It can happen without any warning. You might hear an extremely loud popping noise that grows quieter, followed by pressure in your head, ringing in your ears, and dizziness. You may simply wake up one morning and not be able to hear out of one ear. A third possibility is a feeling of fullness in your ear with gradual loss of hearing over a few days. Any of these scenarios is frightening and especially disconcerting when tests and exams don’t uncover an underlying cause.
Known as sudden sensorineural hearing loss (SSHL) or sudden deafness, this type of hearing loss varies in severity and usually impacts just one ear (unilateral). Although low-tone SSHL is a well-known clinical diagnosis, most people experience high-tone SSHL, which has a worse prognosis. An estimated 1–4% of cases involve both ears (bilateral), although simultaneous occurrence is even rarer.
For the vast majority of people who suffer from sudden hearing loss in just one ear, the cause remains a puzzling medical mystery. The medical term for this is idiopathic SSHL, which refers to a medical condition of unknown origin. SSHL is considered a medical emergency, so if this happens to you or a loved one, it’s important to seek immediate medical treatment. If you wait longer than 72 hours to seek help, there’s often nothing that can be done to help the condition.
An obvious sign of SSHL is the loss of at least 30 decibels in three connected sound frequencies within 72 hours. This would make conversational speech sound like a whisper. In addition, many people experience a feeling of stuffiness, ringing in the ear, and vertigo. The doctor will ask about your medical history and perform a physical examination to look for potential causes. In most cases, the ear exam is normal. A complete audio-vestibular evaluation is performed to help determine if the hearing loss is related solely to an inner ear problem or other issues. Hearing tests typically include pure-tone audiometry, speech in noise testing, and otoacoustics emissions.
Pure-tone audiometry: A test that assesses your hearing threshold, this is the primary diagnostic tool used to differentiate between conductive and sensorineural hearing loss. Pure-tone thresholds indicate the softest audible sound you can hear at least 50% of the time. Your hearing sensitivity will be plotted on a graph displaying intensity as a function of frequency, called an audiogram.
Speech-in-noise (SIN) testing: This test is used to evaluate your ability to hear in noisy settings. It is useful for evaluation and measurement of the functional capacity of your hearing system and is especially effective for single-sided deafness.
Otoacoustic emissions: A small probe is inserted into your ear canal to measure extremely soft vibrating sounds produced when the outer hair cells in your inner ear are stimulated. When there is blockage, there’s no nerve response.
Magnetic resonance imaging MRI: Over the past decade, MRI has provided new insights about underlying causes of SSHL because high-resolution sequences are able to detect subtle changes in the inner ear. Neuroradiologists specifically look for asymmetry of the signal between the affected and unaffected sides and unusual inflammatory patterns. About 30–50% of people with SSHL have abnormalities on their MRI scans.
Like regular sensorineural hearing loss, SSHL is associated with damage to the inner ear or auditory pathway between the ear and brain. For individuals who suffer sudden hearing loss in both ears, more than 100 underlying causes have been identified. Specific signs provide clues about some causes. For example, if a person experiences sudden hearing loss in both ears or recurrent episodes of sudden hearing loss, bilateral Meniere disease, primary neurologic disorders, or autoimmune or metabolic disorders are suspected causes.
Inner ear disease: A disorder called Ménière’s disease has been identified as a cause, especially in recurrent episodes of SSHL. This disorder is believed to result from abnormalities in the quantity, composition, and/or pressure of the fluid in the endolymphatic sac, a compartment located in your inner ear.
Viral infections: Researchers have found evidence of viral infections in individuals with sudden hearing loss. Some experts believe viral disease is responsible for 60% of SSHL cases. Viral-related hearing loss is likely caused by inflammation of the inner ear or auditory nerve. In some cases, the person doesn’t experience pain, fever, muscle cramps, or any other signs of a viral illness. Mumps is the only virus that has definitively been tied to SSHL, and it is associated with other symptoms.
