Definition

Motion sickness is a common problem when individuals travel for extended periods in various modes of transportation such as cars, trains, planes, and ships. While it can affect people of all ages, it is commonly observed in children, pregnant women, and individuals taking specific medications. The primary symptom is nausea, with the term "nausea" derived from the Greek word "naus," meaning ship. This association is because motion sickness is frequently encountered in seasickness, particularly during travel on the sea.

Causes

Motion sickness occurs due to lateral or horizontal shaking, slow-frequency vertical shaking, or virtual simulator movement. These motions create a conflict between sensory inputs from different senses, leading to a neural mismatch. This sensory conflict involves the visual system, the balance system, and sensory perceptions from muscles, joints, and skin, which detect stimuli such as touch, pressure, pain, temperature, position, movement, and vibration.

The sense of balance is communicated to the brain, and the brain also receives stimuli from vision and position. When there is a mismatch between these stimuli, the brain responds by increasing involuntary or autonomous organ reactions and stimulating the vomiting center. An illustrative example of stimulus mismatch is experienced when reading a book in a moving car, where the eyes perceive the stationary text in the book, while the ears and balance center detect the moving stimulus of the car.

Risk factor

Motion sickness can affect all individuals with intact balance function, as those who have lost their balance function entirely are not susceptible to it. However, the degree of susceptibility varies among individuals. Certain patterns and factors influence the likelihood of experiencing motion sickness:

• Gender: Females tend to be more susceptible than males to motion sickness.
• Age: Motion sickness can commence around 6 years old, peak at 9 years old, and decrease during the teenage years as individuals habituate to motion.
• Elderly: Among all age groups, the elderly are less prone to experiencing motion sickness.
• Physical Activity: People who regularly engage in aerobic exercise may be more susceptible to motion sickness, as their bodies are more reactive to movement.
• Medical Conditions: Conditions that affect balance, such as vertigo, Meniere's disease, and migraines, can increase the risk of motion sickness.
• Hormonal Changes: Hormonal changes, such as those occurring during pregnancy and certain menstrual cycle phases, can elevate the risk of motion sickness.

Symptoms

The symptoms of motion sickness can vary, with the most common ones being nausea and vomiting. Additional symptoms may include:

• Cold sweat
• Paleness
• Headache
• Sleepiness
• Yawning
• Loss of appetite
• Increased saliva production

Typically, these symptoms are triggered by shaking or distinct movements, such as traveling in a motor vehicle or playing video games. In rare cases, individuals may experience unusual symptoms as the inability to walk, paralysis, unstable posture, intractable vomiting, and social isolation. 

Diagnosis

Motion sickness can typically be diagnosed early through a detailed medical history and physical examination. Diagnostic tests, such as laboratory tests and imaging, are generally unnecessary, particularly if the individual has a history of motion sickness. However, if someone is experiencing motion sickness for the first time, tests may be conducted to identify any migrainous-type headaches, as there is a known connection between migraines and motion sickness. Medications used to prevent migraines can also help alleviate symptoms of motion sickness.

In rare cases, motion sickness may be attributed to a total blockage of the basilar artery, located at the base of the skull. Symptoms of total blockage include dizziness and motion sickness, often accompanied by other signs such as double vision, difficulty moving the tongue, trouble swallowing, and sudden falls without an apparent trigger. This condition can be potentially life-threatening, necessitating a contrast-enhanced CT scan to determine if there is a blockage in the artery. If such blockage is ruled out, further examinations may explore other potential causes, including benign paroxysmal positional vertigo (BPPV), migraines affecting the balance center, vestibular neuritis, and more.

Management

Early treatment of motion sickness can be initiated independently through various strategies:

• Positioning: To reduce the effects of shaking, sit in the front seat of a car or in the middle of a ship.
• Visual Focus: Look at the horizon to help orient yourself.
• Fresh Air: Breathe in fresh air by opening car windows or finding a well-ventilated area.
• Relaxation Techniques: Close your eyes, breathe slowly, and focus on your breathing.
• Distraction: Engage in activities like talking, listening to music, or singing, especially for children.
• Rest Breaks: Take short breaks during the journey to get fresh air, drink water, or take a short walk.
• Ginger Consumption: Consume ginger in various forms, such as tablets, biscuits, or tea, as it has anti-vomiting effects.
• Over-the-counter Medications: Use over-the-counter anti-motion sickness drugs like dimenhydrinate or diphenhydramine. Note that these medications may cause drowsiness.

Long-term treatment involves habituation, where individuals gradually expose themselves to motion, helping the body adapt. This approach, often used in military training programs, has a high success rate with long-term effects. General exposure to continuous movement, with intervals less than a week between exposures, can lead to symptom disappearance for 24-72 hours.

It's important to note that anti-nausea and anti-vomiting drugs like metoclopramide and ondansetron are not effective in preventing motion sickness.

Complications

Most individuals experiencing motion sickness typically have mild to moderate symptoms that resolve independently. Once the triggering motion stops, motion sickness often clears up within 24 hours. However, a small percentage of affected individuals may experience severe nausea and vomiting, leading to complications such as dehydration, electrolyte imbalance, or even Mallory-Weiss tears. 

Prevention

To prevent motion sickness, consider the following precautions:

• Avoid activities that involve focusing on nearby moving objects, such as reading, watching films, or using electronic devices during travel.
• Refrain from looking at other moving objects, like passing cars or waves.
• Avoid consuming heavy, spicy foods or alcohol before traveling.
• Steer clear of sitting near smokers or in a smoky environment.
• Take antihistamine drugs like dimenhydrinate before traveling; however, be aware of potential side effects such as drowsiness.
• Avoid strong odors like spicy and oily foods or alcohol.
• Choose a seat at the back when on a long journey.
• Take on the driver's role if possible, as this may help prevent motion sickness during long trips.

For susceptible individuals, choose specific seats based on the mode of transportation:

• Ships: Opt for a front or middle seat near the water's surface.
• Plane: Once the journey begins, request a seat near the wings and direct the air conditioner towards your face.
• Train: Choose a seat facing forward and by the window.
• Car, bus, etc.: Drive or sit in the front seat. Children should preferably sit in age-appropriate seats and wear seatbelts.

When to see a doctor?

If you experience motion sickness accompanied by severe vomiting, double vision, paralysis, difficulty speaking, swallowing problems, or a sudden loss of balance resulting in a fall, it is advisable to consult a doctor. While motion sickness is a common and usually mild condition, the mentioned signs and symptoms could indicate a potentially serious or life-threatening condition that requires medical attention beyond basic first aid measures.

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