Tinnitus is noise perceived in the ears that does not come from sound generated in the external environment. Most cases of tinnitus occur in conjunction with hearing loss. Continuous or intermittent noise may occur as buzzing, ringing, roaring, clicking or hissing. The National Institute on Deafness and Other Communication Disorders reports that approximately 25 million people in the United States experience tinnitus, which most commonly affects adults.
Inner Ear Hearing Loss
Abnormalities of the inner ear structures that lead to hearing loss can cause tinnitus. Age-related hearing loss, or presbycusis, proves to be a common cause of tinnitus. According to the National Institute on Deafness and Other Communication Disorders, approximately one-third of Americans age 65 to 75 have presbycusis. Exposure to loud noise also causes inner ear-related hearing loss. Repetitive exposure to excessively loud noise over time or exposure to a single, blast-like noise can cause this form of hearing loss. Other possible causes of inner ear hearing loss include exposure to ear-toxic medications, head injuries, Meniere's disease, inner ear infections, vitamin B12 deficiency, acoustic neuroma, thyroid disease and multiple sclerosis. Scientists and physicians postulate that hearing loss may cause abnormal activity in the brain region responsible for sound perception, leading to tinnitus. Tinnitus is usually most noticeable and disruptive in quiet environments.
Middle Ear Hearing Loss
The middle ear is the region between the eardrum and the inner ear. It contains three minute bones, the ossicles, which transmit sound-induced vibrations from the eardrum to the inner ear. Abnormalities in the middle ear can cause hearing loss, which may precipitate tinnitus. In a review article on tinnitus published in the journal "American Family Physician," Drs. Richard Crummer and Ghinwa Hassan report that middle ear problems that may lead to tinnitus include eardrum rupture, disruption or scarring of the ossicles and fluid accumulation in the middle ear. In contrast to inner ear-related hearing loss, most middle ear abnormalities that cause hearing loss prove reversible. Alleviating middle ear disease and restoring normal hearing typically relieves or eliminates associated tinnitus.
Blood Flow Disturbances
Blood flow disturbances near the middle ear may cause pulsatile tinnitus--noise that occurs in rhythm with the heartbeat. The examining physician can sometimes hear this unusual form of tinnitus by placing a stethoscope on the skin near the ear. "The Merck Manual for Healthcare Professionals" explains that increased or exceptionally turbulent blood flow may precipitate this form of tinnitus. Possible causes include abnormal blood vessel growths called arteriovenous malformations; tumors of the middle ear such as glomus tympanicum and glomus jugulare; and atherosclerosis of the carotid arteries.
References
- National Institute on Deafness and Other Communication Disorders: The Noise in Your Ears
- Mayo Clinic: Tinnitus, Causes
- American Academy of Otolaryngology--Head and Neck Surgery: Tinnitus
- Merck Manual for Healthcare Professionals: Tinnitus
- "American Family Physician"; Diagnostic Approach to Tinnitus; Richard W. Crummer, M.D., Ghinwa A. Hassan, M.D.; January 2004
