HEARING LOSS Peter M. Rabinowitz, MD, MPH Week 23 Educational Objectives: 1. Learn two basic screening questions for the detection of hearing loss 2. Understand the impact of hearing loss on function and well-being 3. Define conductive, sensorineural, and mixed types of hearing loss and outline steps in evaluation of an individual with respect to these conditions Background: Hearing loss is one of the most common chronic medical conditions7, and because its prevalence increases with age, clinicians will increasingly have to deal with hearing loss in their patients as the United States population ages. At the same time, studies have found that primary care clinicians often fail to screen patients for hearing loss.3 Reasons given in one survey include “lack of time” and “more pressing issues.” The gradual onset of most cases of hearing loss and the subtle impact of the condition on physical and psychosocial functioning may result in under diagnosis as well as delayed diagnosis and treatment of this condition. The U.S. Preventive Services Task Force (USPSTF) in 1996 found sufficient evidence to recommend screening older adults for hearing impairment by periodically questioning them about their hearing, counseling them about the availability of hearing aid devices, and making referrals for abnormalities when appropriate ("B" recommendation).6 At that time, the USPSTF found insufficient evidence for screening adults with audiometry. However, based on recent evidence, the USPSTF recommendations for the screening of hearing loss are under revision, and new recommendations are expected soon. Screening for Hearing Loss: The simplest way to screen for hearing loss is to inquire whether the patient has noticed any problem with his/her hearing. Sample questions include “Have you noticed any problems with your hearing?” and “Has your family noticed any problems with your hearing?” One study of adult men found that while 55% admitted to some hearing loss, only 12% sought help.1 Because most hearing loss affects the high frequencies of the speech range, speech discrimination may be the first problems noticed. This occurs when the person has trouble clearly distinguishing spoken words, especially when there is background noise, such as in crowded restaurants or parties. Some patients may be reluctant to admit hearing loss since it is associated with the stigma of aging. Family members may provide helpful clues about the diagnosis. There are also a number of standardized questionnaires, such as the Hearing Handicap Inventory; in practice, the sensitivity of such instruments ranges from 42%-80%.2 If the patient complains of hearing loss, or if the responses to any of the screening questions are abnormal, audiometry is a reasonable next step, in addition to a basic physical examination of the ears. CASE ONE: John Hoh, a 55 year-old man is seen by his primary care physician for blood pressure control and depression. Lab work is ordered. The cholesterol is elevated at 270. The clinician calls the patient to discuss the results. On the telephone, the patient asks the doctor several times to repeat herself, and then passes the telephone to his wife. The wife reports that he often has difficulty understanding conversations. A repeat office visit is scheduled. At follow-up, the patient reports progressive difficulty understanding speech and constant tinnitus over the last five years. He and his wife argue frequently about TV volume. He describes being embarrassed about having what he feel is a “disability.” Questions: 1. What are the major types of hearing loss and their causes? Hearing loss can be divided into three categories: sensorineural, conductive, and mixed. The most common cause of sensorineural hearing loss is agerelated loss (presbycusis). This causes a high frequency loss with gradual onset over time. Noise-induced hearing loss also causes a sensorineural loss that closely resembles presbycusis, but may be seen in younger individuals exposed to excessive noise at work or through recreational activities, such as listening to amplified music or using power tools.1 Other causes of sensorineural hearing loss include ototoxic drugs, Meniere’s disease, head trauma, and acoustic neuroma. Conductive loss involves damage to the tympanic membrane or the ossicular chain in the middle ear that conducts sound to the cochlea. Common causes include otitis media, tympanic membrane perforation, cerumen impaction, cholesteatoma, and otosclerosis. Many causes of conductive hearing loss are reversible, making it even more important to detect in the evaluation of a patient with hearing loss. Mixed hearing loss is a combination of both sensorineural and conductive etiologies. 2. What is the next appropriate step in the evaluation of Mr. Hoh’s hearing complaint? In this case, the patient has already admitted to hearing loss symptoms. The next step would be to take additional history about risk factors for the hearing loss, with attention to the causes listed above, perform a basic physical examination of the ears, and get a hearing test (audiogram) to assess the loss. CASE ONE CONTINUED: The physician takes additional history and finds that Mr. Hoh has worked as a longshoreman for the past 25 years loading steel girders onto ships. He has not always worn hearing protection. The physician performs a physical exam including a Rinne and Weber test (see Rabinowitz article). He sends the patient for a screening tympanogram and audiogram. The results of this testing are as follows: Otoscopy: keratinaceous debris on tympanic membrane on left Rinne: air conduction > bone conduction (right), bone>air (left) Weber: Lateralizes to the left Tympanometry: normal middle ear compliance right, decreased compliance left Audiogram: bilateral hearing loss, worse on the left, air-bone gap on left (see below) Right Ear Left Ear 3. Do the results of this testing suggest that the hearing loss is conductive, sensorineural, or mixed? What are possible causes of the hearing loss? The audiogram shown above was created by the patient indicating at what intensity level he could hear pure tones at various frequencies. The intensity at which sounds must be presented to the ear to be heard at a particular frequency (the “hearing threshold level”) is recorded on the graph. Hearing loss is defined according to the hearing threshold levels as follows: normal range or no impairment = 0 dB to 20 dB; mild loss = 20 dB to 40 dB; moderate loss = 40 dB to 60 dB; severe loss = 60 dB to 80 dB; profound loss = 80 dB or more. A typical audiogram tests frequencies between 250 and 8000 cycles per second (Hz), which is roughly the range of human speech. Frequencies above 2000 Hz are often referred to as “higher frequencies”, while frequencies below 