Motion Sickness treatment strategies

Motion sickness is not really a 'sickness' per se but a normal physiological response to real, perceived, or anticipated movement and can be triggered by the movement of a car, train, airplane or amusement park ride. The symptoms of motion sickness tend to be limited to the duration of the motion experienced and include nausea and vomiting, dizziness, vertigo, cold sweating, disorientation, and fatigue.

Motion sickness can be debilitating and particularly interfere with functioning at work for those whose jobs entail motion. Motion sickness can be visually induced (when there is no real motion) in virtual environments, such as simulators, cinemas, and video games. Motion sickness indiscriminately affects air, sea, road and space travelers. All individuals (humans and animals) possessing an intact vestibular apparatus (inner ear 'balance center') can get motion sickness given the right quality and quantity of provocative stimulation, although there are wide and consistent individual differences in the degree of susceptibility.

Although nausea is the hallmark symptom, motion sickness comprises a much broader syndrome. It includes a wide range of signs and symptoms including cold sweating, pallor of varying degrees, increases in salivation, drowsiness, headache, and even severe pain, as well as nausea and vomiting.

What is Motion Sickness?

The sensory organs control the body's sense of balance by signaling the brain as to the direction in which the body is pointing or moving, and if it is standing still or turning.

These messages are relayed by:

• Inner ears  - balance center or vestibular system
• Eyes - visual system
• Skin pressure receptors - such as in those in the feet
• Muscle and joint sensory receptors -
  proprioceptive system which tracks what body parts are moving

All incoming sensory information is processed by the brain and spinal cord (central nervous system).

Causes Motion Sickness?

The cause of motion sickness is complex and not fully understood. Many theories of motion sickness have been proposed over the years.

The evolutionary theory -  holds that motion sickness initially evolved as a response to poisoning. The notion is that when a noxious substance was ingested, nausea and vomiting resulted, inactivity would be induced and symptoms would thus be attenuated because of reduced levels of ingested toxins.

The ecological theory -  of motion sickness is based on the hypothesis that motion sickness is caused by postural instability or a loss of postural control. The concept is that as postural instability increases, motion sickness will develop.

The sensory conflict theory - of motion sickness is the most widely accepted theory of motion sickness. Nearly all situations that elicit motion sickness involve some form of intersensory conflict. According to this theory, motion sickness results when the brain receives conflicting information about body movements from the visual (eyes) and vestibular receptors (inner ear) and the proprioceptive system (muscle and joint receptors).

An example of this type of intersensory conflict is when someone is reading a book in the back seat of a moving car. The inner ears and skin receptors sense the motion, but the eyes only register the stationary pages of the book.

This conflicting information may cause the usual motion sickness symptoms of dizziness, nausea and vomiting.

Mal de Débarquement Syndrome

Generally, after ending the motion stimulus, motion sickness symptoms rapidly disappears, but in some instances, the sensation of persists. This phenomenon is called Mal de Débarquement syndrome or Disembarkment syndrome.

It most often develops following an ocean cruise or other type of water travel. Symptoms usually begin shortly after the cessation of the motion stimulus and often increase when in an enclosed space or when attempting to be motionless (sitting, lying down, or standing in a stationary position). The motion sensation may seem to disappear when in passive motion such as in a moving car, airplane, or train.

Common symptoms include a persistent sensation of motion such as rocking, swaying, tumbling, and/or bobbing. This sensation is often associated with anxiety, fatigue, difficulty maintaining balance, unsteadiness, and difficulty concentrating.

Sopite Syndrome

One facet of motion sickness that often is not recognised is the "sopite syndrome." It refers to the profound drowsiness and persistent fatigue that can follow brief exposures to highly provocative stimulation or prolonged exposures to low-intensity motion stimulation. Yawning has recently been shown to be a potential behavioural marker for onset of the sopite syndrome. The sopite syndrome can persist for hours or even days and when exposure is prolonged, even longer. It is characterised by boredom, apathy, failure of initiative, increased irritability, and even changes in personality. It may be one of the only syndromes that persist when nausea is not elicited or has abated. The sopite syndrome has been attributed to motion-induced drowsiness such as that experienced by a baby when rocked.

The Severity of Motion Sickness

Three key factors affect motion sickness development: the person's sensitivity to stimulation, the rate of adaptation to stimulation, and the speed of resolution of elicited symptoms.

