Tag: neurology

Sarin Gas Likely the Cause of Mysterious Gulf War Illness

Photo by Pablo Stanic on Unsplash

Since the 1990s, scientists have debated the underlying cause of Gulf War illness (GWI), a constellation of unexplained and chronic symptoms affecting veterans of the Persian Gulf War. Now researchers have solved the mystery, showing through a detailed genetic study that the nerve gas sarin was largely responsible for the syndrome. The findings were published in Environmental Health Perspectives.

Dr Haley’s research group not only discovered that veterans with exposure to sarin were more likely to develop GWI, but also found that the risk was modulated by a gene that helps break down the nerve gas. Sarin-exposed Gulf War veterans with a weak variant of the gene were more likely to develop symptoms of GWI than other exposed veterans with the strong form of the gene.

“Quite simply, our findings prove that Gulf War illness was caused by sarin, which was released when we bombed Iraqi chemical weapons storage and production facilities,” said Robert Haley, MD, at UT Southwestern, a medical epidemiologist who had led that study and has been investigating GWI for 28 years. “There are still more than 100 000 Gulf War veterans who are not getting help for this illness and our hope is that these findings will accelerate the search for better treatment.”

Multiple causes of Gulf War illness suggested

After the Gulf War, more than a quarter of the US and coalition veterans began reporting a range of chronic symptoms, including fatigue, fever, night sweats, memory and concentration problems, difficulty finding words, diarrhoea, sexual dysfunction, and chronic body pain. Since then, military and academic researchers have studied a list of possible causes of GWI, ranging from stress, vaccinations, and burning oil wells to exposure to pesticides, nerve gas, anti-nerve gas medication, and depleted uranium used in weapons.

“What makes this new study a game-changer is that it links GWI with a very strong gene-environment interaction that cannot be explained away by errors in recalling the environmental exposure or other biases in the data.”

Study leader Robert Haley, MD, medical epidemiologist

Over the years, these studies have identified statistical associations with several of these, but no cause has been widely accepted. Most recently, Dr Haley and a colleague reported a large study testing veterans’ urine for depleted uranium that would still be present if it had caused GWI and found none.

Studies have shown statistical associations with several of these causes, though none received wide acceptance. Dr Haley and a colleague recently reported a large study that found no depleted uranium in veterans’ urine, which would have still been present if it had caused GWI.

“As far back as 1995, when we first defined Gulf War illness, the evidence was pointing toward nerve agent exposure, but it has taken many years to build an irrefutable case,” said Dr Haley.

Sarin’s effects

Sarin is a toxic nerve agent, production of which was banned in 1997. When people are exposed to either the liquid or gas form, sarin enters the body through the skin or breathing and attacks the nervous system. High-level sarin often results in death, but studies on survivors have revealed that lower-level sarin exposure can lead to long-term impairment of brain function. A large release of this gas occurred when a chemical weapons storage plant was bombed, causing thousands of nerve gas alarms to sound.

Previous studies have found an association between Gulf War veterans who self-reported exposure to sarin and GWI symptoms. However, this has raised criticisms of recall bias. “What makes this new study a game-changer is that it links GWI with a very strong gene-environment interaction that cannot be explained away by errors in recalling the environmental exposure or other biases in the data,” Dr Haley said.

In the new paper, Dr Haley and his colleagues studied 508 deployed veterans with GWI and 508 deployed veterans who did not develop any GWI symptoms. They asked whether the veterans had heard chemical nerve gas alarms, indicating sarin exposure, and also collected blood and DNA samples.

The role of PON1

The researchers tested the samples for variants of a gene called PON1, which has two variants. The Q variant generates a blood enzyme that efficiently breaks down sarin while the R variant helps the body break down other chemicals but is not efficient at destroying sarin. Everyone has either a QQ, RR or QR genotype.

For Gulf War veterans with the QQ genotype, hearing nerve agent alarms — a proxy for chemical exposure — raised their chance of developing GWI by 3.75 times, those with the QR genotype had an a 4.43 fold risk increase. And for those with RR genotype, the chance of GWI increased by 8.91 times. Those soldiers with both the RR genotype and low-level sarin exposure were over seven times more likely to get GWI due to the interaction per se, over and above the increase in risk from both risk factors acting alone. For genetic epidemiologists, this number leads to a high degree of confidence that sarin is a causative agent of GWI.

