What is Motion Sickness?
Motion sickness is a syndrome that occurs when the brain receives conflicting information from the vestibular system (inner ear), visual system, and proprioceptive receptors about body movement—either from actual physical motion or the illusion of motion in virtual environments. 1, 2
Core Mechanism
- The condition arises from a sensory mismatch between what the eyes see, what the vestibular apparatus in the inner ear senses, and what the body's position sensors detect, compared to the brain's expected pattern of movement 1, 2
- The vestibular system, visual inputs, and proprioceptive receptors send contradictory signals that the brain cannot reconcile with stored patterns of normal movement 2
- Research has identified that velocity storage of semicircular canal signals (the integration of rotational movement signals over time) plays a key role in triggering motion sickness 3
Clinical Presentation
Nausea is the hallmark symptom, but it is typically preceded by a constellation of other manifestations 1:
- Early warning signs include stomach awareness, malaise, drowsiness, and irritability 1
- Common symptoms encompass anorexia, yawning, sighing, increased salivation, burping, headache, and blurred vision 2
- Neurological symptoms may include non-vertiginous dizziness, drowsiness, spatial disorientation, and difficulty concentrating 2
- Severe cases progress to vomiting 1, 2
Triggering Conditions
Motion sickness can be induced by multiple types of stimuli 2:
- Physical motion: Low-frequency vertical, lateral, angular, or rotary movements during air, sea, or land transportation 2, 4
- Visual motion: Exposure to moving visual environments without actual body movement 2, 3
- Virtual motion: Simulated movement in virtual reality or other artificial environments 2, 3
Susceptibility and Vulnerability
- Nearly everyone is susceptible at some point in their lifetime, with only individuals lacking a functioning vestibular system being fully immune 2, 3
- The range of vulnerability in the normal population varies approximately 10,000 to 1, meaning some individuals are extraordinarily sensitive while others are highly resistant 3
- Sleep deprivation enhances susceptibility to motion sickness 3
- Motion sickness is more likely to occur when exposed to motion patterns to which an individual has not yet adapted 2
Important Clinical Distinction
Motion sickness should not be confused with vertigo, which is defined as a false sensation of self-motion or spinning of the visual surroundings 5. While motion sickness involves nausea triggered by actual or perceived motion, vertigo represents a specific type of dizziness with rotational characteristics that may indicate inner ear pathology such as benign paroxysmal positional vertigo (BPPV) or Ménière's disease 5.