motion sickness

Definition

Motion sickness is the uncomfortable dizziness, nausea, and vomiting that people experience when their sense of balance and equilibrium is disturbed by constant motion. Riding in a car, aboard a ship or boat, or riding on a swing all cause stimulation of the vestibular system and visual stimulation that often leads to discomfort. While motion sickness can be bothersome, it is not a serious illness, and can be prevented.

Description

Motion sickness is a common problem with nearly 80% of the population enduring its affects at one time in their lives. While it may occur at any age, motion sickness most often afflicts children over the age of two, with the majority outgrowing this susceptibility.

When looking at why motion sickness occurs, it is helpful to understand the role of the sensory organs. The sensory organs control a body's sense of balance by telling the brain what direction the body is pointing, the direction it is moving, and if it is standing still or turning. These messages are relayed by the inner ears (or labyrinth); the eyes; the skin pressure receptors, such as in those in the feet; the muscle and joint sensory receptors, which track what body parts are moving; and the central nervous system (the brain and spinal cord), which is responsible for processing all incoming sensory information.

Motion sickness and its symptoms surface when conflicting messages are sent to the central nervous system. An example of this is reading a book in the back seat of a moving car. The inner ears and skin receptors sense the motion, but the eyes register only the stationary pages of the book. This conflicting information may cause the usual motion sickness symptoms of dizziness, nausea and vomiting.

— Beth A. Kapes

For more information on motion sickness, visit Britannica.com.

At some point in their lives, most individuals experience motion sickness, in one form or another, while being transported in moving vehicles. There is a wide variability in susceptibility, with a greater prevalence in females than males, and in children between 3 and 12 years of age. It is characterized by initial feelings of dizziness, general discomfort, pallor, and cold sweating, followed by nausea, vomiting, and apathy. It has been given many specific names relating to the mode of transport involved (such as sea-, air-, space-, or even camel-sickness), but all forms are thought to arise from the same basic cause.

The first known report of sea-sickness was by Hippocrates, and the word ‘nausea’ actually derives from the Greek for ship (naus). The precise cause has been difficult to establish, although it has long been realized that it is associated with stimulation of the vestibular system of the inner ear. Thus, motion sickness is never experienced by individuals who have no vestibular function. Older texts often suggest that the cause is over-stimulation of the vestibular system, but current opinion favours an explanation in terms of what has been called the sensory conflict theory of motion sickness. This is based on the notion that the stimuli which cause motion sickness are those that generate sensations that do not conform with a repertoire of expected sensations that has been built up and stored in the brain on the basis of past experience of the sensory stimulation associated with motion.

Two major sources of sensory conflict are recognized: intra-vestibular and visual-vestibular. Intra-vestibular conflict arises from the fact that there are two types of sensory organ in the vestibular system, the semicircular canals, which respond to rotation, and the otolith organs, which respond to linear motion and to changes in orientation with respect to gravity. If a rotational movement of the head is made, such as pitching the head forward to look down at the ground, the otoliths and canals independently give signals about the magnitude of the movement during and after the motion. Because such head movements are made very frequently, an internal representation of the association between these two signals is built up, so that they are then accepted as compatible. However, if the same head movement is made in a different context, the signals may become incompatible. For example, if such a head movement is made during prolonged rotation on a fairground carousel the sensation of head rotation will be influenced by the rotation of the carousel, resulting in a conflict with signals arising from the otolith organs. Equally, head movements made in space, where gravitational acceleration is almost eliminated, will elicit sensations of turning from the canals, which are not matched by the normal otolithic signals.

Visual-vestibular conflict may arise from the fact that the vestibular stimulation experienced with head motion stimuli is normally associated with a compatible visual impression of movement. If the motion of the visual scene is modified, as it is for example when viewing the world through binoculars from a moving vehicle, the incompatibility between the vestibular sensation and the visual motion sensation may be sufficient to induce motion sickness. Viewing the horizon from the deck of a ship on a rough sea helps to reduce motion sickness because the vestibular sensation is compatible with a stable visual world, whereas viewing the wave motion of the sea itself is likely to generate conflict. Apparent motion of the visual world, as generated by large, projected moving images (e.g. cinerama), in the absence of the head movement that would normally occur when seeing such images, may also provide sufficient conflict to induce motion sickness.

Associated with the concept of the sensory conflict hypothesis is the notion that continued exposure to new combinations of visual and vestibular motion stimuli should lead to adaptation of the internal model and thereby to reduced susceptibility. This is supported by the observation that individuals may initially experience motion sickness on a sea voyage, but quickly adapt and gain their ‘sea-legs’ within a period of 3-6 days. For those susceptible individuals who are continually exposed to provocative motion stimuli it is possible to carry out a process of adaptation based on this principle. For more limited periods of exposure there are some anti-motion sickness drugs (scopolamine, dimenhydrinate) that are effective in preventing the onset of sickness, at least for the period of the journey.

