Motion sickness will present as the following signs and symtoms :
Motion sickness generally does not require an intensive work up. A detailed history will reveal travelling or the use of a stimulant .
To rule out any brain disease, a sensory, motor and cerebellar examination may be performed .
A blood test may be conducted to rule out any poisons or toxins.
Treatment of motion sickness may be divided into three types:
Visually Induced Motion Sickness (VIMS) may be relieved by withdrawing the stimulant causing the sickness such as a video, computer game or simulator, etc . Motion sickness due to motion felt but not visually seen may be relieved by fixing the gaze on a moving object, bringing the two opposing signals in sync with each other .
Some drugs such as Scopolamine, administered via transdermal patches, may be used. Other drugs like Dimenhydrinate and Meclizine may also be effective.
A common method of preventing and treating motion sickness, particularly used by people travelling long distances, is the use of an elastic band fitted with a small hard object. This band is worn on both arms with the hard object facing inwards . This puts pressure on a fixed point and based on the principles of acupressure, acts on relieving motion sickness. An eyewear device may be used to block out external movements during road travel . A highly computerised digital device may be worn during travels that creates fixed reference points for the eyes with relation to the user's position.
Motion sickness is not actually a disease, but rather it is a condition. This condition may begin from just a feeling of unease and cold sweats to nausea and dizziness to finally vomiting.
Vomiting may occur just once, or there may be several episodes till the cause is removed .
For example, if a person is reading a book (fixed visual stimuli) while travelling by car (motion picked by vestibular system) the brain will receive contradictory inputs. This will confuse the brain about whether the body is actually moving or not. As a result, the vomiting centres of the brain will become active and the person will develop nausea, dizziness and finally vomiting.
This may be resolved by simple measures such as looking out the window (the passing view will be in sync with the input of the vestibular system) and the brain will not be confused any more, so no motion sickness will occur.
The Area Postrema
The area postrema is a region of the brain that functions to detect toxins and discordance between visual and balance stimuli. If any toxic or poisonous substance is detected in the blood, the area postrema immediately induces vomiting, which in this case is a physiological defence mechanism that acts to remove the offensive substance from the body.
The theory about how motion sickness occurs is: In the case of mixed sensations received by the brain, as occurring in motion sickness, such as motion that is only felt by the vestibular system present in the inner ear and not seen by the eyes, or the motion that is visually perceived but not detected by the vestibular system, a discordance occurs.
Contradictory sensations confuse the brain. In this case, the brain comes to the conclusion that one of the sensory systems is not functioning properly and this impaired functioning is due to toxins. As a result, the area postrema induces vomiting, again as a protective mechanism, but this time against the brain's 'assumed' presence of toxins.
Another theory regarding how motion sickness occurs is the Nystagmus Hypothesis.
This theory has three main aspects. The first aspect highlights the close linkage between the oculomotor and vestibular systems. Stimuli perceived by the inner ear's otolith organs and the semi circular canals relay commands to the eyes' ocular muscles causing their movement. This involuntary movement indicates the close relation between the vestibular system and the oculomotor system.
The second aspect of the Nystagmus Hypothesis is regarding the Sherrington's Law. This law deals with the reciprocal inhibition that occurs every time during motion between muscle pairs of agonist/antagonist muscles. In the case of the Nystagmus Hypothesis, this law is taken into consideration with regards to extraocular muscles.
The third and last aspect is about Vagal stimulation. Note the sequence followed by the first two aspects showing first vestibular sensations and stimuli, then the involvement of ocular muscles. Next in sequence should be the contraction and stretching of the ocular muscles leading to vagal stimulation.
Thus, this hypothesis proposes that the stimulation of the vagus nerve is the causative agent of motion sickness.
Summing up, whatever the exact cause of motion sickness may be, one thing is crystal clear; kinetosis occurs due to a discordance between the sensations perceived by the visual system and those perceived by the inner ear's vestibular system.
There is no known evidence of a predisposition of motion sickness in any race .
Children are generally more susceptible to motion sickness, however, it may occur in people of all ages.
