Sea Sick
   HOME

TheInfoList



OR:

Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...
, cold sweat, headache,
dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...
, tiredness, loss of appetite, and increased
salivation Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be e ...
. Complications may rarely include
dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
,
electrolyte problems Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function, ...
, or a
lower esophageal tear Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...
. The cause of motion sickness is either real or perceived motion. This may include from car travel, air travel, sea travel, space travel, or
reality simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...
. Risk factors include
pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
,
migraines Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...
, and
Ménière's disease Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initial ...
. The diagnosis is based on symptoms. Treatment may include behavioral measures or medications. Behavioral measures include keeping the head still and focusing on the
horizon The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...
. Three types of medications are useful:
antimuscarinics A muscarinic receptor antagonist (MRA) is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. The muscarinic receptor is a protein involved in the transmission of signals through certain parts of the ...
such as
scopolamine Scopolamine, also known as hyoscine, or Devil's Breath, is a natural or synthetically produced tropane alkaloid and anticholinergic drug that is formally used as a medication for treating motion sickness and postoperative nausea and vomiting ...
, H1 antihistamines such as
dimenhydrinate Dimenhydrinate, sold under the brand name Dramamine, among others, is an over-the-counter drug used to treat motion sickness and nausea. Dimenhydrinate is a theoclate salt composed of diphenhydramine, an ethanolamine derivative, and 8-chloroth ...
, and
amphetamines Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative compounds which are formed by replacing, or substituting, one or more hydrogen atoms in the amphetamine core structure with sub ...
such as
dexamphetamine Dextroamphetamine is a central nervous system (CNS) stimulant and an amphetamine enantiomer that is prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is also used as an athletic performance and c ...
. Side effects, however, may limit the use of medications. A number of medications used for nausea such as
ondansetron Ondansetron, sold under the brand name Zofran among others, is a medication used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, or surgery. It is also effective for treating gastroenteritis. It can be given by ...
are not effective for motion sickness. Nearly all people are affected with sufficient motion and most people will experience motion sickness at least once in their lifetime. Susceptibility, however, is variable, with about one-third of the population being highly susceptible while most other people are affected under extreme conditions. Women are more easily affected than men. Motion sickness has been described since at least the time of
Homer Homer (; grc, Ὅμηρος , ''Hómēros'') (born ) was a Greek poet who is credited as the author of the ''Iliad'' and the ''Odyssey'', two epic poems that are foundational works of ancient Greek literature. Homer is considered one of the ...
( eighth century BC).


Signs and symptoms

Symptoms commonly include
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...
, cold sweat, headache,
dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...
, tiredness, loss of appetite, and increased
salivation Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be e ...
. Occasionally, tiredness can last for hours to days after an episode of motion sickness, known as "sopite syndrome". Rarely severe symptoms such as the inability to walk, ongoing vomiting, or social isolation may occur while rare complications may include
dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
,
electrolyte problems Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function, ...
, or a
lower esophageal tear Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...
from severe vomiting.


Cause

Motion sickness can be divided into three categories: # Motion sickness caused by motion that is felt but not seen, as in terrestrial motion sickness; # Motion sickness caused by motion that is seen but not felt, as in space motion sickness; # Motion sickness caused when both systems detect motion but they do not correspond, as in either terrestrial or space motion sickness.


Motion felt but not seen

In these cases, motion is sensed by the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
and hence the motion is felt, but no motion or little motion is detected by the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
, as in terrestrial motion sickness.


Carsickness

A specific form of
terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
motion sickness, being carsick is quite common and evidenced by disorientation while reading a map, a book, or a small screen during travel. Carsickness results from the sensory conflict arising in the brain from differing sensory inputs. Motion sickness is caused by a conflict between signals arriving in the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
from the inner
ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
, which forms the base of the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
, the sensory apparatus that deals with movement and balance, and which detects motion mechanically. If someone is looking at a stationary object within a vehicle, such as a magazine, their eyes will inform their brain that what they are viewing is not moving. Their inner ears, however, will contradict this by sensing the motion of the vehicle. Varying theories exist as to cause. The sensory conflict theory notes that the eyes view motion while riding in the moving vehicle while other body sensors sense stillness, creating conflict between the eyes and inner ear. Another suggests the eyes mostly see the interior of the car which is motionless while the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
of the inner ear senses motion as the vehicle goes around corners or over hills and even small bumps. Therefore, the effect is worse when looking down but may be lessened by looking outside of the vehicle. In the early 20th century, Austro-Hungarian scientist Róbert Bárány observed the back and forth movement of the eyes of railroad passengers as they looked out the side windows at the scenery whipping by. He called it "railway
nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...
". Also called "optokinetic nystagmus". It causes nausea and vomiting. His findings were published in the journal ''Laeger'', 83:1516, Nov.17, 1921.


