As spring and summer bring an increase in outdoor activities, this is the right time of year to be more aware of speech and hearing issues. Typical recreational activities can increase exposure to potentially damaging problems.

Experts in the audiology and speech pathology department at The Methodist Hospital in Houston have a few tips to keep your speech and hearing in working order.

1) Protect your hearing: If you’re mowing the lawn, working on an outdoor project that involves loud power tools or watching a fire works display, wear noise protection. These can be ear plugs or other hearing protectors. Noise from exploding fireworks can top 130 decibels. Research has shown that exposure to 105 decibels for one hour can put you at risk of hearing damage.

2) Use your normal voice: Parties are fun, but they can actually lead to vocal and hearing damage. Loud music and large groups of people talking loudly can cause voice damage and/or hearing impairment. Try to use your normal voice, avoid throat clearing and don’t whisper. Whispering is as hard on your voice as talking very loudly. Also, if you feel strain or tension in your throat, neck or shoulders, you’re talking too loud. Avoid further irritation of the vocal cords caused by smoking or drinking alcohol. Finally, drink lots of clear liquids when your throat is dry.

3) You may have a hearing loss if you:

— Frequently ask people to repeat themselves

– Often turn your ear toward a sound to hear it better

– Keep the volume on your radio or TV at a level that others say is too loud

– Have pain or ringing in your ears (tinnitus)

– Have an ear infection (swimmer’s ear)

– Have a perforated eardrum

4) Common voice disorders: Most of these disorders are related to trauma to the vocal folds from excessive or intense voice use. Vocal nodules, polyps and cysts are common use-related problems that occur in adults. Irritants, such as acid reflux and environmental allergies, also account for many throat and voice complaints. Treating these irritants can go a long way to preserving your voice.

5) Swallowing disorders: As people age, they may have difficulty swallowing. These problems frequently accompany difficulty with speech. Studies suggest the prevalence of dysphagia (swallowing disorders)may be as high as 22 percent in those over 50. To help alleviate swallowing problems, sit upright when eating, drinking and taking medication; chew food thoroughly; and brush your teeth after each meal.

About The Methodist Hospital

The Methodist Hospital in Houston is one of the nation’s largest private, non-profit general hospitals. Dedicated to providing the highest level of patient care, Methodist has a 90 year legacy of medical breakthroughs, such as the world’s first multiple-organ transplant in the 1960s, gene therapy for prostate cancer, and the first islet cell transplants in Texas.

Methodist is ranked among the country’s top centers in 14 specialties in U.S News & World Report’s 2007 America’s Best Hospitals issue. The hospital ranked in more specialties than any other hospital in Texas. Methodist is also 10th on FORTUNE’s “100 Best Companies to Work For” in 2008.

Methodist is primarily affiliated with Weill Cornell Medical College and New York Presbyterian Hospital, two of the nation’s leading centers for patient care, medical education and research. Methodist also is affiliated with the University of Houston.

Methodist Hospital, Houston
6565 Fannin St.
Houston, TX 77030
United States
http://www.methodisthealth.com

Medtronic, Inc. (NYSE: MDT) announced that the American Academy of Otolaryngology - Head and Neck Surgery approved a policy statement concluding that the use of micropressure for Ménière’s disease including the Medtronic Meniett® device is appropriate when other medical treatments fail.

In the policy statement both the Equilibrium Committee and Board of Directors conclude that, “…there is convincing and well-controlled medical evidence to support the use of micropressure therapy (such as the Meniett device) in certain cases of Ménière’s disease. Micropressure therapy is best used as a second level therapy when medical treatment has failed. The device represents a largely non-surgical therapy that should be available as one of the many treatments for Ménière’s disease.”

“This is a large step forward from the Board and Equilibrium Committee at the Academy,” said Mark Fletcher, president of the ENT business at Medtronic. “With this new policy statement in place, we can now show that the medical community considers the Meniett a widely accepted and approved therapy in certain cases of Ménière’s disease, allowing us to work toward removing the ‘investigational’ label that many insurance carriers have on the therapy.”

