These formations help maintain balance and, depending on the movement of the head, transmit the sense of acceleration to the otolithic organs of the vestibular system (ie utricle and saccule). Being heavier than the matrix that contains them, in fact, the otoliths stimulate the sensory hair cells of the ear when a change of position or movement is initiated. In turn, the latter send signals to the brain, informing it of the body's variations in space.
When the inner ear is affected by trauma, infection or other conditions, the otoliths can detach, moving into the semicircular canals. The latter are incorrectly stimulated and become sensitive to head positions they would not normally pay attention to (note: the semicircular canals are responsible for perceiving the rotation of the head). The consequence of this phenomenon is benign paroxysmal positional vertigo (or otolith detachment vertigo).
Anatomy of the ear (in short)
To better understand how otoliths are involved in benign paroxysmal positional vertigo, it is necessary to remember some notions relating to the structure of the auditory organ.
The ear can be anatomically divided into three parts:
- EXTERNAL EAR: it is formed by the auricle, consisting of skin and cartilage, and by the external auditory canal. Thanks to its structure, the external ear conveys the sound waves towards the eardrum membrane, which provides the useful surface for the collection of sound and vibrates in response to the acoustic stimulus.
- MIDDLE EAR: it is a small cavity placed between the eardrum and the inner ear, to which it transmits the mechanical vibratory energy of sound through a system of three auditory ossicles (in sequence: hammer, anvil and stirrup).
- INTERNAL EAR: consists of a complex series of structures (vestibular apparatus and cochlea), contained deep in the bones of the skull. The function of the cochlea is acoustic and consists in transforming the sound waves transmitted by the middle ear into electrical impulses which, through the acoustic nerve, are sent to the brain. "utricle, and by three semicircular canals. This system is involved in the maintenance of posture and is responsible for the sense of balance: the sensory hair cells perceive the impulses concerning the movements of the head and the inertial effects produced by the force of gravity, then transmit this information to the central nervous system (CNS), via the vestibular nerve.
