Background Antiepileptic drugs (AEDs) are the primary treatment modality for patients with epilepsy. However, approximately one-third of patients with epilepsy continue to have seizures on medication. ¹ When medications have failed to control seizures, non-pharmacologic options such as: epilepsy surgery, ketogenic diet, and vagus nerve stimulator (VNS) therapy may be used.²

Multiple large case series have reported responder rates of greater than 50% reduction of seizures in patients implanted with VNS. ^3,4,5

Aims Our primary aim was to assess the effectiveness of VNS in reducing seizure frequency and/or severity and improving quality of life in our cohort of patients with complex epilepsy.

Methods We performed a retrospective study, analysing the files of patients with complex epilepsy treated with neurostimulation in a tertiary hospital in South East of England. Data on the effectiveness of VNS in different domains were collected using the attached proforma from clinical records obtained from their parents, carers and clinicians over a 5 year period.

Results We identified 25 students treated with VNS. 60% (n=15) were male with a mean age of 18.08 (IQR 17 – 20 years). Based on the nature and complexity of their seizures, patients were classified into 4 major groups: refractory (n=4,16%), symptomatic (n=9, 36%) lennox gastaut syndrome (n=6, 24%) and others (n=6, 24%).. All had documented EEGs and neuroimaging, 64% (n=16) with abnormal MRI findings. 28% of patients (n=7) reported no reduction in seizure frequency, 28% (n=7) reported that their seizures were reduced by a quarter, 20% (n=5) had a 50% reduction, and 12% (n=3) a reduction by three-quarters. The remaining were either variable or not recorded (12%, n=3). 32% of patients felt the severity of seizure was reduced after 12 months of VNS treatment while 24% (n=6) had their medication reduced. The most commonly reported side effect was cough (36%, n=9), followed by swallowing difficulty (16%, n=4). Overall, more than one third of patients (36%, n=8) reported improvement in their quality of life.

Conclusions VNS treatment is effective in reducing seizure frequency, however, our audit showed a slightly lower rate of response compared with previously published data. This finding may be attributed to the large number of structural epilepsies of our cohort.

References

1. Kwan P, Brodie MJ. Early identification of refractory epilepsy. N Engl J Med. 2000;342(5):314.

2. Berg AT, Kelly MM Defining intractability: comparisons among published definitions. Epilepsia. 2006;47(2):431.

3. Elliott RE, Morsi A, Kalhorn SP et al; Vagus nerve stimulation in 436 consecutive patients with treatment-resistant epilepsy: long-term outcomes and predictors of response. Epilepsy Behav. 2011;20(1):57.

4. Vonck K, Thadani V, Gilbert K, et al; Vagus nerve stimulation for refractory epilepsy: a transatlantic experience.J Clin Neurophysiol. 2004;21(4):283.

5. De Herdt V, Boon P, Ceulemans B et al; Vagus nerve stimulation for refractory epilepsy: a Belgian multicenter study. Eur J Paediatr Neurol. 2007 Sep;11(5):261–9. Epub 2007 Mar 28.