Tag: neurology

Categories : NeurologyTags :

Long-term Anaesthesia Causes Changes in Neural Connections

On By ModernMedia

New research has shown that there may be neurological consequences after long-term anaesthesia.

Prolonged anesthesia, also known as medically induced coma, takes the brain to a state of deep unconsciousness beyond short-term anaesthesia for surgical procedures. It is used to treat refractory intracranial hypertension and status epilepticus.

Though they are life-saving practices performed in ICUs the world over, they are not without cognitive side effects. Family members often report that their loved ones are not quite the same when they are discharged from hospital following prolonged anaesthesia.

“It is long known that ICU survivors suffer lasting cognitive impairment, such as confusion and memory loss, that can languish for months and, in some cases, years,” said lead author Michael Wenzel, MD, a former postdoctoral researcher at Columbia University with experience as a physician in neuro-intensive care in Germany.

Dr Wenzel said cognitive dysfunction after hospitalisation will likely become more widespread in the wake of COVID, with large numbers of ventilated patients awakening from days to weeks of unconsciousness.

Senior author Rafael Yuste, a professor of Biological Sciences at Columbia and senior author of the paper said that to date there had been no research on the direct effects of anaesthesia on neural connections.

“This is because it is difficult to examine the brains of patients at a resolution high enough to monitor connections between individual neurons,” Yuste said.

Yuste and Wenzel sought to investigate the connections between neurons, or synapses, and related cognitive effects of prolonged anaesthesia, using mice. With a specially built miniature ‘ICU’ for mice, they performed continuous anaesthesia for up to 40 hours, much longer than the longest animal study so far.

The researchers used in vivo two-photon microscopy to observe cortical synapses in the sensory cortex, combined with repeated assessment of behaviour in the cortex.

They found that, contrary to the view that neural connections in adult brains are stable in short-term anaesthesia, in long-term anaesthesia there are significant changes in synaptic architecture at any age.

“Our results should ring an alarm bell in the medical community, as they document a physical link between cognitive impairment and prolonged medically induced coma,” Wenzel said.

Further study is needed, the researchers said, adding that it will be important to test a range of anesthetics, as well as the combination of anesthetics administered to patients. Anaesthetics are not tailored to patients in any systematic fashion.

“We are well aware that anaesthesia is a life-saving procedure,” Wenzel said. “Refining treatment plans for patients and developing supportive therapies that keep the brain in shape during prolonged anaesthesia would substantially improve clinical outcomes for those whose lives are saved, but whose quality of life has been compromised.”

Source: Medical Xpress

Journal information: Michael Wenzel et al, Prolonged anesthesia alters brain synaptic architecture, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2023676118

Categories : Injury & Trauma Neurology Pain ManagementTags :

New Surgery Improves Prosthetic Use and Reduces Pain

On By ModernMedia

A new type of surgery that links muscles together may improve the precision of prosthetic use and also relieve pain.

In typical amputations, the muscle pairs (such as triceps and biceps) that work together to control the joints are severed. However, an MIT team has discovered that reconnecting these muscles that are in an agonistic-antagonistic (‘push-pull’) relationship improves the sensory feedback and thus precision of the affected limb.

“When one muscle contracts, the other one doesn’t have its antagonist activity, so the brain gets confusing signals,” explained Srinivasan, a former member of the Biomechatronics group now working at MIT’s Koch Institute for Integrative Cancer Research. “Even with state-of-the-art prostheses, people are constantly visually following the prosthesis to try to calibrate their brains to where the device is moving.”

The 15 patients who received the AMI surgery were able to flex their prosthetic ankle joint with more precision than those without it, who were only able to fully extend or flex their joint.

“Through surgical and regenerative techniques that restore natural agonist-antagonist muscle movements, our study shows that persons with an AMI amputation experience a greater phantom joint range of motion, a reduced level of pain, and an increased fidelity of prosthetic limb controllability,” says Hugh Herr, a professor of media arts and sciences, head of the Biomechatronics group in the Media Lab, and the senior author of the paper.

The surgery also had a completely unexpected benefit: the reduction of pain in the amputated area, which can be from neuromas or phantom limb pain. Phantom limb pain can occur in 80% of amputess. Six of the 15 AMI patients reported zero pain. This may be significant as in the five centuries since phantom limb pain was first described, there has not been much advancement in the understanding of it.

“Our study wasn’t specifically designed to achieve this, but it was a sentiment our subjects expressed over and over again. They had a much greater sensation of what their foot actually felt like and how it was moving in space,” Srinivasan says. “It became increasingly apparent that restoring the muscles to their normal physiology had benefits not only for prosthetic control, but also for their day-to-day mental well-being.”

To treat patients who had received the traditional amputation surgery, the team is also working on using muscle grafts to create a ‘regenerative AMI’ procedure that restores the effect of agonist and antagonist muscles.

