by Michael K. Wynne, Allan O. Diefendorf, and Michael H. Fritsch
Radio personality Rush Limbaugh recently brought public attention to sudden hearing loss when he revealed his own hearing loss to millions of listeners and subsequently announced that he won’t be deaf for long, as he will receive a cochlear implant in early 2002.
Like Limbaugh, an estimated 4,000 people will develop sudden sensorineural hearing loss each year in the United States. Sudden sensorineural hearing loss occurs across the entire age spectrum with equal prevalence in men and women, but most patients are between 50–60 years of age. More than half also experience tinnitus, aural fullness, and/or vertigo.
The hearing loss often starts as a sudden drop in hearing in one ear—only 2% develop bilateral hearing loss. The characteristics of the hearing loss and whether hearing will improve, fluctuate, stabilize, or progressively deteriorate depends on the underlying etiology. Only 10% of all patients will have their sudden hearing loss definitively diagnosed. For most, the hearing loss is diagnosed as sudden idiopathic sensorineural hearing loss.
Numerous etiologies can lead to sudden sensorineural hearing loss. A partial list includes autoimmune inner ear disease (AIED), compromised vascular supply to the inner ear, intracochlear membrane breaks, neurologic and neoplastic lesions, traumatic insults, and viral infections. Patients with enlarged vestibular aqueduct syndrome (EVAS) or syphilis also may have sudden sensorineural hearing loss that is both fluctuating and progressive. The table on page 7 lists additional etiologies associated with sudden sensorineural hearing loss.
Sudden hearing loss—like a sudden loss of vision—is a medical emergency. An immediate otologic and audiologic work-up is paramount and should be scheduled as soon as possible. With some etiologies, expeditious treatment can recover or stabilize the patient’s hearing. The otolaryngologist must increasingly rely on the judgment and contributions of the audiologist. Likewise, the audiologist requires the input of the otologist in the evaluation of the patient with sudden sensorineural hearing loss. The practice of each discipline should be in conjunction with each other—not to the exclusion of the other. An audiologic-otologic team will provide the patient with the highest quality care.
The initial examination of the patient’s complaint should begin with a thorough history and physical examination. It’s not uncommon for a patient to notice hearing loss after a specific event, such as receiving a trauma to the head, straining to lift an object, flying, scuba diving, or exposure to loud sound. Other patients may report a history of recent or concurrent viral or upper respiratory infections, recent illness or surgeries, or changes in their prescriptions/medications.
Patients who note hearing loss on awakening present a special problem: the loss could have developed instantaneously or over the course of several hours while sleeping. In all cases, the patient’s medical history should be reviewed for metabolic, vascular, and neurologic diseases and disorders. Although a complete head and neck examination should be conducted to rule out external and middle ear disorders, this examination will be negative in most cases of sudden and/or progressive hearing loss.
Laboratory studies should be conducted based on the patient’s complaint, history, and suspected etiologies. Hematologic examination includes complete blood count, determination of erythrocyte sedimentation rate, and sickle-cell test. Urinalysis is completed as well as serum chemistry for sodium, potassium, blood urea nitrogen, calcium, creatinine, blood glucose, uric acid, total bilirubin, alkaline phosphatase, cholesterol, and triglycerides. Serologic testing for syphilis and HIV and a Lyme titer are also conducted. Depending on the patient’s history, testing for lymphocyte transformation to rule out AIED is useful. A CT scan and MRI should be obtained to examine the physical integrity of the skull base, temporal bone structures, and soft tissues of the head and neck and rule out identifiable lesions.
The audiologic test battery should include tympanometry, acoustic reflexes, pure-tone audiometry, speech audiometry, and otoacoustic emission testing. Electrophysiologic tests, including early-, middle-, and late-evoked potentials, and vestibular assessment, including electronystagmography and rotary chair testing, may also be conducted. The frequency of audiometric testing depends on the identified etiology, the medical intervention initiated, the rate of progression of any hearing loss, the degree to which the hearing loss fluctuates, and the patient’s reports of any changes in hearing or overall health.
