Rationale:
Drug-resistant epilepsy (DRE) is characterized by non-responsiveness to antiepileptic drugs and is observed in almost 30% of patients with epilepsy. Vagus nerve stimulation (VNS) is an adjunctive neuromodulation therapy used for patients with DRE who are unsuitable candidates for resective epilepsy surgery. The aim of this study was to assess the efficacy of VNS therapy for patients with DRE.
Method:
This single-center, retrospective, and cross-sectional study was performed at the Epilepsy program of King Fahad Medical City, Riyadh, Saudi Arabia. We examined the database of all epilepsy patients who underwent VNS implantation from November 2008 to April 2018; patients’ demographics, epilepsy type, etiology, number of anti-epileptic medications (AED) pre/post implantation, neuroimaging, as well as VNS parameters and adverse effects were considered. The response rate was determined based on seizure frequency before implantation and at latest follow-up. The responders were then subcategorized as follows: R50 (greater than 50% reduction of the seizure frequency), R75 (greater than 75% reduction of the seizure frequency), and seizure-free (SF).
Results:
Forty-four patients (23 male, 21 female), with ages ranging from 8-53 years old (mean age: 25.4 years ± 10.5), were included in the study. The age at implantation for the patients ranged from 2-47 years old (mean age: 18.5 ± 10.1) and their epilepsy duration ranged from 2-50 years (mean epilepsy duration: 20 ± 9.2). Five patients (11.3 %) had undergone prior epilepsy surgery before VNS implantation. AEDs pre- and post-VNS ranged from 1-5 (mean: 3.1 and 3.2, respectively). Thirty patients had generalized epilepsy, 13 had focal epilepsy, while one patient displayed multifocal epilepsy. Etiological analysis revealed that epilepsy was caused due to structural factors in 19 patients (43.1%), genetic factors in seven patients (15.9%), infectious factors in five patients (11.3%), and unknown factors in 13 patients (29.5%). Pre-implantation seizure frequency was daily in 30 patients (68.1%), weekly in 10 patients (22.7%), and monthly in four patients (9%). Thirty-two patients (72.7%) were found to have associated cognitive, intellectual, or behavioral disorders. Neuroimaging was conducted in 42 patients and 25 (56.8%) showed a brain lesion. 33 patients (75%) were responders to VNS therapy and can be categorized as follows: R50 - 10 patients (30.3%), R75 - 22 patients (66.6%), seizure free - 1 patient (3%). Eleven patients (25%) showed no response (seizure reduction < 50%) . The duration of post-VNS implantation follow-up ranged from 12 to 120 months (mean duration: 60.8 months). The average output current at last follow-up was 1.9 mA (Table 1). Thirteen patients (29.5%) reported transient VNS related adverse effects, most commonly hoarseness and cough.
Conclusion:
VNS is a well-tolerated and effective adjunctive therapy in patients with drug-resistant epilepsy in Saudi Arabia.
Funding:
:None
FIGURES
Figure 1