Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Sudden Sensorineural Hearing Loss Sudden sensorineural hearing loss is a confusing and controversial issue in otolaryngology that most of us will encounter in our practice. The impact of the loss of hearing on the patient can be catastrophic and most physicians consider it a medical emergency. On the other hand, it usually becomes frustrating for the physician, as the cause is most often not obvious and the treatment empiric and poorly understood. There is no accepted definition of the problem, no standard method for evaluating these patients, no agreement on what the usual etiology is, no easy way to stage the loss and no clearly effective treatment. Some authors feel strongly that sudden sensorineural hearing loss is just a symptom and not a disease entity. The most useful definition of sudden sensorineural hearing loss is an idiopathic loss greater than 30 Db in three contiguous frequencies and that occurs in less than 3 days. Most sudden losses occur within minutes to several hours, and about 1/3 of these patients awaken in the morning with a hearing loss. Approximately 1/2 note imbalance or vertigo and the intensity of vertigo correlates in general with the degree of hearing loss. Byl reported an incidence of between 5-20 cases per 100,000 population per year. Doug Mattox and Blair Simmons at Stanford reported a 5 year prospective study involving 166 patients, looking at the natural history of the process. They found that males and females were equally affected with a mean age of 46 years. There was no seasonal or geographic clustering. They noted that 65% of patients showed some degree of recovery without any medical or surgical intervention at all. The likelihood of recovery was influenced by the shape of the audiogram - all but one patient with an upward sloping audiogram had complete or good recovery and all but two patients with a severely downsloping audiogram had a fair or poor recovery. Other poor prognostic indicators that are generally agreed upon in the literature include sensitivity loss greater than 90 Db in the mid-frequencies, advanced age, and the presence of vertigo. In his triologic thesis, Dr. Frederick Byl compiled data from 225 patients over an eight year period forming a prognostic table. He also noted the direct relationship between the severity of the initial hearing loss and potential recovery and recorded several modifying factors. The study confirmed that the sooner a patient is seen, the better the prognosis for recovery. Unfortunately, there is no better understanding of the etiology of sudden sensorineural hearing loss than there was 1 or 2 decades ago. It is certain that there is no single etiology -the loss of hearing is just the final outcome for many potential insults to the inner ear. The four most accepted hypothetical etiologies are viral infections, vascular insult, labyrinthine membrane rupture, and autoimmune disease. Although viral infection of the inner ear is an attractive theoretical explanation for sudden hearing loss, the supporting evidence is not conclusive and consists of 4 types: 1) coincident symptoms suggesting coincident viral infection; 2) serological data showing coincident viral infection; 3) histopathological studies showing similarities between known viral infections and cases of sudden hearing loss; 4) extrapolations from the degeneration of the inner ear seen in viral disease such as the prenatal rubella syndrome. Uncontrolled studies from Van Dishoeck, Jaffe, and Schuknecht reported "flu-like" symptoms in 20 - 60% of patients suffering idiopathic sudden sensorineural hearing loss. However, a study by Rowson and Hinchcliffe in 1975 found the same symptoms of upper respiratory tract infection to be present in approximately 40% of the general population. Veltri et al looked at 77 unmatched patients with sudden sensorineural hearing loss and found a conversion rate of 65%. Multiple viruses were implicated including influenza A and B, rubeola, rubella, mumps, herpes simplex, and CMV. Wilson and coworkers studied 122 patients, 63% of whom seroconverted compared with 40% of controls. Other studies from Morrison and Booth as well as Rowson and Hinchcliffe failed to demonstrate a viral titer rise in sudden hearing loss patients. The most consistent evidence supporting viral etiology is the histopathologic findings of varying degrees of atrophy of the organ of Corti, stria vascularis, and tectorial membrane with variable loss of the neuronal population as shown by Schuknecht and others. Perhaps the strongest evidence for the involvement of viruses in hearing loss comes from the use of immunofluorescent antigen studies such as those performed by Davis and Johnson, demonstrating the ability of rubeola and mumps to infect the inner ears of animal models. A vascular cause for sudden hearing loss