Vagus Nerve Stimulation Therapy: Good and Not So Good
VNS stimulates the limbic system, a group of related brain structures that affect mood, motivation, sleep, appetite, alertness and other factors commonly altered by depression.
VNS is delivered to the left cervical vagus nerve by a stopwatch-sized generator – the NeuroCybernetic Prosthesis (NCPâ) System – implanted just under the skin in the left chest area.
VNS delivers pre-programmed, mild, intermittent electrical pulses to the left vagus nerve 24 hours a day. The implantation procedure takes approximately one hour and usually requires no overnight hospitalization.
VNS is safe and does not cause the side effects normally associated with depression medications, such as weight gain, loss of sexual function, cognitive impairment and insomnia.
Side effects associated with VNS typically occur only when stimulation is on. They include voice alteration, shortness of breath, neck discomfort and coughing, all of which are reported less frequently over time. From Mike. WHY? What neuromuscular adaptations are occurring that are not being documented?
VNS with the Cyberonics NCP System was recently approved for sale in the European Union and in Canada as a treatment of depression in patients with treatment-resistant or treatment-intolerant major depressive episodes including unipolar depression and bipolar disorder (manic depression).
VNS with the Cyberonics NCP System was approved by the FDA in 1997 for use as an adjunctive therapy in reducing the frequency of seizures in adults and adolescents over 12 years of age with medically refractory partial onset seizures. In addition, the NCP System is currently approved for epilepsy in all the member countries of the European Union, Canada, Australia and other markets.
Contacts: Ellen Bank, Medical University of South Carolina, 843-792-2626
Samantha Narcisse, Porter Novelli, 212-601-8276
Interscapular placement of a vagal nerve stimulator pulse generator for prevention of wound tampering. Technical note. Le H, Chico M, Hecox K, Frim D.
Section of Pediatric Neurosurgery, University of Chicago Children's Hospital, Chicago, Ill 60637, USA.
In some cognitively delayed children who require a vagal nerve stimulator for treatment of their seizures, there is a risk of wound breakdown and infection from obsessive tampering with the wound. We describe the interscapular placement of the vagal nerve stimulator pulse generator as a method to reduce this risk. Copyright 2002 S. Karger AG, Basel
VNS therapy in clinical practice in children with refractory epilepsy.
Nagarajan L, Walsh P, Gregory P, Lee M.
Department of Neurology, Princess Margaret Hospital for Children, Perth, Western Australia, Australia. email@example.com
OBJECTIVES: To study the efficacy, tolerability and safety of the vagus nerve stimulation (VNS) therapy in clinical practice, in 16 children and adolescents with refractory epilepsy.
METHODOLOGY: We assessed the efficacy of VNS therapy, retrospectively by comparing seizure frequency, duration and severity at the time of most recent follow up (av: 24.9 months) to that in the 4 weeks prior to VNS surgery. Changes in quality of life, sleep and behaviour at last review was compared with that prior to VNS.
Adverse effects elicited by specific questioning, spontaneous reporting and clinical examination are described. RESULTS: Vagus nerve stimulation resulted in a >50% reduction in seizure frequency in 62.5% of children with 25% achieving a >90% reduction. Vagus nerve stimulation was well tolerated in all but one of our cohort, with no serious side-effects. CONCLUSION: Our results support its role as one of the options in intractable childhood epilepsy.
PMID: 11903103 [PubMed - indexed for MEDLINE]
The anticonvulsant effect of electrical fields.
Departments of Neurology and Pediatrics, George Washington University School of Medicine, Children's Hospital National Medical Center, 111 Michigan Avenue NW, Washington, DC 20010, USA. firstname.lastname@example.org
The use of electrical fields to treat epilepsy is undergoing increased scrutiny as an alternative to medications and resective surgery. Much recent attention has been focused on ionic channels and seizure control; however, nonsynaptic mechanisms may be crucial for seizure onset, raising the possibility of using electrical field application to abort seizures.
Furthermore, the inhibitory effects may outlast the immediate treatment and possibly be a prophylactic intervention. This paper reviews the use of brain stimulation for treatment of epilepsy, but also cites instances where the antithetical results occur. The greatest detail focuses on disrupting the onset or shortening the seizure. The paper does not extensively review deep brain or vagal nerve stimulation.
PMID: 11898511 [PubMed - indexed for MEDLINE]
Vagus nerve stimulation - a new option for the treatment of chronic pain syndromes?
Kirchner A, Birklein F, Stefan H, Handwerker HO.
Neurologische Klinik, Friedrich-Alexander-Universitat Erlangen.
