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Motion Sickness

Timothy C. Hain, MD Page last modified: July 21, 2013

Motion sickness is the nausea, disorientation and fatigue that can be induced by head motion. The first sign is usually pallor (a pale appearance). Yawning, restlessness and a cold sweat forming on the upper lip or forehead often follow. As symptoms build, an upset stomach, fatigue or drowsiness may occur. The final stages are characterized by nausea and vomiting.

Motion sickness is a general term.  It can be subdivided into sickness due to visual stimulation, due to vestibular stimulation, and occasionally, forms occur associated with somatosensory stimulation (e.g. treadmill sickness), or head-on-neck motion (e.g. cervical vertigo).  By far the most common subgroup are pure visual sensitivity -- usually called "visual dependence". In visual dependence, people become sick due to visual motion (such as going to a movie). 

Who gets motion sickness ?

Motion sickness is common and normal. Nearly anyone can be made motion sick by an appropriate stimulus, except for individuals with no vestibular system (William James). In a large study done in India, the prevalence of motion sickness was about 28%, and females were more susceptible (27%) were more susceptible than males (16.8%). Individuals with more active occupations are less susceptible (Sharma, 1997). In medical transport personnel, 46% of personnel reported nausea and 65%, the Sopite syndrome (sleepiness caused by motion). (Wright, 1995)

Horses, cows, monkeys, chimpanzees, birds and sheep have been reported in scientific publications to show motion sickness. Rats, unfortunately I suppose, do not vomit so cannot serve as experimental subjects.

According to Benson, nearly 100% of (human) occupants of life rafts will vomit in rough seas. 60% of student aircrew members suffer from air sickness at some time during their training. For vertical motion (heave), oscillation at a frequency of about 0.2 hz is the most provocative. Motion at 1 Hz is less than 1/10th as provocative. About 7% of seagoing passengers report vomiting during a journey (Lawther and Griffin, 1988).

Women are more sensitive to motion than men, by a ratio of about 5:3, although this may be related to reporting differences rather than true physiological differences( Cheung, B. and K. Hofer , 2002). Women are more sensitive to motion around the times of their menstrual cycle (Glunfeld and Gresty, 1996). This may be due to interactions between migraine and motion sickness.

Children are said to be almost immune to motion sickness up to the age of 2. As children grow older, the severity of motion sickness increases up to roughly the age of 15 (Takahasi et al, 1994). In our dizziness practice, we have noticed women of childbearing age become more prone to motion sickness as their migraine tendency increases.  There are two spikes of migraine in women of childbearing age -- one at 35, and another around menopause.

There are certain illness that eliminate motion sickness. These include bilateral loss of inner ear function (William James, the Pragmatist philospher), and lesions of the cerebellar nodulus (Bard). These illnesses are even worse than motion sickness, and there has been no attempt to use this observation clinically.

What Causes Motion Sickness ?

In order for the body to determine where it is at all times, the brain combines visual information, touch information, inner ear information, and internal expectations. Under most circumstances, the senses and expectations agree. When they disagree, there is conflict, and motion sickness can occur.

For example, consider the situation when one is reading in the back seat of a car. Your eyes, fixed on the page, say that you are still. However, as the car goes over bumps and accelerates/decelerates, your ears disagree. This is why motion sickness in this situation is common. The driver has an advantage, as they have a better internal model of motion, and as well, their eyes are generally fixed on the outside world.

Another situation where motion sickness is common is in outer space.  There, the otoliths no longer register the effect of gravity (which is no longer there), but continue to signal linear acceleration.  It is presently thought that the very common space motion sickness is due to a loss of the usual otolith signal associated with head movement away from the gravitational axis.  When the head is pitched, the brain misses the otolithic signal saying that pitch has occured, but continues to receive the canal signal. A partial vestibular loss (for a subset of otolithic input) is associated with strong motion sickness.

Acquired susceptibility to motion sickness is rare.

Migraine is a definite risk factor for motion sickness, with roughly a 5 fold greater incidence than non-migraineurs, and a roughly 50% prevalence (Marcus et al, 2005). See table below. Female gender and youth is also a risk factor. In women, days 9-15 of the menstrual cycle appear to have a higher incidence of nausea (Grunfeld and Gresty, 1999; Ramsay, 1994) but not all agree (Cheung, B., R. Heskin, et al. 2001). Medications that prevent migraine may also prevent motion sickness (see below).