— Graham Barnes

See also vestibular system.

Definition

Motion sickness is a condition characterized by uncomfortable sensations of dizziness, nausea, and vomiting that people experience when their sense of balance and equilibrium is disturbed by constant motion. Riding in a car, aboard a ship or boat, or riding on a swing all cause stimulation of the vestibular system and visual stimulation that often lead to discomfort. While motion sickness can be bothersome, it is not a serious illness, and can be prevented.

Description

Motion sickness is a common problem, with nearly 80% of the general population suffering from it at one time in their lives. People with migraine headaches or Ménière's syndrome, however, are more likely than others to have recurrent episodes of motion sickness. Researchers at the Naval Medical Center in San Diego, California, reported in 2003 that 70% of research subjects with severe motion sickness had abnormalities of the vestibular system; these abnormalities are often found in patients diagnosed with migraines or Ménière's disease.

While motion sickness may occur at any age, it is more common in children over the age of two, with the majority outgrowing this susceptibility.

When looking at why motion sickness occurs, it is helpful to understand the role of the sensory organs. The sensory organs control a body's sense of balance by telling the brain what direction the body is pointing, the direction it is moving, and if it is standing still or turning. These messages are relayed by the inner ears (or labyrinth), the eyes, the skin pressure receptors, such as in those in the feet, and the muscle and joint sensory receptors (which track what body parts are moving). The central nervous system (the brain and spinal cord), is responsible for processing all incoming sensory information.

Motion sickness and its symptoms surface when conflicting messages are sent to the central nervous system. An example of this is reading a book in the back seat of a moving car. The inner ears and skin receptors sense the motion, but the eyes register only the stationary pages of the book. This conflicting information may cause the usual motion sickness symptoms of dizziness, nausea, and vomiting.

Causes & Symptoms

While all five of the body's sensory organs contribute to motion sickness, excess stimulation to the vestibular system within the inner ear (the body's "balance center") has been shown to be one of the primary reasons for this condition. Balance problems, or vertigo, are caused by a conflict between what is seen and how the inner ear perceives it, leading to confusion in the brain. This confusion may result in higher heart rates, rapid breathing, nausea, and sweating, along with dizziness and vomiting. There are people who suffer from constant motion sickness. Names for these conditions vary, such as positional dizziness.

Pure optokinetic motion sickness is caused solely by visual stimuli; that is, by what is seen. The optokinetic system is the reflex that allows the eyes to move when an object moves. Many people suffer when they view rotating or swaying images, even if they are standing still. Optokinetic motion sickness is of particular concern to the civilian aviation industry as well as to military aerospace programs. In the United States, both the Federal Aviation Agency (FAA) and the National Aeronautics and Space Administration (NASA) have research programs for the prevention and treatment of optokinetic motion sickness.

Additional factors that may contribute to the occurrence of motion sickness include:

• Poor ventilation lowers a person's threshold for experiencing motion.
• Anxiety or fear also lowers the threshold.
• Food. Physicians recommend avoiding heavy meals of spicy or greasy foods before and during a trip.
• Alcohol. A drink is often thought to help calm the nerves, but in this case it could upset the stomach further. A hangover for the next morning's trip may also lead to motion sickness.
• Pregnancy. Susceptibility in women to vomiting during pregnancy appears to be related to motion sickness, although the precise connections are not well understood as of 2004.
• Genetic factors. Research suggests that some people inherit a predisposition to motion sickness. This predisposition is more marked in some ethnic groups than in others; one study published in 2002 found that persons of Chinese or Japanese ancestry are significantly more vulnerable to motion sickness than persons of British ancestry.

Often viewed as a minor annoyance, some travelers are temporarily immobilized by motion sickness, and a few continue to feel its effects for hours and even days after a trip (the "mal d'embarquement" syndrome). For those with constant motion sickness, it may not stop at all.

Diagnosis

Most cases of motion sickness are mild and self-treatable disorders. If symptoms such as dizziness become chronic, a doctor may be able to help alleviate the discomfort by looking further into a patient's general health. Questions regarding medications, head injuries, recent infections, and other questions about the ear and neurological system will be asked. An examination of the ears, nose, and throat, as well as tests of nerve and balance function, may also be completed.

Severe cases of motion sickness symptoms, and those that become progressively worse, may require additional specific tests. Diagnosis in these situations deserves the attention and care of a doctor with specialized skills in diseases of the ear, nose, throat, equilibrium, and neurological system.

Treatment

Alternative treatments for motion sickness have become widely accepted as a standard means of care. They include herbal therapy, acupressure, and homeopathy.

Herbal Therapy

Ginger (Zingiber officinale) in its various forms is often used to calm the stomach, and it is now known that the oils it contains (gingerols and shogaols) appear to relax the intestinal tract in addition to mildly depressing the central nervous system. Some of the most effective forms of ginger include the powdered, encapsulated form; ginger tea prepared from sliced ginger root; or candied pieces. All forms of ginger should be taken on an empty stomach when treating motion sickness.