“Your risk is going up step by step depending on your genotype, because those genes are mediating how well your body inactivates sarin,” said Dr Haley. “It doesn’t mean you can’t get Gulf War illness if you have the QQ genotype, because even the highest-level genetic protection can be overwhelmed by higher intensity exposure.”

This kind of strong gene-environment interaction is considered a gold standard for showing that an illness like GWI was caused by a particular environmental toxic exposure, he added. The research doesn’t rule out that other chemical exposures could be responsible for a small number of cases of Gulf War illness. However, Dr. Haley and his team carried out additional genetic analyses on the new data, testing other factors that could be related, and found no other contributing causes.

“There’s no other risk factor coming anywhere close to having this level of causal evidence for Gulf War illness,” said Dr Haley.

The team is continuing research on GWI’s impacts on the body, particularly the immune system, whether any of its effects are reversible, and whether there are biomarkers to detect prior sarin exposure or GWI.

Source: UT Southwestern Medical Center

Scientists Discover the Neurological Basis of Food Cravings in Pregnancy

Photo by Andriyko Podilnyk on Unsplash

By examining mice, which get pregnancy cravings similar to humans, scientists have identified the neurological basis of food craving during pregnancy.

During pregnancy, the mother’s body undergoes a series of physiological and behavioural changes to create an environment facilitating the embryo’s development. Frequent consumption of tasty, high calorie foods driven by the cravings contributes to weight gain and obesity in pregnancy, with possible negative consequences for the baby’s health.

“There are many myths and popular beliefs regarding these cravings, although the neuronal mechanisms that cause them are not widely known,” noted study leader March Claret, at the University of Barcelona and leader of the study published in the journal Nature Metabolism.

The researchers found that the brains of pregnant female mice undergoes changes in the functional connections of the brain reward circuits, as well as the taste and sensorimotor centres. Mice, like pregnant women, are also more sensitive to sweet food, and develop binge-eating behaviours towards high calorie foods. “The alteration of these structures made us explore the mesolimbic pathway, one of the signal transmission pathways of dopaminergic neurons. Dopamine is a key neurotransmitter in motivational behaviours,” notes Claret, member of the Department of Medicine of the UB and the Diabetes and Associated Metabolic Diseases Networking Biomedical Research Centre (CIBERDEM).

The team saw that dopamine levels and dopamine receptor (D2R) activity increased in the nucleus accumbens, a brain region involved in the reward circuit. “This finding suggests that the pregnancy induces a full reorganisation of the mesolimbic neural circuits through the D2R neurons,” noted study leader Roberta Haddad-Tóvolli. “These neuronal cells – and their alteration – would be responsible for the cravings, since food anxiety, typical during pregnancy, disappeared after blocking their activity.”

The team demonstrated that persistent cravings have consequences for the offspring, affecting the metabolism and development of neural circuits that regulate food intake, leading to weight gain, anxiety and eating disorders. “These results are shocking, since many of the studies are focused on the analysis of how the mother’s permanent habits – such as obesity, malnutrition, or chronic stress – affect the health of the baby. However, this study indicates that short but recurrent behaviours, such as cravings, are enough to increase the psychological and metabolic vulnerability of the offspring,” concluded Claret.

The conclusions of the study could contribute to the improvement of nutritional guidelines for pregnant women in order to ensure a proper prenatal nutrition and prevent the development of diseases.

Source: University of Barcelona

Mental Processing of Autistic and Non-autistic People is Similar

Source: Pixabay

Findings published in Journal of Psychopathology and Clinical Science reveal there are fundamental similarities between autistic and non-autistic people in mental processing. The study findings were made available online ahead of ahead of World Autism Day on the 2nd of April.

The brain uses two systems to process information: System 1 for quicker intuitive judgements, and System 2 for slower rational thinking. In autistic people, these systems are thought to work differently ad underlie difficulties they may have in daily life and the workplace.

Yet, this landmark study reports that these fundamental psychological systems are not impaired in autistic people as once thought. The study, involving more than 1000 people, tested the link between autism and ‘quick’ intuitive and ‘slow’ rational thinking.

In three experiments, they analysed the link between autistic personality traits and thinking style. In the fourth, they compared 200 autistic and over 200 non-autistic people. Overall, their results showed that autistic people think as quickly and as rationally as non-autistic people.

Based on these findings, the researchers conclude that certain, fundamental mental processes are more similar between autistic and non-autistic people than prior belief. In light of these findings, they call for a shift in the way that society thinks about autism as a mental processing disorder.

