Uneven Effectiveness of Vagus Nerve Stimulation in Bilateral Frontal Lobe Epilepsy
Overview
This case study reports a patient with drug-resistant bilateral frontal lobe epilepsy who underwent left-sided vagus nerve stimulation (VNS). Postoperative stereoelectroencephalography (SEEG) revealed a marked reduction in seizures originating from the right hemisphere, indicating uneven VNS efficacy based on seizure lateralization.
Background
Vagus nerve stimulation is an established surgical treatment for drug-resistant epilepsy, typically applied to the left vagus nerve to modulate thalamic and limbic networks. The impact of seizure focus laterality on VNS effectiveness remains unclear, with limited evidence suggesting lateralization may influence outcomes. This study presents detailed SEEG data post-VNS implantation in a patient with bilateral frontal lobe seizure foci, providing insight into lateralized therapeutic effects.
Data Highlights
Parameter
Right Hemisphere
Left Hemisphere
Number of SEEG electrodes
2
5
Subclinical seizures recorded over 3 days
2
31
Seizure frequency pre-VNS
Similar to left hemisphere
Similar to right hemisphere
Seizure frequency post-VNS
Markedly reduced
Persisted
Key Findings
VNS was implanted on the left vagus nerve in a patient with bilateral frontal lobe epilepsy.
Pre-VNS video-EEG showed seizures originating with similar frequency from both hemispheres.
Post-VNS SEEG monitoring revealed a marked reduction in right hemisphere seizures (2 recorded) compared to left hemisphere seizures (31 recorded).
Seizure lateralization influenced VNS efficacy, with better control of right-sided seizures despite left-sided stimulation.
Subsequent left frontal tumor resection and epileptogenic zone removal resulted in seizure freedom (Engel class I outcome).
Clinical Implications
This case highlights the importance of considering seizure lateralization when selecting candidates for VNS therapy, as efficacy may vary between hemispheres. Left-sided VNS may preferentially reduce seizures originating from the contralateral (right) hemisphere. Detailed lateralized seizure evaluation using SEEG can guide surgical planning and optimize treatment strategies in patients with bilateral epileptic foci.
Conclusion
The study demonstrates uneven VNS effectiveness in bilateral frontal lobe epilepsy, with significant seizure reduction on the right side following left vagus nerve stimulation. These findings underscore the need for individualized assessment of seizure laterality to maximize therapeutic outcomes.
References
Hödl et al. -- Impact of Seizure Lateralization on VNS Efficacy
Multiple studies [17, 18] -- Efficacy of Vagus Nerve Stimulation in Drug-Resistant Epilepsy
Anatomical and physiological basis of VNS [14, 15, 16, 19]
