By Dr. Giorgos Gavalas MD, Maud / Notol, ENT – Neuro-otologist, Director of the Department of Otology - Acoology – Neuro-otology, Athens Medical Center
The appearance of dizziness or vertigo during or at the end of a journey is a common phenomenon. So common that almost everyone can report an incident of someone in their environment with such sensitivity.
But is it the voyage itself by any means of transport that causes the dizziness or is it that just some means of transport that are responsible? Both may be true. There are people that feel dizzy only on a boat or only in the car and others who get dizzy on any means of transport.
To help those suffering, we need to know the mechanisms that trigger these symptoms.
There are two categories of causes:
The first case includes patients who are easily affected by motion sickness. By this we refer to a group of symptoms that occur after excessive irritation of a receptor of the labyrinth (semicircular canals, otolithic system) due to multiple accelerations in different directions (Coriolis effect) or simultaneous stimulation of two or more receptors whose information (nerve impulses) arriving at the vestibular nuclei are contradictory (e.g. linear acceleration in the horizontal axis in combination with a rotary acceleration in the vertical axis).
Symptoms that may occur in motion sickness are: paleness, yawning, nausea, a sense of weight in the stomach, tachycardia, cold sweat, dizziness, vertigo, malaise, vomiting.
We have to stress that patients who easily develop motion sickness are also suspected of having a latent fear because they believe that travel can be a dangerous condition for their health or even lead them to death. Strong phobia leads to anxiety and symptoms from the vegetative nervous system, including dizziness, as we mentioned earlier.
In these cases, patients avoid e.g. airplane or if they travel by airplane they get dizzy overwhelmed, while on the contrary if they travel by the train or by bus they do not get dizzy because they feel safer.
The latter case concerns patients suffering from temporary or permanent underfunctioning of the vestibular system (case of incomplete central compensation), without that being known or perceived in normal daily activities. However, because modern lifestyles for most people of productive age are associated with intense anxiety and fatigue and alternating rest and relaxation, this, coupled with barometric low atmospheres, creates hemodynamic changes in the spinal cord arterial system that can lead to functional deregulation of the vestibular nuclei.
In children, motion sickness is facilitated on the one hand by the incomplete development of the vestibule and, on the other hand, due to reduced adaptation and limited addiction. Thus, in the childhood, the vestibular system requires about 10 years until it is fully completed and coordinated right and left, but mainly with the supra-nuclear neurons (oculomotor, network formation, cerebellar, vegetative nervous system, vestibular cortex, vestibulospinal).
At the same time, the addiction / adaptation mechanism is delayed, as we have seen, with the exception of children from their early years are in constant motion, climbing on trees, playing all day (e.g. gypsy children, children training in dancing or acrobats etc.).
Due to the above, when children are exposed to obvious kinetic stimuli (e.g. accelerations, decelerations - road turns etc.), which for the developed (normal) vestibular system are not compounding, they constitute transcendental stimuli and lead to dizziness, nausea, sweating etc. Thus, when children sit in the back seat of the car while the car is running (vestibular stimulus) either because they see the interior of the car as immobile or because they read (visual irritation) that creates a dissonance of the neural motions coming to the vestibular nuclei and mobility is facilitated.
In adults, where the vestibular system has been fully developed, there are cases where a factor has caused unilateral damage, which has never been compensated. These individuals get transcendent stimuli to vestibular receptors (frequent steep road turns, storm at sea) and get easily dizzy, especially when there is no possibility of staring at an immobile target, while the person is in motion (such as when in a closed cabin of a ship without window).
Naturally, there may also be patients who report travel dizziness during the last months or years. Here, we have to think of some recent vestibular condition (recurrent hemodynamic vestibulopathy, incomplete compensation after vestibular neuropathy, early acoustic neuroma, etc.).
The conditions of a journey may additionally affect a person who is already suffering from a vestibular disorder (subthreshold - threshold) due to sudden changes in altitude (e.g. in the airplane), sudden changes in atmospheric pressure (e.g. small airplanes not equipped with a system for automatic adjustment of atmospheric pressure changes) and sudden fluctuations / alternations of ambient lighting (bright light, backlighting, constant alternating of visual field).
The intensity of the symptoms that will appear on the journey is related to the type of vestibular disorder the patient has, the type of the vehicle (ship, airplane, etc.) and the environmental conditions of the journey (many steep road turns, sea storm, etc.). However, the person’s activities that preceded the journey or those that are scheduled to take place after the end of the journey are of great importance. Thus, if e.g. a journey is professional (e.g. closing an agreement, speaking at a foreign university, etc.) it creates conditions of insecurity and uncertainty in case of failure. This leads to anxiety and phobia.
