Motion sickness general, but no perfect cure yet

Press, 10 August 1985, Page 13

Motion sickness general, but no perfect cure yet

DOCTOR’S ADVICE

From the Collge of Genera] Practitioners Most people have been carsick. If you have never experienced motion sickness, you have either never travelled far, or have abnormal ears. Motion sickness has a long history. The motion of ships is so often associated with a feeling of sicness, that the words nautical and nausea come from the same Greek word for a ship. It has plagued man ever since he gave up walking everywhere and used animals and devices for transport. Julius Caesar and Lord Nelson were sufferers; even Lawrence of Arabia was “seasick” on that ship of the desert, the camel. So much for the myth that those who were seasick lacked moral fibre. Dr Wendell Lovan, writing in the “American Family Physician,” notes that in addition to the nausea and vomiting, the sufferer may experience drowsiness, apathy, headache, dizziness, dry mouth (or conversely excess salivation), pallor, sighing, swallowing and yawning. The labyrinth, the balance organ in the inner ear, is the problem piece. It must function normally for motion sickness to occur, and we have known for more than a 100 years that a high proportion of the totally deaf do not get seasick, nor do those with infectious or other damage to their balance organ. But 90 per cent of the rest of us do when there is enough stimulus, and for long enough. Women are more susceptible than men, and girls more than boys. Infants under two years of age are immune, which is just as well when you think of the rocking they experienced two years before in the womb; but otherwise the young are more prone than the old, with the peak from age two to 12. Motion sickness is uncommon after the age of 50. The air temperature has

no effect, nor does the time of day, nor the time elapsed since eating. Weightlessness is a problem for those who venture up in spacecraft. Try a rapid descent in a lift, or a loop-the-loop roller coaster if you want to approach the same feeling. During tl.e four .. mission of the space shuttle programme half the astronauts were sick. It is not always necessary to experience the actual stimulation of the balance organ to be motion sick — for some, even the sight of the sea, or even a picture of a boat, is enough. Moving the view while the person stays still may do it. Fortunately, adaptation generally occurs — people adapt to movement if they are exposed to it for long enough. But then they may be sick when they return to a normal environment. For some, dry land seems to move for days after the end of a sea voyage. For the last 25 years, medical investigators have accepted what is called the conflict theory of motion sickness. The images are out of step — the eyes cannot believe what the ears tell them. In other words, the offending motion, involving changing velocity (acceleration or deceleration), provides signals that provoke conflicting information from visual and balance systems. “Here I am in the back seat of the car, reading my book. My eyes tell me the page are still, vpt my balance system tells me my body is moving. This does not match my memory of what should happen. I feel sick. If I look out of the window, the scene is moving, just as my body thought. There, I feel better.”

The really effective way to avoid motion sickness is to go on foot. A difficult

proposition for most of us, so we have .to look for alternative, less effective methods. Adaptation works well for most people. We adapt to our own mode of transport and have no symptoms. Once sick, little can be done. Lying down, or exposure to cool air may help, but generally we have to stop the motion. Certainly medicines by mouth are of no value at this stage. A number of medications block the various brain pathways involved in balance, and are useful for prevention of motion sickness. Most of these medicines have side effects, such as sleepiness, blurred vision, dry mouth and so on, especially if taken by mouth. Recently one such medication, Scopolamine, has been produced as a stick-on patch, which allows a small amount of the active ingredient to be absorbed through the skin for three days: enough to prevent the motion sickness, but not enough to cause side effects, as least for most people. But not all. The perfect medicine for motion sickness has not been found yet.