is attractive because it is logically consistent with immediate onset of symptoms and because there are established models of acute hearing loss secondary to vascular occlusion in hypercoagulable states such as leukemia and sickle cell disease. However, most of the experimental and clinical evidence casts serious doubt on a vascular etiology. One would expect that older patients with known peripheral vascular disease would be the ones most often afflicted, but in fact, most patients are younger and have no stigmata of systemic vascular disease. Perlman and other investigators have demonstrated permanent loss of the cochlear microphonic and action potential occurs after only 30 minutes of ischemia. The histopathology of ears affected by sudden hearing loss also differs significantly from temporal bones examined after experimental vascular occlusion. Permanent obstruction leads to marked degeneration of the neurons followed by fibrous and osseous proliferation within the inner ear, changes that are not seen typically in sudden sensorineural hearing loss. Intracochlear membrane breaks were proposed as a cause of sudden hearing loss by Simmons in 1968, but the evidence is only coincidental. Schuknecht and Donovan studied 12 temporal bones of patients afflicted with sudden sensorineural hearing loss, and found no evidence of Reissner's or basilar membrane rupture. There are several known autoimmune diseases that are epidemiologically associated with sudden sensorineural hearing loss, including Cogan's syndrome, systemic lupus erythematosus, and temporal arteritis. Some of the most convincing evidence has come out of the University of Tennessee by Yoo and coworkers who showed that monoclonal antibodies specific for type II collagen can activate an immunologic response in the inner ear of the rat leading to sensorineural hearing loss as documented by ABR testing. They were able to demonstrate perivascular inflammation and fibrosis and degeneration of the spiral ganglion on histopathology, and using immunofluorescent techniques they saw immune complexes in the otic capsule. Unfortunately, the lack of scientific understanding of the etiology or etiologies of the problem limits its treatment to simple empiricism. Every proposed treatment has study to support it, but corroborative data from independent researchers is usually lacking. Perhaps the fatal flaw in most of those studies is that a single treatment is applied to a symptom that undoubtedly has multiple etiologies. Wilson and his colleagues did a double blind study of 67 patients with sudden sensorineural hearing loss. 33 were treated with oral steroids and 34 received placebo. 52 additional subjects served as controls. 76% of patients who had hearing loss greater than 90 Db failed to recover regardless of whether or not they received steroids. 78% of the steroid treated patients with hearing loss less than 90 Db improved, compared with only 38% of matched untreated patients. There have been a few other studies supporting these findings. However, Dr. Wilson returned to his lab and several years later published a report failing to demonstrate improved recoveries in patients with proven viral antibody seroconversions treated with steroids. The use of diuretics is sort of borrowed from their use in the treatment of Meniere's disease. The use of heparin and warfarin is borrowed from their use in cerebral vascular occlusion in which they seem to promote better collateral circulation. Dextran is an example of an effective plasma expander that is useful in reducing red cell sludging and improving microcirculation. Stellate ganglion blocks produce Horner's syndrome with vasodilation and increased blood flow and is done by making an injection lateral and inferior to the thyroid gland to the C-7 vertebra, and then backing off slightly to the area of the ganglion and injecting Lidocaine. Haug, Draper and Haug demonstrated a 70% chance for a patient to recover a 10 Db pure tone gain and 10 dB discrimination improvement with this procedure compared to a 20% chance of a similar gain if not treated with stellate ganglion blocks. They also noted that the most successful cases were treated in the first 20 weeks after symptoms appeared. Some of the vasodilators commonly employed include nylidrin hydrochloride, papaverine hydrochloride, nicotinic acid, histamine, atropine, and carbogen. Despite the many studies over the years looking at various vasodilators, there has been no adequately controlled study that supports the use of vasodilators in sudden hearing loss. Suga and Snow in their 1969 report actually demonstrated experimentally that vasodilators could in fact reduce cochlear blood flow by causing shunting. Professor Fisch performed several elegant studies and concluded that carbogen was the safest and most effective. "Shotgun" therapy includes as many potentially