Tinnitus

Tinnitus is the perception of a sound which has no external source.  It is a common symptom with multiple causes.  Occasionally tinnitus can be a symptom of serious disease.  Primary tinnitus may be idiopathic or may be associated with sensorineural hearing loss.  Secondary tinnitus is associated with a specific cause other than sensorineural hearing loss such as middle or inner ear dysfunction, auditory nerve pathology, intracranial hypertension or myoclonus.

EPIDEMIOLOGY

Twenty five percent of people have experienced tinnitus.  Eight percent experience it frequently and approximately 20% of these will require medical intervention.  Tinnitus is more commonly present in males, in caucasians, in individuals with a BMI greater than 30 and in patients with hypertension, diabetes, hyperlipidemia, anxiety and a history of loud noise exposure.

Tinnitus carries significant economic costs.  It is estimated that 2.75 billion dollars is spent annually in disability compensation for US veterans alone.  Tinnitus is the most prevalent service connected disability.  Tinnitus also reduces employee productivity.

PRESENTATION

There is great variability in the sound that is perceived as tinnitus.  It may be described as a ringing, a roaring, a buzzing, a clicking or as pulsations.  Tinnitus may be in one or both ears and there is a variable effect on the quality of life.  Insomnia is one of the most prominent symptoms when tinnitus first presents.  Tinnitus can also interfere with understanding normal speech, can result in depression and interfere with concentration and sleep.   There is a 48 to 60% incidence of depression among tinnitus sufferers and there is a direct correlation between the severity of the tinnitus and the incidence of depression.  The severity of tinnitus can be constant or can fluctuate.  There is a natural process of habituation which may improve the tolerance to tinnitus in some patients, but others may worsen with time.  Tinnitus may be completely subjective but in some individuals tinnitus may be objective and be heard by a listener.

The pathophysiology, evaluation, workup and treatment of tinnitus differs significantly depending on whether the tinnitus is primary or secondary.  They will be presented here separately.

PRIMARY TINNITUS

Pathophysiology:  Primary tinnitus may result from central adaptation to hearing loss from injury in the cochlea.  Peripheral injury releases inhibitory tone of frequency specific afferents along tonotopic pathways.  Tinnitus frequency usually correlates with the frequency of the hearing loss. The tinnitus frequency is usually at the point of the audiogram where the slope of the hearing loss is the greatest.  This may be because of cortical overrepresentation of pathways from this region of the greatest slope.

WORKUP OF  TINNITUS

The workup of tinnitus involves a targeted history and physical in order to identify potentially treatable conditions of secondary tinnitus or coexisting conditions such as depression and anxiety.  The onset, duration, character, laterality, pulsatile character, effect on quality of life, associated hearing loss, noise exposure history, history of ototoxic medication use, presence of dizziness, depression and anxiety are all ascertained.  It is important to determine if the patient has severely bothersome tinnitus with a large effect on quality of life, communication, sleep or concentration.  There are validated questionnaires and indices of tinnitus severity.  If the tinnitus is persistent and has been present for greater then 6 months, it is less likely to resolve spontaneously.  New onset tinnitus may improve over time with habituation.

A head and neck exam, otoscopy and a focus neurotologic exam as well as auscultation of the head and neck are important in every patient with tinnitus.

A routine audiologic exam should be performed for all patients regardless of the duration, laterality or their perceived hearing ability as tinnitus may be a sign of hearing loss not appreciated by the patient.  When hearing loss is identified hearing remediation treatment can be started.  In patients who have tinnitus that is single-sided, of new onset or associated with hearing impairment it is important to perform a comprehensive audiologic exam promptly within a period of 2 weeks.

Unilateral tinnitus is more likely to be associated with vascular pathology or schwannoma.  Imaging is useful only in unilateral or pulsatile tinnitus, asymmetric hearing loss or in patients with focal neurologic abnormalities.  Imaging is not useful or cost effective in patients with bilateral tinnitus and symmetric hearing.