They also recommend that it might be important to redesign educational, clinical, and workplace support for autistic people and their families. Support should be much more targeted, instead of assuming that autistic people all have mental processing difficulties, they say.

The research team argue that the requirement to make ‘reasonable adjustments’ such as allowing extra time in exams and extending deadlines, is not an evidence-based way to support neurodivergent people.

Instead, more fundamental changes could be necessary – for example, changing social and sensory environments, making them more equitable autistic people.

Source: University of Bath

The Claustrum: A Mysterious Brain Region Involved with Pain

Man wearing mask with headache
Source: Usman Yousaf on Unsplash

A new review paper, published in the journal Brain, has shown that a mysterious brain region called the claustrum may play an important role in the experience of pain. This densely interconnected, but difficult to access area of the brain may be the next frontier in improving outcomes for brain damage patients.

The claustrum is a brain region that has been investigated for over 200 years, yet its precise function remains unknown. A 2005 article suggested it to be critically linked to consciousness, which spurred a renewed interest in this region, with recent research revealing its high level of interconnectedness.

Credit: Oxford University

Oxford University researchers reviewed studies of patients with rare cases of lesions in the claustrum, which show cognitive impairments and seizures. There may be many more cases to be uncovered due to the lack of clinical focus on the claustrum.

They also uncovered an underappreciated link between the claustrum and pain. It is already known that there are links between the claustrum and perception, salience and the sleep-wake cycle, but this is the first time a research team has shown how the claustrum might be more involved in the debilitating experience of pain.

Dr. Adam Packer, the lead author of the study, says that “The problem with understanding how the claustrum works is that it is deep inside the brain, and damage that is specific to it is a very rare occurrence. What makes it more difficult to work out what the claustrum actually does is that these rare occurrences are also linked to such a broad range of symptoms.”

“Clearly, when the claustrum is damaged the effects are severe and better therapies are urgently needed. It is possible that claustrum damage is more common than we currently realise, and it may be a crucial component in many more brain damage cases.”

“This work is important because it gives us some insight into the cognitive and neurological processes in which the claustrum may be involved, and gives us targets to pursue in basic research in the lab.”

The researchers found several recorded instances of either infection, autoimmune, or other process that attacked the claustrum in particular, and by analysing the results of these studies and others the most common symptoms in patients were cognitive impairment and seizures.

Additional research is needed for a better understanding of the claustrum and the impact of damage to the claustrum, which could eventually change clinical guidelines.

Source: University of Oxford

Invasive Mechanical Ventilation in PICU has Lasting Neurocognitive Impacts

Photo by Margaret Weir on Unsplash

Children in paediatric ICUs (PICUs) that undergo invasive mechanical ventilation for acute respiratory failure are left with lasting neurocognitive effects, according to a study published in JAMA.

Little is known about whether children undergoing invasive mechanical ventilation worse long-term neurocognitive function than children who do not undergo such procedures. There are concerns about neurotoxic effects of critical illness and its treatment on the developing brain. Therefore, infants and young children may be uniquely susceptible to adverse neurocognitive outcomes after invasive mechanical ventilation.

Researchers conducted a four-year sibling-matched cohort study conducted at 31 PICUs and associated neuropsychology testing centres. Children who survived PICU hospitalisation for respiratory failure and were discharged without severe cognitive dysfunction were found to have significantly lower subsequent IQ scores than their matched siblings.

“While the difference in IQ scores between patients and unexposed siblings was small, the data provide strong evidence of the existence and epidemiology of paediatric post-intensive care syndrome (PICS-p) after a single typical episode of acute respiratory failure necessitating invasive ventilation among generally healthy children,” said Martha A.Q. Curley, PhD, RN, FAAN, Professor of Nursing at the University of Pennsylvania School of Nursing (Penn Nursing) and the study’s lead researcher.

The study reaffirms the importance of assessing long-term outcomes as part of any trial evaluating acute interventions in pediatric critical care. It also underscores the importance of further study to understand which children may be at highest risk, what modifiable factors could cause it, and how it can be prevented.

Source: University of Pennsylvania

Peptide Discovery Could Halt Nerve Degeneration

A healthy neuron.
A healthy neuron. Credit: NIH

Promising results have been found in the quest for a treatment to halt nerve cell degeneration in disorders like Parkinson’s disease, by preventing their mitochondria from breaking apart with a particular peptide.

