Scientists at the University of Utah have explained the mechanism behind the Tullio phenomenon - dizziness caused by loud or ordinary everyday sounds. According to the findings of the researchers, the syndrome is caused by false signals from the inner ear to the brain, resulting in uncontrolled eye movements. This is reported by Science Alert.
The phenomenon, which was first described by the Italian biologist Pietro Tullio in 1929, is known to arise from defects (usually holes) in the middle or inner ear. This condition is usually caused by a gap (dehiscence) in the bony wall of the semicircular canals, which are tiny tubes in the inner ear filled with fluid (endolymph). The canals are part of the vestibular apparatus, which is responsible for the correct perception of head movements and maintaining balance.
Pietro Tullio discovered this condition when he experimented with pigeons by drilling tiny holes in the tubes of the vestibular apparatus. However, it later turned out that in about two percent of people, the bone wall in the upper semicircular canal (VPK) has holes or is too thin at a rate of 0.67-0.38 millimeters. This condition is known as the superior semicircular canal dehiscence syndrome (SDVDK). At loud sounds, people with ADVPK feel dizziness, nausea, and they also develop nystagmus - oscillatory eye movements of high frequency. However, the exact mechanism linking dehiscence and dizziness remained unknown.
In the new work, scientists conducted computer simulations to simulate the movement of endolymph in the semicircular canals, and also studied the toad fish Opsanus tau, in which the vestibular apparatus is similar to that of humans. It turned out that dehiscence promotes the appearance of traveling mechanical waves in a liquid at a loud sound. These waves irritate the receptors in the inner ear, which in turn send false signals to the brain to turn the head. Nystagmus occurs as a reflex designed to visually stabilize, but in this case, when the head is actually motionless, it causes dizziness.