Motion Sickness

Motion sickness is an unpleasant condition that occurs when persons are subjected to motion or the perception of motion. It results in the common symptoms of nausea, nonvertiginous dizziness, and malaise. It is generally considered to be of physiological origin. Nearly all individuals experience it if exposed to enough motion stimuli.

Although the motion associated with travel is the most commonly reported form of the syndrome, it has other names with slightly different characteristics. These similar conditions have been called sea sickness, travel sickness, space sickness, and cybersickness.

The brain estimates motion based on the combined input from vestibular, visual, and proprioceptive receptors. Motion sickness most likley occurs when the stimuli applied to these receptors appear to be in conflict. This apparent conflict causes more severe symptoms when the patient is passively moved at certain frequencies. It is much less common during active movements such as walking or swimming.

Nearly all people experience motion sickness if given a strong enough motion stimuli. In many typical conditions, such as on cruise ships, the prevalence ranges from 3-60%, depending on the study.[1, 2, 3]

Motion sickness results in mortality and/or morbidity very rarely. Mortality and morbidity most commonly results from falls but can also result from a combination with other travel, recreational, or occupational hazards.

Two small studies have reported an association between Chinese ethnicity and increased susceptibility to motion sickness.[4, 5]

Several studies show that females report increased frequency and severity of symptoms and pregnant women are much more susceptible to motion sickness.[6]

Persons under 2 years rarely show signs and symptoms of motion sickness. Children between 3 and 12 years may have the highest incidence, and elderly people seem to have reduced susceptibility.

Exposure to real or perceived motion stimuli is required for the syndrome to be categorized as motion sickness. Motion stimuli may be categorized as a vertical linear acceleration (heave), horizontal translational motion in the lateral direction (sway), the fore-and-aft movement (surge), and/or an angular roll. The maximum symptoms frequently appear with motions with a frequency of 0.2 Hz (one cycle every 5 seconds). Long period motions like those experienced on a tilting train or large ship can be barely perceptible but still cause the syndrome. Virtual motions such as in a large video screen, microfiche reader, or other visual motions can precipitate motion sickness.[7]

Nausea is the hallmark symptom, although it is frequently preceded by several more subtle symptoms. These preceding symptoms are commonly described as generalized feeling of unwellness (malaise), drowsiness, fatigue, and irritability. They can be quite subtle and easily mistaken for emotional responses to the situation. An early sensation of “stomach awareness,” described as a fullness and discomfort in the epigastrium, is frequently the first reported symptom.

Nausea and vomiting in motion sickness and can be quite severe. A nonvertiginous dizziness sometimes associated and exaggerated sense of motion and difficulty ambulating.

Sopite syndrome, which is a constellation of symptoms that involves apathy, depression, disinclination for work, and decreased participation in group activities, can occur.[8] These and other neurophysiologic symptoms such as maliase, lethargy and agitation can persist for some time after the motion stimuli has ended.

The sensation of movement frequently persists after the cessation of motion. This syndrome, called mal de debarque, is considered worrisome if it lasts for longer than 3 days.[9]

Patients who have previously experience motion sickness are much more likely to experience it again. Along with pregnant women, patients with previous vestibular syndromes or illness, a propensity toward nausea, and patients with a migraine headache history have increased rates of motion sickness.

Besides vomiting, there are few detectable physical signs of motion sickness. Yawning and belching can be observed before conscious symptoms develop. Peri-oral and facial pallor can give patients a green appearance and can occur along with increased salivation, diaphoresis, and flushing. Increased postural sway, changes in electrogastrography, and decreases in skin resistance have all been correlated with the sensations of motion sickness.

See Pathophysiology.

The evaluation of motion sickness rarely requires any laboratory or imaging studies except on the rare occasion when ruling out another condition may be necessary.

A pregnancy test is likely to be the most useful additional lab study.

Imaging is rarely indicated except for persistent neurological symptoms lasting for weeks after the cessation of motion. A CT scan of the brain and temporal bones or an MRI brain scan help to exclude central causes.

Audiography and vestibular testing can be conducted in collaboration with otolaryngology and neurology.

The bedside performance of canalith-repositioning maneuvers may be appropriate if the differential diagnosis of peripheral vertigo is considered, but it is not an effective treatment for motion sickness.

In considering treatment for motion sickness, the medical provider and the patient must understand that prevention 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 application of the motion stimuli and should certainly work best if applied before the appearance of significant symptoms.