Table: Patients with Migraine having Motion Sickness
Percent of migraine patients with motion sickness Comment Authors
49% Children Bille (1962)
45% Children (60) Barabas et al (1983)
50.7% Unselected Kayan and Hood (1984)
50%   Marcus et al, 2005

 

The space-military industrial complex has developed a theory of motion sickness that depends on asymmetry in otoconial mass (Scherer et al, 1997). Perhaps this mechanism is applicable in outer space, but it seems to us to have very little relevance to "down to earth".  The more logical military explanation is the previously mentioned mechanism where the otoliths no longer provide gravity information.

Motion sickness is sometimes associated with prolonged vestibular responses (Hoffer et al. 2003). Motion sickness immunity is generally found in persons with absent vestibular responses (William James; Cheung et al. 1991).

Age is probably not a large factor in motion sickness (Cheung and Money, 1992) although children below the age of 2 are said to be immune. They happily vomit.  In our practice, the only substantial age effect seems to be in women who are experiencing migraines.

Treatment of Motion sickness:

There are three strategies to treat motion sickness:

When all three strategies are used, it is extremely uncommon to find a person who does not get substantially better.

Behavioral Strategies for Motion Sickness

Boat

One can often avoid motion sickness by anticipating the motion. Drivers have much less motion sickness than passengers, because they are controlling the motion, and know when they are turning, starting and stopping. Drivers on familiar routes are less prone to getting motion sick than drivers in new territory.

Medication for Motion Sickness

From a systems perspective, medication might change vestibular input (ordinarily always reduce), or reduce the consequences of motion stimulation. In other words, they might suppress input, or suppress central reactions to the input.

Most medications for motion sickness need to be taken at least 30 minutes before exposure to the activity that can cause the problem. Persons with glaucoma or prostate problems should not take most of these medications unless so advised by their doctor.

We so far have rarely encountered an individual who could not avoid motion sickness by pretreating with klonapin and ondansetron. That being said, here are more details.

Medications for nausea and vomiting

Treatment of motion sickness differs from treatment of nausea and vomiting. A discussion of the treatment of vomiting can be found here.

Exercises for motion sickness. Habituation

It is reasonable to assume that habituation (repeated motion exposure) makes one less motion sensitive. (Cheung, B. and K. Hofer, 2005). In fact, the military uses a "habituation" protocol to overcome motion sickness. This requires expensive equipment (a rotating chair).

A somewhat similar approach was reported by Dai et al recently (2011), in a civilian apparatus. It again involved a rotatory chair as well as a simultaneously rotating optokinetic surround. In our practice in Chicago, we are attempting to implement this protocol with our own equipment.

Habituation can be obtained through sports activities or physical therapy procedures. These procedures generally involve use of visual-vestibular mismatches, called "times 2" and "times 0" viewing. Stimulators with "disco balls" are often used too.  We are unsure if these procedures are effective.

A home exercise method has been proposed to overcome motion sickness -- the "Puma" method. These exercises were developed by a flight surgeon (Sam Puma), to assist pilots with motion sickness in overcoming their sensitivity to motion. They are very stimulating exercises, that may be useful to extremely motivated people, who are not able to use more conventional methods of management of motion sickness such as medications. The Puma method appears to us to be a habituation protocol -- repeated exposure to the things that make one ill. This may well work -- if you can tolerate the process. We are cautiously hopeful about this method -- although it seems to us to be likely to cause a lot of nausea itself. When we sometimes suggest this to our patients in our dizziness practice, we suggest that they use ondasetron to avoid nausea.  It is rare that someone with motion sensitivity is able to tolerate these exercises.

Activities that promote formation of "internal models" of motion may also be useful for motion sickness prevention. We do not know of any formal protocols that use this idea.

We recently have proposed a protocol for visual dependence that may be useful in treatment of motion sickness (Chang and Hain, 2007). See the page on visual dependence for more detail.

Alternative medications

Experimental treatments -- surgery and vestibular ablation.

 

REFERENCES:

Acknowledgements:

Copyright March 24, 2014 , Timothy C. Hain, M.D. All rights reserved. Last saved on March 24, 2014