Acupressure

Placing manual pressure on the Neiguan or Pericardium-6 acupuncture point (located about three finger-widths above the wrist on the inner arm), either by acupuncture, acupressure, or a mild, electrical pulse, has shown to be effective against the symptoms of motion sickness. Elastic wristbands sold at most drugstores are also used as a source of relief due to the pressure they place in this area. Pressing the small intestine 17 (just below the earlobes in the indentations behind the jawbone) may also help in the functioning of the ear's balancing mechanism.

Homeopathy

There are several homeopathic remedies that work specifically for motion sickness. They include Cocculus, Petroleum, Ipecacuanha, and Tabacum.

Traditional Chinese Medicine

In traditional Chinese medicine, cases of chronic motion sickness would be considered a "wind" disorder because it is an abnormality movement as the wind causes. Herbs and acupuncture may treat this.

Allopathic Treatment

There are a variety of medications to help ease the symptoms of motion sickness, and most of these are available without a prescription. Known as over-the-counter (OTC) medications, it is recommended that these be taken 30-60 minutes before traveling to prevent motion sickness symptoms, as well as during an extended trip.

Drugs

The following OTC drugs consist of ingredients that have been considered safe and effective for the treatment of motion sickness by the Food and Drug Administration:

• Marezine (and others). Includes the active ingredient cyclizine and is not for use in children under age six years.
• Benadryl (and others). Includes the active ingredient diphenhydramine and is not for use in children under age six years.
• Dramamine (and others). Includes the active ingredient dimenhydrinate and is not for use in children under age two years.
• Bonine (and others). Includes the active ingredient meclizine and is not for use in children under age 12 years.

Each of these active ingredients, including such other antiemetics as cinnarizine, are antihistamines whose main side effect is drowsiness. Caution should be used when driving a vehicle or operating machinery, and alcohol should be avoided when taking any drug for motion sickness. Medications for motion sickness may also cause dry mouth and occasional blurred vision. People with emphysema, chronic bronchitis, glaucoma, or difficulty urinating due to an enlarged prostate should not use these drugs unless directed by their physician.

The side effects of cinnarizine and the other antihistamine antiemetics indicate that they should not be used by members of flight crews responsible for the control of aircraft or for other tasks that require sustained attention and alertness.

Longer trips may require a prescription medication called scopolamine (Transderm Scop). Scopolamine gel is most effective when smeared on the arm or neck and covered with a bandage. In chronic cases, such anti-seizure drugs as clonazepam (Klonopin) are used.

Another prescription drug that is sometimes given for motion sickness is ondansetron (Zofran), which was originally developed to treat nausea associated with cancer chemotherapy. Unlike cyclizine, ondansetron appears to be safe for use in children under the age of six.

Several newer antiemetic medications are under development as of early 2004. The most promising of these newer drugs is a class of compounds known as neurokinin-1 (substance P) antagonists. The neurokinins are being tested for the control of nausea following cancer chemotherapy as well as nausea related to motion sickness. In March 2003 the Food and Drug Administration (FDA) approved the first of this new class of antiemetic drugs. Known as aprepitant, it is sold under the trade name Emend.

Expected Results

While there is no cure for motion sickness, its symptoms can be controlled or even prevented. Most people respond successfully to the variety of treatments, or avoid the unpleasant symptoms through prevention methods.

Prevention

Because motion sickness is easier to prevent than treat once it has begun, the best treatment is prevention. The following steps may help deter the unpleasant symptoms of motion sickness before they occur:

• Avoiding reading while traveling, and choosing a seat that faces forward.
• Always riding where the eyes may see the same motion that the body and inner ears feel. Safe positions include the front seat of the car while looking at distant scenery; the deck of a ship where the horizon can be seen; and sitting by the window of an airplane. The least motion on an airplane is in a seat over the wings and the worst is in the tail section.
• Maintaining a fairly straight-ahead view.
• Eating a light meal before traveling, or avoiding food altogether.
• Avoiding conversation with another traveler who is having motion sickness.
• Taking a motion sickness medication at least 30–60 minutes before travel begins, or as recommended by a physician.
• Learning to live with the condition. Even those who frequently endure motion sickness can learn to travel by anticipating the conditions of their next trip. Research also suggests that increased exposure to the stimulation that causes motion sickness may help decrease its symptoms on future trips.

Resources

Books

Blakely, Brian W., and Mary-Ellen Siegel. "Peripheral Vestibular Disorders." In Feeling Dizzy: Understanding and Treating Dizziness, Vertigo, and Other Balance Disorders. New York: Macmillan, 1995.

"Motion Sickness." In The Medical Advisor: The Complete Guide to Alternative & Conventional Treatments. Richmond, VA: Time-Life, Inc., 1996.