Approximately 2.6 million people in the United States and Europe1 suffer from Ménière’s disease, a disorder associated with excess fluid in the inner ear. This complex disease is characterized by vertigo in combination with hearing loss, tinnitus (ringing in the ear) and pressure in the ear. The origin is unknown and there is no cure, which makes managing the disease difficult when symptoms are severe. Unpredictable vertigo attacks with nausea and vomiting can be very debilitating, with patients unable to work or perform routine activities.2

About the ENT Business at Medtronic

Located in Jacksonville, Fla., the ENT business at Medtronic (http://www.MedtronicENT.com) is a leading developer and manufacturer of products to treat diseases of the ear, nose and throat (ENT). Patients seeking additional information about Ménière’s disease and the Meniett device should visit http://www.meniett.com.

About Medtronic

Medtronic, Inc. , headquartered in Minneapolis, is the global leader in medical technology - alleviating pain, restoring health, and extending life for millions of people around the world.

Any forward-looking statements are subject to risks and uncertainties such as those described in Medtronic’s Annual Report on Form 10-K for the year ended April 27, 2007. Actual results may differ materially from anticipated results.

References

1. Stahle J, Stahle C, Arenberg IK. The incidence of Ménière’s disease. Arch Otolaryngol Head Neck Surg. 1978;104:99-102.

2. Anderson JP and Harris JP. Impact of Ménière’s disease on quality of life. Otol Neurotol. 2001;22:888-894.

Medtronic

A child spikes a high fever, sometimes as high as 104 or 105 degrees, and sometimes causing seizures. She’s rushed to the emergency room, the hospital runs test after test, specialists are brought in, but no explanation is found.

Many families though no one knows how many go through this cyclical nightmare. The fevers seem to come like clockwork, aren’t accompanied by any obvious symptoms and don’t respond to antibiotics or fever reducers like Motrin or Tylenol. Instead, they vanish on their own after four to five days, only to return four to six weeks later.

A report in last month’s Archives of Otolaryngology and Head and Neck Surgery finds that tonsillectomy (with or without removal of the adenoids) is almost always curative. No one knows why the tonsils and adenoids show no evidence of unusual infection or other abnormality when pathologists study them. But desperate families are opting for surgery as a last-ditch measure and finding it to be life-changing.

The paper, describing 27 children treated at Children’s Hospital Boston from 2004 through 2007, offers the largest reported surgical experience to date with this syndrome, currently known as PFAFA (periodic fever, aphthous ulcers, pharyngitis and adenitis). Of the 27 children, 26 had complete fever resolution. Many had suffered cyclical fevers for years.

“Why taking out tonsils and adenoids works is unclear, but it works in almost every single kid,” says Children’s otolaryngologist Greg Licameli, MD, FACS, the paper’s first author. “I tell parents, ‘I don’t know why this works, but it has a good chance of ridding your child of fevers.’”

Licameli has now seen 60 children with PFAFA, first described in the medical literature in 1987, and the findings continue to hold up. Given how many children he’s seen in just five years, he thinks the condition isn’t all that uncommon, though it is underrecognized and unknown to most pediatricians and otolaryngologists.

Licameli’s introduction to PFAFA was a personal one: His first patient, described as a case report in the paper, was his own daughter, who at 19 months was getting fevers every three weeks. “There was nothing to break the fevers,” he recalls. “She was seen by several experts at Children’s. The workup was always negative.”

Searching the medical literature for answers, Licameli found two small case studies in Europe, where doctors diagnosed PFAPA, removed the tonsils and the children got better, and decided to try this approach. It worked, with an immediate cessation of his daughter’s fever cycles (she’s now almost 6), and other doctors began referring patients to him.

The hallmark of PFAFA is high fevers of a cyclical nature parents can often look at their calendars and predict what day the fevers will arrive. There are typically no other symptoms. Some children have sore throat, swollen glands and small mouth ulcers, but these symptoms aren’t very specific and can be very subtle.

“On the face of it, it doesn’t seem like a surgical problem,” Licameli says. “The tonsils and adenoids appear normal, even when you study them pathologically, yet surgery is immediately curative.”

Before undergoing surgery, patients are evaluated for any rheumatologic or infectious etiologies that can also cause cyclical fever.