Airsickness

Air sickness is a kind of terrestrial motion sickness induced by certain sensations of air travel. It is a specific form of motion sickness and is considered a normal response in healthy individuals. It is essentially the same as carsickness but occurs in an airplane. An airplane may bank and tilt sharply, and unless passengers are sitting by a window, they are likely to see only the stationary interior of the plane due to the small window sizes and during flights at night. Another factor is that while in flight, the view out of windows may be blocked by clouds, preventing passengers from seeing the moving ground or passing clouds.


Seasickness

Seasickness is a form of terrestrial motion sickness characterized by a feeling of
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
and, in extreme cases,
vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...
experienced after spending time on a boat. It is essentially the same as carsickness, though the motion of a watercraft tends to be more regular. It is typically brought on by the rocking motion of the craft or movement while the craft is immersed in water. As with airsickness, it can be difficult to visually detect motion even if one looks outside the boat since water does not offer fixed points with which to visually judge motion. Poor visibility conditions, such as fog, may worsen seasickness. The greatest contributor to seasickness is the tendency for people being affected by the rolling or surging motions of the craft to seek refuge below decks, where they are unable to relate themselves to the boat's surroundings and consequent motion. Some people with carsickness are resistant to seasickness and vice versa. Adjusting to the craft's motion at sea is called "gaining one's sea legs"; it can take a significant portion of the time spent at sea after disembarking to regain a sense of stability "post-sea legs".


Centrifuge motion sickness

Rotating devices such as
centrifuges A centrifuge is a device that uses centrifugal force to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities (e.g. cream from milk) or l ...
used in astronaut training and amusement park rides such as the
Rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator * Helicopter rotor, the rotary wing(s) of a rotorcraft ...
, Mission: Space and the
Gravitron The Gravitron is an amusement ride, most commonly found as a portable ride at fairs and carnivals. The Gravitron first appeared at Morey's Piers in 1983 and quickly became a fixture at amusement parks in many countries. It is a modification of ...
can cause motion sickness in many people. While the interior of the centrifuge does not appear to move, one will experience a sense of motion. In addition,
centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is paralle ...
can cause the vestibular system to give one the sense that downward is in the direction away from the center of the centrifuge rather than the true downward direction.


Dizziness due to spinning

When one spins and stops suddenly, fluid in the inner ear continues to rotate causing a sense of continued spinning while one's visual system no longer detects motion.


Virtual reality

Usually, VR programs would detect the motion of the user's head and adjust the rotation of vision to avoid dizziness. However, some cases such as system lagging or software crashing could cause lags in the screen updates. In such cases, even some small head motions could trigger the motion sickness by the
defense mechanism In psychoanalytic theory, a defence mechanism (American English: defense mechanism), is an unconscious psychological operation that functions to protect a person from anxiety-producing thoughts and feelings related to internal conflicts and o ...
mentioned below: the
inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
transmits to the brain that it senses motion, but the eyes tell the brain that everything is still.


Motion seen but not felt

In these cases, motion is detected by the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
and hence the motion is seen, but no motion or little motion is sensed by the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
. Motion sickness arising from such situations has been referred to as "visually induced motion sickness" (VIMS).


