It may present with bilaterally symmetrical symptoms, or asymmetrically, with one ear developing the condition after the other or not at all. The time frames for progress of the disease vary greatly and symptoms of hearing loss may be temporary or permanent.The vestibule and semi-circular canal are inner-ear components that comprise the vestibular system. Together they detect all directions of head movement. Two types of otolith organs are housed in the vestibule: the saccule, which points vertically and detects vertical acceleration, and the utricle, which points horizontally and detects horizontal acceleration. The otolith organs together sense the heads position with respect to gravity when the body is static; then the heads movement when it tilts; and pitch changes during any linear motion of the head. The saccule and utricle detect different motions, which information the brain receives and integrates to determine where the head is and how and where it is moving. The semi-circular canals are three bony structures filled with fluid. As with the vestibule, the primary purpose of the canals is to detect movement. Each canal is oriented at right angles to the others, enabling detection of movement in any plane. The posterior canal detects rolling motion, or motion about the X axis; the anterior canal detects pitch, or motion about the Y axis; the horizontal canal detects yaw motion, or motion about the Z axis. When a medication is toxic in the vestibule or the semi-circular canals, the patient senses loss of balance or orientation rather than losses in hearing.
It was found that in all operations involving this complication the preoperative sterilization was done with chlorhexidine. The ototoxicity of chlorhexidine was further confirmed by studies with animal models.Several other skin preparations have been shown to be potentially ototoxic in the animal model. These preparations include acetic acid, propylene glycol, quaternary ammonium compounds, and any alcohol-based preparations. However, it is difficult to extrapolate these results to human ototoxicity because the human round window membrane is much thicker than in any animal model. Other medicinal ototoxic drugs
At high doses, quinine, aspirin and other salicylates may also cause high-pitch tinnitus and hearing loss in both ears, typically reversible upon discontinuation of the drug. Erectile dysfunction medications may have the potential to cause hearing loss. However the link between erectile dysfunction medications and hearing loss remains uncertain.Previous noise exposure has not been found to potentiate ototoxic hearing loss. The American Academy of Audiology includes in their position statement that exposure to noise at the same time as aminoglycosides may exacerbate ototoxicity. The American Academy of Audiology recommends people being treated with ototoxic chemotherapeutics avoid excessive noise levels during treatment and for several months following cessation of treatment. Opiates in combination with excessive noise levels may also have an additive effect on ototoxic hearing loss. Ototoxicants in the environment and workplace
Ototoxic effects are also seen with quinine, pesticides, solvents, asphyxiants, and heavy metals such as mercury and lead. When combining multiple ototoxicants, the risk of hearing loss becomes greater.