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 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; 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.

Causes and 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.

Pure optokinetic motion sickness is caused solely by visual stimuli, or what is seen. The optokinetic system is the reflex that allow the eyes to move when an object moves. Many people suffer when what they view is rotating or swaying, even if they are standing still.

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

Poor ventilation.
Anxiety or fear. Both have been found to lower a person's threshold for experiencing motion sickness symptoms.
Food. It is recommended that a heavy meal of spicy and greasy foods be avoided 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.

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.
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.

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).

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

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 6.
Benadryl (and others). Includes the active ingredient diphenhydramine and is not for use in children under age 6.
Dramamine (and others). Includes the active ingredient dimenhydrinate and is not for use in children under age 2.
Bonine (and others). Includes the active ingredient meclizine and is not for use in children under age 12.

Each of the active ingredients listed above 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. Large doses of OTC drugs for motion sickness may also cause dry mouth and occasional blurred vision.

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.

The Food and Drug Administration (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.

Longer trips may require a prescription medication called scopolamine (Transderm Scop). Formerly used in the transdermal skin patch (now discontinued), travelers must now ask their doctor to prescribe it in the form of a gel. In gel form, scopolamine is most effective when smeared on the arm or neck and covered with a bandage.

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 FDA approved the first of this new class of antiemetic drugs. Known as aprepitant, it is sold under the trade name Emend.

Alternative treatment

Alternative treatments for motion sickness have become widely accepted as a standard means of care. 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.

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 it places 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

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:

Avoid reading while traveling, and do not sit in a backward facing seat.
Always ride 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.
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 30-60 minutes before travel begins, or as recommended by a physician.
Learn 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

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, Supplement 5 (May 2002): 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 September 17, 2002. http://emedicine.com/neuro/topic693.htm.

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 April 29, 2002. http://emedicine.com/aaem/topic476.htm.

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. 〈http://www.cami.jccbi.gov〉.

National Aeronautics and Space Administration. Office of Biological and Physical Research. http://www.spaceresearch.nasa.gov.

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

motion

[mo´shun]

movement.

motion sickness discomfort felt by some people on a moving boat, train, airplane, or automobile, or even on an elevator or a swing. The discomfort is caused by irregular and abnormal motion that disturbs the organs of balance located in the inner ear. There may be mild symptoms of nausea, dizziness, or headache, as well as pallor and cold perspiration. In more acute cases, there may be vomiting and sometimes prostration. Though most people quickly adapt to travel by airplane, ship, and automobile, few are wholly immune to motion sickness. Even astronauts become ill if the inner ear organs of balance are continuously stimulated by unusual motion. Fortunately, most cases of motion sickness vanish quickly once the journey is over, leaving no ill effects.

Causes. The inner ear possesses three semicircular canals, located at right angles in three different planes. People are accustomed to movement in the horizontal plane, which stimulates certain semicircular canals, but not to vertical movements such as the motion of an elevator or a ship pitching at sea. These vertical movements stimulate the semicircular canals in an unusual way, producing the sensation of nausea, or motion sickness.

Anxiety, grief, or other emotions can also cause motion sickness. A person unaccustomed to traveling by boat or airplane may be apprehensive or nervous and therefore may develop symptoms of nausea. Some individuals with previous experience of motion sickness become ill on a boat at dock or on an airplane prior to take-off.

Airsickness usually occurs during a bumpy flight caused by stormy weather or turbulent air. However, it may also be triggered by poorly ventilated cabins, hunger, digestive upset, overindulgence in food and drink, and unpleasant odors, particularly tobacco smoke.

Treatment. Certain antihistamines have proved highly effective in treating symptoms of seasickness. Like depressants, they may be used alone or in combination with mild sedatives. Those who suffer from motion sickness should ask their health care provider for advice before they embark on a trip. Symptoms may also be reduced if the seasick person rests lying down, with the head low, in a comfortable, well aired place.

Prevention. Being rested and in good health prior to a journey helps to prevent motion sickness. During a voyage by boat, it is advisable for the passenger to remain near the center of the ship, where there will be the least motion. Ample fresh air and exercise and avoidance of stuffy rooms and disagreeable smells are also good precautions. The traveler should keep comfortably warm and avoid overeating and eating rich foods.

For those traveling by air, adequate hydration and small, easily digested meals taken during the flight help to prevent airsickness. The passenger who experiences motion sickness may benefit from reclining in the seat as far as possible and closing the eyes.

Carsickness is often relieved if the journey is interrupted for short walks in the fresh air and by keeping a window open. Children will frequently find it helpful to glance down, and to refrain from reading. Tobacco smoke can also be an aggravating factor.

mo·tion sick·ness

[MIM*158280]

the syndrome of pallor, nausea, weakness, and malaise, which may progress to vomiting and incapacitation, caused by stimulation of the semicircular canals during travel or motion as on a boat, plane, train, car, swing, or rotating amusement ride.

Synonym(s): kinesia

motion sickness

Nausea and dizziness induced by motion, as in travel by aircraft, car, or ship.

motion sickness

Physiology Vertigo, often accompanied by nausea which occurs in those susceptible to vehicular motion; MS is attributed to vestibular system activation, which may be related to the central triggering zone Travel medicine A condition triggered by vestibular or by visual stimulation, through linear and/or angular acceleration of the head Clinical Autonomic Sx–hypersalivation, frequent swallowing; ↓ gastric motility, appetite–food may evoke nausea, then vomiting, vertigo, cold sweats, headache, malaise, pallor, ↓ digestion; hyperventilation ergo hypocapnia, pooling of blood in legs, predisposing victim to postural hypotension Treatment H₁ type antihistamines–scopolamine, dimenhydrinate, which ↓ vestibular nucleus activity; visual-vestibular conflict may trigger MS. See Visual-vestibular conflict, Weightlessness.

mo·tion sick·ness

(mō'shŭn sik'nĕs)

The syndrome of pallor, nausea, weakness, and malaise, which may progress to vomiting and incapacitation, caused by stimulation of the semicircular canals during travel or motion as on a boat, airplane, train, car, swing, or rotating amusement ride.
Synonym(s): kinesia.

motion sickness

Nausea or vomiting induced by any sustained, repetitive, passive movement of the body in any vehicle of transportation. There is abdominal discomfort, pallor, sweating, salivation, depression, nausea, vomiting, apathy, loss of appetite and sometimes a loss of the will to live. The cause is unknown, but it is related to repetitive stimulation of the inner ear balancing mechanisms. Motion sickness is treated with small doses of atropine or hyoscine, or antihistamine drugs such as cyclizine (Valoid) or promethazine (Avomine). The word nausea derives from the Greek word naus , a ship.