Motion Sickness

Motion sickness – What is motion sickness?

Motion sickness, also termed kinetosis, is a generalized term that is used to describe an unpleasant set of symptoms like nausea, vomiting and dizziness that occurs when a person is travelling.

As the travel course progresses the symptoms may improve while the body adapts to the conditions leading to the sickness.

Motion sickness may occur while travelling on the road, by air and commonly occurs while travelling on water (sea sickness). Some individuals fail to experience a lessening of their symptoms until they stop travelling. 1-5

What causes motion sickness?

To understand the cause of motion sickness the vestibular system deep inside the ears needs to be understood. This vestibular apparatus is a set of tube like canals with a special fluid called the endolymph.

Normally movement of the head leads to movement of this fluid and stimulation of the tiny hair cells within the tubes called the membranous labyrinth. These in turn tell the brain about the position of the body and regulate the balance and posture. The eyes too send in signals to the brain regarding the position of the body.

Motion sickness occurs when there is a conflict between what the eyes see and what the inner ear detects. The brain receives a jumble of information from these inputs. This leads to dizziness, nausea and sometimes vomiting.

Motion sickness is brought about by unusual movements during travelling. This could be repeated acceleration, deceleration, going over bumps, or round in a circle.

Symptoms other than the common ones include sweating, drooling saliva, headaches, going pale etc.

Travel may not be the only reason for motion sickness. Anxiety, strong smells or even trying to read while in a moving vehicle may trigger motion sickness.

Other varieties of motion sickness include space sickness, virtual reality sickness, ski sickness, and even camel and elephant sickness.

Who is at risk of motion sickness?

Although almost everyone at some point in life may get motion sickness, some are particularly more vulnerable. Sea sickness – a form of motion sickness that affects sea farers may affect almost anyone especially if the sea is rough.

Among the rest around 3 in 10 individuals may have symptoms of motion sickness regularly on journeys by road, sea or air.

In addition women are more likely to get motion sickness than men. This is especially so if they are pregnant or are menstruating. It is speculated that hormonal changes may be responsible for this propensity.

Migraine suferrers are also more likely to suffer from motion sickness. Children between ages 2 and 12 are at a greater risk of motion sickness. Most of them grow out of the tendency as they become teenagers.

How can motion sickness be treated?

Mild symptoms of motion sickness usually can be treated by self-care methods like closing the eyes – thereby cutting down information inputs from the eyes and by distractions like listening to music. Those with more serious forms of motion sickness need therapy with medications such as Hyoscine.

Prevention of motion sickness

For prevention vulnerable individuals may ask to sit in the front of a car, over the wing of a plane, on deck in the middle of a boat. This keeps the motion to its minimum.

These individuals are advised to keep their eyes closed or sleep, avoid reading or watching a film or video, avoid looking at moving objects such as sea waves or other moving vehicles but stare at a fixed spot over the horizon and avoid heavy meals, spicy or greasy foods or alcohol before or during travel.

Causes of motion sickness

The vestibular apparatus & maintenance of balance

The basis for motion sickness lies deep within the ear in the vestibular apparatus. The vestibular system is a complex neural system that provides balance and posture related information to the brain.

The system has tiny organs, tubes, fluids and a complex system of nerve channels to the brain. This system helps the brain know the position of the body, its motion relative to the environment and give out signals that help in maintaining a posture without falling. 1-4

The vestibular system consists of the vestibular apparatus that has three strategically placed semi-circular tubes connected with each other. These tubes contain tiny hair like cells on their inner linings. The tubes are further filled with a fluid called endolymph.

As the head moves the fluid moves and stimulats the hair cells. These hair cells are connected to a tiny but extremely sensitive network of nerves. These carry the signals about the motion to the brain.

The vestibular apparatus senses linear acceleration that may be gravitational and inertial (vertical and horizontal movements respectively). The brain has nerve projections into the spinal cord, and back of the brain (cerebellum) that adjusts the body posture in relation to the perceived position.

