The effectiveness results were as follows:
The mean (SD) seizure frequency decreased from 14 (13.8) seizures per month (range: 2-40) in the period before implantation to 9 (12.3) seizures per month (range: 0-30) (p=0.0003) after implantation.
The mean number and dosage of AEDs remained unchanged in 14 patients after implantation. In one patient two AEDs were tapered, in one patient one AED was tapered. In 4 patients an additional AED was administered.
Regarding the side-effects of the treatment, it was reported that all patients experienced an indescribable throat sensation during the first stimulation trains, which subsided over 24 hours and was considered as an intrinsic and minor side-effect of VNS that did not cause pain or discomfort to the patient.
Hoarseness, voice change, paresthaesias in the throat or in the area around the stimulator, dysphagia and persistent coughing during stimulation were reported in 10 patients during ramping-up.
In three patients these side-effects required a temporary reduction of output current but in none of the patients did stimulation have to be interrupted.
Six patients reported side effects at the time of maximum follow-up. These side effects did not require any change of stimulation output and subsided over time.