Sudden hearing loss is moderate to severe sensorineural hearing loss Pathophysiology Worldwide, about half a billion people (almost 8% of the world's population) have hearing loss ( 1). More than 10% of people in the US have some degree of hearing loss that compromises their... read more that develops suddenly, within a few hours, or is noticed on awakening. It affects about 1/5000 to 1/10,000 people each year. Initial hearing loss is typically unilateral (unless drug-induced) and may range in severity from mild to profound. Many also have tinnitus Tinnitus Tinnitus is a noise in the ears. It is experienced by 10 to 15% of the population. Subjective tinnitus is perception of sound in the absence of an acoustic stimulus and is heard only by the... read more , and some have dizziness, vertigo Dizziness and Vertigo Dizziness is an imprecise term patients often use to describe various related sensations, including Faintness (a feeling of impending syncope) Light-headedness Feeling of imbalance or unsteadiness... read more , or both.
Sudden hearing loss has some causes that differ from chronic hearing loss and must be addressed urgently (1 General reference Sudden hearing loss is moderate to severe sensorineural hearing loss that develops suddenly, within a few hours, or is noticed on awakening. It affects about 1/5000 to 1/10,000 people each year... read more ).
(See also Hearing Loss Hearing Loss Worldwide, about half a billion people (almost 8% of the world's population) have hearing loss ( 1). More than 10% of people in the US have some degree of hearing loss that compromises their... read more .)
Etiology of Sudden Hearing Loss
The following are common characteristics of sudden hearing loss:
Most cases are idiopathic (see table ).
Some occur in the course of an obvious explanatory event.
A few represent the initial manifestation of another, initially occult, but identifiable disorder.
There are numerous theories for which some evidence (although conflicting and incomplete) exists. The most promising possibilities include viral infections (particularly involving herpes simplex Overview of Herpesvirus Infections Eight types of herpesviruses infect humans ( see Table: Herpesviruses That Infect Humans). After initial infection, all herpesviruses remain latent within specific host cells and may subsequently... read more ), autoimmune attacks, and acute microvascular occlusion.
Some causes of sudden hearing loss are readily apparent.
Blunt head trauma with temporal bone fracture or severe concussion involving the cochlea can cause sudden hearing loss.
Large ambient pressure changes Ear and Sinus Barotrauma Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume. It can affect the ear (causing ear pain, hearing loss, and/or vestibular symptoms) or the sinuses... read more (eg, caused by diving) or strenuous activities (eg, weightlifting) can induce a perilymphatic fistula between the middle and inner ear, causing sudden, severe symptoms. Perilymphatic fistula can also be congenital; it can spontaneously cause a sudden loss or loss may occur after trauma or severe pressure changes.
Ototoxic drugs Drug-Induced Ototoxicity A wide variety of drugs can be ototoxic. Factors affecting ototoxicity include Dose Duration of therapy Concurrent renal failure read more can result in hearing loss occurring sometimes within a day, especially with an overdose (systemically or when applied to a large wound area, such as a burn). There is a rare genetic mitochondrial-transmitted disorder that increases the susceptibility to aminoglycoside ototoxicity.
A number of infections cause sudden hearing loss during or immediately after acute illness. Common causes include bacterial meningitis Acute Bacterial Meningitis Acute bacterial meningitis is rapidly progressive bacterial infection of the meninges and subarachnoid space. Findings typically include headache, fever, and nuchal rigidity. Diagnosis is by... read more , Lyme disease Lyme Disease Lyme disease is a tick-transmitted infection caused by the spirochete Borrelia species. Early symptoms include an erythema migrans rash, which may be followed weeks to months later by... read more , and many viral infections that affect the cochlea (and sometimes the vestibular apparatus). The most common viral causes in the developed world are mumps Mumps Mumps is an acute, contagious, systemic viral disease, usually causing painful enlargement of the salivary glands, most commonly the parotids. Complications may include orchitis, meningoencephalitis... read more and herpes simplex Overview of Herpesvirus Infections Eight types of herpesviruses infect humans ( see Table: Herpesviruses That Infect Humans). After initial infection, all herpesviruses remain latent within specific host cells and may subsequently... read more . Measles Measles Measles is a highly contagious viral infection that is most common among children. It is characterized by fever, cough, coryza, conjunctivitis, an enanthem (Koplik spots) on the oral mucosa... read more is a very rare cause because most of the population is immunized.
