Many forms of dizziness come on all of a sudden, making us extremely uncomfortable for minutes, hours, or even days — and then leave. Sometimes these attacks recur, but other times they don't. For others, dizziness doesn't come in spurts, but instead is a constant: something that needs to be managed every minute of every day. It is rare, frankly, for any clear cause of this dizziness to be found, in which case someone may be diagnosed with chronic subjective dizziness. First, though, other potential causes should be ruled out.
Mal de Debarquement Syndrome
Mal de debarquement, which means "sickness of disembarkment," was originally described by sailors who, after having come ashore, still felt as if they were aboard a rocking ship. This sensation is actually still quite common even in healthy people who step off a boat or plane. Some people, though, develop a sense of rocking that goes on for months or even years. The sensation has been described as walking in an earthquake, with the ground undulating like a suspension bridge.
Symptoms can begin immediately after leaving a vehicle or can come on up to a couple of days afterwards. Interestingly, people with mal de debarquement feel better when they are back in motion. For example, someone who felt the symptoms after leaving a ship might feel better if they were to get back on the ocean again. The rocking sensation is often made worse by viewing something that is visually complex or in motion. Walking down grocery aisles, for example, tends to be very uncomfortable.
There are no neurological abnormalities detectable by special testing of people with mal de debarquement. Still, some people will order vestibular function testing to ensure no other problems are responsible for the symptoms.
Mal de debarquement is associated with other disorders linked to motion sickness, such as anxiety and migraine. Hormonal changes may increase the risk of this chronic rocking sensation.
The disorder usually goes away on its own. No well-studied treatment exists, but anecdotally there may be some benefit to clonazepam or selective serotonin reuptake inhibitors (SSRIs). Drugs that are usually given to help vertigo and nausea, such as meclizine, scopolamine and promethazine, are less helpful.
The vestibular system is normally responsible for controlling our balance and posture by relaying information about how our body is moving in space. Information about head position is translated into electronic signals that automatically control reflexes in our eyes and spine.
Signals to our brain about balance and position come from the inner ears at both sides of our head, traveling along the vestibular nerve to the brainstem. If one inner ear is damaged, it can result in an uncomfortable sense of vertigo, but the body can generally learn to compensate.
However, if both inner ears are damaged, profound instability can result. Symptoms include imbalance that is worse in the dark or on uneven surfaces, when other senses cannot compensate for the loss of vestibular input.
Such bilateral injury to the inner ears can result from medications like aminoglycosides, meningitis or encephalitis — or in severe Meniere disease. Two tenetic disorders also cause vestibular dysfunction. These are the deafness, neurosensory, autosomal recessive genes 9 and 11, both of which are uncommon.
A more common term for vestibular schwannoma is acoustic neuroma, but the latter term is misleading, since the abnormal growth affects the vestibular, not the auditory, part of the vestibulocochlear nerve — and more commonly is an abnormal growth of the Schwann cells that surround the nerve than the nerve itself. The tumor is rare, only arising in about 1 to 2 per 100,000 people every year, making them a very rare cause of dizziness.
A vestibular schwannoma can cause problems with walking, a feeling of the ground moving, and true rotational vertigo. Hearing loss or ringing in the ears (tinnitus) is also a common complaint in those with this tumor. The tumor grows very slowly and is very rarely life threatening.
Other tumors like a meningioma or lipoma near the vesitublocochlear nerve could mimic a vestibular schwannoma, but even so, the likelihood of a tumor in this location's being the cause of dizziness is very rare. One estimated the chances as being about one in 638. The use of magnetic resonance imaging to find these tumors may be an unnecessary expense, unless there is some other reason to be concerned.
Newman-Toker, DE, Symptoms and Signs of Neuro-otologic Disorders, Continuum Lifelong Learning Neurol 2012;18(5):1016–1040.