Posts Tagged Nerve

[WEB SITE] Researchers study how neurostimulator can improve rehabilitation for stroke patients

 

Researchers at The Ohio State University Wexner Medical Center are among the first in the world studying how a specific type of neurostimulator can improve rehabilitation for stroke patients.

As part of the clinical trial, an electrical device called a vagus nerve stimulator is surgically implanted in the patient’s chest wall. The Vivistim device, which connects to the vagus nerve in the neck, is used to “rewire” circuits in the brain associated with certain motor functions. Stroke can result in the loss of brain tissue and negatively affect various bodily functions from speech to movement, depending on the location of the stroke.

In an earlier pilot study, this approach known as Paired Vagus Nerve Stimulation was shown to benefit approximately 85 percent of the people who received the nerve stimulation, said Dr. Marcie Bockbrader, research physiatrist for the Neurological Institute at The Ohio State University Wexner Medical Center.

“This nerve stimulation is like turning on a switch, making the patient’s brain more receptive to therapy,” Bockbrader said. “The goal is to see if we can improve motor recovery in people who have what is, in effect, a brain pacemaker implanted in their body. The idea is to combine this brain pacing with normal rehab, and see if patients who’ve been through all of the other usual therapies after a stroke can get even better.”

The study is recruiting patients who suffered a stroke and have been left with poor arm function as a result. The study is open to patients who have suffered a stroke at least nine months ago up to 10 years ago.


Each participant will receive three one-hour sessions of intensive physiotherapy each week for six weeks to help improve their arm function.

Half of the group will also receive an implanted vagus nerve stimulator. During rehabilitation therapy sessions, when a patient correctly performs an exercise, the therapist pushes a button to trigger the device to stimulate the vagus nerve. This neurostimulator signals the brain to remember that movement.

“We are trying to see if this neurostimulator could be used to boost the effective therapy, creating a sort of ‘supercharged therapy.’ We want to determine if patients can recover more quickly through the use of this stimulation,” Bockbrader said.

Previous research indicates that vagus nerve stimulation causes the release of the brain’s own chemicals, called neurotransmitters that will help the brain form new neural connections which might improve participant’s ability to use their arm.

Traditional vagus nerve stimulation has been used in the United States and around the world to treat more than 100,000 patients for epilepsy.

 

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[WEB SITE] Researchers demonstrate synaptic plasticity in new-born neurons

Repeated stimulation enlarges dendritic spines

Even in adult brains, new neurons are generated throughout a lifetime. In a publication in the scientific journal PNAS, a research group led by Goethe University describes plastic changes of adult-born neurons in the hippocampus, a critical region for learning: frequent nerve signals enlarge the spines on neuronal dendrites, which in turn enables contact with the existing neural network.

Practice makes perfect, and constant repetition promotes the ability to remember. Researchers have been aware for some time that repeated electrical stimulation strengthens neuron connections (synapses) in the brain. It is similar to the way a frequently used trail gradually widens into a path. Conversely, if rarely used, synapses can also be removed – for example, when the vocabulary of a foreign language is forgotten after leaving school because it is no longer practiced. Researchers designate the ability to change interconnections permanently and as needed as the plasticity of the brain.

Plasticity is especially important in the hippocampus, a primary region associated with long-term memory, in which new neurons are formed throughout life. The research groups led by Dr Stephan Schwarzacher (Goethe University), Professor Peter Jedlicka (Goethe University and Justus Liebig University in Gieβen) and Dr Hermann Cuntz (FIAS, Frankfurt) therefore studied the long-term plasticity of synapses in new-born hippocampal granule cells. Synaptic interconnections between neurons are predominantly anchored on small thorny protrusions on the dendrites called spines. The dendrites of most neurons are covered with these spines, similar to the thorns on a rose stem.

In their recently published work, the scientists were able to demonstrate for the first time that synaptic plasticity in new-born neurons is connected to long-term structural changes in the dendritic spines: repeated electrical stimulation strengthens the synapses by enlarging their spines. A particularly surprising observation was that the overall size and number of spines did not change: when the stimulation strengthened a group of synapses, and their dendritic spines enlarged, a different group of synapses that were not being stimulated simultaneously became weaker and their dendritic spines shrank.

“This observation was only technically possible because our students Tassilo Jungenitz and Marcel Beining succeeded for the first time in examining plastic changes in stimulated and non-stimulated dendritic spines within individual new-born cells using 2-photon microscopy and viral labeling,” says Stephan Schwarzacher from the Institute for Anatomy at the University Hospital Frankfurt. Peter Jedlicka adds: “The enlargement of stimulated synapses and the shrinking of non-stimulated synapses was at equilibrium. Our computer models predict that this is important for maintaining neuron activity and ensuring their survival.”