So what causes this condition, and why does surgery work? Licameli suspects the tonsils may harbor a chronic indolent infection to which the immune system is hypersensitive. He and his colleagues at Children’s including specialists in infectious disease, rheumatology and immunology — plan to pursue these questions further.

In the meantime, they hope that increased physician awareness will allow children struggling with this condition to be offered surgery sooner.

The study was supported by the Clinical Research Program, Committee of Clinical Investigation and Department of Otolaryngology at Children’s Hospital Boston.

Reference: Arch Otolaryngol Head Neck Surg 2008 Feb; 134:136-140.

Children’s Hospital Boston is home to the world’s largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 12 members of the Howard Hughes Medical Institute comprise Children’s research community. Founded as a 20-bed hospital for children, Children’s Hospital Boston today is a 397-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children’s also is the primary pediatric teaching affiliate of Harvard Medical School.

Children’s Hospital Boston
21 Autumn St., 2nd Fl.
Boston, MA 02115
United States
http://www.childrenshospital.org

More than 7,000 attendees are gathering at the Charlotte Convention Center in Charlotte, NC, April 2 - 5, for AudiologyNOW! - an experience in knowledge, science, and technology for audiologists. Along with educational sessions, events, and technological innovations of interest to audiologists, this year’s AudiologyNOW! also celebrates the 20th Anniversary of the American Academy of Audiology with the theme “Hear to Stay.”

Twenty years ago this past January, a group of audiology leaders met at the invitation of Dr. James Jerger, then at the Baylor College of Medicine in Houston, Texas, to establish an independent national organization of, by, and for audiologists. In celebration of the first 20 years, the General Assembly, held from 10:00 am - 11:30 am, on Thursday, April 3, will highlight the professional victories and accomplishments in the field of audiology with a special session, “The Future of Audiology: 20 Years Later.”

This year, the Marion Downs Lecture in Pediatric Audiology, will be presented by Daniel Christaan De Wet Swanepoel, PhD, of the University of Pretoria in South Africa. Dr. Swanepoel’s presentation, “Hearing Loss: Silent Epidemic of Developing Countries,” will focus on infant hearing loss as a major health-care concern in developing countries, where over 90 percent of children who suffer from hearing loss reside without the prospect of early identification or intervention. This year’s WOW presenter, A. James Hudspeth, PhD, will present on hair cell physiology. Dr. Hudspeth’s research at the Rockefeller University has led to better understanding of the intricacies of the inner ear, as well as their contributions to hearing and hearing loss.

Returning to this year’s AudiologyNOW! after its debut at last year’s convention in Denver is the DiscovEARy Zone! - a free interactive and educational experience about the human ear and the hearing loss that’s guaranteed fun for kids of all ages. Located on Level 2, near the grand staircase of the Charlotte Convention Center, the exhibit will be open to the public from 9:00 am - 4:00 pm, April 3 - 5, 2008. The DiscovEARy Zone will feature a series of interactive computer kiosks, hands-on learning tables, a giant graphic display of the anatomy of the ear, listening stations, and a quiet room where kids can have their hearing checked by an audiologist.

This year, Audiology Solutions will feature more than 200 exhibitors and over 280,000 square feet of cutting-edge hearing technology and audiological products and services, including assistive listening/altering and signaling devices, audiometers, batteries and battery accessories, bone conduction devices, diagnostic instruments, earphones, earmold/impression materials, evoked potential equipment/NB screeners, hearing aid accessories, hearing aid maintenance/repair, hearing protection, implantable devices, industrial hearing conservation, infant hearing screening equipment, OAE test equipment, real ear systems, swim plugs, tinnitus devices, vestibular test equipment, vibrotactile devices, video otoscopes, and wireless devices.

As the largest gathering of audiologists, AudiologyNOW! 2008, April 2 - 5, in Charlotte, NC, features exciting learning modules, educational sessions, learning labs, exhibitor courses, focus and discussion groups, research pods, poster presentations, and a student research forum. For more information, please visit AudiologyNOW.org.

The American Academy of Audiology is the world’s largest professional organization of, by, and for audiologists. With an active membership of more than 10,000 audiologists, the Academy promotes quality hearing and balance care by advancing the profession of audiology through leadership, advocacy, education, public awareness, and support of research. To learn more about the audiology profession and how audiologists are helping the 31 million Americans who experience hearing loss, please visit the Academy’s Web site at http://www.audiology.org.

