of the patients.

Conclusion: High sensitivity (>80%) of seizure-detection was described in short time observations. In another study 35% of detected seizures were treated with auto-stimulation. Here we provide long-term results for sensitivity and specificity of the CBSD algorithm. While sensitivity seems to be high, we presume specificity to be weak. An extremely high number of auto-stimulations is supposedly false-positive. Yet, treatment was well tolerated by the patients without any adverse events and battery life did not seem to be compromised, despite the high number of auto-stimulations. CBSD is a promising development, yet the algorithm should be revised to provide a better specificity.