Multiple pharmacologic treatments exist.[10] As previously stated, they are more effective in preventing motion sickness than treating it and should be taken before motion exposure. In choosing a pharmacological therapy, the patient's age, comorbidities, and current medications should be considered, as well as the length of voyage in which the patient may be susceptible to motion sickness. The 2 classes most commonly used are anticholinergic agents (scopolamine) and antihistamines (dimenhydrinate [Dramamine]). They are discussed in detail, by class, under Medication.

Non-pharmacological prevention

Although pharmacological treatments for motion sickness are generally very effective, non-pharmacological treatments for prevention should be tried as well. Recognizing situations and motions that are likely to produce motion sickness is the most important factor to allow for prevention of symptoms. Minimizing the amount of conflicting vestibular, visual, and proprioceptive sensory information is the goal of the most of the non-pharmacologic treatments.

Avoiding uncomfortable motion stimuli completely by not traveling is rarely practical, but selecting vehicles that produce a minimal amount of motion can help. Large ships on calm seas, comfortable cars (riding in the front seats), and smoothly accelerating trains produce fewer symptoms than small boats in rough weather, buses on mountain roads, and rocking trains.

Habituation

Patients who slowly acclimatize to the motion stimuli generally have less severe symptoms. For example, if preparing for a sea voyage, patients should visit the vessel at dock as early as possible, and spend as much time inside a calm harbor before experiencing the open ocean.

Positioning on the vehicle

Selecting the most stable portion of the vessel is helpful. Patients should attempt to locate themselves near the centerline of the vessel and nearest to the ground or waterline. Conversely, locations below deck and high in the vessel often produce the most uncomfortable motion. Supporting the head to minimize additional head motion and to reduce neck strain helps reduce both vestibular and proprioceptive stimuli.

After all attempts to decrease the amount of motion have been made, adjustments to the characteristics of the motion can be tried. Facing forward or in-line with the direction of the largest motion can reduce the amount of off-axis motion, which can reduce symptoms. Reclining the head back 30º or more can alleviate symptoms by isolating the motion to a single axis within the semicircular canal.

Attempting to reduce conflicting visual stimuli can best be accomplished by attempting to maintain a steady visual horizon with an expansive of a view as possible. Looking down at the floor or water may seem comfortable, but watching the horizon or looking up is more likely to minimize symptoms. Patients should avoid closed spaces without an accurate horizon. Window seats and open-air locations are preferable. If possible, looking forward toward the source of the motion in order to be able anticipate the movements is optimal.

Body position is also very important. In addition to minimizing head motion and neck twisting relative to the patient’s body, patients should face forward in the location of the vehicle with minimal motion. Safely standing with flexed knees and actively anticipating the motion can be effective.

Finally, lying completely prone (with closed eyes) often reduces symptoms to a manageable level presumably by aligning full-body symmetrical proprioceptive input.

Activity on the vehicle

Patients should be instructed to avoid close work, reading, or watching a video screen. Sunglasses can reduce visual input and may be beneficial. If other preventive strategies fail to improve symptoms, closing one’s eyes can reduce symptoms.

Piloting the vessel is another method to synchronize the visual, vestibular, and proprioceptive stimuli. Steering forces the patient to watch the visual horizon, stabilize their head, and receive proprioceptive input from the wheel through their arms. A psychological benefit is likely from taking control of their situation.

Non-pharmacological treatments

Discussing the symptoms of motion sickness often precipitates the condition and frequently increases the symptom severity in persons with mild symptoms. Patients should attempt to reduce as many other noxious stimuli as possible. Avoid any noxious stimuli such as odors, particularly the smell of emesis or hydrocarbons. Avoiding alcohol and other nausea producing substances is essential. The cessation of nicotine ingestion can reduce symptoms. Caffeine may increase some patients’ nausea. Controlled breathing has been shown to suppress symptoms in mild cases.[11]

Patients should avoid becoming dehydrated, getting too cold, too warm, or any other sources of discomfort.

A small study has suggested visually induced motion sickness may be allieviated with pleasant odors.[12]

The importance of psychological and emotional factors on the experience of motion sickness cannot be overlooked. Patients who have anxiety about other portions of their travel experience are much more likely to report the sensations of motion sickness as extremely unpleasant while those individuals who frequently overcome unpleasant noxious stimuli often report motion sickness as a minor inconvenience.[13]

Tips for helping minimize motion are as follows:

• Pick a stable vehicle.

• Occupy the location at the center or the front of vehicle.

• Choose a location near the midline of the vehicle.

• Choose a location at the ground floor or waterline.

Tips for reducing vestibular symptoms are as follows:

• Reduce off-axis motion.

• Support the head.

• Recline head back 30º.

Visual tips for minimizing motion sickness are as follows:

• Try to see a wide horizon.

• Look toward motion.

• Do not do any close work or read.

• Wear sunglasses.