Pelletier, Dr. Kenneth R. The Best Alternative Medicine. New York: Simon and Schuster, 2002.

Periodicals

Black, F. O. "Maternal Susceptibility to Nausea and Vomiting of Pregnancy: Is the Vestibular System Involved?" American Journal of Obstetrics and Gynecology 185 (May 2002)(Supplement 5): S204-S209.

Bos, J. E., W. Bles, and B. de Graaf. "Eye Movements to Yaw, Pitch, and Roll About Vertical and Horizontal Axes: Adaptation and Motion Sickness." Aviation, Space, and Environmental Medicine 73 (May 2002): 434-444.

Hamid, Mohamed, MD, PhD, and Nicholas Lorenzo, MD. "Dizziness, Vertigo, and Imbalance." eMedicine, 17 September 2002. .

Harm, D. L., and T. T. Schlegel. "Predicting Motion Sickness During Parabolic Flight." Autonomic Neuroscience 31 (May 2002): 116-121.

Hoffer, M. E., K. Gottshall, R. D. Kopke, et al. "Vestibular Testing Abnormalities in Individuals with Motion Sickness." Otology and Neurotology 24 (July 2003): 633–636.

Keim, Samuel, MD, and Michael Kent, MD. "Vomiting and Nausea." eMedicine, 29 April 2002. .

Liu, L., L. Yuan, H. B. Wang, et al. "The Human Alpha (2A) AR Gene and the Genotype of Site -1296 and the Susceptibility to Motion Sickness." [in Chinese] Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai) 34 (May 2002): 291-297.

Loewen, P. S. "Anti-Emetics in Development." Expert Opinion on Investigational Drugs 11 (June 2002): 801-805.

Nicholson, A. N., et al. "Central Effects of Cinnarizine: Restricted Use in Aircrew" Aviation, Space, and Environmental Medicine 73 (June 2002): 570-574.

O'Brien, C. M., G. Titley, and P. Whitehurst. "A Comparison of Cyclizine, Ondansetron and Placebo as Prophylaxis Against Postoperative Nausea and Vomiting in Children." Anaesthesia 58 (July 2003): 707–711.

Patel, L., and C. Lindley. "Aprepitant—A Novel NK1-Receptor Antagonist." Expert Opinion in Pharmacotherapy 4 (December 2003): 2279–2296.

Organizations

Civil Aerospace Medical Institute. P. O. Box 20582, Oklahoma City, OK 73125. (202) 366-4000. .

National Aeronautics and Space Administration, Office of Biological and Physical Research. .

Vestibular Disorders Association. PO Box 4467, Portland, OR 97208-4467. (800) 837-8428. http://www.teleport.com/veda.

[Article by: Mai Tran; Rebecca J. Frey, PhD]

Definition

Motion sickness is uncomfortable dizziness, nausea, and vomiting that people experience when their sense of balance and equilibrium is disturbed because their brain cannot make sense of conflicting information about their body's location in space and motion in their environment.

Description

Motion sickness is connected to the role of the sensory organs. The sensory organs control a body's sense of balance by telling the brain what direction the body is pointing, the direction it is moving, and if it is standing still or turning. These messages are relayed by the inner ear (or labyrinth); the eyes; the skin pressure receptors (such as in those in the feet), the muscle and joint sensory receptors, which track what body parts are moving to the central nervous system (the brain and spinal cord). The brain then is responsible for processing all incoming information and making sense out of it. Riding in a car, being on a ship, or taking an amusement park ride can cause conflicting stimulation of the different sense organs. The result is motion sickness.

For example, when reading a book in the back seat of a moving car, the inner ears and skin receptors sense the motion, but the eyes register only the stationary pages of the book. This conflicting information may cause the usual motion sickness symptoms of dizziness, nausea, and vomiting. While motion sickness can be bothersome, it is not a serious illness, and it can be prevented.

Demographics

Although nearly 80 percent of the general population experiences motion sickness at one time in their lives, children between the ages of four and ten are most vulnerable. Children often out grow motion sickness. Toddlers under age two are rarely motion sick. Adults who frequently get migraine headaches are more likely than others to have recurrent episodes of motion sickness.

Researchers at the Naval Medical Center in San Diego, California, reported in 2003 that 70 percent of research subjects with severe motion sickness had abnormalities of the vestibular system. Research also suggests that some people inherit a predisposition to motion sickness. This predisposition is more marked in some ethnic groups than in others. One study published in 2002 found that persons of Chinese or Japanese ancestry are significantly more vulnerable to motion sickness than persons of British ancestry.

Causes and Symptoms

While all of the body's sensory organs contribute to motion sickness, excess stimulation to the vestibular system within the inner ear (the body's balance center) has been shown to be one of the primary reasons for this condition. Balance problems (vertigo) are often caused by a conflict between what is seen and how the inner ear perceives it, leading to confusion in the brain. This confusion may result in higher heart rates, rapid breathing, nausea and sweating, along with dizziness and vomiting.