TREATMENT

Patient education:  Patients should be reassured that tinnitus is a symptom and not itself a dangerous condition, and that workup can identify or exclude a condition that would require treatment.  Patients with noise-induced hearing loss will be identified and hearing protection can be prescribed to prevent further cochlear injury.

Although there is no cure for primary tinnitus, there are strategies to manage symptoms.  Some of these include a hearing aid for patients with hearing loss and bothersome tinnitus.  This is perhaps the most effective way to improve tinnitus, as the tinnitus becomes more tolerable when it is masked by noise that is from the environment and that is useful in that it is supplying information in frequencies at which there is hearing loss.  Some patients may benefit from cognitive behavioral therapy.  This is used to identify and restructure negative thoughts about tinnitus, to teach relaxation techniques and sleep hygiene.  This is performed by mental health professionals with a special interest in this therapy technique.  The format usually involves weekly sessions for 8 to 24 weeks.  Studies show improvement in questionnaire scores and quality of life, but not in the tinnitus loudness itself.

Masking using an external sound source in the room or on the ear can be useful especially in quiet environments where there is a significant contrast between the sound of the tinnitus and the quiet of the room.  Appropriately used, sound therapy should be loud enough to decrease contrast and not to mask the tinnitus completely.  When this is done the perception of tinnitus changes, the patient’s reaction to the tinnitus improves, and habituation is promoted.

MEDICATIONS AND SUPPLEMENTS FOR PRIMARY TINNITUS

Medications and supplements for primary tinnitus are of questionable value, although anxiolytics may be useful as a bridge in severely effected patients while cognitive behavioral therapy is arranged.  They, along with antidepressant and anticonvulsants have not been shown to be effective and may have many side-effects.  There is also no proven efficacy in high quality studies for gingko biloba, melatonin, zinc or other dietary supplements.  There has been no evidence of benefit for intratympanic injection of steroid over placebo.

Acupuncture can be helpful but a review of studies shows conflicting data regarding efficacy of acupuncture among tinnitus patients.  Repetitive Transcranial Magnetic Stimulation has reduced tinnitus in many subjects but because of conflicting data there is no proof of long term benefit or recommendation for mainstream use.

SECONDARY TINNITUS

Secondary tinnitus may be spontaneous, it may have a mechanical cause or it may be pulsatile.

Spontaneous secondary tinnitus may be due to otoacoustic emissions and may be present and reversible if a conductive hearing loss is corrected.  A conductive hearing loss causes otoacoustic emissions which usually emanate through the middle ear to the external canal from doing so. They create a feedback loop in the ear if a conductive hearing loss is present, and tinnitus may result.  Approximately 50% of otosclerosis patients with tinnitus will have an improvement in the symptom of tinnitus if the air bone gap is improved to within 15 decibels.
Mechanical causes of secondary tinnitus include myoclonus.  This can involve the tensor veli palantini muscle, the levator veli palantini, the salpingopharyngeus, stapedis or tensor tympani muscles.  Myoclonus is the most common nonvascular cause of mechanical tinnitus.  It may cause an objective pulsatile tinnitus and patients may actually feel a sense of movement in their middle ear when the tensor tympani or stapedius muscles are involved.  This is more common in the first 3 decades of life. Tensor tympani myoclonus is often associated with headache and responds to headache treatment.

A patulous eustachian tube results in autophony and is usually present in a patient with a recent large weight loss.  The patient will complain especially of respiratory and voice autophony and respiratory movements of the tympanic membrane can usually be seen on otoscopy.  Because the eustachian tube may engorge and close when the patient is recumbent, symptoms may disappear when the patient lies down.  These patients benefit from weight gain.  Tympanostomy tube placement can be helpful in approximately half of patients and other severely affected patients may benefit from eustachian tube obstruction surgery.

PULSATILE TINNITUS

Patients with pulsatile tinnitus are much more likely to have venous pulsations than arterial pulsations.  Pulsatile tinnitus may occur because of stenosis, compression, abnormal change in the vascular contour of or increased flow that may lead to turbulent blood flow. Pulsatile tinnitus tends to be unilateral.  Examples of arterial pulsatile tinnitus are arteriovenous malformations, arteriovenous fistulas, Paget’s disease, aneurysm, atherosclerosis, fibromuscular dysplasia of the carotid artery, vascular loop and glomus tumors.  Examples of venous pulsatile tinnitus include benign intracranial hypertension (BIH), jugular bulb diverticula, lateral sinus stenosis and superior canal dehiscence.