• Close your eyes.

Proprioceptive tips for minimizing motion sickness are as follows:

• Connect with steering device.

• Support head

• Avoid neck torsion

• Stand

• Recline as much as possible

• Lay prone

Other advice for reducing motion sickness is as follows:

• Slowly increase motion stress.

• If possible, pilot the vehicle.

• Avoid other noxious stimuli.

• Avoid noxious odors.

• Avoid alcohol.

• Avoid dehydration.

• Stay comfortably warm and dry.

• Eat soft, bland, light meals.

• Avoid discussing motion sickness.

• Treat gastritis.

• Control negative emotions.

Alternative medicine treatments

Acupuncture and acupressure have been reported to reduce both motion sickness and nausea for many years. Many commercial products purport to treat motion sickness by applying stimulation (eg, needles, pressure, electrical current, magnetic fields, capsicum plaster) to the P6 pressure point on the wrist. None of these devices have been shown to be effective compared to placebos in good quality trials.[14, 15, 16]

Although a large systematic review and metaanalysis has not shown P6 stimulation to be effective for preventing postoperative nausea, some papers have shown them to be effective in in reducing the symptoms of motion sickness in a few small studies.[17, 18, 19]

Other treatment modalities

An entire host of technologies have attempted to prevent motion sickness in laboratory and real-world conditions. These devices typically attempt to synchronize visual and vestibular by altering the visual input. None have been shown to be effective in real-world conditions.

Consultations are rarely necessary. Nearly all motion sickness can be prevented or treated with standard behavioral and pharmacological interventions. If standard treatments are unsuccessful and the condition is impacting important aspects of the patient’s quality of life, the case can be discussed with an expert in the field. Typically, flight surgeons who specialize in aeromedical conditions, as well as otolaryngology, neurology, or neuro-otology physicians, have experience with these cases and may accept referrals.

Reports exist that a bland diet that is high in carbohydrates and low in fats may reduce symptoms. Spicy foods, acidic foods, and other foods that produce gastritis or gastroesophageal reflux are more likely to be associated with stomach awareness, nausea, and vomiting. Patients with a history of gastritis should take measures to treat this before they start vomiting.

Sailors experienced with motion sickness frequently choose to eat sweet, non-spicy, “slippery” foods, which are less uncomfortable for them to vomit after the initiation of seasickness.

Although ginger has been reported as a treatment for motion sickness for many years, few trials show its effectiveness.[20, 21, 22] The literature on ginger for other forms of nausea is larger, but an analysis of these studies don’t not convincingly show any improvement compared to placebo.[23] The history behind ginger as a treatment is long, and some individuals may be helped if they believe in the treatment.[24]

Further Inpatient Care

No inpatient care is needed.

Further Outpatient Care

Education about prevention and treatment of motion sickness and outpatient prescriptions for pharmacological treatments are frequently the only required outpatient care.

Transfer

Patients with motion sickness very rarely require medical transport primarily. However, patients being transported for other medical reasons frequently develop motion sickness and are often appropriate candidates for preventative pharmacological treatment.

Deterrence/Prevention

See section on non-pharmacological treatments.

Complications

Dehydration, anxiety, and depression are the most common complications of motion sickness.

Prognosis

Symptoms resolve in nearly all patients within 72 hours after the cessation of the motion stimuli.

Patient education is the probably the most important aspect of patient care. Avoidance, motion acclimation, and minimization of motion stimuli are key strategies for avoiding motion sickness. Educating patients to attempt to synchronize vestibular, visual, and proprioceptive stimuli. Informing patient about the importance of personal awareness of the more subtle neurological, psychological, and gastrointestinal symptoms that often precede the nausea and vomiting. Assuring that patients understand that pharmacological treatment works best if started before the onset of symptoms cannot be emphasized enough. Finally, it is important to assure patient that, although severe motion sickness may make patients wish they would die, it is extremely unlikely to kill them.

Special concerns

Self-treatment and prevention of motion sickness is frequently required in situations in which the medical provider is likely to be treating other patients for motion sickness.[25, 26] Prevention and pretreating oneself in the appropriate manner should be carried out before attempting to initiate medical care on others who may be suffering from motion sickness.

The goal of pharmacological therapy is to prevent motion sickness, or relieve the symptoms of motion sickness, such as nausea.

Anticholinergic Agents

Scopolamine, an anticholinergic, is used for the prevention of motion sickness and for acute treatment. Scopolamine’s effectiveness is likely due to its central anticholinergic properties.

Common adverse effects can include dry mouth/nose/throat, drowsiness, loss of visual accommodation, and sensitivity to bright light. Less common adverse effects include palpitations, urinary retention, bloating, constipation, headache, and confusion.

