Abstracts

Rationale: Vagal nerve stimulation (VNS) is a technique of neuromodulation approved for the management of drug-refractory epilepsy by the FDA in 1997. The side effects of VNS are generally limited to dysphonia, cough, or shortness of breath. Serious adverse effects such as cardiac bradyarrhythmia or asystole are very rare and have been described during implantation and initial lead testing. To date, there have been very few documented cases of cardiac arrhythmia years after VNS insertion or unrelated of seizures.

Methods: A 32-year-old left-handed woman with intractable epilepsy from the age of 24, presented with multiple daily dialeptic seizures (sz), preceded by auditory aura or somatic cold sensation in her head. Rare progressions to bilateral tonic clonic sz also reported. At the moment of evaluation patient on LEV, CBZ, ZNS.

Born to consanguineous parents. Family history of congenital heart disease, epilepsy, and autism in 1st and 2nd-degree relatives. Brain MRI revealed cerebellar dysplasia with disorganized cerebellar fissuration (see Fig.1). Bifrontal (right >left) spike-wave discharges and bilateral independent parietal paroxysmal fast activity seen on EEG. She was implanted with a VNS for better sz control.

Results: An EKG Holter performed prior to VNS insertion was normal. The implantation and its functioning were uneventful for 2 years. Slight reduction in sz frequency observed. However new episodes of falls reported. An ambulatory EEG was performed to characterize these episodes. An episode of asystole preceded by a heart rate reduction from 78 beats per minute (bpm) to 36 bpm was observed (see fig.2). EEG simultaneously showed diffuse slowing followed by 15-20 seconds background attenuation. The EEG background normalized once the heart rhythm reached 70 bpm. During this event, the patient reported headache and shortness of breath followed by loss of consciousness. She was referred to cardiology, and a 72 hours cardiac Holter revealed events of third-degree AV block preceded by first- and second-degree AV block at night during 3 consecutive nights and a short episode of atrial fibrillation. Transthoracic echocardiography was normal. VNS was turned off, and the Holter repeated, which reported sinus rhythm with no pauses. She has not had any syncopal events since. In view of the strong family history of consanguinity, congenital cardiac anomalies, and epilepsy, whole exome sequencing (WES) and chromosomal microarray (CMA) were done. CMA did not reveal any pathogenic variants. The WES revealed a homozygous variant of uncertain significance (VUS) in the EPB41 gene and a heterozygous VUS in the MACF1 gene.

Conclusions: The vagus nerve regulates cardiac function; hence, VNS could affect the cardiac rhythm through mechanisms that are yet to be unravelled. Understanding the patients at risk of cardiac arrhythmias following VNS implant is crucial for optimizing patient selection for the device. Identifying any genetic predisposition or other risk factors (such as specific medications) can enhance the safety of the treatment. Performing an EKG Holter before and after VNS implant could be recommended in certain cases.

Funding: none