Additional factors that may contribute to the occurrence or severity of motion sickness include the following:

• nancy (
• poor ventilation
• anxiety or fear (Both have been found to lower a person's threshold for experiencing motion sickness symptoms.)
• food (A heavy meal of spicy and greasy foods before traveling is thought to increase motion sickness symptoms.)
• alcohol consumption
• genetic factors
• preg
• Susceptibility in women to vomiting during pregnancy appears to be related to motion sickness, although the precise connections are not well understood as of 2004.)

Often viewed as a minor annoyance, some travelers are temporarily immobilized by motion sickness, and a few continue to feel its effects for hours and even days after a trip.

When to Call the Doctor

Most cases of motion sickness are mild and self-limiting. Parents should call the doctor before giving young children over-the-counter medications for motion sickness. Some remedies are recommended only for older children.

Diagnosis

Most cases of motion sickness are self-diagnosed. If symptoms such as dizziness become chronic, a doctor may be able to help alleviate the discomfort by looking further into a patient's general health. Questions regarding medications, head injuries, recent infections, and other questions about the ear and neurological system will be asked. An examination of the ears, nose, and throat, as well as tests of nerve and balance function, may also be performed.

Severe cases of motion sickness or those that become progressively worse may require additional, specific tests. Diagnosis in these situations deserves the attention and care of a doctor with specialized skills in diseases of the ear, nose, throat, equilibrium, and neurological system.

Treatment

Medications to help ease the symptoms of motion sickness are available without a prescription (over-the-counter or OTC). Normally these are taken 30 to 60 minutes before traveling to prevent motion sickness symptoms, as well as during extended trips.

Over-The-Counter Drugs

The following OTC drugs contain ingredients that are considered by the United States Food and Drug Administration (FDA) to be safe and effective for the treatment of motion sickness:

• Marezine (and others) includes the active ingredient cyclizine and is not for use in children under six years of age.
• Benadryl (and others) includes the active ingredient diphenhydramine and is not for use in children under age two without a doctor's permission.
• Dramamine (and others) includes the active ingredient dimenhydrinate and is not for use in children under two years of age.
• Bonine (and others) includes the active ingredient meclizine and is not for use in children under age 12.

The FDA recommends that people with emphysema, chronic bronchitis, glaucoma, or difficulty urinating due to an enlarged prostate do not use OTC drugs for motion sickness unless directed by their doctor. Children should not be given OTC motion sickness medication without first checking with a healthcare professional.

Prescription Drugs

Longer trips may require a prescription medication called scopolamine available in the form of a skin patch or gel that is rubbed on the skin. Another prescription drug that is sometimes given for motion sickness is ondansetron (Zofran), which was originally developed to treat nausea associated with cancer chemotherapy. It appears to be safe for use in children under the age of six. In March 2003, the FDA approved a new anti-emetic (anti-nausea) drug. Known as aprepitant, it is sold under the brand name Emend.

Alternative Treatment

Ginger (Zingiber officinale) in its various forms is often used to calm the stomach, and the oils it contains (gingerols and shogaols) appear to relax the intestinal tract in addition to mildly depressing the central nervous system. Some of the most effective forms of ginger are the powdered, encapsulated form; ginger tea prepared from sliced ginger root; and candied pieces. All forms of ginger should be taken on an empty stomach.

Placing manual pressure on the Neiguan or Pericardium-6 acupuncture point (located about three finger-widths above the wrist on the inner arm), either by acupuncture, acupressure, or a mild, electrical pulse, has shown to be effective against the symptoms of motion sickness. Elastic wristbands sold at most drugstores are also used as a source of relief due to the pressure they place in this area. Pressing the small intestine 17 (just below the earlobes in the indentations behind the jawbone) may also help in the functioning of the ear's balancing mechanism.

There are several homeopathic remedies that work specifically for motion sickness. They include Cocculus, Petroleum, and Tabacum.

Prognosis

Motion sickness is not a serious disorder and almost always resolves once the conflicting motion messages have stopped.

Prevention

Because motion sickness is easier to prevent than treat once it has begun, the best treatment is prevention. The following steps may help deter the unpleasant symptoms of motion sickness before they occur:

• Avoid reading while traveling.
• Ride in a location that allows the eyes to see the same motion that the body and inner ears feel. Safe positions include the front seat of the car (for older children) while looking at distant scenery; the deck of a ship where the horizon can be seen; and sitting by the window of an airplane. The least motion on an airplane is in a seat over the wings.
• Maintain a fairly straight-ahead view.
• Eat a light meal before traveling, or if already nauseated, avoid food altogether.
• Avoid watching or talking to another traveler who is having motion sickness.
• Take motion sickness medicine at least 30 to 60 minutes before travel begins or as recommended by a physician.