Scopolamine, which is most commonly prescribed as a transdermal patch, should be administered at least 30 minutes prior to exposure to motion stimuli. It should be placed behind the ear on the mastoid on a clean, hairless area.

Antihistamines

Many antihistamines are also commonly taken for motion sickness. They are available over the counter and can be used for pediatrics at the recommended doses. They should also be used to prevent motion sickness rather than treating it.

Their effectiveness is likely due to both their central antihistamine and central anticholinergic properties. The nonsedating antihistamines like cetirizine that do not cross the blood-brain barrier are not effective in either preventing or treating motion sickness.

Common side effects can include: dry mouth/nose/throat, drowsiness and sensitivity to bright light (secondary to mydriasis). Less common include palpitations, urinary retention, bloating, constipation, headache and confusion. They should be taken 1 hour prior to departure.

• Cinnarizine (Stugeron) is an antihistamine (not marketed in the US), that is reported to be effective if administered at a 50mg oral dose before a rough voyage.[27] Although cinnarizine is not licensed by the FDA in the United States, several studies report cinnarizine as the most effective antihistamine with the fewest side effects.[28]

• Dimenhydrinate (Dramamine, Gravol, Driminate), Meclizine (Bonine, Bonamine, Antivert, Postafen, and Sea Legs), and Cyclizine( Marezine, Bonine For Kids, Cyclivert) are long-acting piperazine antihistamines and generally cause less sedation than other antihistamines.

• Promethazine (Phenergan) is prescribed for treating nausea or vomiting, motion sickness, and allergic reactions, but causes more sedation than other antihistamines.

Sympathomimetics

Sympathomimetics, while have shown some effectiveness in preventing and treating motion sickness, are most commonly used to counteract the sedation of other motion sickness treatments. They have not been shown to be superior to other medications. Due to concerns regarding their addictive potential, they are not as often prescribed.

Amphetamines

While having been shown to have some efficacy in preventing motion sickness, these are a controlled substance with a high abuse potential, and therefore should be prescribed with caution.[29]

Caffeine

Caffeine has been shown to be of benefit in treating motion sickness only when combined with other pharmacological treatments such as promethazine.[30]

Other Medications

Antiemetics are taken to relieve nausea, but have not been shown to prevent motion sickness.

Ondansetron is the most often recommended antiemetic but has been shown to be a poor treatment choice for motion sickness.[31, 32]

Benzodiazepines such as diazepam have been shown to prevent motion sickness but not as well as other options.[33] This fact, along with its sedation properties, make it a poor choice. However, for resistant and severe cases, especially for patients with incapacitating motion sickness, a benzodiazepine, if used safely, may be the most humane option.

Class Summary

Alkaloids with anti-cholinergic properties that are used for the prevention of motion sickness rather than acute treatment.

Scopolamine

Scopolamine is most commonly used as a transdermal patch that is applied behind the ear for up to 72 hours, at which point it can be replaced. Transdermal scopolamine is the most effective pharmaceutical for the prevention and treatment of motion sickness.[32, 33] The patch should be applied 4 hours prior to departure.[34]

Oral tablets are also available and should be taken 1 hour prior to departure at their recommended doses. Some experts report the dose can be safely doubled by wearing either two patches or by supplementing the patch with oral scopolamine.[35, 36] Intranasal scopolamine may also work.[37] Scopolamine may also be used in conjunction with antihistamines, although this will increase the chance of the user experiencing side effects.

Class Summary

Long-acting piperazine antihistamines generally cause less sedation than other antihistamines.

Dimenhydrinate

Mixture of 1:1 salt consisting of 8-chlorotheophylline and diphenhydramine. Believed to be useful, particularly in treatment of vertigo. Diminishes vestibular stimulation and depresses labyrinthine function through central anticholinergic effects. However, prolonged treatment may decrease rate of recovery of vestibular injuries.

Meclizine

Decreases excitability of middle ear labyrinth and blocks conduction in middle ear vestibular-cerebellar pathways. These effects are associated with relief of nausea and vomiting.

Cyclizine

Mechanisms of action are not understood. In nausea, and other vertigo symptoms, may have an effect on labyrinthine apparatus, chemoreceptor trigger zone, in addition to central actions.

Class Summary

Sympathomimetics, while have shown some effectiveness in preventing and treating motion sickness, are most commonly used to counteract the sedation of other motion sickness treatments.

Ephedrine

One study showed ephedrine used in combination with an antihistamine (chlorphenamine) was effective in treating some symptoms of motion sickness once they have begun and was reported to decrease the sedative effects of the antihistamine.[38]