Description

• Motion sickness is a physiologic response in affected individuals to a situation in which sensory conflict about body motion exists among visual receptors, vestibular receptors, and body proprioceptors.
• Often induced when patterns of motion differ from those previously experienced or expected
• Differs from “cybersickness” or “virtual reality sickness” (symptoms, including dizziness, that result from exposure to computer based stimuli) in the fact that some form of actual movement is generally required to diagnose motion sickness
• Systems affected: nervous, gastrointestinal
• Synonym(s): car sickness; sea sickness; air sickness; space sickness; physiologic vertigo; kinetosis

Epidemiology

Incidence
Predominant sex: female > male

Prevalence
Estimation is complex; syndrome occurs in ~25% due to travel by air, ~29% by sea, and ~41% by road. Estimates for vomiting are 0.5% by air, 7% by sea, and 2% by road.

Etiology and Pathophysiology

• Precise etiology unknown; thought to be due to a mismatch of vestibular and visual sensations
• Rotary, vertical, and low-frequency motions produce more symptoms than linear, horizontal, and high-frequency motions.
• Nausea and vomiting occur as a result of increased levels of dopamine and acetylcholine, which stimulate chemoreceptor trigger zone and vomiting center in CNS. Other signals which can be involved in this process include histamine, norepinephrine, and γ-aminobutyric acid (1).

Genetics
Heritability estimates range from 55% to 75%.

Risk Factors

• Motion (auto, plane, boat, amusement rides)
• Visual stimuli (e.g., moving horizon)
• Poor ventilation (fumes, smoke, carbon monoxide)
• Emotions (fear, anxiety)
• Zero gravity
• Pregnancy, menstruation, oral contraceptive use
• History of migraine headaches, especially vestibular migraine

General Prevention

See “General Measures.”

Pediatric Considerations

• Rare in children <2 years of age
• Incidence peaks between 6 and 12 years of age.
• Antihistamines may cause excitation in children.

Geriatric Considerations

• Age confers some resistance to motion sickness.
• Elderly are at increased risk for anticholinergic side effects from treatment.

Pregnancy Considerations

• Pregnant patients are more likely to experience motion sickness.
• Treatment with medications is thought to be safe during morning sickness (e.g., meclizine, dimenhydrinate).
• Scopolamine, meclizine, diphenhydramine, and promethazine are generally considered safe during breastfeeding.

Commonly Associated Conditions

• Migraine headache
• Vestibular syndromes