Space motion sickness

Zero gravity interferes with the vestibular system's gravity-dependent operations, so that the two systems, vestibular and visual, no longer provide a unified and coherent sensory representation. This causes unpleasant disorientation sensations often quite distinct from terrestrial motion sickness, but with similar symptoms. The symptoms may be more intense because a condition caused by prolonged weightlessness is usually quite unfamiliar. Space motion sickness was effectively unknown during the earliest spaceflights because the very cramped conditions of the spacecraft allowed for only minimal bodily motion, especially head motion. Space motion sickness seems to be aggravated by being able to freely move around, and so is more common in larger spacecraft. Around 60% of
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
astronauts experienced it on their first flight; the first case of space motion sickness is now thought to be the Soviet
cosmonaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...
Gherman Titov Gherman Stepanovich Titov (russian: Герман Степанович Титов; 11 September 1935 – 20 September 2000) was a Soviet cosmonaut who, on 6 August 1961, became the second human to orbit the Earth, aboard Vostok 2, preceded by Y ...
, in August 1961 onboard ''
Vostok 2 Vostok 2 (russian: Восток-2, ''Orient 2'' or ''East 2'') was a Soviet space mission which carried cosmonaut Gherman Titov into orbit for a full day on August 6, 1961, to study the effects of a more prolonged period of weightlessness on the ...
'', who reported dizziness, nausea, and vomiting. The first severe cases were in early Apollo flights;
Frank Borman Frank Frederick Borman II (born March 14, 1928) is a retired United States Air Force (USAF) colonel, aeronautical engineer, test pilot, businessman, and NASA astronaut. He was the commander of Apollo 8, the first mission to fly around the Moo ...
on ''
Apollo 8 Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. These ...
'' and
Rusty Schweickart Russell Louis "Rusty" Schweickart (also Schweikart; born October 25, 1935) is an American aeronautical engineer, and a former NASA astronaut, research scientist, U.S. Air Force fighter pilot, as well as a former business executive and governm ...
on ''
Apollo 9 Apollo 9 (March 313, 1969) was the third human spaceflight in NASA's Apollo program. Flown in low Earth orbit, it was the second crewed Apollo mission that the United States launched via a Saturn V rocket, and was the first flight of the ful ...
''. Both experienced identifiable and quite unpleasant symptoms—in the latter case causing the mission plan to be modified.


Screen images

This type of terrestrial motion sickness is particularly prevalent when susceptible people are watching films presented on very large screens such as
IMAX IMAX is a proprietary system of high-resolution cameras, film formats, film projectors, and theaters known for having very large screens with a tall aspect ratio (approximately either 1.43:1 or 1.90:1) and steep stadium seating. Graeme F ...
, but may also occur in regular format theaters or even when watching TV or playing games. For the sake of novelty, IMAX and other panoramic type theaters often show dramatic motions such as flying over a landscape or riding a
roller coaster A roller coaster, or rollercoaster, is a type of amusement ride that employs a form of elevated railroad track designed with tight turns, steep slopes, and sometimes inversions. Passengers ride along the track in open cars, and the rides are o ...
. This type of motion sickness can be prevented by closing one's eyes during such scenes. In regular-format theaters, an example of a movie that caused motion sickness in many people is ''
The Blair Witch Project ''The Blair Witch Project'' is a 1999 American supernatural horror film written, directed and edited by Daniel Myrick and Eduardo Sánchez (director), Eduardo Sánchez. It is a fictional story of three student filmmakers—Heather Donahue, Mic ...
''. Theaters warned patrons of its possible nauseating effects, cautioning pregnant women in particular. ''Blair Witch'' was filmed with a handheld
camcorder A camcorder is a self-contained portable electronic device with video and recording as its primary function. It is typically equipped with an articulating screen mounted on the left side, a belt to facilitate holding on the right side, hot-swa ...
, which was subjected to considerably more motion than the average movie camera, and lacks the stabilization mechanisms of
steadicam Steadicam is a brand of camera stabilizer mounts for Movie camera, motion picture cameras invented by Garrett Brown and introduced in 1975 by Cinema Products Corporation. It was designed to isolate the camera from the camera operator's movement ...
s. Home movies, often filmed with a cell phone camera, also tend to cause motion sickness in those who view them. The person holding the cell phone or other camera usually is unaware of this as the recording is being made since the sense of motion seems to match the motion seen through the camera's viewfinder. Those who view the film afterward only see the movement, which may be considerable, without any sense of motion. Using the zoom function seems to contribute to motion sickness as well since zooming is not a normal function of the eye. The use of a tripod or a camera or cell phone with
image stabilization Image stabilization (IS) is a family of techniques that reduce blurring associated with the motion of a camera or other imaging device during exposure. Generally, it compensates for pan and tilt (angular movement, equivalent to yaw and pit ...
while filming can reduce this effect.


