Motion Sickness Health Article

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.