Vagal Nerve Stimulator
Managing seizures in pediatric patients is a common occurrence in the Emergency Department. We have discussed seizure related issues in the past: Seizure Mimics, Neonatal Seizures, Simple Febrile Seizures, and Complex Febrile Seizures. Some seizures require us to remember unique pediatric conditions (ex, Pyridoxine Dependent Seizures) and some others require us to know unique therapies (ex, Ketogenic Diet). As with any therapy, there are pros and cons to understand. Let us look at the pros and cons related to Vagal Nerve Stimulators (VNS):
Vagal Nerve Stimulator: What is that?
- A pulse generator (similar to a cardiac pacemaker) is implanted in the chest.
- It’s electric lead is attached to the vagus nerve in the neck (no brain surgery is needed).
- The VNS generator is programmed to stimulate the vagus nerve in regular intervals (ex, for 30 seconds every 5 minutes). [See Epilepsy Foundation)
- The frequency, amplitude, and duration of the stimulation pulses can also be adjusted.
- Placing a magnet over the VNS can also lead to extra stimulation.
- Patients who have focal seizures or auras may abort seizures themselves.
- Family members (or other providers) may also utilize the VNS via the magnet.
- Intermittent stimulation of the cervical vagus nerve via VNS has been shown to be effective and safe. [Serdaroglu, 2016; Terra, 2014; Connor, 2012]
- The mechanism of action of vagal stimulation is still not fully understood.
Vagal Nerve Stimulator: Is it helpful?
- 10-30% of children with seizure disorders will continue to have significant seizures despite optimal medical or surgical (resection) options.
- The VNS is used for difficult to control seizure disorders, so its “success” is marked in relative terms.
- Long-term studies have shown that patients can have reduction seizure burden. [Serdaroglu, 2016; Terra, 2014]
- 62.5% of cases had 50% reduction in seizure frequency.
- The percentage of those who had reduction of seizures increased each year.
- There is also reduction in traumas and other seizure-related morbidities.
- VNS can also reduce number of days of inpatient care.
Vagal Nerve Stimulator: The Complications
- Generally, the VNS is well tolerated and has minimal side-effects. [Serdaroglu, 2016]
- The setting of the VNS stimulation frequency, amplitude and duration can influence side-effects.
- Side-effects are: [Serdaroglu, 2016; Smyth, 2003]
- Sore Throat
- Tingling sensation in throat
- Outbursts of laughter
- Shoulder abduction
- Torticolis and neck spasms
- Urinary retention
- Complications do occur: [Smyth, 2003]
- Superficial infections
- Deep space infections (~3.5%)
- Stridor and Sleep Apnea
- Contraction of supraglottic structures and vocal folds [Kelts, 2014]
- Ipsilateral vocal cord paralysis
- Cardiac arrhythmia [Cantarin-Extremera, 2015]
- Generally the left vagus nerve is selected to stimulate as it innervates the SA node while the right vagus nerve innervates the AV node.
- Cases still exist of arrhythmias with using the left vagus nerve.
- Lead fracture
- May occur due to patient manipulation of the device.
- “Twiddler Syndrome”
- Classically occurs in adults who repeatedly manipulate their cardiac pacemaker/defibrillator.
- Similar behavior can lead to VNS lead fracture in children. [Trout, 2013]
- Facial muscle paresis