Quality-of-life metrics with vagus nerve stimulation for epilepsy from provider survey data

Abstract

Objective: Drug-resistant epilepsy is a devastating disorder associated with diminished quality of life (QOL). Surgical resection leads to seizure freedom and improved QOL in many epilepsy patients, but not all individuals are candidates for resection. In these cases, neuromodulation-based therapies such as vagus nerve stimulation (VNS) are often used, but most VNS studies focus exclusively on reduction of seizure frequency. QOL changes and predictors with VNS remain poorly understood.

Method: Using the VNS Therapy Patient Outcome Registry, we examined 7 metrics related to QOL after VNS for epilepsy in over 5000 patients (including over 3000 with ≥12months follow-up), as subjectively assessed by treating physicians. Trends and predictors of QOL changes were examined and related to post-operative seizure outcome and likelihood of VNS generator replacement.

Results: After VNS therapy, physicians reported patient improvement in alertness (58-63%, range over follow-up period), post-ictal state (55-62%), cluster seizures (48-56%), mood change (43-49%), verbal communication (38-45%), school/professional achievements (29-39%), and memory (29-38%). Predictors of net QOL improvement included shorter time to implant (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.6), generalized seizure type (OR, 1.2; 95% CI, 1.0-1.4), female gender (OR, 1.2; 95% CI, 1.0-1.4), and Caucasian ethnicity (OR, 1.3; 95% CI, 1.0-1.5). No significant trends were observed over time. Patients with net QOL improvement were more likely to have favorable seizure outcomes (chi square [χ²]=148.1, p<0.001) and more likely to undergo VNS generator replacement (χ²=68.9, p<0.001) than those with worsened/unchanged QOL.

Significance: VNS for drug-resistant epilepsy is associated with improvement on various QOL metrics subjectively rated by physicians. QOL improvement is associated with favorable seizure outcome and a higher likelihood of generator replacement, suggesting satisfaction with therapy. It is important to consider QOL metrics in neuromodulation for epilepsy, given the deleterious effects of seizures on patient QOL.

Keywords: Epilepsy; Quality of life; Surgery; VNS; Vagus nerve stimulation.

Figure 1. Change in QOL metrics with VNS

A) Improvement rates in various metrics related to QOL are shown. Patients were subjectively rated by the treating physician as improved, worsened, or no change with regard to each metric, compared to pre-operative baseline. B) Percentage of patients rated as net improved, worsened, or no change across all 7 QOL metrics. For A and B, no significant trends over time were observed (F < 11, p > 0.05 per metric, Bonferroni corrected). N = 4,666 (0-4 months), 3,277 (4-12 months), 3,182 (12-24 months), and 1,194 (24-48 months) patients. QOL, quality of life; VNS, vagus nerve stimulation.

Figure 2. QOL metrics in seizure responders vs. non-responders after VNS

A) Over time with VNS, a significant increase is seen in both the median reduction in seizure frequency (F = 214.6, p < 0.01, Bonferroni corrected), and in the proportion of patients who respond to VNS, which is defined as ≥ 50% reduction in seizure frequency (F = 43.0, p = 0.04, Bonferroni corrected). B-C) Seizure responders (B) are significantly more likely to show improvement in QOL metrics than non-responders (C) (χ² = 148.1, p < 0.001), though no significant trend over time is seen in either group (F < 5, p > 0.05, Bonferroni corrected). and N = 4,666 (0-4 months), 3,277 (4-12 months), 3,182 (12-24 months), and 1,194 (24-48 months) patients. QOL, quality of life; VNS, vagus nerve stimulation.

Figure 3. VNS generator replacement rates stratified by QOL metrics and seizure response

Overall, 71.4% of patients underwent VNS generator replacement, suggesting perceived benefit from continued therapy in these individuals. A) Patients with net improvement in QOL metrics were significantly more likely to undergo VNS generator replacement than those with worsened or unchanged QOL metrics (χ² = 68.9, p < 0.001, Bonferroni corrected). B) Individuals who were seizure responders (≥ 50% reduction in seizure frequency) were also significantly more likely to undergo generator replacement than non-responders (χ² = 40.0, p < 0.001, Bonferroni corrected). N = 3,085 patients with generator replacement data. QOL, quality of life; VNS, vagus nerve stimulation.