The scientists now want to study the impenetrable, spiny forest of new-born neuron dendrites in detail. They hope to better understand how the equilibrated changes in dendritic spines and their synapses contribute the efficient storing of information and consequently to learning processes in the hippocampus.

 

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[WEB SITE] Research provides insights for why some epilepsy patients continue to experience postoperative seizures

New research from the University of Liverpool, published in the journal Brain, has highlighted the potential reasons why many patients with severe epilepsy still continue to experience seizures even after surgery.

Epilepsy continues to be a serious health problem and is the most common serious neurological disorder. Medically intractable temporal lobe epilepsy (TLE) remains the most frequent neurosurgically treated epilepsy disorder.

Many people with this condition will undergo a temporal lobe resection which is a surgery performed on the brain to control seizures. In this procedure, brain tissue in the temporal lobe is resected, or cut away, to remove the seizure focus.

Unfortunately, approximately one in every two patients with TLE will not be rendered completely seizure free after temporal lobe surgery, and the reasons underlying persistent postoperative seizures have not been resolved.

Reliable biomarkers

Understanding the reasons why so many patients continue to experience postoperative seizures, and identifying reliable biomarkers to predict who will continue to experience seizures, are crucial clinical and scientific research endeavours.

Researchers from the University’s Institute of Translational Medicine, led by Neuroimaging Lead Dr Simon Keller and collaborating with Medical University Bonn (Germany), Medical University of South Carolina (USA) and King’s College London, performed a comprehensive diffusion tensor imaging (DTI) study in patients with TLE who were scanned preoperatively, postoperatively and assessed for postoperative seizure outcome.

Diffusion tensor imaging (DTI) is a MRI-based neuroimaging technique that provides insights into brain network connectivity.

The results of these scans allowed the researchers to examine regional tissue characteristics along the length of temporal lobe white matter tract bundles. White matter is mainly composed of axons of nerve cells, which form connections between various grey matter areas of the brain, and carry nerve impulses between neurons allowing communication between different brain regions.

Through their analysis the researchers could determine how abnormal the white matter tracts were before surgery and how the extent of resection had affected each tract from the postoperative MRI scans.

Surgery outcomes

The researchers identified preoperative abnormalities of two temporal lobe white matter tracts that are not included in standardised temporal lobe surgery in patients who had postoperative seizures but not in patients with no seizures after surgery.

The two tracts were in the ‘fornix’ area on the same side as surgery, and in the white matter of the ‘parahippocampal’ region on the opposite side of the brain.

The tissue characteristics of these white matter tracts enabled researchers to correctly identify those likely to have further seizures in 84% of cases (sensitivity) and those unlikely to have further seizures in 89% of cases (specificity). This is significantly greater than current estimates.

The researchers also found that a particular temporal lobe white matter tract called the ‘uncinate fasciculus’ was abnormal – and potentially involved in the generation of seizures – in patients with excellent and suboptimal postoperative outcomes.

However, it was found that significantly more of this tract was surgically resected/removed in the patients with an excellent outcome.

New insights

Dr Simon Keller, said: “There is scarce information on the prediction of postoperative seizure outcome using preoperative imaging technology, and this study is the first to rigorously investigate the tissue characteristics of temporal lobe white matter tracts with respect to future seizure classifications.

“Although there is some way to go before this kind of data can influence routine clinical practice, these results may have the potential to be developed into imaging prognostic markers of postoperative outcome and provide new insights for why some patients with temporal lobe epilepsy continue to experience postoperative seizures.”

Source: Research provides insights for why some epilepsy patients continue to experience postoperative seizures

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[WEB SITE] Study shows continuous electrical stimulation suppresses seizures in patients with epilepsy.

When surgery and medication don’t help people with epilepsy, electrical stimulation of the brain has been a treatment of last resort. Unfortunately, typical approaches, such as vagal nerve stimulation or responsive nerve stimulation, rarely stop seizures altogether. But a new Mayo Clinic study in JAMA Neurology shows that seizures were suppressed in patients treated with continuous electrical stimulation.

Epilepsy is a central nervous system disorder in which nerve cell activity in the brain becomes disrupted. In the study, 13 patients with drug-resistant epilepsy were deemed unsuitable for resective surgery, which removes a portion of the brain — usually about the size of a golf ball — that was causing seizures. When patients are evaluated for surgery, a grid of electrical contacts is placed on the brain to record seizures and interictal epileptiform discharges (IEDs). IEDs are electrical discharges that occur intermittently during normal brain function, and have been used as markers to locate portions of brain affected by epilepsy.

In the study, the grid of electrical contacts was used for stimulation at levels the patient would not notice. If the stimulation provided clinical benefit to the patient, this temporary grid was replaced with more permanent contacts that could offer continuous stimulation.