Women are generally more sensitive and thus may be slightly more susceptible to motion sickness than men. Studies show that pregnant women are at a higher risk of suffering from motion sickness.
Motion sickness, as explained above, is due to a mismatch in the input received from various sensory systems . On the basis of the type of sensory system in effect, motion sickness can be classified into three broad categories:
Visually Induced Motion Sickness (VIMS)
As the name indicates, this is the type where the eyes see movement but the inner ear does not feel it at all, or picks up very little of it.
Watching videos showing increased level of movements, particularly if the audience is highly sensitive, may lead to motion sickness. In such cases, the person watching the video is usually seated and thus not moving, so the vestibular system does not pick up any motion, but the eyes detect motion so a discordance occurs.
This results due to movement detected by the visual system by a stimulant like computer or video games or simulators. The rapidly moving pictures and figures and changing colours on the screen may result in motion sickness.
Motion Detected by Vestibular System
This type of motion sickness occurs when movement is detected by the vestibular system only, i.e movement is felt, but not seen by the eyes. It is the most common type of kinetosis. It can be subdivided on the basis of type and medium of movement.
This is an extremely common manifestation occurring during road travel. In this case, the vestibular system feels that that the body is moving but the interior of the vehicle, i.e the environment as seen by the person, is not moving. This causes a discordance between the visual input and the vestibular input, leading to motion sickness. So, a person when trying to read a book while riding a car feels nauseas and dizzy because the visual stimulus (book) is fixed while the vestibular system feels movement (of the car). This can be lessened by looking out the window to the things passing by.
This is also a very common form of motion sickness. Although essentially the same as car sickness, seasickness is brought upon by the rocking movement of the boat. The person feels to be in motion while the interior of the boat, or the deck, appears to be stationary.
This type occurs during flights and although, is also essentially based on the same principle as the first two types, it may be slightly more severe than the other two forms. This is because air turbulence may cause more sharply felt movements. The small windows, the view through which is often obscured by clouds, may prevent the person from fixing his gaze on the moving exterior, and so the person becomes unable to do anything to reverse the discordance and vomiting occurs.
This usually occurs either in space crafts that are rapidly spinning to create an artificial gravity effect or in amusement park rides. In both cases, the spinning motion causes the fluid in the semicircular canals to spin as well, so when the spinning abruptly stops, the fluid still remains in spin motion, thus causing dizziness and vomiting.
Motion felt by both Visual and Vestibular Systems but does not correspond
In this category, motion sickness occurs when even though both sensory pathways, as well as other sensory pathways like proprioception, skin sensations, etc relay the occurrence of motion, but the type of degree of motion may not be equal, or in sync with each other.
Motion sickness may be prevented by:
Motion sickness, also known as kinetosis, is a condition in which there is a discordance in the sensory perception of movement in our body. As we know, our brain receives signals from various body parts in relation to movement and then puts them together to determine how exactly the body is moving and where. If the sensations received by the brain happen to be contradictory, the brain becomes confused and motion sickness occurs.
Motion sickness can occur during car rides, airplane flights and most commonly, during travels by sea. Since the common factor in the above mentioned things is travelling, motion sickness is also commonly called travel sickness.
The rocking motion of a boat, the turbulence experienced during air travel and the speed bumps felt while travelling by car may all provoke the feeling of nausea and dizziness. It can also be felt during train journeys and even the rides in an amusement park.
Since the centre of balance and equilibrium is affected, motion sickness is a type of spatial disorientation which is quick to occur, but also resolves either spontaneously or if the factor that caused the sickness attack is withdrawn.
Motion sickness is a discordance between various sensory input of the body. It is usually the condition you feel when the motion felt by your inner ear is not in sync with what you see with your eyes.
The most common cause of motion sickness is travelling. It may be due to road, air or sea travel. In some rare cases, it may be not be due to travelling but by watching high resolution videos or computer games.
Signs and Symptoms
It can be be treated by a change in activity, taking appropriate medication and the use of certain devices.
Motion sickness may be prevented by the use of electronic devices during travels, taking medication before long journeys and by a change in the activity.