Virtual reality

Motion sickness due to
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), educ ...
is very similar to simulation sickness and motion sickness due to films. In virtual reality the effect is made more acute as all external reference points are blocked from vision, the simulated images are
three-dimensional Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position of an element (i.e., point). This is the informal ...
and in some cases stereo sound that may also give a sense of motion. The NADS-1, a simulator located at the
National Advanced Driving Simulator The National Advanced Driving Simulator (NADS) at the University of Iowa College of Engineering is among the largest ground vehicle driving simulator in the world along with Toyota's driving simulator at Higashifuji Technical Center. National Hi ...
, is capable of accurately stimulating the vestibular system with a 360-degree horizontal field of view and 13 degrees of freedom motion base. Studies have shown that exposure to rotational motions in a virtual environment can cause significant increases in nausea and other symptoms of motion sickness. In a study conducted by the U.S. Army Research Institute for the Behavioral and Social Sciences in a report published May 1995 titled "Technical Report 1027 – Simulator Sickness in Virtual Environments", out of 742 pilot exposures from 11 military flight simulators, "approximately half of the pilots (334) reported post-effects of some kind: 250 (34%) reported that symptoms dissipated in less than one hour, 44 (6%) reported that symptoms lasted longer than four hours, and 28 (4%) reported that symptoms lasted longer than six hours. There were also four (1%) reported cases of spontaneously occurring flashbacks."


Motion that is seen and felt

When moving within a rotating reference frame such as in a centrifuge or environment where gravity is simulated with centrifugal force, the
coriolis effect In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...
causes a sense of motion in the vestibular system that does not match the motion that is seen.


Pathophysiology

There are various hypotheses that attempt to explain the cause of the condition.


Sensory conflict theory

Contemporary sensory conflict theory, referring to "a discontinuity between either visual, proprioceptive, and somatosensory input, or semicircular canal and otolith input", is probably the most thoroughly studied. According to this theory, when the brain presents the mind with two incongruous states of motion; the result is often nausea and other symptoms of disorientation known as motion sickness. Such conditions happen when the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
and the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
do not present a synchronized and unified representation of one's body and surroundings. According to sensory conflict theory, the cause of terrestrial motion sickness is the opposite of the cause of space motion sickness. The former occurs when one perceives visually that one's surroundings are relatively immobile while the
vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes ...
reports that one's body is in motion relative to its surroundings. The latter can occur when the visual system perceives that one's surroundings are in motion while the vestibular system reports relative bodily immobility (as in zero gravity.)


Neural mismatch

A variation of the sensory conflict theory is known as neural mismatch, implying a mismatch occurring between ongoing sensory experience and long-term memory rather than between components of the vestibular and visual systems. This theory emphasizes "the limbic system in the integration of sensory information and long-term memory, in the expression of the symptoms of motion sickness, and the impact of anti-motion-sickness drugs and stress hormones on limbic system function. The limbic system may be the neural mismatch center of the brain."


Defense against poisoning

It has also been proposed that motion sickness could function as a defense mechanism against
neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
s. The
area postrema The area postrema, a paired structure in the medulla oblongata of the brainstem, is a circumventricular organ having permeable capillaries and sensory neurons that enable its dual role to detect circulating chemical messengers in the blood and ...
in the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
is responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When feeling motion but not seeing it (for example, in the cabin of a ship with no portholes), the
inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. As a result of the incongruity, the brain concludes that the individual is
hallucinating A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...
and further concludes that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin. Treisman's indirect argument has recently been questioned via an alternative direct evolutionary hypothesis, as well as modified and extended via a direct poison hypothesis. The direct evolutionary hypothesis essentially argues that there are plausible means by which ancient real or apparent motion could have contributed directly to the evolution of aversive reactions, without the need for the co-opting of a poison response as posited by Treisman. Nevertheless, the direct poison hypothesis argues that there still are plausible ways in which the body's poison response system may have played a role in shaping the evolution of some of the signature symptoms that characterize motion sickness.


