What Is Motion Sickness (Travel Sickness)? What Causes Motion Sickness?

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Article Date: 15 Jan 2010 - 0:00 PDT

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Motion sickness is a very common disturbance of the inner ear that is caused by repeated motion such as from the swell of the sea, the movement of a car, the motion of a plane in turbulent air, etc.

According to Medilexicon's medical dictionary:

Motion sickness is 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.

In the inner ear (which is also called the labyrinth), motion sickness affects the sense of balance and equilibrium and, hence, the sense of spatial orientation.

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.

There is no difference between motion sickness and sea sickness. Some people experience nausea and even vomiting when riding in an airplane, automobile, or amusement park ride. This condition is generally called motion sickness. Many people experience motion sickness when riding on a boat or ship. This is commonly referred to as sea sickness (mal de mer), even though it is the same disorder. Individuals and animals without a functional vestibular system are immune to motion sickness.

What are the symptoms of Motion Sickness?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.

The symptoms overall of motion sickness include nausea, vomiting, and dizziness (vertigo). Other common signs are sweating and a general feeling of discomfort and not feeling well (malaise).

Mild symptoms are categorized as headache, mild unease and yawning. More serious symptoms include nausea, vomiting, pallor, sweating, drooling, short breath, dizziness and drowsiness.

The symptoms of motion sickness appear when the central nervous system receives conflicting messages from the other four systems: the inner ear, eyes, skin pressure receptors, and the muscle and joint sensory receptors.

What are the causes of Motion Sickness?

Motion is sensed by the brain through three different pathways of the nervous system that send signals coming from the inner ear (sensing motion, acceleration, and gravity), the eyes (vision), and the deeper tissues of the body surface (proprioceptors).

When the body is moved intentionally, for example, when we walk, the input from all three pathways is coordinated by our brain. When there is unintentional movement of the body, as occurs during motion when driving in a car, the brain is not coordinating the input, and there is thought to be discoordination or conflict among the input from the three pathways. It is hypothesized that the conflict among the inputs is responsible for motion sickness.

The cause of motion sickness is complex, however, and the role of conflicting input is only a hypothesis for its development. Without the motion-sensing organs of the inner ear, motion sickness does not occur, suggesting that the inner ear is critical for the development of motion sickness.

Visual input seems to be of lesser importance, since blind people can develop motion sickness. Motion sickness is more likely to occur with complex types of movement, especially movement that is slow or involves two different directions (for example, vertical and horizontal) at the same time.

The conflicting input within the brain appears to involve levels of the neurotransmitters (substances that mediate transmission of signals within the brain and nervous system) histamine, acetylcholine, and norepinephrine. Many of the drugs that are used to treat motion sickness act by influencing or normalizing the levels of these compounds within the brain.

Diagnosing Motion Sickness

Most cases of motion sickness are mild and self-treatable. However, very severe cases and those that become progressively worse deserve the attention and care of a physician with special skill in diseases of the ear, balance (equilibrium), and the nervous system.

Most people who have had motion sickness in the past ask their health care provider how to prevent it next time. A doctor will ask about symptoms and find out what usually causes the problem (such as riding in a boat, flying in a plane, or driving in car). Laboratory tests are generally not necessary to establish a diagnosis of motion sickness.

What are the treatment options for Motion Sickness?

The distressing symptoms of motion sickness usually stop when the motion that causes it ceases. But this is not always true. There are people who suffer symptoms for even a few days after the trip is over.

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 sweets 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.

Ginger has also been found to reduce motion sickness. This is available in tablet form or a fresh stem of ginger can also be chewed to relive symptoms.

Some studies suggest that acupressure may help reduce symptoms of motion sickness in the same way as acupuncture, although the evidence is not clear. An acupressure practitioner works with the same points used in acupuncture, but stimulates these healing sites with finger pressure, rather than inserting fine needles.

Preventing Motion Sickness

Always ride where your eyes will see the same motion that your body and inner ears feel. In a car, sit in the front seat and look at the distant scenery. On a boat, go up on the deck and watch the motion of the horizon. In an airplane, sit by the window and look outside. Also, in a plane, choose a seat over the wings where the motion is minimized.

Do not read while traveling if you are subject to motion sickness, and do not sit in a seat facing backward. Also do not watch or talk to another traveler who is having motion sickness.

Avoid strong odors and spicy or greasy foods that do not agree with you (immediately before and during your travel). Medical research has not yet investigated the effectiveness of popular folk remedies such as "soda crackers and 7 Up" or "cola syrup over ice," or ginger products.

Medications are also a good way also to prevent motion sickness and are best taken before travelling etc, and using such for treatment may be too late to avoid or treat the condition.

Scopolamine (Transderm Scop) is most commonly prescribed medication for motion sickness. It must be taken before symptoms start. It is available as a patch form that is placed behind the ear 6 - 8 hours before travel. The effects last up to 3 days. Side effects may include dry mouth, drowsiness, blurred vision, and disorientation.

Promethazine (Phenergan) should be taken 2 hours before travel. The effects last 6 - 8 hours. Side effects may include drowsiness and dry mouth.

Cyclizine (Marezine) is most effective when taken at least 30 minutes before travel. It is not recommended for children younger than 6, and side effects are similar to scopolamine.

Dimenhydrinate (Dramamine) is taken every 4 - 8 hours. Side effects are similar to scopolamine.

Meclizine (Bonine) is most effective when taken 1 hour before travel. It is not recommended for children under 12, and side effects may include drowsiness and dry mouth.

Written by Sy Kraft (B.A.)
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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