Sudden hearing loss rarely can be an isolated first manifestation of some disorders that usually have other initial symptoms. For example, sudden hearing loss rarely may be the first manifestation of an acoustic neuroma Vestibular Schwannoma A vestibular schwannoma, also called an acoustic neuroma, is a Schwann cell–derived tumor of the 8th cranial nerve. Symptoms include unilateral hearing loss. Diagnosis is based on audiology... read more , multiple sclerosis Multiple Sclerosis (MS) Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness... read more , Meniere disease Meniere Disease Meniere disease is an inner ear disorder that causes vertigo, fluctuating sensorineural hearing loss, and tinnitus. There is no reliable diagnostic test. Vertigo and nausea are treated symptomatically... read more , or a small cerebellar stroke. Syphilis Syphilis Syphilis is caused by the spirochete Treponema pallidum and is characterized by 3 sequential symptomatic stages separated by periods of asymptomatic latent infection. Common manifestations... read more reactivation in HIV-infected patients rarely can cause sudden hearing loss.
Cogan syndrome Cogan Syndrome Cogan syndrome is a rare autoimmune disease involving the eye and the inner ear. Cogan syndrome affects young adults, with 80% of patients between 14 and 47 years. The disease appears to result... read more is a rare autoimmune reaction directed against an unknown common autoantigen in the cornea and inner ear; > 50% of patients present with vestibuloauditory symptoms. About 10 to 30% of patients also have a severe systemic vasculitis, which may include life-threatening aortitis.
Some vasculitic disorders can cause hearing loss, some of which is acute. Hematologic disorders, such as Waldenström macroglobulinemia Macroglobulinemia Macroglobulinemia is a malignant plasma cell disorder in which B cells produce excessive amounts of IgM M-proteins. Manifestations may include hyperviscosity, bleeding, recurring infections... read more , sickle cell disease Sickle Cell Disease Sickle cell disease (a hemoglobinopathy) causes a chronic hemolytic anemia occurring almost exclusively in people with African ancestry. It is caused by homozygous inheritance of genes for hemoglobin... read more , and some forms of leukemia Overview of Leukemia Leukemia is a malignant condition involving the excess production of immature or abnormal leukocytes, which eventually suppresses the production of normal blood cells and results in symptoms... read more , rarely can cause sudden hearing loss.
Evaluation of Sudden Hearing Loss
Evaluation consists of detecting and quantifying hearing loss and determining etiology (particularly reversible causes).
History of present illness should verify that loss is sudden and not chronic. The history should also note whether loss is unilateral or bilateral and whether there is a current acute event (eg, head injury, barotrauma Otic Barotrauma Otic barotrauma is ear pain or damage to the tympanic membrane caused by rapid changes in pressure. To maintain equal pressure on both sides of the tympanic membrane (TM), gas must move freely... read more [particularly a diving injury], infectious illness). Important accompanying symptoms include other otologic symptoms (eg, tinnitus, ear discharge), vestibular symptoms (eg, disorientation in the dark, vertigo), and other neurologic symptoms (eg, headache, weakness or asymmetry of the face, abnormal sense of taste).
Review of systems should seek symptoms of possible causes, including transient, migratory neurologic deficits (multiple sclerosis Multiple Sclerosis (MS) Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness... read more ) and eye irritation and redness (Cogan syndrome Cogan Syndrome Cogan syndrome is a rare autoimmune disease involving the eye and the inner ear. Cogan syndrome affects young adults, with 80% of patients between 14 and 47 years. The disease appears to result... read more ).
Past medical history should ask about known HIV or syphilis infection and risk factors for them (eg, multiple sex partners, unprotected intercourse). Family history should note close relatives with hearing loss (suggesting a congenital fistula). Drug history should specifically query current or previous use of ototoxic drugs Drug-Induced Ototoxicity A wide variety of drugs can be ototoxic. Factors affecting ototoxicity include Dose Duration of therapy Concurrent renal failure read more and whether the patient has known renal insufficiency or renal failure.
The examination focuses on the ears and hearing and on the neurologic examination.
The tympanic membrane is inspected for perforation, drainage, or other lesions. During the neurologic examination, attention should be paid to the cranial nerves (particularly the 5th, 7th, and 8th) and to vestibular and cerebellar function because abnormalities in these areas often occur with tumors of the brain stem and cerebellopontine angle.