Nystagmus hypothesis

Yet another theory, known as the nystagmus hypothesis, has been proposed based on stimulation of the
vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right ...
resulting from the stretching or traction of extra-ocular muscles co-occurring with eye movements caused by vestibular stimulation. There are three critical aspects to the theory: first is the close linkage between activity in the vestibular system, i.e.,
semicircular canals The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals. Structure The ...
and
otolith organs An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
, and a change in tonus among various of each eye's six extra-ocular muscles. Thus, with the exception of voluntary eye movements, the vestibular and oculomotor systems are thoroughly linked. Second is the operation of Sherrington's Law describing reciprocal inhibition between agonist-antagonist muscle pairs, and by implication the stretching of
extraocular muscle The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...
that must occur whenever Sherrington's Law is made to fail, thereby causing an unrelaxed (contracted) muscle to be stretched. Finally, there is the critical presence of afferent output to the Vagus nerves as a direct result of eye muscle stretch or traction. Thus, tenth nerve stimulation resulting from eye muscle stretch is proposed as the cause of motion sickness. The theory explains why labyrinthine-defective individuals are immune to motion sickness; why symptoms emerge when undergoing various body-head accelerations; why combinations of voluntary and reflexive eye movements may challenge the proper operation of Sherrington's Law, and why many drugs that suppress eye movements also serve to suppress motion sickness symptoms. A recent theory argues that the main reason motion sickness occurs is due to an imbalance in vestibular outputs favoring the semicircular canals ( nauseogenic) vs.
otolith An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
organs (anti-nauseogenic). This theory attempts to integrate previous theories of motion sickness. For example, there are many sensory conflicts that are associated with motion sickness and many that are not, but those in which canal stimulation occurs in the absence of normal otolith function (e.g., in
free fall In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on i ...
) are the most provocative. The vestibular imbalance theory is also tied to the different roles of the otoliths and canals in autonomic arousal (otolith output more sympathetic).


Diagnosis

The diagnosis is based on symptoms. Other conditions that may present similarly include
vestibular disorders A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance ...
such as
benign paroxysmal positional vertigo Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. * T ...
and
vestibular migraine Vestibular migraine (VM) is vertigo with migraine, either as a symptom of migraine or as a related neurological disorder. A 2010 report from the University of British Columbia published in the journal ''Headache'' said that Migraine associated v ...
and
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
.


Treatment

Treatment may include behavioral measures or medications.


Behavioral measures

Behavioral measures to decrease motion sickness include holding the head still and lying on the back. Focusing on the horizon may also be useful. Listening to music, mindful breathing, being the driver, and not reading while moving are other techniques.
Habituation Habituation is a form of non-associative learning in which an innate (non-reinforced) response to a stimulus decreases after repeated or prolonged presentations of that stimulus. Responses that habituate include those that involve the intact org ...
is the most effective technique but requires significant time. It is often used by the military for pilots. These techniques must be carried out at least every week to retain effectiveness. A head-worn, computer device with a transparent display can be used to mitigate the effects of motion sickness (and
spatial disorientation Spatial disorientation results in a person being unable to determine their position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular ...
) if visual indicators of the wearer's head position are shown. Such a device functions by providing the wearer with digital reference lines in their field of vision that indicate the horizon's position relative to the user's head. This is accomplished by combining readings from
accelerometers An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...
and
gyroscopes A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotat ...
mounted in the device. This technology has been implemented in both standalone devices and
Google Glass Google Glass, or simply Glass, is a brand of smart glasses developed and sold by Google. It was developed by X (previously Google X), with the mission of producing an ubiquitous computer. Google Glass displays information to the wearer using ...
. One promising looking treatment is to wear LCD shutter glasses that create a stroboscopic vision of 4 Hz with a dwell of 10 milliseconds.