A new five-year study at the University of Texas Medical Branch at Galveston confirms the suspected close link between the two most common diseases of young children: colds and ear infections.

The study, which appears in the March 15 issue of Clinical Infectious Disease, confirmed the suspected close link between the two most common diseases of young children, viral colds and ear infections. It also identified the viruses associated with higher rates of ear infections.

“Understanding how viruses and ear infections are linked will definitely help us find new ways to prevent ear infections,” said Dr. Tasnee Chronmaitree, a pediatric infectious disease specialist who is the study’s principal investigator. “To break the link you must first understand it.”

Ear infections are the driving force behind antibiotic resistance, a troubling medical issue, as physicians often administer antibiotics for the painful, persistent ailment.

Chonmaitree has studied otitis media (ear infection) for more than two decades. She said parents could best protect their children by avoiding exposure to sick children and to have their children vaccinated against influenza. She suggested that children in day care might face reduced exposure to viruses if they are enrolled in smaller day care facilities with fewer children.

Funded by the National Institutes of Health, Chonmaitree and colleagues followed 294 children ages 6 months to 3 years for up to one year each. Researchers documented about 1,300 cold episodes and a 61 percent rate of ear infection complication including asymptomatic fluid in the middle ear, which can cause hearing problems. Researchers also identified the types of cold viruses - adenovirus, respiratory syncytial virus and coronavirus - that most often resulted in ear infection.

“Because we now know that the common cold is the precursor to an ear infection, it is important for parents to make extra efforts to prevent their children from catching colds,” Chonmaitree said. “It’s important to avoid exposure to sick children or adults, to avoid day care attendance, if possible, and if that’s not an option, to choose a smaller group day care.”

Chonmaitree also recommended the use of influenza vaccine, the only vaccine available to prevent respiratory viral infection, which is now available for children older than 6 months. The antiviral drug has also been shown to prevent ear infections associated with influenza, she said.

Chonmaitree and colleagues will continue to study the role of viruses in ear infection aiming to find a way to prevent the disease. Continued funding from the NIH will allow them to study children born with genetic variations who are prone to having ear infections and at the interactions between genes and the environment.

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Clinical Infectious Diseases is an official publication of the Infectious Disease Society of America.

The University of Texas Medical Branch at Galveston
Public Affairs Office
301 University Boulevard, Suite 3.102
Galveston, Texas 77555-0144
http://www.utmb.edu/

Source: Marsha Canright
University of Texas Medical Branch at Galveston

If a patient develops respiratory problems after taking analgesics, this indicates that the active substances are poorly tolerated. This is pointed out by Prof. Hanns-Wolf Baenkler, Erlangen University Medical School, in the current edition of the Deutsches Arzteblatt International (Dtsch Arztebl Int 2008; 105(8): 137-42). One should also think of analgesic intolerance when patients suffer from chronic irritation of the gastrointestinal tract, without any recognizable allergy or infection.

Patients with these symptoms exhibit enhanced sensitivity and changes in the pattern of the so-called eicosanoids - important mediators of pain and inflammation. This change in pattern explains the specific reaction to salicylates and related COX inhibitors in analgesics, cosmetics, and vegetable foods. The classical symptoms of intolerance are rhinitis, bronchial asthma or nasal polyps, accompanied by inflammatory reactions in the intestine or skin and urticaria.

The diagnosis is based on symptoms immediately after taking salicylates or on recurrent polyp formation. Blood tests can be an important diagnostic aid, particularly in difficult cases. Discontinuation of treatment helps, as does corticosteroid treatment. Biological treatment is also possible, based on adaptation by administering increasing doses of acetylsalicylic acid.

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Source: Dr. Stephan Mertens
Deutsches Aerzteblatt International

There is no cure for tinnitus - but the British Tinnitus Association (BTA) is helping to search for a treatment that will help sufferers. The BTA are currently sponsoring two students studying tinnitus research and treatment. The MSc studentships are part of the BTA research and training programme.