We have found that individuals with sudden sensorineural hearing loss have a wide variation in hearing thresholds and word recognition abilities—one patient had a 105 dB change in thresholds over a week. Some patients have frequent hearing changes, whereas others have a more stepwise pattern of progression or fluctuation in hearing. In all cases, clear communication about changes in hearing and subsequent alterations in treatment plans is paramount between patient, neurotologist, and audiologist.
The treatment of sudden sensorineural hearing loss depends on identification of the etiology of the hearing loss. If no diagnosis is made, empiric treatment may be initiated in hope of a response. But the type of treatment remains controversial because no regimen has been clearly demonstrated as effective. The low incidence of sudden hearing loss, the large number of cases with an undefined etiology, and the high rate of spontaneous recovery for sudden idiopathic sensorineural hearing loss makes the study of treatment efficacy difficult at best. The following general treatment categories have been reported: vasodilators, diuretics, anticoagulants, plasma expanders, corticosteroids, antiviral agents, surgery, vitamins, and combined therapy.
High doses of steroids are often used to treat a patient whose hearing loss is associated with AIED or EVAS or is idiopathic in nature. Typically, prednisone is used at 1mg/kg per day for 2–4 weeks, rapidly tapering the drug if there is a complete recovery of hearing. In cases where hearing does not completely recover, reducing the dosages of the medication should occur much more slowly. The best outcome is achieved when steroids are administered as quickly as possible after the onset of the drop in hearing. These patients also may benefit from diuretics; a low-sodium diet; a restriction in the use of stimulants, alcohol, and tobacco; and avoidance of excessive physical activity and noise exposure.
In treating sudden hearing loss due to a vascular disorder, the patient may receive carbogen, a combination of 95% oxygen and 5% carbon dioxide. As an inpatient procedure, carbogen inhalation therapy is given for about 10 minutes each 6–8 hours over a three-day period by a respiratory therapist. This treatment is thought to increase the oxygen in the perilymph by dilating the cochlear artery. In some geographic regions, carbogen treatments are not covered by insurance.
Patients who are found to have a structural defect such as a perilymph fistula or acoustic neuroma may benefit from surgery. The preservation of hearing depends on the degree of structural anomaly and its impact on the peripheral auditory mechanism.
Hearing aids, cochlear implants, and assistive listening devices may be the remaining treatment options to address the communication needs of patients who do not completely recover their hearing through medical intervention. Hearing aids with multi-memories and/or volume-control wheels offer a larger number of options to appropriately fit the dynamic changes in the hearing loss over time. These systems offer two advantages. First, patients have the flexibility to adjust the characteristics of their amplification systems as their hearing changes. A second advantage is that the devices give many patients a sense of control over their communication abilities in spite of a physiological system that may change because of factors beyond their control.
When the hearing loss progresses and stabilizes in the severe-to-profound range, cochlear implantation becomes a reasonable means to address the patient’s communication needs. There are no simple rules or algorithms regarding when and how to implant these patients, as several factors contribute to the decision for implantation.
Sudden and progressive hearing loss is a complex disorder that does not lend itself to simple solutions or static interactions. We find that patients are best served when providers have a commitment to the science and art of clinical practice—and to a truly interdisciplinary approach.
Michael K. Wynne is an associate professor at Indiana University School of Medicine and Purdue University. He serves as an associate editor for the American Journal of Audiology and is the coordinator of Special Interest Division 9, Hearing and Hearing Disorders in Children. Contact Wynne by email at firstname.lastname@example.org.
Allan O. Diefendorf is an associate professor at Indiana University School of Medicine and Purdue University. He serves as the director of audiology and speech-language pathology at Riley Hospital for Children, University Hospital, and Wishard Memorial Hospital in Indianapolis, IN.
Michael H. Fritsch is a neurotologist and an associate professor at Indiana University School of Medicine. He has authored numerous publications and co-authored several manuscripts with audiologists across a wide range of topics related to the evaluation and management of hearing disorders.
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