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ImageThe Vagus Nerve Stimulator and how it can be useful for treating epilepsy in children: Feature Article

For this issue of the Northeast Regional Epilepsy Group newsletter, Sloka Iyengar, PhD, clinical researcher at NEREG sat down with Dr. Lorraine Lazar to talk about how the vagus nerve stimulator (VNS), a thin round pacemaker-like device, can be useful for treating children with epilepsy. 

Lorraine Lazar, M.D., Ph.D. is a pediatric epileptologist and child neurologist who earned her M.D. and Ph.D. at Mount Sinai School of Medicine.  She completed her residency in Neurology and Child Neurology at the New York Hospital-Cornell University Medical Center of New York, her residency in Senior Pediatrics at Columbia University Medical Center of New York and her Fellowship in Clinical Neurophysiology at the New York Hospital-Cornell University Medical Center of New York.  She is Board certified in the American Board of Psychiatry and Neurology with Special Qualifications in Child Neurology and in Clinical Neurophysiology.  Her office is in New Brunswick, NJ.

Could you explain the VNS procedure is in simple terms? How does VNS provide a reduction in seizures?

Dr. Lazar- The vagus nerve stimulator (VNS) is a thin round pacemaker-like device surgically implanted under the skin of the left upper chest connected to an electrical lead (thin wire) running under the skin attached to the left 'vagus nerve' in the neck.  Within one or few days of surgical implantation, the VNS device is turned on and programmed to send gentle repetitive (day and night) electrical impulses to the vagus nerve.  The VNS is programmed by a computerized 'wand' held over the left upper chest which sends magnetic signals through the skin directly to the device without being felt by the patient.  Programmed increases in the intensity level of current delivered to the vagus nerve results in seizure reduction over time. The precise mechanism of seizure reduction using this technology is still not fully understood.

How do considerations for implanting VNS differ in the pediatric population as compared to adults?  

Dr. Lazar - Similar to adults, a child might be considered for VNS implantation if they have medication resistant epilepsy (where medications are not controlling the seizures) and are not deemed candidates for resective neurosurgery, or those children whose anti-seizure medications have caused intolerable side effects and require consideration of non-drug therapies.

Technically, the surgical implantation of a VNS device is similar for both adults and pediatric patients. Two small incisions are typically required.  The VNS generator is implanted through a 4-cm incision just in front of the axilla (armpit).  In the young patient, this incision can be moved 1 to 2 cm into the axilla to avoid having the surgical incision directly over the device. The second incision site is typically made along a natural horizontal skin crease in the middle of the left side of the neck, for access and attachment of the VNS lead wire to the vagus nerve. This second incision may vary in length, but usually requires no greater than 4-cm in a child.  Intravenous antibiotics administered before skin incision typically prevent wound infection. 

What are some of the common side-effects of VNS in general and in the pediatric population?

Dr. Lazar- Side effects of VNS in children are typically well tolerated and less noticeable over time, similar to adults.  The most common side effects are post-implantation hoarseness, throat discomfort, difficulty swallowing and coughing, evident during VNS "on time" when the vagus nerve is actively stimulated as programmed (for example, for 30 seconds every 5 minutes).  As the degree of hoarseness has been related to the intensity level of current delivered to the vagus nerve, discomfort can be limited by modifying the VNS settings.

What is the success rate for VNS in the pediatric population? Are there certain epilepsy syndromes (e.g. Lennox-Gastaut syndrome) that would benefit more from VNS as compared to other syndromes?

Dr. Lazar- Most studies have shown an overall reduction in drug resistant partial epilepsy or severe multifocal epilepsy in children following VNS implantation, particularly the longer it remains used (not turned off).  A landmark study was published in 1999 by the Pediatric VNS Study Group (Murphy et al).  Since then, some children have become seizure free with the use of this technology, though these numbers are small.  More commonly, the improvement in seizure control using VNS allows a reduction in number and/or dose of anti-seizure medications. However, as with all therapies for refractory epilepsy, not all patients respond to VNS therapy.   

Patients with drug resistant partial epilepsy have continued to demonstrate the best outcomes for seizure control using VNS.  Patient with Lennox-Gastaut syndrome and other severe multifocal pediatric epilepsies have also demonstrated significant clinical responsiveness to VNS therapy, with greater reduction in seizure frequency correlating with longer time from implantation.  For some, improvement with VNS treatment is seen in reduced seizure length or reduced seizure intensity without significant change in seizure number.   In some patients with Dravet syndrome (severe myoclonic epilepsy in infancy), a significant reduction in seizures has been accompanied by increased alertness and improved communication skills.   The causes of pediatric seizures amenable to improved seizure control by VNS is diverse and has included tuberous sclerosis, hypothalamic hamartoma (with additional improvement in autistic behaviors) and chromosomal anomalies.  

Do we provide VNS for children at NEREG? 

Dr. Lazar- The Northeast Regional Epilepsy Group (NEREG) recommends Vagal Nerve Stimulation as a valuable therapeutic option for pediatric patients with medication refractory epilepsy who are not candidates for resective neurosurgery.  NEREG board certified epileptologists have the required expertise for programming the VNS and determining the optimal settings for seizure control in each individual patient. 

Thank you, Dr. Lazar for spending time with us and answering our questions about this most interesting topic.  

 

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