Even those who frequently endure motion sickness can learn to travel by anticipating the conditions of their next trip. Research also suggests that increased exposure to the stimulation that causes motion sickness may help decrease symptoms on future trips.

Parental Concerns

Parental concerns center primarily on making the child comfortable and anticipating the logistics of traveling with a child who is motion sick. Rarely do children vomit to the point of becoming dehydrated. Prevention and practical steps such as taking something for the child to vomit into and carrying a change of clothes can ease parents' worries about motion sickness.

Resources

Books

ABBE Research Division Staff. Air, Sea, and Car MotionSickness: Index and Analysis of New Knowledge. Washington, DC: A B B E Publishers Association, 2004.

Motion Sickness: A Medical Dictionary, Bibliography, and AnAnnotated Research Guide to Internet References. San Diego, CA: Icon Group International, 2004.

Pelletier, Kenneth R. The Best Alternative Medicine. New York: Simon and Schuster, 2002.

Periodicals

Black, F. O. "Maternal Susceptibility to Nausea and Vomiting of Pregnancy: Is the Vestibular System Involved?" American Journal of Obstetrics and Gynecology 185 (May 2002)(Supplement 5): S204–9.

Hoffer, M. E., et al. "Vestibular Testing Abnormalities in Individuals with Motion Sickness." Otology and Neurotology 24 (July 2003): 633–6.

O'Brien, C. M., et al. "A Comparison of Cyclizine, Ondansetron, and Placebo as Prophylaxis against Postoperative Nausea and Vomiting in Children." Anaesthesia 58 (July 2003): 707–11.

Organizations

Vestibular Disorders Association. PO Box 4467, Portland, OR 97208–4467. Web site: www.teleport.com/~veda.

Web Sites

Hamid, Mohamed, and Nicholas Lorenzo. "Dizziness, Vertigo, and Imbalance." eMedicine, October 28, 2004. Available online at www.emedicine.com/neuro/topic693.htm (accessed January 12, 2005).

Keim, Samuel, and Michael Kent. "Vomiting and Nausea." eMedicine, July 13, 2004. Available online at www.emedicine.com/aaem/topic476.htm (accessed January 12, 2005).

[Article by: Tish Davidson, A.M.
Beth Kapes
Rebecca Frey, PhD]

Discomfort observed by some companion animals while being transported. It is caused by irregular and abnormal motion that disturbs the organs of balance located in the inner ear. There may be hypersalivation, restlessness and vomiting.

For the album by Bright Eyes, see Motion Sickness.

Motion sickness
Classification and external resources
ICD-10	T75.3
ICD-9	994.6
OMIM	158280
DiseasesDB	11908
MeSH	D009041

Motion sickness or kinetosis, also known as Travel Sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement. Depending on the cause it can also be referred to as seasickness, car sickness, simulation sickness, airsickness, or space sickness.^[1]

Dizziness, fatigue, and nausea are the most common symptoms of motion sickness.^[2] Sopite syndrome is also a side effect of motion sickness. In fact, nausea in Greek means seasickness (naus means ship).^[3][4] If the motion causing nausea is not resolved, the sufferer will frequently vomit. Unlike ordinary sickness, vomiting in motion sickness tends not to relieve the nausea.^[1]

About 33% of people are susceptible to motion sickness even in mild circumstances such as being on a boat in calm water, although nearly 66% of people are susceptible in more severe conditions.^[1][5] Approximately 50% of the astronauts in the U.S. space program have suffered from space sickness.^[6] Individuals and animals without a functional vestibular system are immune to motion sickness.^[7]

Motion sickness on the sea can result from being in the berth of a rolling boat without being able to see the horizon. Sudden jerky movements tend to be worse for provoking motion sickness than slower smooth ones, because they disrupt the fluid balance more.^[1] A "corkscrewing" boat will upset more people than one that is gliding smoothly across the oncoming waves. Cars driving rapidly around winding roads or up and down a series of hills will upset more people than cars that are moving over smooth, straight roads. Looking down into one's lap to consult a map or attempting to read a book while a passenger in a car may also bring on motion sickness.

The most common hypothesis for the cause of motion sickness is that it functions as a defense mechanism against neurotoxins.^[7] The area postrema in the brain is responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When feeling motion but not seeing it (for example, in a ship with no windows), the inner ear transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. As a result of the disconcordance, the brain will come to the conclusion that one of them is hallucinating and further conclude that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin.

Contents 1 Types 1.1 Airsickness 1.2 Sea-sickness 1.3 Simulation sickness 1.4 Space sickness 2 Treatment 2.1 Natural 2.2 Chemical 2.3 Electronic 3 References 4 External links

Types

Airsickness

Main article: Airsickness

Airsickness is a sensation which is induced by air travel.^[1] It is a specific form of motion sickness, and is considered a normal response in healthy individuals. Airsickness occurs when the central nervous system receives conflicting messages from the body (including the inner ear, eyes and muscles) affecting balance and equilibrium.

