VNS

Vagus Nerve Stimulation for Children With Epilepsy.

Posted by

0


The Vagus Nerve Stimulator

The first vagus nerve stimulator (VNS) was implanted in 1988.[1]Since then, more than 70,000 have been implanted for epilepsy worldwide.[2]

The VNS consists of a generator, typically implanted in the chest, and an electrode surgically fastened to the left vagus nerve. In addition, an external handheld magnet may be used if the patient senses an aura or to stop a seizure already in progress.

US Food and Drug Administration Approval

In 1997, VNS received US Food and Drug Administration (FDA) approval for the adjunctive treatment of refractory seizures in patients older than 12 years.[3] In 2005, the VNS was approved for the treatment of chronic or recurrent depression in patients older than 18 years.

VNS may also have a beneficial effect on mood in patients with epilepsy in addition to its antiepileptic effect.[1] The mechanism of action of VNS is uncertain, but may be related to metabolic activation of brain stem, limbic, or thalamic structures.[4]

To date, the VNS is the only FDA-approved medical device for the treatment of epilepsy. However, other approaches, such as deep-brain stimulation of the anterior nucleus of the thalamus, responsive neurostimulation, trigeminal nerve stimulation, and transcranial magnetic stimulation, are in development.

Phase 3 Trials for Epilepsy

A randomized, multicenter, clinical trial (Study E03) of 114 patients with partial seizures demonstrated a mean seizure reduction of 31% and a 50% seizure reduction in 39% of patients.[5] A second randomized trial (Study E05) of 254 patients with intractable partial seizures demonstrated an average reduction in seizure frequency of 28% in the high-stimulation group vs a 15% reduction in the low-stimulation (pseudo-placebo) group (P = .04).[4] These results are modest, but similar to those obtained with new antiepileptic drugs in phase 3 trials. Unlike antiepileptic drugs, VNS efficacy appears to improve over time.[3]

Adverse Effects of VNS

Compared with antiepileptic drugs, VNS has a completely different side effect profile. Adverse effects are related to the surgical implantation of the generator, which may result in discomfort and deep or superficial infection. The lead attached to the vagus nerve is subject to breakage. In addition, the electrical stimulation in the neck may be uncomfortable and result in cough, hoarseness, or a feeling of shortness of breath.[4] On the other hand, VNS does not cause sedation or adverse cognitive effects, which are often limiting factors with antiepileptic drug treatment.[6]

Magnet Activation of VNS

Neurostimulation by the VNS occurs at prespecified, continuous intervals (eg, 30 seconds on, 5 minutes off). In addition, the patient may trigger additional stimulation on demand by holding a magnet over the implanted device. Magnet-activated stimulation may abort, diminish, or terminate a seizure.

A retrospective analysis of seizure data collected from the E03 trial demonstrated an increased likelihood of improved seizure control (aborted and decreased) after magnet activation (P = .0479). In the E04 trial, 31% of patients were able to diminish seizures and 22% of patients terminated seizures, but 47% reported no effect with the magnet.[1] The magnet may offer psychological benefits to patients by providing some sense of control over seizures when they occur.[1]

Personal Experience

Years ago, I enrolled 5 of my patients with intractable epilepsy in the open-label E04 VNS safety trial. None of the patients became seizure-free, although as a group they experienced a modest benefit in seizure reduction. One college student did not like the stimulator and insisted that it be removed, even though he had not allowed adequate time for us to assess its therapeutic effects. The other 4 patients continued to use the VNS.

Source: Medscape.com

Researchers Find Early Success in New Treatment for Stroke Recovery – News Center – The University of Texas at Dallas

Posted by

0


Navid Khodparast

Dr. Navid Khodaparast was the lead author of the study.

Researchers at The University of Texas at Dallas have taken a step toward developing a new treatment to aid the recovery of limb function after strokes.

In a study published online in the journal Neurobiology of Disease, researchers report the full recovery of forelimb strength in animals receiving vagus nerve stimulation.

“Stroke is a leading cause of disability worldwide,” said Dr. Navid Khodaparast, a postdoctoral researcher in the School of Behavioral and Brain Sciences and lead author of the study. “Every 40 seconds, someone in the U.S. has a stroke. Our results mark a major step in the development of a possible treatment.”

Vagus nerve stimulation (VNS) is an FDA-approved method for treating various illnesses, such as depression and epilepsy. It involves sending a mild electric pulse through the vagus nerve, which relays information about the state of the body to the brain.

Khodaparast and his colleagues used vagus nerve stimulation precisely timed to coincide with rehabilitative movements in rats. Each of the animals had previously experienced a stroke that impaired their ability to pull a handle.

Dr. Michael Kilgard

Dr. Michael Kilgard, professor of neuroscience and senior author of the study, first demonstrated the ability of vagus nerve stimulation to enhance brain adaptability in 2011.

Stimulation of the vagus nerve causes the release of chemicals in the brain known to enhance learning and memory called neurotransmitters, specifically acetylcholine and norepinephrine. Pairing this stimulation with rehabilitative training allowed Khodaparast and colleagues to improve recovery.