Source: Medical Xpress

Journal information: Shriya S. Srinivasan el al., “Neural interfacing architecture enables enhanced motor control and residual limb functionality postamputation,” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2019555118

Categories : NeurologyTags :

Short Window for Recovery After Stroke

On By ModernMedia

Researchers have found that there is a short window for brain repair to be most effective after a stroke, which peaked at two weeks after the incident.

Brain scans conducted by the study showed that the brains of stroke survivors retained plasticity and an improved ability to rewire itself, the first time this had been observed in humans. The study took place in Adelaide and London.

The researchers regularly scanned the brains of 60 stroke survivors as they recovered over a period of 12 months. To assess neural plasticity, the researchers repeatedly activated the brain’s motor cortex using continuous transcranial magnetic stimulation (cTBS). The laboratory in London tested the non-damaged motor cortex, which is also important for stroke recovery while the one in Adelaide tested the damaged motor cortex. In the first few days following an ischaemic stroke, the brain had greater plasticity.

“Earlier animal studies suggested this was the case, but this is the first time we have conclusively demonstrated this phenomenon exists in humans,” Dr Hordacre said.

Only eight minutes of daily rehabilitation time after a stroke is spent on the upper limbs.

“Delivering more treatment within this brief window is needed to help people recover after a stroke,” Dr Hordacre said. “The next step is to identify techniques which prolong or even re-open a period of increased brain plasticity, so we can maximise recovery.”

Source: News-Medical.Net

Journal information: Hordacre, B., et al. (2021) Evidence for a Window of Enhanced Plasticity in the Human Motor Cortex Following Ischemic Stroke. doi.org/10.1177/1545968321992330.

Categories : Neurology PaediatricsTags :

No Evidence for Strep Exacerbating Chronic Tics in Kids

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A new study has found that children with chronic tic disorders, mainly Tourette syndrome, do not have tic exacerbations when exposed to group A Streptococcus.

No significant association with tic exacerbations emerged across four definitions of pharyngeal strep exposure with a mean follow-up of 16 months, though a weak link was observed in trend, reported Davide Martino, MD, PhD, of the University of Calgary, and co-authors.

Strep was however significantly associated with longitudinal changes in hyperactivity-impulsivity symptom severity of 17% to 21%.
“The link between Streptococcus and tics in children is still a matter of intense debate,” Martino stated. “We wanted to look at that question, as well as a possible link between strep and behavioral symptoms like obsessive-compulsive disorder and attention deficit hyperactivity disorder.

“While our findings suggest that strep is not likely to be one of the main triggers for making tics worse, more research is needed into other possible explanations. For example, the social stress of having this disorder could be implicated in making tics worse more than infections. It’s also possible another pathogen might be triggering an immune response associated with tic worsening.”

In an invited editorial, Andrea Cavanna, MD, PhD, of the University of Birmingham, and Keith Coffman, MD, of Children’s Mercy Hospital in Kansas City, observed that group A Streptococcus had been posited as a potential environmental factor in tic disorders for the past two decades.

The editorialists noted that, on the basis of isolated clinical observations, tic disorders should be included as a collateral feature in conditions which are known as pediatric autoimmune neuropsychiatric disorders associated with Streptococcus (PANDAS) infections. However, the results of longitudinal clinical studies were inconclusive, with a case control study even arguing against the association.

Drawing data from the EMTICS study, recruiting children with chronic tic disorders from 2013 to 2016, one arm of the study prospectively examined associations between new group A Streptococcus throat exposures and tic exacerbations, obsessive-compulsive disorder (OCD), and attention deficit hyperactivity disorder (ADHD) symptoms.

Four definitions of strep exposure were used: new definite (newly positive throat swab regardless of serological results), new possible (elevated anti-streptolysin O [ASOT] or anti-DNAseB [ADB] titers with negative or no throat swab), ongoing definite, and ongoing possible.

Initially, 59 children had a positive throat swab; as the study progressed, 103 children had new definite strep exposure. During follow-up, 308 children (43%) had tic exacerbations. The proportion of exacerbations temporally associated with strep exposure ranged from 5.5% to 12.9%, depending on exposure definition. No association between OCD symptoms and strep exposure was seen.

“Our study of the largest prospective cohort of youth with chronic tic disorders ever documented to date provides evidence against a temporal association between group A Streptococcus exposure and clinically relevant tic exacerbations,” the researchers wrote.

“This result indicates that specific diagnostic work-up or active management of group A Streptococcus infections in the context of worsening of tic severity in patients with chronic tic disorders is not warranted,” the researchers added.

The researchers noted that limitations included the data being collected from specialist centres in different countries, and that some cases of strep may have been missed.

Source: MedPage Today

Journal information (article): Martino D, et al “Association of Group A Streptococcus Exposure and Exacerbations of Chronic Tic Disorders: A Multinational Prospective Cohort Study” Neurology 2021; DOI: 10.1212/WNL.0000000000011610.

Journal information (editorial): Cavanna A, Coffman K “Streptococcus and Tics: Another Brick in the Wall?” Neurology 2021. DOI: 10.1212/WNL.0000000000011608.