Sea-sickness

Main article: Seasickness

Seasickness is a form of motion sickness characterized by a feeling of nausea and, in extreme cases, vertigo experienced after spending time on a craft on water.^[1] It is typically brought on by the rocking motion of the craft^[8] or movement while immersed in water.^[9]

Simulation sickness

Simulation sickness, or simulator sickness, is a condition where a person exhibits symptoms similar to motion sickness caused by playing computer/simulation/video games.^[1]

The most common theory for the cause of simulation sickness is that the illusion of motion created by the virtual world, combined with the absence of motion detected by the inner ear, causes the area postrema in the brain to infer that one is hallucinating and further conclude that the hallucination is due to poison ingestion. The brain responds by inducing nausea and mass vomiting, to clear the supposed toxin.^[7] According to this theory, simulation sickness is just another form of motion sickness.

The symptoms are often described as quite similar to that of motion sickness. Some can range from headache, drowsiness, nausea, dizziness, vomiting and sweating. A research done at the University of Minnesota had students play Halo for less than an hour, and found that up to 50 percent felt sick afterwards.^[10]

In a study conducted by U.S. Army Research Institute for the Behavioral and Social Sciences in a report published May 1995 titled "Technical Report 1027 - Simulator Sickness in Virtual Environments", out of 742 pilot exposures from 11 military flight simulators, "approximately half of the pilots (334) reported post-effects of some kind: 250 (34%) reported that symptoms dissipated in less than 1 hour, 44 (6%) reported that symptoms lasted longer than 4 hours, and 28 (4%) reported that symptoms lasted longer than 6 hours. There were also 4 (1%) reported cases of spontaneously occurring flashbacks".^[11][12]

However, the phenomenon was well known in popular culture before it was known as simulation sickness. In the 1983 theatrical flop Joysticks, the manager and grandson of the owner of a local video arcade claims "The reason why I never play any of these games, well, they make me physically ill. I mean, every time I look in one of the screens, they make me dizzy".

Space sickness

Main article: Space adaptation syndrome

Space sickness was effectively unknown during the earliest spaceflights, as these were undertaken in very cramped conditions; it seems to be aggravated by being able to freely move around, and so is more common in larger spacecraft.^[1] Around 60% of all Space Shuttle astronauts currently experience it on their first flight; the first case is now suspected to be Gherman Titov, in August 1961 onboard Vostok 2, who reported dizziness and nausea. However, the first significant cases were in early Apollo flights; Frank Borman on Apollo 8 and Rusty Schweickart on Apollo 9. Both experienced identifiable and reasonably severe symptoms—in the latter case causing the mission plan to be modified.

Treatment

Many cures and preventatives for motion sickness have been proposed.

Natural

One common suggestion is to simply look out of the window of the moving vehicle and to gaze toward the horizon in the direction of travel. This helps to re-orient the inner sense of balance by providing a visual reaffirmation of motion.

In the night, or in a ship without windows, it is helpful to simply close one's eyes, or if possible, take a nap. This resolves the input conflict between the eyes and the inner ear. Napping also helps prevent psychogenic effects (i.e. the effect of sickness being magnified by thinking about it).

A simple method for relieving common and mild car sickness is chewing. Chewing Gum has an uncanny effectiveness for reducing car sickness in those affected. Chewing Gum, however, is not the only thing one may chew to relieve mild effects of car sickness, snacking on lollies or just chewing in general seems to reduce adverse effects of the conflict between vision and balance.

Fresh, cool air can also relieve motion sickness slightly, although it is likely this is related to avoiding foul odors which can worsen nausea. ^[13]

Chemical

Over-the-counter and prescription medications are readily available, such as Dramamine (dimenhydrinate)^[14], Stugeron (cinnarizine) and Bonine/Antivert (meclizine).

Scopolamine is effective^[15] and is sometimes used in the form of transdermal patches (1.5mg) or as a newer tablet form (0.4mg). The selection of a transdermal patch or scopolamine tablet is determined by a doctor after consideration of the patient's age, weight, and length of time treatment is required.

Interestingly, many pharmacological treatments which are effective for nausea and vomiting in some medical conditions may not be effective for motion sickness. For example, metoclopramide and prochlorperazine, although widely used for nausea, are ineffective for motion-sickness prevention and treatment. This is due to the physiology of the CNS vomiting centre and its inputs from the chemoreceptor trigger zone versus the inner ear. Sedating anti-histamine medications such as promethazine work quite well for motion sickness, although they can cause significant drowsiness.

