Motion sickness refers to a general term for conditions such as car sickness, seasickness, airsickness, and illnesses caused by various forms of swaying, bumping, spinning, or accelerated motion.

bubble_chart Pathogenesis

The pathogenesis of motion sickness is not yet fully understood and is primarily related to effects on vestibular function. The maculae of the utricle and saccule in the membranous labyrinth of the inner ear vestibular apparatus detect linear movements in vertical and horizontal directions, while the hair cells of the three semicircular canals sense rotational movements. When the maculae or hair cells are stimulated by abnormal motion beyond a certain threshold, the resulting neural impulses are transmitted sequentially via the vestibular nerve to the vestibular nuclei, then to the cerebellum and hypothalamus, leading to a series of clinical manifestations dominated by vertigo. Stimulation of the vestibular system affects the reticular formation, causing a drop in blood pressure and vomiting. The vestibular nuclei send fibers via the medial longitudinal fasciculus to the ocular motor nuclei, inducing eye tremor. Neural impulses reaching the cerebellum and hypothalamus alter overall muscle tone. Motion sickness may also have a visual component; for instance, staring at rapidly moving or rotating objects can trigger the condition. Cerebellar stimulation may represent another mechanism. Additionally, factors such as high temperature, high humidity, poor ventilation, noise, strong odors, emotional stress, sleep deprivation, excessive fatigue, hunger or overeating, physical weakness, and inner ear diseases can all predispose individuals to motion sickness.

This disease often occurs within minutes to hours after riding in a car, sailing, flying, or other forms of motion. Initially, there is discomfort in the upper abdomen, followed by nausea, pale complexion, cold sweating, and soon after, vertigo, mental depression, increased saliva secretion, and vomiting. There may also be a drop in blood pressure, deep and slow breathing, and eye tremor. Severe vomiting can lead to dehydration and electrolyte imbalance. Symptoms usually disappear or lessen within tens of minutes to a few hours after the motion stops or slows down. In some cases, they may persist for several days before gradually subsiding, accompanied by listlessness and weakness in the limbs. Symptoms may reappear upon repeated motion or accelerated movement. However, after multiple episodes, symptoms may lessen or even cease to occur.

bubble_chart Diagnosis

This disease often occurs within minutes to hours after riding in a car, sailing, flying, or other forms of motion. Initially, there is discomfort in the upper abdomen, followed by nausea, pale complexion, cold sweating, and soon after, vertigo, depression, increased saliva secretion, and vomiting. There may also be a drop in blood pressure, deep and slow breathing, and eye tremor. Severe vomiting can lead to dehydration and electrolyte imbalance. Symptoms generally subside or lessen within tens of minutes to several hours after the motion stops or slows down. In some cases, recovery may take several days, accompanied by listlessness and weakness in the limbs. Symptoms may reappear upon repeated motion or accelerated movement. However, after multiple episodes, symptoms may lessen or even cease to occur.

During an episode, the patient should lie on their back with eyes closed. When sitting, the head should be firmly supported against a fixed chair back or object to avoid significant swaying. The environment should be quiet and well-ventilated. Additionally, antihistamines and anticholinergic drugs can be selected, commonly including the following:

1. Scopolamine hydrobromide, 0.3–0.6 mg, three times daily. Side effects include dry mouth, drowsiness, and blurred vision. Contraindicated in glaucoma.
2. Dimenhydrinate (Theohydramin), 25–50 mg orally each time, three times daily. Side effects include drowsiness.
3. Betahistine hydrochloride, 4–8 mg orally each time, three times daily.
4. Meclizine hydrochloride, 25 mg orally each time, three times daily. Side effects include drowsiness, blurred vision, dry mouth, and fatigue.
5. Other medications such as metoclopramide, chlorpromazine, and diazepam (Valium) may also be used as antiemetics or sedatives as appropriate.

bubble_chart Prevention

Exercise training can be used to provide a certain amount of stimulation involving directional information conflicts (such as rotational or swaying movements) to enhance adaptability and reduce sensitivity. Alternatively, 0.3–0.6 mg of scopolamine can be taken half an hour before exposure to the motion environment. After the onset of symptoms, removing oneself from the causative environment usually leads to their disappearance. Fixing one's vision on a stable, motionless environment or a specific target can also help prevent the condition.

This disease should be differentiated from conditions such as Meniere's disease, vestibular neuritis, and vertebrobasilar insufficiency.