Scientists have identified a new type of vertigo with no known cause, that may respond to treatments.
With vertigo, people have episodes of dizziness that can last from minutes to days. Vertigo can be caused by serious conditions, such as tumours, or conditions that are fairly benign, such the inner ear disorder Meniere's disease. However, for some people, no cause can be found.
In a study published in the journal Neurology, scientists have identified a new type of vertigo where treatment may be effective.
"These conditions can be difficult to diagnose and quite debilitating for people, so it's exciting to be able to discover this new diagnosis of a condition that may respond to treatment," said Ji-Soo Kim, of Seoul National University in South Korea.
Then the patient opens his or her eyes and a video recording is taken of eye movements. The neurologists discovered that after the test people with this new condition had eye movements called nystagmus that lasted longer than for other people.
The new condition is called recurrent spontaneous vertigo with head-shaking nystagmus.
Among 338 people with vertigo with no known cause, 35 had this new condition and were included in the study. The participants had attacks of vertigo ranging from two or three times a week to once a year.
The test measured the time constant, or the time that represents the speed with which the reflexive eye movements can respond to change.
For those with the new condition, the time constant during the primary phase of the nystagmus was 12 seconds, while it was six seconds for those with Meniere's disease and five seconds for those with vestibular neuritis and vestibular migraine.
The neurologists also found that people with the new type of vertigo were more likely to have severe motion sickness than those with other types of vertigo.
A total of 20 of the 35 people with the new type of vertigo who had frequent attacks and severe symptoms were given preventive medication. About one-third of those had partial or complete recovery with the new medication.
During the long-term follow-up of an average of 12 years after the first symptoms for 31 participants, five reported no more attacks, 14 said their symptoms had improved and only one said symptoms had gotten worse.
Kim said that people with this condition may have a hyperactive mechanism in their vestibular system that helps the brain respond to movement of the body and in the environment.
"It's possible that the vertigo occurs when this unstable mechanism is disrupted by factors either within the person's body or in their environment," Kim said.
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