Ginger root is commonly thought to be an effective anti-emetic. One trial review indicated that sucking on crystallized ginger or sipping ginger tea can help to relieve the nausea,^[16] while an earlier study indicated that it had only a placebo effect.^[17] Tests conducted on the television show Mythbusters support the theory that ginger is an effective treatment for the nausea caused by motion sickness.^[18]

Ginger is reported to calm the pyloric valve located at the base of the stomach.^[16] This relaxation of the valve allows the stomach to operate normally whereby the contents will enter the small intestine instead of being retained within the stomach. It is this undesirable effect of retention in the stomach that eventually results in vomiting. Vomiting is not seasickness but is only a symptom or side effect; although the effect most commonly associated with seasickness. This link reports on a ginger study; notice the comment about less vomiting when taking ginger, but not less nausea. ^[19] Stugeron is not available in the U.S. either over-the-counter or by prescription. It has been implicated in triggering palsy and has been banned by the FDA.^[20]

Electronic

As astronauts frequently have motion sickness, NASA has done extensive research on the causes and treatments for motion sickness. One very promising looking treatment is for the person suffering from motion sickness to wear LCD shutter glasses that create a stroboscopic vision of 4 Hz with a dwell of 10 milliseconds.^[21]

References

1. ^ ^{a b c d e f g h} Benson AJ (2002). "35". Motion Sickness. In: Medical Aspects of Harsh Environments. 2. Washington, DC. http://www.bordeninstitute.army.mil/published_volumes/harshEnv2/harshEnv2.html. Retrieved 2008-05-09. 
2. ^ Motion Sickness Prevention and Treatment
3. ^ Woodhouse's English-Greek Dictionary Page 745
4. ^ Woodhouse's English-Greek Dictionary Page 766
5. ^ PC Today Article - Motion Sickness
6. ^ The Shorthorn Online | NEWS | Speech dispels space myths
7. ^ ^{a b c} General Medical Officer (GMO) Manual: Clinical Section: Motion Sickness
8. ^ Gahlinger PM (2000). "A comparison of motion sickness remedies in severe sea conditions". Wilderness Environ Med 11 (2): 136–7. PMID 10921365. 
9. ^ Norfleet WT, Peterson RE, Hamilton RW, Olstad CS (January 1992). "Susceptibility of divers in open water to motion sickness". Undersea Biomed Res 19 (1): 41–7. PMID 1536062. http://archive.rubicon-foundation.org/2621. Retrieved 2008-05-09. 
10. ^ Could video games be making your kids sick?
11. ^ CyberEdge Information Services: Health & Safety, Simulator Sickness in Virtual Environments: Executive Summary
12. ^ Video Game Simulator Sickness
13. ^ FAA Medical Certification / Alcohol / Substance / Drugs - Motion Sickness
14. ^ Weinstein SE, Stern RM (October 1997). "Comparison of marezine and dramamine in preventing symptoms of motion sickness". Aviat Space Environ Med 68 (10): 890–4. PMID 9327113. 
15. ^ Spinks A, Wasiak J, Villanueva E, Bernath V (2007). "Scopolamine (hyoscine) for preventing and treating motion sickness". Cochrane database of systematic reviews (Online) (3): CD002851. doi:10.1002/14651858.CD002851.pub3. PMID 17636710. 
16. ^ ^{a b} Ernst, E.; and M. H. Pittler (01 Mar 2000). "Efficacy of ginger for nausea and vomiting: a systematic review of randomized clinical trials" (PDF). British Journal of Anaesthesia 84 (3): 367–371. PMID 10793599. http://bja.oxfordjournals.org/cgi/content/abstract/84/3/367. Retrieved 2006-09-06. 
17. ^ Wood CD. Pharmacological countermeasures against motion sickness. In Crampton GH, ed. Motion and Space Sickness. CRC Press, Boca Raton, 1990, p. 344.
18. ^ Wikipedia. "Episode Listing (Wikipedia)". http://en.wikipedia.org/wiki/MythBusters_%282005_season%29#Seasickness_-_Kill_or_Cure.3F. 
19. ^ http://www.esys.org/seekrank/sekrnk11.html
20. ^ Letter to editor Latitude 38 Magazine April 2006, by medical doctor detailing the dangers of Stugeron
21. ^ Stroboscopic Vision as a Treatment for Space Motion Sickness

External links

Look up motion sickness in Wiktionary, the free dictionary.

• Motion Sickness from MedlinePlus
• Motion Sickness Prevention and Treatment, from a Medical College of Wisconsin website
• Visually induced motion sickness research
• Golding JF., Motion Sickness Susceptibility Autonomic Neuroscience: Basic and Clinical 129 (2006) 67–76
• Rolnick, A., & Bles, W. (1989). Performance and well being under tilting conditions: the effects of visual reference and artificial horizon. Aviation, Space and Environmental Medicine, 60, 779-785
• Rolnick, A. & Gordon, C. R. (1991). The effects of motion induced sickness on military performance. In R. Gal & J. Mangelsdorff (Eds.), Handbook of Military Psychology. Chichester: Wiley.
• Rolnick, A., Lubow, R.E., 1991. Why is the driver rarely sick? The role of controllability in motion sickness. Ergonomics 34, 867–879.

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