MSc students Glynn Riddiford and John Beharrell have been sponsored by the BTA during the 2007-8 and 2007-9 academic periods. Glyn Riddiford of Chase Farm Hospital, Enfield has enrolled on a two year part-time MSc in Audiological Rehabilitation at Bristol University. Glyn’s dissertation will build on the ‘Learning from the Research Methods’ unit and the ‘Evidence-based Healthcare’ unit. John Beharrell is on a part-time MSc in Rehabilitation Studies at Aston University. John’s MSc dissertation includes an important opportunity for him to conduct an original piece of research to increase understanding of tinnitus or its management.

Martin Wass, Director of the BTA said “We are interested in supporting research into tinnitus at any level and any scale and consider all applications on their merits. As our MSc studentships indicate, we are keen to nurture junior researchers.”

Glyn Riddiford said “I have been interested in meteorological conditions in relation to health for many years, both personally and professionally, but have never been in a position to carry out acceptable and valid, scientific research - until now that is! I wish to investigate any connection between changes in tinnitus awareness and changes in meteorological conditions. Now, thanks to the BTA sponsorship and the MSc course at Bristol, I have the tools to do this.”

John Beharrell commented “This scholarship will enable me to complete the Rehabilitation Studies MSc course that otherwise I could not afford consequently allowing me to better understand the psychological principles that appear to play such a powerful role in Tinnitus.”

Application forms for BTA grants can be downloaded in the Applications for Grants section of the BTA website http://www.tinnitus.org.uk.

British Tinnitus Association

Professor Howard Jenkinson in the Department of Oral & Dental Science (Dental School) at the University of Bristol has been awarded a grant of 285,000 pounds from The Wellcome Trust to research ways to combat diseases caused by Streptococcus bacteria.

Familiar to those who suffer from ’strep’ throat, Streptococcus are the most common bacteria in the human mouth and throat. They are linked to a number of health problems, some mild, some life-threatening, ranging from tooth and gum disease to meningitis, pneumonia, endocarditis (inflammation of the inner layer of the heart) and necrotizing fasciitis (’flesh-eating disease’). Streptococcus are potent bacteria which are becoming increasingly resistant to treatment by antibiotics. The rate of severe invasive Streptococcus infections is about 60 per 100,000.

The bacteria cause disease in the body by first attaching to tissues. By looking at how this happens, Professor Jenkinson and his team will be able to develop new ways to block the bacteria. One goal is to reduce the rates at which disease-causing Streptococcus are transferred between humans. This could be achieved by developing user-friendly vaccines or natural biological products, which can be taken by mouth, to eliminate the harmful bacteria. This approach lessens antibiotic usage and would significantly decrease infection rates in those most susceptible e.g. children, expectant mothers and the elderly.

Professor Jenkinson says, ‘Streptococcus bacteria are amongst the most commonly encountered in infections, and for the most part we depend totally on antibiotics to fight them. Our research will help develop new infection-control methods that do not rely on conventional antibiotics, and will also help identify people who are at higher risk of infections.’

The research will look at the interactions between a protein called AgI/II, which is found on the surface of Streptococcus bacteria, and a protein called gp340, which is found on teeth, in saliva and in airways. The team will measure how ’sticky’ the Streptococcus bacteria proteins are as they attach to gp340 on tissue surfaces. By pinpointing the sticky parts of the protein, the team will be able to identify which are responsible for streptococci invading and attacking the body. The research will look at how to block this process and thus develop new ways to prevent bacterial infection.

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The study involves Drs Michele Barbour, Linda Franklin and Sarah Maddocks, also from the Department of Oral & Dental Science; Dr Aras Kadioglu, University of Leicester and Dr Nicklas Str?mberg, Ume? University. The first results are due to be presented internationally in June 2008.

1. The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over ￡500 million each year to support the brightest scientists with the best ideas. The Trust supports public debate about biomedical research and its impact on health and wellbeing.

Source: Dara O’Hare
University of Bristol

Scientists in the US have shown that listening to a cell phone while driving was enough distraction to cause drivers to make the same type of driving errors as they would under the influence of alcohol.

The study is the work of neuroscientist Dr Marcel Just and colleagues at the Center for Cognitive Brain Imaging at Carnegie Mellon University in Pittsburgh, Pennsylvania, and is to be published shortly in the journal Brain Research.

