Health risks for women suffering from Migraine with aura

Women who have migraines with aura, which are often visual disturbances such as flashing lights, may be more likely to have problems with their heart and blood vessels, and those on newer contraceptives may be at higher risk for blood clots,

The first study showed that migraine with aura is a strong contributor to the development of major cardiovascular events such as heart attack and stroke. After high blood pressure, migraine with aura was the second strongest single contributor to risk of heart attacks and strokes, It came ahead of diabetes, current smoking, obesity, and family history of early heart disease. while people with migraine with aura have an increased risk, it does not mean that everyone with migraine with aura will have a heart attack or stroke. People with migraine with aura can reduce their risk in the same ways others can, such as not smoking, keeping blood pressure low and weight down and exercising.

The second study looked at women with migraine who take hormonal contraceptives and the occurrence of blood clots. The study involved women with migraine with and without aura who were taking both newer contraceptives such as the contraceptive patch and ring and older contraceptives. Women with migraine with aura were more likely to have experienced blood clot complications such as deep vein thrombosis with all types of contraceptives than women with migraine without aura. The occurrence of blood clot complications was also higher in women with migraine who took contraceptives than women taking the contraceptives who did not have migraine.

Women who have migraine with aura should be sure to include this information in their medical history and talk to their doctors about the possible higher risks of newer contraceptives

Migraine with aura is associated with a twofold increased risk of stroke, The risk was highest among young women with migraine with aura who smoke and use estrogen containing contraceptives. An international team of researchers analysed the results of nine studies on the association between any migraine (with and without aura) and cardiovascular disease. They show that migraine with aura is associated with a twofold increased risk of ischemic stroke. This risk is further increased by being female, age less than 45 years, smoking, and estrogen containing contraceptive use. In light of these findings, the authors recommend that young women who have migraine with aura should be strongly advised to stop smoking, and methods of birth control other than estrogen containing contraceptives should be considered. They suggest that patients who have migraine with aura should be followed closely and treated aggressively for modifiable cardiovascular risk factors.

Citations:

American Academy of Neurology (AAN). "Migraine with aura may lead to heart attack, blood clots for women." ScienceDaily, 15 Jan. 2013. Web. 3 Mar. 2013.

Location and role of ion channels of the cochlea

Anthony Ricci, PhD, associate professor of otolaryngology, and colleagues at the University of Wisconsin and the Pellegrin Hospital in France found that the ion channels responsible for hearing aren't located where scientists previously thought. The discovery turns old theories upside down, and it could have major implications for the prevention and treatment of hearing loss

Location is important, because our entire theory of how sound activates these channels depends on it. Now we have to re-evaluate the model that we've been showing in textbooks for the last 30 years."

Deep inside the ear, specialized cells called "hair cells" sense vibrations in the air. The cells contain tiny clumps of hairlike projections, known as stereocilia, which are arranged in rows by height. Sound vibrations cause the stereocilia to bend slightly, and scientists think the movement opens small pores, called ion channels. As positively charged ions rush into the hair cell, mechanical vibrations are converted into an electrochemical signal that the brain interprets as sound.

But after years of searching, scientists still haven't identified the ion channels responsible for this process. To pinpoint the channels' location, Ricci and colleagues squirted rat stereocilia with a tiny water jet. As pressure from the water bent the stereocilia, calcium flooded into the hair cells. The researchers used ultrafast, high-resolution imaging to record exactly where calcium first entered the cells. Each point of entry marked an ion channel.

The results were surprising: Instead of being on the tallest rows of stereocilia, like scientists previously thought, Ricci's team found ion channels only on the middle and shortest rows.

Ion channels on hair cells not only convert mechanical vibrations into signals for the brain, but they also help protect the ear against sounds that are too loud. Through a process called adaptation, the ear adjusts the sensitivity of its ion channels to match the noise level in the environment. Most people are already familiar with this phenomenon, Ricci said, though they might not realize it. "If you watch TV in bed and you have the sound turned down low, you can hear fine when you're going to sleep," he said. "But then when you get up in the morning and turn on the news, you have to turn the volume up."

That's because at night, when everything is quiet, the ear turns up its amplifier to hear softer sounds. "But when you get up in the morning," Ricci said, "and the kids are running around and the dog is barking, the ear has to reset its sensitivity so you can hear in noisier conditions without hurting your ear."

Defects in the ear's adaptation process put people at risk for both age-related and noise-related hearing loss. Understanding adaptation is a fundamental step in preventing hearing loss, said Robert Jackler, MD, the Edward C. and Amy H. Sewall Professor in Otorhinolaryngology at Stanford.

"Many forms of hearing loss and deafness are due to disturbances in the molecular biology of the hair cell," said Jackler, who was not involved in the study. "When you understand the nuts and bolts of how the hair cell works, you can understand how it goes wrong and can set about learning how to fix it."

Other scientists have attempted similar experiments in the past, but they used less-sensitive imaging techniques. "Our microscope took images at 500 frames per second," said Ricci, who led the imaging experiments. "That's much faster than it's ever been done before."

Ricci and colleagues also used hair cells from rats, while previous experiments had been done in bullfrogs. Because mammals have fewer, more widely spaced rows of stereocilia, the team was able to determine the precise location of the ion channels.