The range of sensitivity to motion sickness in the general population varies by about 10 to 1, and the rate of adaption to stimulation also ranges from 10 to 1. By contrast, the speed of symptom resolution varies by 100 to 1.

The significance of these values is that susceptibility to motion sickness in the general population varies by about 10,000 to 1 – a vast range.

Risk Factors 

Risk factors for the development of motion sickness include:

• Age—children aged 2–12 years are especially susceptible, but infants and toddlers are generally immune.
• Sex—women are more likely to have motion sickness, especially when pregnant, menstruating, or on hormones.
• Migraines—people who get migraine headaches are more prone to motion sickness, especially during a migraine.
• Medication—some medications can worsen the nausea of motion sickness16
• 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 contribute to nausea.
• Genetic factors—research suggests that some people inherit a predisposition to motion sickness. This predisposition is more marked in certain ethnic groups; for example, Asians are more susceptible than other ethnic groups.
• Pregnancy— susceptibility in women to vomiting during pregnancy appears to be related to motion sickness, although the precise connections are not well understood.
• Sleep deprivation—increases susceptibility to motion sickness.

Is Motion Sickness Preventable?

Non-pharmacologic treatment

Behavioural techniques and complementary alternative medicine

Prevention of motion sickness is much more effective than trying to “cure” symptoms once they have started. Both pharmacological and nonpharmacological treatments are more effective if applied before the motion stimulus. Patients should learn to identify situations that will lead to motion sickness and minimise the amount of unpleasant motion to which they are exposed while traveling. For example:

• Optimise position to reduce motion or motion perception—for example, driving a vehicle instead of riding in it, sitting in the front seat of a car or bus, or sitting over the wing of an aircraft. Cabin location on a cruise ship does not appear to influence the likelihood of motion sickness.
• Slow, intermittent exposure to the motion can reduce symptoms.
• Reducing sensory input by looking at the true visual horizon, tilting the head into turns, shutting the eyes, or lying prone.
• Nutritional tips to reduce motion sickness include avoiding fatty or spicy meals; staying well hydrated; drinking ginger ale; and eating small, frequent meals.

Among alternative therapies, acupressure, wristbands and ginger have been proposed as safe treatments.

Other potential remedies include biofeedback training and relaxation deep breathing techniques, and cognitive-behavioral therapy, modalities that have been tested on airplane pilots and were found to be helpful.

Music Therapy

More recently, the use of relaxing and pleasant music has been proposed as a non-invasive and inexpensive counter-measure to visually induced motion sickness. During a visually induced motion sickness experience, persons who listened to music that they self-reported as 'pleasant', showed a significant reduction in motion sickness symptoms, with concomitant improved mood and emotion, compared with those who did not listen to 'pleasant' music.

Pharmacologic treatment

If nonpharmacological measures are insufficient, the use of pharmacological agents is advised in adults and children over the age of two years. It is generally agreed that infants are highly resistant to motion sickness.

Hyoscine

Hyoscine is the most effective drug for the prevention of motion sickness. 

Antihistamines

 Over-the-counter antihistamines are commonly used in the prevention and treatment of motion sickness and are the drugs of choice for motion sickness in children. There is no specific paediatric data for these drugs in motion sickness and dosing has been extrapolated from studies done in adults. In Australia, sedating antihistamines have recently become prescription-only for children less than two years of age. They should be avoided in children with seizure disorders. These medications appear to act by reducing the stimulation of the inner ear. The most common side effect is sedation. The newer non-sedating antihistamines, such as loratidine and cetirizine, do not cross the blood-brain barrier and are not effective against motion sickness. Antihistamines should be taken one hour prior to departure.

Examples of antihistamine medications effective in the prevention of motion sickness include:

• Dexchlorpheniramine (Polaramine)
• Diphenhydramine (Benadryl)
• Promethazine (Phenergan, Avomine)

Sympathomimetic drugs

A number of sympathomimetic drugs (drugs which mimic the effects of adrenaline and noradrenaline), particularly amphetamine and ephedrine, have been reported to have anti-motion sickness effects alone or in combination with hyoscine or promethazine. These agents are mainly used during space flights. However, sympathomimetic drugs are not used in routine clinical situations and should not be used in children.

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