Vagal Nerve Stimulation for Epilepsy
We are pleased to offer a new treatment at Cave Veterinary Specialists for dogs affected by refractory epilepsy: External Vagal Nerve Stimulation.
What is refractory epilepsy in dogs?
Epilepsy is common in dogs and it affects a large proportion of the dog population: 0.5 to 5% depending on studies.
Treating epilepsy is challenging because 20 to 30% of dogs are refractory to the medical arsenal available to veterinarians. This means that some dogs, despite taking more than two medications at high dosages, still experience frequent seizures. Some breeds, such as Border collies, are known to be especially difficult to treat.
What is vagal nerve stimulation in dogs?
The large number of dogs with refractory epilepsy has driven the search for new therapies and vagal nerve stimulation has emerged as a potential ‘additional’ therapy for dogs with refractory epilepsy. The vagal nerve makes a connection with specific centres in the brain associated with the regulation of mood, emotion, and seizure activity. By stimulating the vagal nerve located in the neck region of the dog, the therapy modulates the chemical balance in the brain to stabilise the brain cells and reduce the risk of occurrence of seizures. Vagal nerve stimulation is an adjunctive therapy approved for use in human patients with refractory epilepsy.
There are two methods of stimulating the vagal nerve:
1. by direct stimulation via an implant placed surgically in the dog’s neck; and
2. by stimulation through the skin (also called ‘transcutaneous’ stimulation) with a device placed on the skin but not penetrating the skin, a technic called ‘non-invasive’.
Stimulation via an external device offers advantages because it does not require surgery and therefore has a much lower cost.
Implantable devices carry many risks:
- infection around the implant: 10% of human patients get an infection around the implant;
- a cough and local pain can be experienced when the device is active as well as vocal cord paralysis;
- changes of the heart rhythm, consequences that have not been studied in dogs;
- prevent the possibility to conduct further MRI scans later in life after the implantation;
- implanted leads from the device can twist / break and a seroma (pocket of fluid under the skin) can occur; it is placed in a region where a neck collar / harness cannot been used; if the implant is dislodged, it can damage the vagal nerve with might have consequences on the heart.
Is your dog a candidate for external vagal nerve stimulation therapy?
External vagal nerve stimulation is indicated in dogs with refractory epilepsy, therefore having persistent and frequent seizures (> 1 seizure a month) despite receiving at least 2 medications.
The neurology service at Cave Veterinary Specialists is staffed with two RCVS and European Specialists in Veterinary Neurology supported by permanent high field (1.5 Tesla) MRI and CT machines. We offer standard of care diagnosis for canine epilepsy.
What to expect with vagal nerve stimulation?
The treatment takes several months to be effective. Response rate with vagal nerve stimulation (either external or surgically implanted stimulators) is ~50% in humans and only 5% of human patients become seizure free after 4 months of treatment. We are lacking data in dogs so we can only be guided by studies in people. There is only one study in dogs conducted by Dr M?nana (North Carolina State University) in 2002: in a randomized, placebo?controlled, crossover study involving 10 dogs, Dr M?nana and colleagues found no significant difference in seizure frequency, severity, or duration between dogs implanted with a vagal nerve stimulator and control dogs over the study period which was 3 months. But she found that there was a 34% decrease in seizure frequency in the last 4 weeks of treatment, suggesting that a study with a longer follow-up period is needed.
We are pleased to be able to offer this therapy for £600, which is considerably less than surgery. To book a consultation please call our Neurology department on 01823 653510.
Interested to read on vagal nerve stimulation?
Brain stimulation as a neuromodulatory epilepsy therapy. Schulze-Bonhage A.
Seizure. 2017 Jan;44:169-175
Transcutaneous vagus nerve stimulation (t-VNS) in pharmacoresistant epilepsies: a proof of concept trial. Stefan H, Kreiselmeyer G, Kerling F, et al.
Transcutaneous vagus nerve stimulation (tVNS) for treatment of drug resistant epilepsy: a randomized, double-blind clinical trial (cMPsE02). Bauer S, Baier H, Baumgartner C, Bohlmann K, Fauser S, Graf W, et al.
Brain Stimul 2016 May-Jun;9(3):356-63.