Additionally, the eyes are examined for redness and photophobia (possible Cogan syndrome Cogan Syndrome Cogan syndrome is a rare autoimmune disease involving the eye and the inner ear. Cogan syndrome affects young adults, with 80% of patients between 14 and 47 years. The disease appears to result... read more ), and the skin is examined for rash (eg, viral infection, syphilis Syphilis Syphilis is caused by the spirochete Treponema pallidum and is characterized by 3 sequential symptomatic stages separated by periods of asymptomatic latent infection. Common manifestations... read more ).
Findings of particular concern are
Abnormalities of cranial nerves (other than hearing loss)
Significant asymmetry in speech understanding between the 2 ears
Other neurologic symptoms and signs (eg, motor weakness, aphasia, Horner syndrome, sensory or temperature sensation abnormalities)
Interpretation of findings
Traumatic, ototoxic, and some infectious causes are usually apparent clinically. A patient with perilymphatic fistula may hear an explosive sound in the affected ear when the fistula occurs and may also have sudden vertigo, nystagmus, and tinnitus.
Focal neurologic abnormalities are of particular concern. The 5th cranial nerve, 7th cranial nerve, or both are often affected by tumors that involve the 8th cranial nerve, so loss of facial sensation and weak jaw clench (5th) and hemifacial weakness and taste abnormalities (7th) point to a lesion in that area.
Fluctuating unilateral hearing loss accompanied by aural fullness, tinnitus, and vertigo also suggests Meniere syndrome Meniere Disease Meniere disease is an inner ear disorder that causes vertigo, fluctuating sensorineural hearing loss, and tinnitus. There is no reliable diagnostic test. Vertigo and nausea are treated symptomatically... read more . Systemic symptoms suggesting inflammation (eg, fevers, rash, joint pains, mucosal lesions) should raise suspicion of an occult infection or autoimmune disorder.
Patients should have an audiogram, and unless the diagnosis is clearly an acute infection or drug toxicity, most clinicians do gadolinium-enhanced MRI to diagnose inapparent causes, particularly for unilateral losses. Patients with an acute traumatic cause also should have MRI. A perilymphatic fistula is typically suspected from an inciting event (eg, excessive strain, barotrauma), and testing may be done by using positive pneumatic pressure to evoke eye movements (nystagmus). CT of the temporal bones is usually done to show the bony characteristics of the inner ear and can help elucidate congenital abnormalities (eg, enlarged vestibular aqueduct), fractures of the temporal bone from trauma, or erosive processes (eg, cholesteatoma).
Patients who have risk factors for or symptoms that suggest causes should have appropriate tests based on clinical evaluation (eg, serologic tests for possible HIV infection or syphilis, complete blood count [CBC] and coagulation profile for hematologic disorders, erythrocyte sedimentation rate [ESR] and antinuclear antibodies for vasculitis).
Treatment of Sudden Hearing Loss
Treatment of sudden hearing loss focuses on the causative disorder when known. Fistulas are explored and repaired surgically when bed rest fails to control symptoms.
In viral and idiopathic cases, hearing returns to normal in about 50% of patients and is partially recovered in others.
In patients who recover their hearing, improvement usually occurs within 10 to 14 days.
Recovery from an ototoxic drug varies greatly depending on the drug and its dosage. With some drugs (eg, aspirin, diuretics), hearing loss resolves within 24 hours, whereas other drugs (eg, antibiotics, chemotherapy drugs) often cause permanent hearing loss if safe dosages have been exceeded.
For patients with idiopathic loss, many clinicians empirically give a course of glucocorticoids (typically prednisone 60 mg orally once a day for 7 to 14 days followed by a 5 day taper). Glucocorticoids can be given orally and/or by transtympanic injection. Direct transtympanic injection avoids the systemic side effects of oral glucocorticoids and appears equally effective except in profound (> 90 decibels) hearing loss. There are data showing that using both oral and intratympanic steroids leads to better outcomes than either alone. Although clinicians often give antiviral drugs effective against herpes simplex (eg, valacyclovir, famciclovir), data show that such drugs do not affect hearing outcomes. There are some limited data suggesting that hyperbaric oxygen therapy may be beneficial in idiopathic sudden hearing loss.
Most cases of sudden hearing loss are idiopathic.
A few cases have an obvious cause (eg, major trauma, acute infection, drugs).
A very few cases represent unusual manifestations of treatable disorders.
Evaluation includes audiometry, CT and MRI, and other tests for suspected causes.
Treatment focuses on known causes, and corticosteroids are given in cases of idiopathic sudden hearing loss.