2000 Hz are considered “lower frequencies”. For reference, middle C on a piano is 250 Hz. The hearing loss from aging, presbycusis, as well as noise exposure, tends to involve the higher frequencies. For our patient’s audiogram above, the audiologist has tested hearing in two ways, by air conduction (presenting a sound via earphones- indicated by circles on the right and x’s on the left ear) and bone conduction (by placing a transducer on the mastoid bone- similar to the Rinne test- indicated by bracket symbols). If the air and bone conduction results are similar (as in the patient’s right ear), the loss is predominantly sensorineural. If there is a discrepancy between air and bone conduction, the “air-bone gap” seen in the patient’s left ear, this indicates at least some component of conductive loss. The tympanogram is a test of middle ear compliance, performed by inserting a probe in the ear canal, producing a sound, and recording the amplitude of the sound reflected off the ear drum (tympanic membrane). A decreased amplitude of reflected sound indicates a problem with the compliance of the tympanic membrane, the conducting bones, or both. The audiogram results therefore show a sensorineural hearing loss on the right, and a mixed hearing loss on the left (note the “air-bone gap” indicating a difference between air and bone conduction due to conductive loss). This is consistent with the results of the Weber and Rinne tests on physical exam. The likely cause for the bilateral sensorineural hearing loss includes occupational noise exposure (note the “notching” of the audiogram around 4000 Hz, consistent with noise induced hearing loss) and superimposed presbycusis. Possible causes for the conductive component of the loss in the left ear includes ear infection, cerumen obstruction, cholesteatoma, and otosclerosis. The following findings support a diagnosis of cholesteatoma: keratinaceous debris on TM seen on otoscopy, lack of cerumen obstruction by otoscopy, and no pain or fever to suggest acute otitis media. 4. What are appropriate triggers for referral of a patient with hearing loss to an otolaryngologist (ENT)? Some indications for referral include asymmetric hearing loss, conductive hearing loss, sudden sensorineural hearing loss, and hearing loss that is at least moderate in severity. CASE ONE CONTINUED: You refer Mr. Hoh for an ENT consultation (based on his asymmetric hearing loss) and an MRI is performed. The otolaryngologist confirms the diagnosis of cholesteatoma, and surgery is scheduled. Mr Hoh, on his follow-up visit, reports that he has had his surgery and his hearing is slightly better, but he still hears better on the right than the left. He may need a followup surgery to finish repairing his left eardrum, and in the meantime is using a hearing aid since, even after the surgery, he still has moderate hearing loss. He says that his hearing aid is helping him in certain situations, but his supervisor at work has told him he can’t wear it on the job, since it prevents him from wearing his required hearing protectors. At the same time, he is concerned that he may not be able to hear warning signals at work. He is reconsidering whether he should continue working in a noisy environment. 5. What are the potential impacts of adult hearing loss on physical and psychosocial functioning? The primary care management of hearing loss includes appropriate screening and referral, and continued monitoring as to whether hearing loss is impacting overall physical and psychosocial functioning. Hearing loss may be associated with depression and anxiety, and may also predispose hospitalized patients to delirium. Hearing loss is also associated with an increased risk of accidental injury. While hearing aids can amplify sounds, they are currently unable to duplicate normal speech discrimination, and many patients report poor adherence to hearing aid use. Patients may have difficulty using hearing aids in certain situations, such as noisy environments, and may require special accommodation in the workplace. Because noise exposure is the most common preventable cause of acquired hearing loss, it is important that clinicians be alert to ongoing noise exposures that can lead to further damage. 6. How can you help Mr. Hoh make adjustments in his job and lifestyle to accommodate his hearing loss? The clinician can arrange for an occupational medicine consultation to evaluate the impact of hearing loss on Mr. Hoh’s job functioning, and to determine whether accommodation in the workplace is possible to allow him to work safely. The clinician can also alert the dispensing audiologist about the problems Mr. Hoh is having with his hearing aid, and determine whether other types of hearing aids or additional rehabilitation services are available and appropriate for him. The clinician should also be alert for the presence of depression and anxiety symptoms that often accompany hearing loss and that might require additional evaluation and treatment. Primary References: 1. Rabinowitz PM. Noise-induced hearing loss. American Family Physician. 2000; 61(9): 2749-2756. http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=3124826&site =ehost-live 2. Yueh B. Shapiro N. MacLean CH. Shekelle PG. Screening and management of adult hearing loss in primary care: scientific review. Journal of the American Medical Association. 2003; 289:1976-1985. http://jama.amaassn.org/cgi/content/full/289/15/1976 Additional References: 3. Wilson PS, Fleming DM, Donaldson I. Prevalence of hearing loss among people aged 65 years and over: Screening and hearing aid provision. British Journal of General Practice. 1993;43:406-409. 5. Parmet S, Lynn C, Glass RM. JAMA patient page. Adult hearing loss. Journal of the American Medical Association. 2007; 298:130. 6. US Preventive Services Task Force Guide to Clinical Preventive Services http://www.ahrq.gov/clinic/uspstfix.htm (accessed 10/15/2007) 7. Bogardus ST, Yueh B, Shekelle PG. Screening and management of adult hearing loss in primary care-clinical applications. Journal of the American Medical Association. 2003;289:1986-1990. Peter Rabinowitz went to medical school at the University of Washington, completed a family medicine residency through the University of California at San Francisco, worked in migrant health clinics in California and Seattle, was the Associate Director of a residency training program , and has completed fellowships at Yale in General Preventive Medicine and Occupational and Environmental Medicine. He is the Director of Clinical Services for the Yale Occupational and Environmental Medicine Program, and conducts research on noise-induced hearing loss, solventinduced hearing loss and occupational infectious diseases at the animal-human interface.