But the same can happen to a person who is preparing to make a long haul journey abroad. If intense anxiety and fatigue has preceded the journey, it is possible that during the latter an abrupt relaxation or satisfaction for the pleasant events that will occur after the trip, leads to the establishment of a non-pre-existing vestibular disorder or burden and a threshold sense of pre-existing vestibular dyspraxia.
Of course, we must not forget that whether dizziness / vertigo occurs or not on the journey, as well as its intensity, also depends on any existing suppression of the vestibular system of some people, either this suppression has been achieved professionally (e.g. sailors, acrobats etc.) by the method of addiction and adaptation, or it has been abnormal (e.g. bilateral reduction of labyrinth function due to the harmful effect of ototoxic medications). In this category of patients, dizziness / vertigo may be non-existent or may occur to a limited extent, even in adverse travel conditions.
Sudden changes in altitude and atmospheric pressure during the journey are particularly aggravating for people who, for various reasons (e.g. chronic rhinitis, nasal polyps, etc.) cannot equalize the pressure in the middle ear due to dysfunction of the Eustachian tube. Labyrinth irritation in this case is created if the pressure difference in the middle ear right / left is greater than 50cm H2O.
But let's look more closely at the causes of the motion sickness.
We have already mentioned that all labyrinth receptors (indirectly through the vestibular nuclei) have a connection to the vegetative nervous system. The effect on the vegetative nervous system is stronger in linear and less rotary acceleration, especially when a person has not previously been exposed to similar accelerations (e.g., one has never traveled on a cruise ship).
In travelling by car, the combination of the stimuli caused by the Coriolis phenomenon and thus the activation of the symptoms of dizziness, vertigo and the already known by the vegetative nervous system, are:
Braking - accelerating on road or steep uphill / downhill,
Driving in a turn or acceleration - deceleration on a straight road, while the individual performs various head movements.
Motion sickness can also occur when during various accelerations a simultaneous stimulus from the visual system (e.g. driving in a turn – vestibular stimulus – while at the same time the head is tilted to the side allowing the view of the surrounding space – optometric stimulus) is added.
Similar vestibular-optic dissonance arises when the individual reads in the car.
In travelling by ship (while there is a sea storm), multiple stimuli are caused to the vestibular receptors as the ship moves along the vertical, horizontal and transverse axes. Sharp movement of the head, as well as reading in a closed cabin without windows, are compounding.
Precautions: We prefer sitting in the middle of the ship and preferably lying down, with open eyes (with eye closure we reset the visual information and the brain has more apparent vestibular information to process). If the cabin has a hanging light, during a storm it does not swinging and this is helpful in fixing the gaze.
Treatment of patients with motion sickness
First of all, a diagnosis must be properly made. This requires a detailed history and a detailed ENT and neuro-otological examination (clinical and laboratory).
In suspicious cases, we should ask for the collaboration of specialized colleagues (psychologists / psychiatrists / neurologists) and order imaging or other laboratory tests, if necessary. The next step involves the treatment of motion sickness either in the background of the concealed condition (recurrent hemodynamic / migraine-associated vestibulopathy), or in the anxiety / phobia that triggers the symptoms, or in the existing difference in vestibular tone. Finally, with the application of specific pharmaceutical formulations and instructions, we are able to reduce the intensity of the motion sickness symptoms.
Disorders that periodically disrupt the function of the vestibular (e.g. migraine) are treated with medication.
Disorders that can trigger vestibular dyspraxia (e.g. nasal polyps - dysfunction of Eustachian tube) are also treated surgically or medicinally.
A necessary condition in diving activities is the ability to equalize pressure in the middle ear. In case of difficulty, we use (if there is no visible cause in nasal / nasopharynx endoscopy) decongestants before diving or we surface to a lesser depth and try again or postpone diving. It is advisable to avoid diving after intense and prolonged fatigue.
In the case of sonophobia avoiding intense environmental sounds or using special earplugs is recommended.
Photosensitivity is treated by avoiding illuminated spaces, dancing clubs and watching light changes in the environment. The use of sunglasses helps.
Patients with anxiety / phobia background should be examined by specialist psychologists / psychiatrists.
There are differences in vestibular tone, as determined by neuro-otological examination that may be helped by vestibular-specific exercise programs.
Instructions for reducing / avoiding the symptoms of motion sickness
In the car
On the plane
On the ship