Ten of the 13 patients, 77 percent, reported improvement for both epilepsy severity and life satisfaction. The majority of patients experienced more than 50 percent reduction in seizures, and 44 percent were free of disabling seizures. The reduction in IED rate occurred within minutes of initiating stimulation.

“This study suggests that subthreshold cortical stimulation is both effective clinically and reduces interictal epileptiform discharges,” says lead author Brian Lundstrom, M.D., Ph.D., a neurology epilepsy fellow at Mayo Clinic. “We think this approach not only provides an effective treatment for those with focal epilepsy but will allow us to develop ways of assessing seizure likelihood for all epilepsy patients. It would be of enormous clinical benefit if we could personalize treatment regimens for individual patients without waiting for seizures to happen.”

During seizures, abnormal electrical activity in the brain sometimes results in loss of consciousness. For people with epilepsy, seizures severely limit their ability to perform tasks where even a momentary loss of consciousness could prove disastrous — driving a car, swimming or holding an infant, for example. Approximately 50 million people worldwide have epilepsy, according to the World Health Organization.

Seizures sometimes have been compared to electrical storms in the brain. Seizure signs and symptoms may include:

•Temporary confusion
•A staring spell
•Uncontrollable jerking movements of the arms and legs
•Loss of consciousness or awareness

Treatment with medications or surgery can control seizures for about two-thirds of people with epilepsy. However, when drug-resistant focal epilepsy occurs in an area of the brain that controls speech, language, vision, sensation or movement, resective surgery is not an option.

“For people who have epilepsy that can’t be treated with surgery or medication, effective neurostimulation could be a wonderful treatment option,” Dr. Lundstrom says.

The risks of subthreshold cortical stimulation are relatively minimal and include typical infection and bleeding risks as well as the possibility that the stimulation would not be subthreshold and would be noticed by the patient, Dr. Lundstrom says. The authors note that further investigation is needed to quantify treatment effect and examine the effect mechanism. The authors plan to examine the efficacy of this approach in a prospective clinical trial.

This study represents ongoing efforts to restore normal function to epileptic brain tissue by using neurostimulation. Other efforts are aimed at understanding the physiologic changes that chronic stimulation produces in brain tissue.

Source: Study shows continuous electrical stimulation suppresses seizures in patients with epilepsy

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[WEB SITE] Small device detects initial signal of epileptic attack and provides effective relief.

Published on August 23, 2016 

The results, from the Laboratory for Organic Electronics at LiU’s Campus Norrköping, have been published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS), with Asst. Prof. Daniel Simon as main author.

According to a recently produced estimate, no less than six percent of the Earth’s population suffers from some type of neurological illness such as epilepsy or Parkinson’s. Some medicines are available, but when these are taken orally or injected into the bloodstream, they also end up where they aren’t needed and may cause serious problems. All medicines have more or less severe side effects, and no fully satisfactory treatment for neurological illnesses is available.

Neurons, or nerve cells, are the cells in the body that both transmit and receive nerve impulses. The small 20×20 µm device developed by the scientists can both capture signals and stop them in the exact area of nerve cells where they arise. No other part of the body needs to be involved.

“Our technology makes it possible to interact with both healthy and sick neurons. We can now start investigating opportunities for finding therapies for neurological illnesses that arise so rapidly and so locally that the patient doesn’t notice them,” says Daniel Simon.

The experiments were conducted in the laboratory on slices of brains from mice. The device consists of a sensor that detects nerve signals, and a small ion pump that doses an exact amount of the neurotransmitter GABA, a substance the body itself uses to inhibit stimuli in the central nervous system.

“The same electrode that registers the activity in the cell can also deliver the transmitter. We call it a bioelectronic ‘neural pixel’, since it imitates the functions of biological neurons,” says Daniel Simon.

“Signalling in biological systems is based on chemical signals in the form of cations, which are passed between transmitters and receptors, which consist of proteins. When a signal is transferred to another cell, the identification of the signal and the triggering of a new one occur within a very small distance – only a few nanometers. In certain cases, it happens at the same point. That’s why being able to combine electronic detection and release in the same electrode is a major advance,” says Professor Magnus Berggren.

The small ion pump, which was developed at the Laboratory for Organic Electronics, attracted a great deal of attention when it´s first application as a therapeutic device was published a year ago. The sensor that captures the nerve signal has subsequently been developed by the LiU researchers’ collaborators at the école Nationale Supérieure des Mines in Gardanne, France. The mouse experiments were performed at Aix-Marseille University. The entire device is manufactured from conductive, biocompatible plastic.

Source: Small device detects initial signal of epileptic attack and provides effective relief

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