The research, published in Brain, examined how the long axons that carry messages between nerve cells in the brain can break down, which causes increasingly worse tightening of the leg muscles, leading to imbalance and eventually paralysis, in addition to other symptoms.

Animal studies have shown it may be a problem with the mitochondria that leads to the axons breaking down or not growing long enough. Since studying human nerve cells is difficult, the researchers made use of human stem cells they modified to become nerve cells with the genetic disorder for a particular type of hereditary spastic paraplegia.

“What we found was that the mitochondria in these cells were breaking apart, what we call mitochondrial fission, and that caused the axons to be shorter and less effective at carrying messages to the brain,” study leader Prof Xue-Jun Li said. “We then looked at whether a particular agent would change the way the nerve cells function — and it did. It inhibited the mitochondrial fission and let the nerve cells grow normally and also stopped further damage.”

What this means for the thousands of people affected by this type of genetic disorder is that this peptide could prove to be useful for a drug or other therapy to stop the nerve cells from becoming damaged or possibly even reverse the course of the damage. Additionally, gene therapy could also prevent mitochondrial damage, the researchers suggested, which would provide another strategy to reverse the nerve damage.

Source: University of Illinois Chicago

Exercise Protects Ageing Synapses

Photo by Barbara Olsen from Pexels

When elderly people stay active, their brains have more proteins that enhance the connections between neurons to maintain healthy cognition, according to a study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

This protective impact was found even in people whose brains at autopsy were riddled with amyloid and tau proteins, associated with Alzheimer’s and other neurodegenerative diseases.

“Our work is the first that uses human data to show that synaptic protein regulation is related to physical activity and may drive the beneficial cognitive outcomes we see,” said lead author Kaitlin Casaletto, PhD.

The beneficial effects of physical activity on cognition have been shown in mice but have been much harder to demonstrate in people.

Dr Casaletto collaborated with William Honer, MD, a professor of psychiatry at the University of British Columbia and senior author of the study, to leverage data from the Memory and Aging Project at Rush University in Chicago. The project tracked the late-life physical activity of elderly participants, who also agreed to donate their brains upon death.

“Maintaining the integrity of these connections between neurons may be vital to fending off dementia, since the synapse is really the site where cognition happens,” Dr Casaletto said. “Physical activity – a readily available tool – may help boost this synaptic functioning.”

The researchers found that elderly people who remained active had higher levels of proteins that facilitate the exchange of information between neurons. This result dovetailed with Prof Honer’s earlier finding that people who had more of these proteins in their brains when they died were better able to maintain their cognition late in life.

Surprisingly, the effects ranged beyond the hippocampus to include other brain regions associated with cognitive function.

“It may be that physical activity exerts a global sustaining effect, supporting and stimulating healthy function of proteins that facilitate synaptic transmission throughout the brain,” Prof Honer said.

The brains of most older adults accumulate amyloid and tau proteins that are the hallmarks of Alzheimer’s disease pathology. Many scientists believe amyloid accumulates first, then tau, causing synapses and neurons to fall apart.

Dr Casaletto previously found that synaptic integrity, whether measured in the spinal fluid of living adults or the brain tissue of autopsied adults, appeared to dampen the relationship between amyloid and tau, and between tau and neurodegeneration.

“In older adults with higher levels of the proteins associated with synaptic integrity, this cascade of neurotoxicity that leads to Alzheimer’s disease appears to be attenuated,” she said. “Taken together, these two studies show the potential importance of maintaining synaptic health to support the brain against Alzheimer’s disease.”

Source: University of California in San Francisco

New Genetic Insights into Basal Ganglia Diseases

Source: Pixabay

A new study published in Developmental Medicine & Child Neurology uncovered a number of genetic causes of basal ganglia diseases.

Basal ganglia are deep grey matter structures in the brain involved in the control of posture and voluntary movements, cognition, behaviour, and motivational states. Several conditions are known to affect basal ganglia during childhood, but many questions remain.

In a study that included 62 children with basal ganglia diseases who were followed for two years, investigators identified multiple genetic aetiologies including mitochondrial diseases (57%), Aicardi–Goutières syndrome (20%), and single-gene causes of dystonia and/or epilepsy (17%) mimicking Leigh syndrome. Radiological abnormalities included T2-hyperintense lesions (n=26) and lesions caused by calcium or manganese mineralisation (n=9).

