The vestibular system of the inner ear provides input to the brain indicating head and body movement and orientation. The semicircular canals and the otoliths comprise the vestibular system. The semicircular canals detect rotational movement while the otoliths sense linear movement. Vestibular dysfunction--abnormality or deficiency in the normal function of the vestibular system--leads to balance disturbances and vertigo, a false sense of spinning. Nausea and vomiting typically accompany episodes of vertigo.
Ménière's Disease
Perilymph fluid surrounds the inner ear structures, preventing them from impacting the surrounding bone during sudden head movements. Endolymph fills the inner ear structures. The chemical composition of perilymph and endolymph differs. These two inner ear fluids normally do not mix. Ménière's disease is a vestibular disorder caused by abnormalities in the chemical composition of the endolymph and perilymph, perhaps due to mixing of the fluids. According to the National Institute on Deafness and Other Communication Disorders, symptoms of Ménière's disease include sudden attacks of vertigo, nausea and vomiting, hearing loss and tinnitus--phantom noise in the ear. Hearing loss and tinnitus are typically limited to one ear. Vertigo attacks usually last several hours before resolving. Tinnitus and hearing loss fluctuate, but typically persist at a low level between attacks. Slowly progressive hearing loss commonly occurs. Medications and dietary changes can help control the symptoms of Ménière's disease.
Labyrinthitis and Vestibular Neuritis
Labyrinthitis and vestibular neuritis result from inflammation of the inner ear, usually due to viral infection. Labyrinthitis refers to inflammation of the inner ear structures. Vestibular neuritis is inflammation of the vestibular nerve, which carries balance and positional information from the inner ear to the brain. The Vestibular Disorders Association explains that vestibular neuritis causes vertigo with associated nausea and vomiting. Labyrinthitis causes similar symptoms in addition to mild hearing loss. Vestibular neuritis and labyrinthitis typically resolve in two to three weeks. Residual unsteadiness that slowly abates over several months may occur. Permanent hearing or vestibular damage occurs rarely.
Ototoxicity
Certain medications and chemicals can damage the inner ear, causing vestibular dysfunction and hearing loss. Typical symptoms include balance disturbances and loss of high-frequency hearing sensitivity. The American Speech-Language-Hearing Association notes that by the time symptoms develop, irreversible damage may have already occurred. Medications associated with a high incidence of ototoxicity include platinum-containing chemotherapy drugs and aminoglycoside antibiotics such as amikacin, gentamicin and tobramycin. Aspirin and quinine may cause ototoxicity, which often proves reversible. Mercury poisoning may cause permanent vestibular dysfunction. Notably, because both ears are affected with ototoxicity, balance and eye movement disturbances are more prominent than vertigo.
