Motion sickness
From Wikipedia, the free encyclopedia
| ICD-10 | T75.3 |
|---|---|
| ICD-9 | 994.6 |
Motion sickness or kinetosis is a condition in which the fluid in the semicircular canals of the inner ear becomes agitated. This causes disagreement between the apparent visually perceived lack of movement and the inner ear's sense of actual movement. Depending on the cause it can also be referred to as seasickness, carsickness, simulation sickness, airsickness, or space sickness.
Dizziness, fatigue, and nausea are the most common symptoms of motion sickness.[1] In fact, nausea in Greek means seasickness (naus means ship). If the motion causing nausea is not resolved, the sufferer will frequently vomit within twenty minutes. Unlike ordinary sickness, vomiting in motion sickness tends not to relieve the nausea.
About one third of people are susceptible to motion sickness in mild circumstances such as being on a boat in calm water, although nearly two thirds of people are susceptible in more severe conditions.[2] Approximately half of the astronauts in the U.S. space program have suffered from space sickness.[3]
Motion sickness on the sea can result from being in the berth of a rolling boat without being able to see the horizon. Sudden jerky movements tend to be worse for provoking motion sickness than slower smooth ones, because they disrupt the fluid balance more. A "corkscrewing" boat will upset more people than one that is gliding smoothly across the oncoming waves. Cars driving rapidly around winding roads or up and down a series of hills will upset more people than cars that are moving over smooth, straight roads. Looking down into one's lap to consult a map or attempting to read a book while a passenger in a car may also bring on motion sickness.
The most common theory for the cause of motion sickness is that it evolved as a defence mechanism against neurotoxins.[4] The area postrema in the brain 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 a ship with no windows), the inner ear transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. The area postrema will always believe the inner ear signal over the eyes, as the eyes are more susceptible to trickery (see optical illusion). As a result, the brain will come to the conclusion that one is hallucinating and further conclude that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin.
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[edit] Treatment
Many cures and preventatives for motion sickness have been proposed.
[edit] Natural
One common suggestion is to simply look out of the window of the moving vehicle and to gaze toward the horizon in the direction of travel. This helps to re-orient the inner sense of balance by providing a visual reaffirmation of motion.
In the night, or in a ship without windows, it is helpful to simply close one's eyes, or if possible, take a nap. This resolves the input conflict between the eyes and the inner ear. Napping also helps prevent psychogenic effects (i.e. the effect of sickness being magnified by thinking about it).
Fresh, cool air can also relieve motion sickness slightly, although it is likely this is related to avoiding foul odors which can worsen nausea. [5]
[edit] Chemical
Other treatments for motion sickness rely on medication. Over-the-counter and prescription medications are readily available, such as Dramamine. Ginger is a mild anti-emetic and sucking on crystalised ginger or sipping ginger tea can help to relieve the nausea. Interestingly, many pharmacological treatments which are effective for nausea and vomiting in some medical conditions may not be effective for motion sickness. For example, metoclopramide and prochlorperazine, although widely used, are ineffective for motion-sickness prevention and treatment. The sedating anti-histamine medications such as promethazine, work quite well for motion sickness, although they can cause significant drowsiness. Scopolamine is sometimes used in the form of transdermal patches.
[edit] External links
- Motion Sickness from MedlinePlus
- Motion Sickness Prevention and Treatment, from a Medical College of Wisconsin website
- Visually induced motion sickness research
- Travel Tips at the MacgyverProject.comAir Travel Tip - How To Avoid And Deal With Airsickness