Apart from information from the vestibular apparatus the eyes also send in information regarding the position of the body and its relative motion by visual cues. The whole circuit of nerves is extremely complex and operates largely without conscious thought.

Pathophysiology of motion sickness

The most accepted theory of causation of motion sickness is that the inputs from the vestibular apparatus and the eyes get jumbled and confuse the brain.

The brain is constantly updated about the body position and movement by the eyes and vestibular system. If for example a person is travelling by car the vestibular apparatus due to lack of movement tells the brain that the body is relatively still, however, the eyes tell the brain that the car is moving.

Vice versa if a person is attempting to read something while moving in a car, the eyes tell the brain that the body is stationary and the bumpy ride reminds the brain via the vestibular apparatus that the body is moving. This mismatch of information can lead to the symptoms of motion sickness, such as nausea and vomiting.

Causes of motion sickness

Travel related causes of motion sickness include travel by:-

  • Car or road vehicle

  • Travel by air

  • Travel by ships or boat

  • Travel by train

  • Travel on a space ship

  • Travel on an animal like elephant or camel

  • Movement on fairground rides or swings

Causes of motion sickness when not travelling

Motion sickness may also occur when a person is not travelling. For example, motion sickness may affect people after they have played a fast-paced computer racing games. Watching a film recorded on a shaky camera or a virtual ride or stimulated game may also cause motion sickness in the susceptible individuals.

Symptoms of motion sickness

Motion sickness, or kinetosis, affects some individuals when they are subjected to motion or movement. This can occur when they are travelling by air, road or on water.

The most common cause of motion sickness is a mismatch between the visual cues of motion and sensations of motion and position of the body by the vestibular apparatus deep within the ear.

As the brain struggles to make sense of the conflicting signals from these organs the symptoms of motion sickness are seen.

Symptoms of motion sickness include discomfort in the upper abdomen, nausea and so forth. 1-4

Upper abdomen discomfort

The symptom starts with a discomfort in the upper abdomen. This is usually a queasy feeling that may be unpleasant or may feel like fluttering within the abdomen. This is called stomach awareness.

This may not be unpleasant and if the provocative motion continues the other unpleasant symptoms begin.

Feelings of nausea

The mismatch between visual signals and those from the inner ear lead to stimulation of the vomiting center of the brain. This leads to feeling nauseous. This is usually preceded by a feeling of warmth and a desire to seek cool air

Other early symptoms

Other early symptoms include:-

  • There may be early belching and flatulence as markers of onset of motion sickness.

  • Dizziness

  • Feelings of being unwell

  • Getting pale. Pallor is seen common in the face and is accompanied with nausea.

Cold sweats

As the condition progresses the symptoms worse. This leads to a cold sweat. Patient is usually covered with a thin layer of sweat all over his or her body. Sweating bouts precede each bout of vomiting and severe nausea.

Other more progressive symptoms of motion sickness

Other symptoms that occur as the condition progresses include:-

  • Feelings of weakness, fatigue and tiredness

  • There may be mood swings, irritability lack of initiative and apathy

  • Increased production of saliva and drooling

Vomiting in severe cases of motion sickness

Vomiting may occur in severe cases. Vomiting may relieve the symptoms temporarily. However, the motion sickness symptoms are not alleviated even after vomiting and retching may continue if the stomach is empty of contents.

The cycles of nausea up to vomiting with waxing and waning symptoms may continue till the travel is completed.

More severe symptoms

More severe symptoms include:-

  • In more severe cases there may be a rapid, shallow breathing. Affliction of the respiratory system includes sighing and yawning that precede vomiting. Those who are anxious may also hyperventilate.

  • There may be headaches. Those with migraine headaches may experience an attack of migraine while they experience motion sickness

  • Drowsiness and sleepiness is common

  • There may be increased excretion of anterior and posterior pituitary hormones during motion sickness. This may lead to elevation of the antidiuretic hormone (ADH) leading to reduced urination.