Electrical stimulation of the vagal nerve (VNS) has become an established method for treating medically refractory epilepsies. From animal experiments it is well known that depending on the stimulation intensity VNS can elicit both inhibition and facilitation of nociception. Recent physiologic investigations demonstrated a similar influence of VNS on pain perception in patients treated by chronic VNS.
However, in humans, a more marked effect was shown for the pain inhibition which is probably mediated by neurobiochemical mechanisms. These findings are discussed in consideration of the physiologic mechanisms underlying the modulation of pain and seizures by VNS known from animal studies. First reports of attenuation of chronic pain by VNS indicate that the method might be an option for pain treatment in the future.
PMID: 11810366 [PubMed - indexed for MEDLINE]
Chronic diarrhea associated with vagal nerve stimulation. Sanossian N, Haut S.
Department of Neurology, Albert Einstein College of Medicine, Bronx, NY, USA.
PMID: 11805274 [PubMed - indexed for MEDLINE]
The left and right vagus nerves possess the greatest extent of innervation of any of the twelve pairs of cranial nerves. These nerves potentiate motor, sensory, and parasympathetic autonomic effects as they traverse through the skull, jugular fossa, thorax, and abdominal cavity.
Important branches of these nerves perform key roles in swallowing, articulating, and regulating cardiac rate and bronchial diameter.
As many as 20% of epileptic patients in the United States are unable to control their seizures by non-pharmacologic therapy. In 1973, Cooper et al. described the possibility of using chronic electrical stimulation of the cerebellum for treating seizures refractive to oral drugs.
Dozens of further studies, however, suggested that limited efficacy and invasive neurosurgery were significant barriers against widespread acceptance of this procedure.
In 1990, the vagal nerve stimulator (VNS) was first reported and is considered a safer, more effective, and less invasive option than cerebellar neurosurgery. Both methods involve mechanisms of releasing the neurotransmitter g-aminobutyric acid (GABA) to inhibit cerebral cortex.
Whereas the cerebellum can only transmit signals to several localized areas of cortex, the vagus nerve is capable of retrograde stimulation of the entire vagal nucleus, thus amplifying the areas of affected cortex.
By 1997, VNS was approved by the Federal Drug Administration (FDA) and in 1998, the use of VNS therapy was extended toward the treatment of neuropsychiatric disorders when the first patient with depression underwent surgical implantation of the device.
In November 1999, Morris and Mueller coordinated a long-term study of VNS and presented their findings in the medical journal Neurology. They evaluated over 400 patients who had undergone VNS implantation between 1988 and 1995, and found that between 35-44% of patients with intractable convulsions remained seizure free after three years of therapy.
Significant adverse effects included hoarseness (19.8%), headaches (4.5%), and dyspnea (3.2%). They also found that patient compliance and desire to continue therapy declined over time (96.1% after one year to 72.1% after three years). VNS is used currently as a therapy of last resort. Implantation can cost as much as $15,000 and battery replacement results in frequent maintenance costs.
The results of an anesthesiologic study in May 2000 suggest that VNS is also capable of lowering the threshold of thermal pain. In August 2001, Kirchner et al. suggested that VNS might be useful in treating unrelenting chronic pain.
It seems that the side effects of VNS might be secondary to recurrent laryngeal nerve hyperstimulation and parasympathomimetic bronchoconstriction. The mechanisms of neuromuscular adaptation that result in resolution of adverse effects with chronic use of VNS are not characterized well, but might involve downregulation of GABAergic receptors in areas of vagal innervation.
Although the clinical effects of VNS against refractory epilepsy and depression appear to be successful, further studies are needed to elucidate the efficacy of VNS in treating chronic pain. Furthermore, the high cost of this therapy and its use as a last resort suggest that the search for other undiscovered forms of therapy may be more cost-effective.
Increasing oxygen saturation likely involves physiologic mechanisms distinct from VNS, however the effects of controlled breathing on refractory seizures, long-term depression, and chronic pain are not well understood, and other mechanisms may be possible.
Muhammad M. Nashatizadeh
Many positive applications for VNS with high $$$cost and some serious side effects. I wonder what is happening to the diaphragm during this therapy. If it is being improved or otherwise.
I suspect a combination of Optimal Breathing, chiropractic adjustments, acupuncture, clinical nutrition and medical marijuana may be a logical FIRST choice for many of these people with seizures, pain and or depression.
There may be much to learn about diaphragm function with this post-surgical VNS population providing pre and post surgery and ongoing video fluoroscopes are documented.
See also Epilepsy