Even if you are not talking, just listening to a cell phone conversation can significantly reduce the amount of brain activity associated with driving, said the researchers, who asked volunteers to drive on a simulator while they observed their brains using an MRI (magnetic resonance image) scanner.

Using cell phones while driving has been a matter of controversy for some time, but this is the first study to look at listening alone as a distraction.

Just and colleagues found that listening alone reduced brain activity associated with driving by 37 per cent. Based on driving simulator results, this would be enough to cause a driver to weave out of their lane, said the researchers.

“Drivers need to keep not only their hands on the wheel; they also have to keep their brains on the road,” said Just in a prepared statement.

Just and colleagues invited 29 volunteers to to use a driving simulator while inside an MRI brain scanner. The simulator gave them a winding road to drive on at a fixed but challenging speed. There were two conditions: undisturbed or while listening. While listening, the volunteers listened to statements and had to decide whether they were true or false, a similar level of cognitive processing as would be involved in a normal listening activity.

The researchers used the latest functional magnetic resonance imaging (fMRI) technology to measure second by second changes in brain activity in 20,000 places, each being about the size of a peppercorn, they said.

Compared to the undisturbed scenario, the listening while driving scenario showed a 37 per cent decrease in activity in the brain’s parietal lobe, the part of the brain that is associated with driving and processes sensory inputs that are important for navigation and spatial awareness. The occipital lobe, which processes visual signals, also showed reduced activity, said the researchers.

Using measures of performance on the simulator, the researchers observed that the driving while listening scenarios resulted in much poorer quality of driving. When in listening while driving mode the volunteers made more errors in lane discipline, such as deviating from the middle and hitting a guardrail.

The study suggests that hands free and voice activated cell phones do not go far enough to ease safety concerns because the distraction of listening would still remain.

The researchers said that other distractions such as listening to the radio, eating or talking to a passenger can also divert a driver, and although there is no evidence of how these distractions compare to listening to a cell phone, they suggest cell phones are different because, as Just explained:

“Talking on a cell phone has a special social demand, such that not attending to the cell conversation can be interpreted as rude, insulting behavior.”

A passenger, on the other hand, because he or she is physically in the car with the driver, can see if anything urgently needs the driver’s attention and will stop talking, it is a situation that is less likely to put social pressure on the driver.

Just said the clear message of this study is that:

“Engaging in a demanding conversation could jeopardize judgment and reaction time if an atypical or unusual driving situation arose.”

He warned that:

“Heavy traffic is no place for an involved personal or business discussion, let alone texting.”

Previous studies had suggested that driving and listening used two differnt parts of the brain and could work independently of each other, thus allowing the driver to “multi-task” safely.

But this study suggests otherwise, said Just, it doesn’t matter how different the tasks are, the brain can only do so much at one time.

The study is an example of the new science of neuroergonomics that studies the match between technology and human ability by bringing together brain science and research on human-computer interaction.

Neuroergonomicists are starting to observe humans operating ships, cars, and other vehicles where the driver’s position is beginning to look more and more like the cockpit of an aircraft with all the technology interfaces that now exist.

Every additional device demands brain activity, increasing the likelihood that resources crucial for making fine judgements on the road are compromised.

If brain resource for safe driving is limited, then perhaps it should be devoted to paying attention to those devices that help the driver make these judgements, rather than the cell phone, iPod, CD, radio, or even DVD player.

“Drivers’ seats in many vehicles are becoming highly instrumented cockpits,” Just explained, “and during difficult driving situations, they require the undivided attention of the driver’s brain.”

“A decrease in brain activation associated with driving when listening to someone speak.”
Marcel Adam Just, Timothy A Kellera and Jacquelyn Cynkara.
Brain Research Article in Press (Accepted Manuscript).
Available online 19 February 2008.
DOI:10.1016/j.brainres.2007.12.075

Click here to see a full preprint issue of the study (from CMU Center for Cognitive Brain Imaging website).

