Sudden sensorineural hearing loss (SSNHL) is defined by a sudden loss of hearing of at least 30 dB in three consecutive frequencies, typically in one ear, that occurs over 72 hours or less (in many cases, in just a few hours). It is a scary experience for a patients since hearing is a critical sense, and it may trigger a fear that it could be the first sign of something worse such as a stroke. Additionally, the hearing loss is often associated with concurrent tinnitus and/or vertigo, which can cause significant distress. While this condition is not common, it affects five to 20 of every 100,000 people (or about 66,000 people each year in the United States alone), and leads to significant impairment in function and quality of life.
Due to the wide-reaching impact of SSNHL, the American Academy of Otolaryngology Head and Neck Surgery (AAO-HNS) published a clinical practice guideline on SSNHL in 2012.1 The guideline was developed by a multidisciplinary team of stakeholders who care for patients with this condition such as otolaryngologists, emergency physicians, nurse practitioners, primary care physicians, radiologists, and a consumer advocate. It was written through a rigorous methodological process for developing evidence-based guidelines and underwent extensive peer review.2 The SSNHL guideline was recently updated and published in the official journal of the AAO-HNS, and widely distributed to medical professionals who diagnose and treat SSNHL.3 In summary, the goals of the update were to evaluate new data regarding SSNHL that have been published over the past seven years and to highlight the importance of both rapid diagnosis and expedited treatment for SSNHL.
Patients with SSNHL may present to the emergency department, an internist/a primary care physician, an audiologist, or an otolaryngologist. Therefore, it is imperative that any health care professional who might be the first point-of-contact for these patients is familiar with the guideline in order to optimize effective care. Specifically, the guideline is meant to help clinicians rapidly identify the problem, perform the proper workup, treat efficiently without unnecessary interventions while offering evidenced-based therapy, and ultimately maximize auditory function and minimize quality of life decrement.
In patients with bilateral sudden hearing loss, recurrent episodes of sudden hearing loss, or sudden hearing loss associated with focal neurological findings, the hearing loss may be a presenting sign of a more serious medical condition such as a neurological disease, an infection, an autoimmune disease, neoplasm, or a cerebrovascular injury (stroke). Stroke patients will typically have associated neurologic complaints (extremity weakness, speech problems, facial weakness, etc.), and should be evaluated immediately by an appropriate medical professional. Clinicians are encouraged to look for features that may be associated with an underlying disease in all patients with presumptive idiopathic SSNHL. While there are known causes of SSNHL that should be considered and ruled out when relevant, in the majority of cases, the cause remains unknown.
NOTABLE GUIDELINE UPDATES
For patients with unexplained hearing loss, evaluation to characterize the type of loss and allow for early initiation of therapy is key. Many patients who present with an acute change in hearing may simply have an ear infection or another identifiable cause of conductive hearing loss (i.e., cerumen). In many cases, this can be easily determined through pneumatic otoscopy and a tuning fork exam (Weber and Rinne test). For those without exam findings to explain their hearing loss or with a tuning fork exam suggestive of SSNHL, audiometry is mandatory and should be done as soon as possible within 14 days of symptom onset. This two-week window was added to the updated guideline because treatment options are most effective if initiated within 14 days of hearing loss onset. Although the guideline uses the standard definition of SSNHL of at least 30 dB hearing loss in three contiguous frequencies over three days as the minimum criterion, in clinical practice, patients with lesser degrees of hearing loss may also have SSNHL and should be treated as such on a case by case basis.
Once audiometric confirmation of sensorineural hearing loss has been made, the guideline strongly recommends against ordering routine computed tomography of the head and/or “shotgun approach” laboratory testing because these rarely provide useful etiologic information and often lead to additional unnecessary testing, exposing the patient to additional risks. The guideline does recommend an assessment for retrocochlear pathology (abnormalities along the cochleovestibular nerve, brainstem, or brain) that could be the cause of hearing loss. The incidence of vestibular schwannoma in patients with SSNHL is much higher than in the general population (1-10% vs. 0.001-0.017%).4 MRI of the brain, brainstem, and inner auditory canal with gadolinium is the most sensitive test for detecting organic pathology, and can detect vestibular schwannomas as small as 2 mm. Auditory brainstem response (ABR) testing is an electrical test of the central auditory pathway, and may be useful for patients who are unable to undergo MRI or for older patients who might choose a less aggressive management should a tumor be diagnosed. The ABR is less sensitive in tumor detection, and may miss as many as 20 percent of small tumors.3 While essential, radiographic workup does not need to be done emergently.