Mal de debarquement syndrome symptoms

Mal de debarquement syndrome (illness of disembarkation) is a more severe and rare form of motion sickness. The condition is triggered by travel usually by sea or by air.

The symptoms last long after the journey has finished. Those with this symptom after they have finished travel feel as though they are rocking or bobbing or moving even when they are not.

Many people normally feel this after a particularly long sea or air journey. However, those with this syndrome may experience these symptoms for months or even years after completion of their travel.

Treatment of motion sickness

Motion sickness is a relatively common occurrence and its severity varies from mild to severe requiring medical attention. In most individuals the condition is diagnosed clinically by a history of feeling ill, nauseous or vomiting while travelling via road, air or on water.

Diagnosis is important when the dizziness and sickness continues beyond the travel duration. In some cases this could be due to viral infections or the inner ear called labyrinthitis or other diseases of the inner ear. This needs to be diagnosed and treated as early as possible.

Treatment of motion sickness includes two broad approaches – self-care and preventive measures and medication therapy. 1-5

Self-care and home remedies for motion sickness

  • By avoidance of head and body movement as much as possible. This can be achieved by sitting in the seat or cabin in the middle of a boat or plane that experiences least movement.

  • Using a headrest or a pillow and lying down or reclining also helps to keep the head still.

  • Vision should not be allowed to wander over waves, moving objects like other vehicles etc. Eyes could be kept closed or could be fixed over a point in the horizon.

  • Patient is advised not to read, play games or watch films while in motion. This can worsen symptoms

  • Open windows and letting in fresh air helps. Those on sea may use the top deck and those in a car may choose to sit by open windows. Excessive heat or cold exposure however should be avoided.

  • Relaxing and distraction techniques. Anxiety about oncoming motion sickness may trigger the symptoms. Patients are advised to relax with music, while focusing on breathing or counting backwards etc. Staying calm prevents onset of the symptoms.

  • While travelling with a child with motion sickness it helps to keep the child distracted with singing, music etc. The child should be discouraged from reading or playing video games. The driver should be asked to take bends gently, to not accelerate and slow down repeatedly.

  • People who are vulnerable should avoid heavy, spicy or greasy foods and alcohol before or during travel. Hydration by drinking cool clear liquids should be maintained.

  • Other alternative home remedies include ginger. This may prevent symptoms of motion sickness. Ginger biscuits and ginger tea may help reduce the nausea.

  • Alternative therapies include acupressure. The utility of these in motion are not proven. This can be applied using a wristband or by pressing a finger against the middle of the inner wrist about three finger widths above the crease where the wrist joins the hand. This presses on certain nerves.

Medication therapy

There are numerous medications that may be used to treat motion sickness. These are usually effective only if taken before the onset of symptoms. This is because motion sickness delays digestion and the body is unable to absorb the medication once the symptoms begin if the pill is taken too late.

Hyoscine

This is also called scopolamine. It is the most common medication used to treat motion sickness. This drug works by blocking some of the nerve signals from the vestibular apparatus to the brain.

The drug also leads to drowsiness or sleepiness as a side effect. Sleep during travel reduces the risk of onset of motion sickness symptoms.

This is available over the counter from pharmacists. The drug needs to be taken at least 30 minutes to an hour before commencement of the journey.

Hyoscine is also available as patches that can be applied over the skin on the back of the ears. For a long sea journey hyoscine patches can be applied to the site every three days.

Side effects include sleepiness, blurring of vision, dry mouth, constipation etc. Those taking the medication are advised not to drive or operate heavy machinery.

Hyoscine should be used with caution in children and in elderly (may lead to confusion), in epileptics, those with liver, heart or kidney disease, and those with digestive system problems like gastroesophageal reflux syndrome etc.

Antihistaminics

Antihistaminics are other alternative medications. They are used to treat the symptoms of allergies and also in nausea. They have fewer side effects but may be less effective than hyoscine.

They include Cyclizine, Promethazine, Cinnarizine etc. These are taken two hours before journey and need to be repeated every 8 hours for long journeys.