Many rehabilitative interventions try to enhance neuroplasticity (the brain’s ability to change) in conjunction with physical rehabilitation to drive the recovery of lost functions, according to Khodaparast. Unfortunately, up to 70 percent of stroke patients still display long-term impairment in arm function after traditional rehabilitation.

“For years, the majority of stroke patients have received treatment with various drugs and/or physical rehabilitation,” Khodaparast said. “Medications can have widespread effects in the brain and the effects can last for long periods of time. In some cases the side effects outweigh the benefits. Through the use of VNS, we are able to use the brain’s natural way of changing its neural circuitry and provide specific and long lasting effects.”

“Through the use of VNS, we are able to use the brain’s natural way of changing its neural circuitry and provide specific and long lasting effects.”

Dr. Navid Khodaparast, a postdoctoral researcher in the School of Behavioral and Brain Sciences

Khodaparast acknowledged the study has some limitations. For example, the animals were young and lacked some of the other illnesses that accompany an aged human population, such as diabetes or hypertension. But Khodaparast and his colleagues said they are optimistic about vagus nerve stimulation as a future tool. They will continue testing in chronically impaired animals with the hopes of translating the technique for stroke patients. Working with MicroTransponder Inc., a partner company in the current study, researchers at the University of Glasgow in Scotland have begun a small-scale trial in humans.

“There is strong evidence that VNS can be used safely in stroke patients because of its extensive use in the treatment of other neurological conditions,” said Dr. Michael Kilgard, professor in neuroscience at UT Dallas and senior author of the study.

Kilgard is also conducting clinical trials using vagus nerve stimulation to treat tinnitus, the medical condition of unexplained ringing in the ears. Kilgard’s lab first demonstrated the ability of vagus nerve stimulation to enhance brain adaptability in a 2011 Nature paper.

Other UT Dallas researchers involved in the study are: postdoctoral fellows Dr. Seth Hays and Dr. Andrew Sloan; graduate student Daniel Hulsey; undergraduate students Andi Ruiz and Maritza Pantoja; and Dr. Robert Rennaker II, associate professor in neuroscience, director of the Texas Biomedical Device Center and head of the Department of Bioengineering.

Early Success in New Treatment for Stroke Recovery.

Posted by

0


Researchers at The University of Texas at Dallas have taken a step toward developing a new treatment to aid the recovery of limb function after strokes.

In a study published online in the journalNeurobiology of Disease, researchers report the full recovery of forelimb strength in animals receiving vagus nerve stimulation.

“Stroke is a leading cause of disability worldwide,” said Dr. Navid Khodaparast, a postdoctoral researcher in the School of Behavioral and Brain Sciences and lead author of the study. “Every 40 seconds, someone in the U.S. has a stroke. Our results mark a major step in the development of a possible treatment.”

Vagus nerve stimulation (VNS) is an FDA-approved method for treating various illnesses, such as depression and epilepsy. It involves sending a mild electric pulse through the vagus nerve, which relays information about the state of the body to the brain.

 

Khodaparast and his colleagues used vagus nerve stimulation precisely timed to coincide with rehabilitative movements in rats. Each of the animals had previously experienced a stroke that impaired their ability to pull a handle.

Stimulation of the vagus nerve causes the release of chemicals in the brain known to enhance learning and memory called neurotransmitters, specifically acetylcholine and norepinephrine. Pairing this stimulation with rehabilitative training allowed Khodaparast and colleagues to improve recovery.

 

Many rehabilitative interventions try to enhance neuroplasticity (the brain’s ability to change) in conjunction with physical rehabilitation to drive the recovery of lost functions, according to Khodaparast. Unfortunately, up to 70 percent of stroke patients still display long-term impairment in arm function after traditional rehabilitation.

 

“For years, the majority of stroke patients have received treatment with various drugs and/or physical rehabilitation,” Khodaparast said. “Medications can have widespread effects in the brain and the effects can last for long periods of time. In some cases the side effects outweigh the benefits. Through the use of VNS, we are able to use the brain’s natural way of changing its neural circuitry and provide specific and long lasting effects.”

“Through the use of VNS, we are able to use the brain’s natural way of changing its neural circuitry and provide specific and long lasting effects.”

 

Khodaparast acknowledged the study has some limitations. For example, the animals were young and lacked some of the other illnesses that accompany an aged human population, such as diabetes or hypertension. But Khodaparast and his colleagues said they are optimistic about vagus nerve stimulation as a future tool. They will continue testing in chronically impaired animals with the hopes of translating the technique for stroke patients. Working with MicroTransponder Inc., a partner company in the current study, researchers at the University of Glasgow in Scotland have begun a small-scale trial in humans.

 

“There is strong evidence that VNS can be used safely in stroke patients because of its extensive use in the treatment of other neurological conditions,” said Dr. Michael Kilgard, professor in neuroscience at UT Dallas and senior author of the study.

 

Kilgard is also conducting clinical trials using vagus nerve stimulation to treat tinnitus, the medical condition of unexplained ringing in the ears. Kilgard’s lab first demonstrated the ability of vagus nerve stimulation to enhance brain adaptability in a 2011Nature paper.