Medication

Three types of medications are useful:
antimuscarinics A muscarinic receptor antagonist (MRA) is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. The muscarinic receptor is a protein involved in the transmission of signals through certain parts of the ...
such as
scopolamine Scopolamine, also known as hyoscine, or Devil's Breath, is a natural or synthetically produced tropane alkaloid and anticholinergic drug that is formally used as a medication for treating motion sickness and postoperative nausea and vomiting ...
, H1 antihistamines such as
dimenhydrinate Dimenhydrinate, sold under the brand name Dramamine, among others, is an over-the-counter drug used to treat motion sickness and nausea. Dimenhydrinate is a theoclate salt composed of diphenhydramine, an ethanolamine derivative, and 8-chloroth ...
, and
amphetamines Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative compounds which are formed by replacing, or substituting, one or more hydrogen atoms in the amphetamine core structure with sub ...
such as
dexamphetamine Dextroamphetamine is a central nervous system (CNS) stimulant and an amphetamine enantiomer that is prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is also used as an athletic performance and c ...
. Benefits are greater if used before the onset of symptoms or shortly after symptoms begin. Side effects, however, may limit the use of medications. A number of medications used for nausea such as
ondansetron Ondansetron, sold under the brand name Zofran among others, is a medication used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, or surgery. It is also effective for treating gastroenteritis. It can be given by ...
and
metoclopramide Metoclopramide is a medication used for stomach and esophageal problems. It is commonly used to treat and prevent nausea and vomiting, to help with emptying of the stomach in people with delayed stomach emptying, and to help with gastroesoph ...
are not effective in motion sickness. Scopolamine is the most effective medication. Evidence is best for when it is used preventatively. It is available as a skin patch. Side effects may include blurry vision. Other effective first generation antihistamines include
doxylamine Doxylamine, sold under the brand name Unisom among others, is an antihistamine medication which is used in the treatment of insomnia and allergies. In combination with pyridoxine ( vitamin B6), it is also used to treat morning sickness in pregna ...
,
diphenhydramine Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremor in parkinsonism, and nausea. It is taken by mouth, injected into a vein ...
,
promethazine Promethazine is a first-generation antihistamine, antipsychotic, sedative, and antiemetic used to treat allergies, insomnia, and nausea. It may also help with some symptoms associated with the common cold and may also be used for sedating people ...
,
meclizine Meclizine, sold under the brand name Bonine, among others, is an antihistamine used to treat motion sickness and dizziness (vertigo). It is taken by mouth. Effects generally begin in an hour and last for up to a day. Common side effects incl ...
,
cyclizine Cyclizine, sold under a number of brand names, is a medication used to treat and prevent nausea, vomiting and dizziness due to motion sickness or vertigo. It may also be used for nausea after general anaesthesia or that which developed from opio ...
, and
cinnarizine Cinnarizine is an antihistamine and calcium channel blocker of the diphenylmethylpiperazine group. It is prescribed for nausea and vomiting due to motion sickness or other sources such as chemotherapy, vertigo, or Ménière's disease. Cinnariz ...
. In pregnancy meclizine, dimenhydrinate and doxylamine are generally felt to be safe. Side effects include sleepiness.
Second generation antihistamines H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping to relieve allergic reactions. Agents where the main therapeutic effect is mediated by negative modulation of h ...
have not been found to be useful. Dextroamphetamine may be used together with an antihistamine or an antimuscarinic. Concerns include their addictive potential. Those involved in high-risk activities, such as SCUBA diving, should evaluate the risks versus the benefits of medications. Promethazine combined with
ephedrine Ephedrine is a central nervous system (CNS) stimulant that is often used to prevent low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred treatment. It is of unclear benefit in ...
to counteract the sedation is known as "the Coast Guard cocktail".


Alternative medicine

Alternative treatments include
acupuncture Acupuncture is a form of alternative medicine and a component of traditional Chinese medicine (TCM) in which thin needles are inserted into the body. Acupuncture is a pseudoscience; the theories and practices of TCM are not based on scientifi ...
and
ginger Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices ...
, although their effectiveness against motion sickness is variable. Providing smells does not appear to have a significant effect on the rate of motion sickness.


Epidemiology

Roughly one-third of people are highly susceptible to motion sickness, and most of the rest get motion sick under extreme conditions. Around 80% of the general population is susceptible to cases of medium to high motion sickness. The rates of space motion sickness have been estimated at between forty and eighty percent of those who enter weightless orbit. Several factors influence susceptibility to motion sickness, including sleep deprivation and the cubic footage allocated to each space traveler. Studies indicate that women are more likely to be affected than men, and that the risk decreases with advancing age. There is some evidence that people with Asian ancestry may develop motion sickness more frequently than people of European ancestry, and there are situational and behavioral factors, such as whether a passenger has a view of the road ahead, and diet and eating behaviors.


See also

*
Mal de debarquement ''Mal de debarquement'' (or ''mal de débarquement'') syndrome (MdDS, or common name disembarkment syndrome) is a neurological condition usually occurring after a cruise, aircraft flight, or other sustained motion event. The phrase "mal de déba ...
- disembarkment syndrome, usually follows a cruise or other motion experience


References


External links

*
Motion Sickness
from
MedlinePlus MedlinePlus is an online information service produced by the United States National Library of Medicine. The service provides curated consumer health information in English and Spanish with select content in additional languages. The site brings t ...
{{DEFAULTSORT:Motion Sickness Neurological disorders Effects of external causes Vomiting Wikipedia medicine articles ready to translate