Sources: Carnegie Mellon University press release.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today

If you cook, you know. Chop an onion and you risk crying over your cutting board as a burning sensation overwhelms your eyes and nose. Scientists do not know why certain chemical odors, like onion, ammonia and paint thinner, are so highly irritating, but new research in mice has uncovered an unexpected role for specific nasal cavity cells. Researchers funded by the National Institute on Deafness and Other Communication Disorders (NIDCD), part of the National Institutes of Health, describe this work in the March issue of the Journal of Neurophysiology, now available online.

Weihong Lin, Ph.D., of the University of Colorado Denver School of Medicine and University of Maryland, Baltimore County, led the study which discovered that a particular cell, abundant near the entry of many animal noses, plays a crucial and previously unknown role in transmitting irritating and potentially dangerous odors. Dr. Lin and colleagues from both universities plus the Mount Sinai School of Medicine identified the role of this solitary chemosensory cell in transmitting irritating chemical odors in the noses of mice.

Scientists have found similar solitary chemosensory cells in the nasal cavities, airways and gastrointestinal tracts of many mammals as well as fish, frogs and alligators; they think it is likely that they are also present in humans, explains Thomas Finger, Ph.D., one of the senior co-authors at the University of Colorado Denver.

Prior to this work, scientists who study smell and taste thought that irritating odors directly stimulated the trigeminal nerve, which senses touch, temperature and pain throughout the head region, including the delicate membranes that line the inside of the nose. The research team, under the guidance of Diego Restrepo, Ph.D., found that solitary chemosensory cells scattered in the epithelium inside the front of the nose respond to high levels of irritating odors and relay signals to trigeminal nerve fibers.

“This elegant research corrects an erroneous assumption about how irritating odors are perceived and expands our understanding of olfaction,” says James F. Battey, M.D., Ph.D., director of NIDCD. “With further investigation, it also might lead to a better understanding of why some people are exceptionally sensitive to irritating odors.”

Solitary chemosensory cells on the surface of the nasal cavity are in close contact with trigeminal nerve fibers which end just below the surface. Earlier research revealed that these cells contain bitter taste receptors and that bitter substances applied to the surface of the nasal cavity trigger a trigeminal nerve response.

Intrigued, Drs. Restrepo and Finger decided to explore whether solitary chemosensory cells respond to irritating odors. Using nasal tissue from mice, the scientists measured a variety of changes in solitary chemosensory cells as they exposed the cells to low and high levels of several irritating, volatile chemical odors.

Among their observations were changes in electrical activity in the cells - which indicates a response to an outside stimulus - and changes in intracellular calcium ion concentration - which indicates signaling to other cells. Their measurements demonstrated that the solitary chemosensory cells responded to the odors and relayed sensory information to trigeminal nerve fibers.

Once stimulated, the trigeminal nerve will convey pain and burning sensations and can trigger protective reflexes such as gagging and coughing. The architecture of nasal tissue with solitary chemosensory cells on the surface and trigeminal nerve fibers just below allows the nose to detect a greater number of irritating odors, the scientists explain.

Fortunately, the threshold for triggering a response is high, so exposure to a small amount of an irritating chemical, as might naturally emanate from some kinds of fresh fruit, will not bring on gagging and coughing. For example, lemons contain the volatile chemicals citral and geraniol but at levels too low to trigger a trigeminal response. Only high, potentially dangerous levels of odors will trigger the protective gagging-and-coughing response.

The researchers point out that their findings provide an example of the Law of Specific Nerve Energies, conceived by Johannes Peter Muller in 1826. Muller said that the way we perceive a stimulus depends on the nerve or sensory system that conveys it rather than the physical nature of the stimulus itself. In the case of irritating odors, we perceive them as irritating because they are transmitted via the trigeminal nerve, leading the brain to interpret the message as pain rather than as a smell.

The researchers say their findings raise new questions about how irritating odors are detected. They say more research is needed to explore whether solitary chemosensory cells are programmed to recognize specific irritants, which receptors are involved, and what steps a solitary chemosensory cell uses to convert a chemical stimulus to a signal it relays to the trigeminal nerve.

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The NIDCD supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information about NIDCD programs, see the Web site at http://www.nidcd.nih.gov/.

NIH - the nation’s medical research agency - includes 27 institutes and centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov/.

Source: Linda Joy
NIH/National Institute on Deafness and Other Communication Disorders