Citations:

1. Stanford University Medical Center. "How Human Ear Translates Vibrations Into Sounds: Discovery Of Ion Channel Turns Ear On Its Head." ScienceDaily, 28 Apr. 2009. Web. 3 Mar. 2013.
2. Maryline Beurg, Robert Fettiplace, Jong-Hoon Nam & Anthony J Ricci. Localization of inner hair cell mechanotransducer channels using high-speed calcium imaging. Nature Neuroscience, 2009; DOI:10.1038/nn.2295

Is there a relationship between hearing and touch?

There are good reasons to suspect that hearing and touch might have a common genetic basis. Sound-sensing cells in the ear detect vibrations and transform them into electrical impulses. Likewise, nerves that lie just below the surface of the skin detect movement and changes in pressure, and generate impulses. The similarity suggests that the two systems might have a common evolutionary origin—they may depend on an overlapping set of molecules that transform motion into signals that can be transmitted along nerves to the brain.

People with a certain form of inherited hearing loss have increased sensitivity to low frequency vibration. The research findings, which were published in Nature Neuroscience,reveal previously unknown relationships between hearing loss and touch sensitivity. Those suffering from hereditary DFNA2 hearing impairment is caused by a mutation which disrupts the function of many hair cells in the inner ear. This mutation, the researchers suspected, might also affect the sense of touch. Tiny, delicate hairs in our inner ear vibrate to the pressure of the sound waves. The vibrations cause an influx of positively charged potassium ions into the hair cells. This electric current produces a nerve signal that is transmitted to the brain which results in hearing. The potassium ions flow through a channel in the cell membrane and again out of the hair cells. This potassium channel, a protein molecule called KCNQ4, is destroyed by the mutation in such hearing-impaired people. The sensory cells gradually die off due to overload. They found that KCNQ4 is present not only in the ear, but also in some sensory cells of the skin. Clearly there are parallels to hearing, As a first step, the researchers in the Jentsch lab created a mouse model for deafness by generating a mouse line that carries the same mutation in the potassium channel as a patient with this form of genetic hearing loss. The touch receptors in the skin where the KCNQ4 potassium channel is found did not die off due to the defective channel like they did in the ear, but instead showed an altered electric response to the mechanical stimuli in the mutated mouse. They reacted much more sensitively to vibration stimuli in the low frequency range. The sensation of touch varies greatly from person to person -- some people are much more sensitive to touch than others. DFNA2 patients are extremely sensitive to vibrations,

In recent years about 70 genes have been identified in humans, mutations in which trigger hearing loss or deafness. Surprisingly, no genes have been found that negatively influence the sense of touch,

In another study, to see whether the sense of touch also has a hereditary component, the researchers first studied 100 pairs of twins -- 66 pairs of monozygotic twins and 34 dizygotic pairs of twins. Monozygotic twins are genetically completely identical; dizygotic twins are genetically identical to 50 percent. The tests showed that the touch sensitivity of the subjects was determined to more than 50 percent by genes. Furthermore, hearing and touch tests showed that there is a correlation between the sense of hearing and touch.

The researchers decided it would take too much time to analyze which of the approximately 70 genes that adversely affect the sense of hearing may also negatively affect the sense of touch. Therefore, the researchers focused specifically on patients with Usher syndrome, a hereditary form of hearing impairment, in which the patients progressively become blind. Usher syndrome patients have varying degrees of hearing impairment, and the disease is genetically very well studied. There are nine known Usher genes carrying mutations which cause the disease. The studies revealed that not all patients with Usher-syndrome have poor tactile acuity and touch sensitivity. The researchers showed that only patients with Usher syndrome who have a mutation in the gene USH2A have poor touch sensitivity. This mutation is also responsible for the impaired hearing of 19 patients. The 29 Usher-syndrome patients in whom the mutation could not be detected had a normal sense of touch. The researchers thus demonstrated that there is a common genetic basis for the sense of hearing and touch.

Citations:

1. Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch. "People with DFNA2 hearing loss show increased touch sensitivity, study shows." ScienceDaily, 12 Dec. 2011. Web. 3 Mar. 2013.
2. Matthias Heidenreich, Stefan G Lechner, Vitya Vardanyan, Christiane Wetzel, Cor W Cremers, Els M De Leenheer, Gracia Aránguez, Miguel Ángel Moreno-Pelayo, Thomas J Jentsch, Gary R Lewin. KCNQ4 K+ channels tune mechanoreceptors for normal touch sensation in mouse and man. Nature Neuroscience, 2011; DOI:10.1038/nn.2985
3. Helmholtz Association of German Research Centres. "Hearing and touch have common genetic basis: Gene mutation leads to impairment of two senses." ScienceDaily, 1 May 2012. Web. 3 Mar. 2013.
4. Henning Frenzel, Jörg Bohlender, Katrin Pinsker, Bärbel Wohlleben, Jens Tank, Stefan G. Lechner, Daniela Schiska, Teresa Jaijo, Franz Rüschendorf, Kathrin Saar, Jens Jordan, José M. Millán, Manfred Gross, Gary R. Lewin. A Genetic Basis for Mechanosensory Traits in Humans. PLoS Biology, 2012; 10 (5): e1001318 DOI:10.1371/journal.pbio.1001318