PMC8330973_01
The VNS device and an intraoperative photograph of the left vagosympathetic trunk. The pulse generator (width 45 mm, height 32 mm, depth 6.9 mm, and weight 16 g) (A). The electrode (B). The left vagosympathetic trunk wrapped by the two helical electrodes and anchor tether (C). VNS, vagus nerve stimulation.
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F1
Despite semiology indicating FS, generally synchronized spike or spike-wave complexes were frequently observed in inter-ictal EEG (Supplementary Figure 1A). TX, USA) and electrode lead with two helical electrodes at the tip (VNS lead M304, LivaNova USA, Inc., Houston, TX, USA) (Figures 1A,B). The method to implant the VNS device was previously described. Briefly, the two helical electrodes and anchor tether were wrapped around the left vagosympathetic trunk in the cervical area (Figure 1C), and the electrode lead was connected to the pulse generator implanted in the subcutaneous space cranial to the left scapula.
Transition of stimulation parameters of VNS therapy in the dog. The red vertical lines mean each visit. VNS, vagus nerve stimulation.
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F2
There was no seroma, and the wound had healed (Supplementary Figure 2A). During the 1-year follow-up, stimulation parameters were adjusted in each visit based on the dog's responses (Figure 2).
The number of FS-GTCS and FS-GTCS clusters per month (A). The number of FS and FS clusters per month (B). The number of seizure days (FS-GTCS and FS) per month (C). The asterisk indicates that VNS therapy was initiated in this month. Months -5 to 0 indicate the retrospective period; months 1 to 12 indicate the follow-up period. FS-GTCS, focal seizures evolving into generalized tonic-clonic seizures; VNS, vagus nerve stimulation.
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F3
The device was activated using an external programming system with stimulation parameters output current 0.25 mA, pulse width 250 mus, frequency 20 Hz, on-time 30 s, and off-time 5 min, which are initial settings commonly recommended for the treatment of epilepsy in humans (Supplementary Figure 3). An 89% reduction in the frequency of FS-GTCS clusters was also achieved (55 clusters for 6 months vs. 12 clusters in 1 year) (Figure 3A). The number of FS-GTCS days also had 76% reduction (93 seizure days for 6 months vs. 45 seizure days in 1 year) (Figure 3C). The owner was instructed to count the number of FS after VNS initiation, and no decreases were noted during the 1-year follow-up (Figures 3B,C).