Motion sickness

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.

KEY TERMS

Acupressure —Often described as acupuncture without needles, acupressure is a traditional Chinese medical technique based on theory of qi (life energy) flowing in energy meridians or channels in the body. Applying pressure with the thumb and fingers to acupressure points can relieve specific conditions and promote overall balance and health. Also known as dian xue.

Acupuncture —Based on the same traditional Chinese medical foundation as acupressure, acupuncture uses sterile needles inserted at specific points to treat certain conditions or relieve pain.

Anti-emetic —A preparation or medication that relieves nausea and vomiting. Cola syrup, ginger, and motion sickness medications are examples of antiemetics.

Vertigo —A feeling of dizziness together with a sensation of movement and a feeling of rotating in space.

Vestibular system —The brain and parts of the inner ear that work together to detect movement and position.

Resources

BOOKS

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

Motion Sickness: A Medical Dictionary, Bibliography, and An Annotated 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: http://www.teleport.com/~veda.

WEB SITES

Hamid, Mohamed, and Nicholas Lorenzo. "Dizziness, Vertigo, and Imbalance." eMedicine , October 28, 2004. Available online at http://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 http://www.emedicine.com/aaem/topic476.htm (accessed January 12, 2005).

Tish Davidson, A.M.
Beth Kapes
Rebecca Frey, PhD