helpful treatment regimens as can be safely combined. However, there are very few studies looking at the efficacy of shotgun therapy and those that do exist obviously have so many variables that they are impossible to control for. The workup and shotgun regimen recommended by the faculty here at Baylor is attached. This treatment protocol was put together based in part on the experience of the faculty and in part on the information available in the literature, but again there is no scientific data to show that it is any more effective than other treatment protocols or even expectant observation. In summary, sudden sensorineural hearing loss remains a poorly understood and frustrating problem for the otolaryngologist. More rational treatment will probably only follow the elucidation of the specific cause or causes of this disease process. Case Presentation A 55-year-old healthy white male smoker with no previous otologic history, noted the acute loss of hearing in his right ear during his usual morning activities. He denied strenuous activity stating that he had finished brushing his teeth and began to put on his clothes when he suddenly noted a crescendo high pitched tone in his right ear and inability to hear. There were no other associated symptoms of dizziness or visual change. After several hours without improvement, he presented to the emergency room and an otorhinolaryngology consult was obtained. Head and neck examination including otoscopy was completely normal. An audiogram revealed a severe primarily sensorineural sensitivity loss on the right. Laboratory studies including SMA-20, CBC, thyroid function tests, and urinalysis were within normal limits. Syphilis serology was non-reactive and erythrocyte sedimentation rate was minimally elevated at 15 mm/hr. The veteran was admitted and placed on the Baylor sudden sensorineural hearing loss protocol which will be described. Bibliography Alford BR, Shaver EF, Rosenberg JJ, Guildford FR. Physiologic and histopathologic effects of microembolization of the internal auditory artery. Ann Otol Rhinol Laryngol 1965;74:728748. Anderson RG, Meyerhoff WI. Sudden sensorineural hearing loss. Otolaryngol Clin N Am 1981;16:189195. Beal DD, Hemenway WG, Lindsay JR. 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Acousticdistortion products: separation of sensory from neural dysfunction in sensorineural hearing loss in human beings and rabbits. Otolaryngol Head Neck Surg 1991;104:159174. Rowson K, Hinchicliffe R. A virological and epidemiological study of patients with acute hearing loss. Lancet 1975;1:471-474. Schuknecht HF, Benitez J, Beekhuis J, Igarashi M, Singleton G, Ruedi L. The pathology of sudden deafness. Laryngoscope 1962;72:11421157. Schuknecht HF, Donovan ED. The pathology of idiopathic sudden sensorineural hearing loss. Arch Otorhinolaryngol 1986;243:115. Shaia FT, Sheehy JL. Sudden sensorineural hearing impairment: a report of 1220 cases. Laryngoscope 1976;86:389398. Shikowitz MJ. Sudden sensorineural hearing loss. Med Clin North Am 1991;75:12391250. Siegel LG. The treatment of idiopathic sudden sensorineural hearing loss. Otolaryngol Clin N Am 1975;8:467473. Simmons FB. Theory of membrane breaks in sudden hearing loss. Arch Otolaryngol 1968;88:4148. Singleton G. Cervical sympathetic chain block in sudden deafness. Laryngoscope 1971;81:734. Suga F, Preston J, Snow JB, Jr. Experimental microembolization of cochlear vessels. Arch Otolaryngol 1970;92:213220. Suga F, Snow JB, Jr. Cochlear blood flow in response to vasodilating drugs and some related agents. Laryngoscope 1969;79:19561979. Van Dishoeck H, Bierman T. Sudden perceptive deafness and viral infection. Ann Otol Rhinol Laryngol 1957;66:963980. Veltri RW, Wilson WR, Sprinkle RM, Rodman SM, Kavesh DA. The implication of viruses in idiopathic sudden hearing loss: primary infection or reactivation of latent viruses? Otolaryngol Head Neck Surg 1981;89:137141. Weber RS, Jenkins HA, Coker NJ. Sensorineural hearing loss associated with ulcerative colitis: a case report. Archives Oto Laryngol 1984;110:810-812. Wilkins SA, Jr., Mattox DE, Lyles A. Evaluation of a "shotgun" regimen for sudden hearing loss. Otolaryngol Head Neck Surg 1987;97:474480. Wilson WR. Why treat sudden hearing loss? Am J Otol 1984;5:481483. Wilson WR, Byl FM, Larid N. The efficacy of steroids in the treatment of idiopathic sudden hearing loss: a double blind clinical trial. Arch Otolaryngol 1980;106:772776. Yoo TJ, Tomoda K, Stuart JM, Cremer MA, Townes AS, Kang AH. Type II collagen induced autoimmune sensorineural hearing loss and vestibular dysfunction in rats. Ann Otol Rhinol Laryngol 1983;92:267-271. Yoon TH, Paparella MM, Schachern PA, Alleva M. Histopathology of sudden hearing loss. Laryngoscope 1990;100:707715. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine
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