Bacterial infections: The two most common bacterial infections known to cause SSHL in the U.S. are Lyme disease and syphilis. Studies suggest that SSHL may coincide with Borrelia burgdorferi infection, the primary bacteria that causes Lyme disease in North America. An acute condition called otosyphilis is a well-known complication of the sexually-transmitted disease syphilis. It can cause sensorineural hearing loss that impacts one or both ears, with rapid progression or sudden onset.
Autoimmune diseases: The association between Cogan syndrome, systemic lupus erythematosus, and other autoimmune rheumatologic disorders and hearing loss is well documented. These account for an estimated 4–6% of SSHL cases. A 2004 study on 51 individuals with SSHL uncovered multiple immune-related disorders.
Exposure to ototoxic drugs: More than 200 different medications are ototoxic, which means they have hearing-related side effects, including SSHL.
Medical procedures: About one in 1,000 patients who undergo cardiopulmonary bypass experience SSHL, while even less people experience this after cervical spine manipulation. SSHL is unusual after general anesthesia for non-cardiac procedures and surgeries not involving the ear. Only 44 cases have been published to date, mostly after gynecologic, abdominal, spinal, and ophthalmic procedures. Although SSHL following dental procedures is extremely rare, a recent study documented the case of a 79-year-old man who experienced immediate acute hearing loss in his left ear and vertigo following tooth extraction under local anesthesia. Although the vertigo cleared up the next day, his hearing loss did not, so he was prescribed vasodilators, high-dose oral steroids, and vitamin B12 injections.
Blood circulation problems: Blood flow change in the inner ear related to circulatory disorders has been a reported major cause of SSHL.
Coronary disease: One study found a connection between coronary risk factors and risk factors for SSHL. Although this study didn’t show that high cholesterol was a risk factor, another much larger 2014 study on 74,000 patients with high cholesterol found a 1.62 times greater incidence of SSHL in this group.
Tumors: About 10–20% of individuals with SSHL have a benign acoustic neuroma (vestibular schwannoma), while cerebellopontine tumors are a much rarer cause.
Multiple sclerosis (MS): Although it’s a rare symptom of MS, SSHL is two to 12 times more common in individuals with this disease than the general population, according to a Finnish study. In two of the 17 patients with MS and SSHL, SSHL was the first symptom of MS and for one, it was the only symptom.
Chronic stress and mental issues: While stress is commonly thought to be linked to the onset of SSHL, few studies have analyzed the relationship between the two. A 2019 study on 42 patients with SSHL found 81% reported greater than normal stress upon admission. Although it could be surmised this stress was related to losing their hearing, researchers concluded these individuals had higher stress levels prior to the onset of SSHL than they typically experienced. A different study showed greater psychological distress and more stressful life events in people with SSHL, while another study reported high levels of mental problems (90%), and psychosomatic disorders (more than 70%) in individuals diagnosed with SSHL.
Due to the high percentage of SSHL cases that appear without a known cause, different treatment protocols are used. These include systemic steroids, antiviral medications, vasodilators, and hyperbaric oxygen. In clinical practice, oral steroid therapy is the mainstay of treatment, although direct intratympanic injection of steroids into the middle ear is an increasing favored approach. After injection, the medication flows from the middle ear to the inner ear. High-dose oral steroids are recommended as soon as possible, with most improvements realized during the first two weeks. It’s crucial that individuals are monitored for steroid side effects during treatment.
Recovery depends on several factors, such as your age, severity of the hearing impairment, and the time-lapse between onset and treatment. Individuals who drink alcohol or have a blood vessel disease have a higher risk of worsening hearing. If treatment is started within the first two weeks after onset, about 80% of individuals experience some improvement, while others recover normal hearing.
Most of the patients reported some improvement according to a Brazilian study
Many people wait for days or weeks before seeking medical treatment, and then are often treated symptomatically before being referred to an otolaryngologist. Unfortunately, SSHL must be treated no more than two to four weeks from the onset of symptoms to be effective. A delay in diagnosis usually results in permanent hearing loss. If you’re suffering from persistent ear fullness, don’t assume it’s from impacted earwax or an allergy. Seek immediate treatment from an audiologist or an ear, nose, and throat doctor because the problem could be SSHL.
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