The researchers identified three clusters: the pallidal, neostriatal, and striatal, plus the last including mtDNA defects in the oxidative phosphorylation system with prominent brain atrophy. Mitochondrial biomarkers showed poor sensitivity and specificity in children with mitochondrial disease, whereas an interferon signature was observed in all patients with Aicardi–Goutières syndrome.

Radiological imaging tests also revealed several characteristics in patients that could help lead to an earlier diagnosis of basal ganglia diseases.

Source: Wiley

About 1% of Hospitalised COVID Patients Develop Neurological Complications

49-year-old female with past medical history of mitral valve disease and tricuspid valve regurgitation who developed headache followed by cough and fever presented to the ER with right upper eyelid ptosis (drooping). Credit: Radiological Society of North America and Scott H. Faro, M.D.

Approximately one in 100 patients hospitalised with COVID will likely develop complications of the central nervous system, according to a large international study. These can include stroke, haemorrhage, and other potentially fatal complications. The study was presented at the annual meeting of the Radiological Society of North America (RSNA).

“Much has been written about the overall pulmonary problems related to COVID, but we do not often talk about the other organs that can be affected,” said study lead author Scott H. Faro, MD, FASFNR, professor of radiology and neurology at Thomas Jefferson University. “Our study shows that central nervous system complications represent a significant cause of morbidity and mortality in this devastating pandemic.”

Dr Faro initiated the study after finding that only a small number of cases informed existing literature on central nervous system complications in hospitalised COVID patients.

To build a more complete picture, he and his colleagues analysed nearly 40 000 cases of hospitalised COVID patients, admitted between September 2019 and June 2020. Their average age was 66 years old, and two thirds were men.

Confusion and altered mental status were the most common causes of admission followed by fever. Comorbidities such as hypertension, cardiac disease and diabetes were common.

There were 442 acute neuroimaging findings most likely associated with the viral infection, with central nervous system complications in 1.2% of this large patient group.

“Of all the inpatients who had imaging such as MRI or a CT scan of the brain, the exam was positive approximately 10% of the time,” Dr Faro said. “The incidence of 1.2% means that a little more than one in 100 patients admitted to the hospital with COVID are going to have a brain problem of some sort.”

Ischaemic stroke, with an incidence of 6.2%, was the most common complication, followed by intracranial haemorrhage (3.72%) and encephalitis (0.47%).

A small percentage of unusual findings was uncovered, such as acute disseminating encephalomyelitis, an inflammation of the brain and spinal cord, and posterior reversible encephalopathy syndrome, a syndrome that mimics many of the symptoms of a stroke.

“It is important to know an accurate incidence of all the major central nervous system complications,” Dr Faro said. “There should probably be a low threshold to order brain imaging for patients with COVID.”

Source: EurekAlert!

Scientists Identify A New Recessive Neurodevelopmental Disorder

Image source: Pixabay

In the Journal of Clinical Investigation, researchers have reported a rare neurodevelopmental condition characterised by intellectual disability, ataxia with cerebellar hypoplasia and delayed puberty with hypogonadotropic hypogonadism (HH).

Patients with this unusual combination of conditions were referred to Mehul Dattani (UCL), and affected individuals were found to carry the same homozygous mutation in the PRDM13 gene, which encodes a chromatin modifying factor that contributes to regulating cell fate. Intriguingly, an unaffected heterozygous carrier of this mutation was identified by screening 42 unaffected individuals in the Maltese population, suggesting that this mutation is present at low levels in the population.

The researchers set out to model this condition and identify the underlying causes using a PRDM13-deficient mouse model. The researchers found evidence that both the cerebellar hypoplasia and reproductive phenotypes resulted from defects in the specification of specific populations of GABAergic neuronal progenitors in the developing cerebellum and hypothalamus, respectively.

The results indicate that this condition results from abnormal cell fate specification during development. Consequently, the hypoplastic cerebellum is deficient in molecular layer interneurons, which play critical roles in regulating cerebellar circuits. In the hypothalamus, fewer Kisspeptin neurons, which are important regulators of gonadotropin releasing hormone and puberty, were present in PRDM13 mutant mice.

Together, these findings identify PRDM13 as a critical regulator of neuronal cell fate in the cerebellum and hypothalamus, providing a mechanistic explanation for the co-occurrence of hypogonadism and cerebellar hypoplasia in this syndrome.

Source: King’s College London