Patient education regarding the diagnosis and natural history of SSNHL is strongly recommended, and shared decision-making regarding therapeutic options is mandatory in managing these patients. Despite being considered the gold standard for treatment of SSNHL, corticosteroid therapy, administered either orally or via intratympanic (IT) injection, is offered only as an option in the guideline for initial management and, when implemented, should be initiated as soon as possible and within two weeks of the diagnosis. Data comparing various dosing schedules and treatment protocols are limited, and the benefits must be weighed against the potential side effects. Hyperbaric oxygen therapy (HBOT) also has evidence supporting its potential effectiveness in the treatment of SSNHL, and is offered as an option for initial management in the updated guideline. Similar to corticosteroid therapy, HBOT should be initiated within two weeks of the initial diagnosis. However, HBOT is not universally available, is expensive, and very time-consuming. Treatment risks and side effects should be discussed with a hyperbaric medicine specialist.
All patients must be reassessed after completing initial therapy to identify those who did not respond or partially responded and have residual hearing loss. For non- and partial-responders, there is strong evidence that salvage IT steroid therapy can improve the hearing outcome in an additional 35 to 50 percent of patients. Accordingly, the guideline recommends offering IT steroid therapy as soon as possible after initial failure and within six weeks. Beyond six weeks, there is little to no evidence that IT injections offer any additional benefit. Like oral steroid therapy, there is no universally accepted protocol for IT therapy, but the randomized controlled trials all employed four injections over two weeks or less. There is some evidence for HBOT as salvage treatment for SSNHL, and the guideline supports offering HBOT as an optional treatment for up to four weeks after SSNHL is diagnosed in conjunction with steroids. No data support the use of additional medical therapies such as antivirals for SSNHL, and their use is strongly recommended against due to lack of data and risk of harm over benefit.
ROLE OF AUDIOLOGISTS
Patients diagnosed with SSNHL should be reassessed with audiometric testing approximately six months after the completion of treatment. Sometimes an underlying cause can be identified (such as Ménière's disease), but more importantly, this provides an opportunity to identify and reconnect with patients who might benefit from hearing rehabilitation. Audiologists play a critical role in counseling these patients regarding their treatment options and in managing the tinnitus that often accompanies the hearing loss. Options for rehabilitation may include traditional hearing aids for patients with serviceable hearing, or in the case of profound hearing loss, transcranial routing of sound to the better hearing ear through devices such as a contralateral routing of signal (CROS) aid, a BiCROS aid, or a bone conduction implant. There is mounting evidence for the use of cochlear implants for patients with single-sided deafness or asymmetric hearing loss as a means of restoring binaural hearing,5 and the FDA has recently approved the MED-EL cochlear implant system for this indication.
The updated clinical practice guideline for SSNHL focuses on early diagnosis and treatment, patient education, and shared decision-making. The audiologist plays a critical role in the diagnosis, outcomes assessment, and ultimate rehabilitation of patients suffering from this condition.
1. Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical Practice Guideline. Otolaryngol Neck Surg
2. Rosenfeld RM, Shiffman RN, Robertson P, et al. Clinical Practice Guideline Development Manual, Third Edition. Otolaryngol Neck Surg
3. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Neck Surg
4. Lin D, Hegarty JL, Fischbein NJ, et al. The Prevalence of “Incidental” Acoustic Neuroma. Arch Otolaryngol Neck Surg
5. Zeitler DM, Dorman MF, Natale SJ, et al. Sound source localization and speech understanding in complex listening environments by single-sided deaf listeners after cochlear implantation HHS Public Access. Otol Neurotol