In benign intracranial hypertension (BIH) tinnitus may be associated with hearing loss, dizziness and aural fullness.  This is caused by increased intracranial pressure usually in obese women of childbearing age.  It is one of the most common causes of venous pulsatile tinnitus.  Another  cause is superior semicircular canal dehiscence when there is a dehiscence between the superior semicircular canal and the superior petrosal sinus.

The jugular venous drainage system is larger on the right side in 85% of individuals. Pulsatile tinnitus may be caused by turbulent flow in the jugular bulb associated with increased flow(anemia, thyrotoxicosis, pregnancy) or increased intracranial pressure and involves the dominant side of venous drainage. Patients with sigmoid sinus diverticulum may have venous pulsatile tinnitus when even small areas of the cortex of the sigmoid sinus or jugular bulb are exposed, because these small areas can cause turbulent flow. Venous pulsatile tinnitus can be caused by stenosis of the transverse sinus.  This is usually associated arachnoid granulations growing within and constricting the sinus, but can also be caused by thrombus formation.

EVALUATION OF PATIENTS WITH PULSATILE TINNITUS

The history in these patients should include the onset, character and modifying factors of the tinnitus.  The age of the patient is important, as in benign intracranial hypertension females tend to be of childbearing age.  Arterial venous malformations become symptomatic in the fifth to sixth decades of life.  Atherosclerosis tends to be present in the elderly.  Fibromuscular dysplasia is present most commonly in women between 20 and 60 years of age.  If a patient has a glomus tumor the pulsatile tinnitus tends to be unilateral and is associated with a conductive hearing loss, as well as findings on otoscopy.

EXAMINATION IN PULSATILE TINNITUS

On otoscopy the middle ear should be evaluated for the presence of glomus tumor, high jugular bulb, diverticula, effusion, a white mass that could be an aberrant carotid artery or abnormal movements of the tympanic membrane which may be present with myoclonus, a patulous eustachian tube or pulsation of an encephalocele.  Auscultation should be performed in the neck over the carotids, ear canal, orbits, and  chest.  By applying pressure over the internal jugular vein or turning the head to one side, which occludes the ipsilateral jugular vein, a decreased in ipsilateral pulsatile tinnitus indicates a venous cause of pulsations.  This is an important maneuver that drives the direction of workup in these patients.  The patient should be able to correlate their own heartbeat with their pulsations.  Nasal endoscopy of the eustachian tube orifice can identify palatal myoclonus.  A funduscopic examination may reveal papilledema.  Valsalva may temporarily reduce tinnitus associated with venous hums or a patulous eustachian tube.  The weber may lateralize from the head or the ankle to an ear with superior canal dehiscence.

AUDIOLOGY

In benign intracranial hypertension patients may have a low frequency hearing loss that actually reverses with internal jugular venous compression.  In superior canal dehiscence patients may have a low frequency conductive hearing loss with supranormal bone thresholds.  Conductive hearing loss itself may make any internal sound more evident.  On tympanometry a patulous eustachian tube shows respiratory movements and stapedes or tensor tympani myoclonus will be visible on tracings.  ABR may be useful on patients with benign intracranial hypertension as a third of patients may show prolonged interpeak latencies.

LABORATORY WORKUP

A metabolic workup of patients with pulsatile tinnitus is rarely revealing but patients with evidence of hyperdynamic flow do deserve a CBC and thyroid function tests, and an inquiry as to their pregnancy status.  A lipid profile and fasting blood glucose may be performed if atherosclerotic disease is suspected.  Alkaline phosphatase will be elevated in patients with Paget’s disease.

Carotid duplex ultrasound including the subclavian arteries can be helpful if patients have a bruit in the neck.  An echocardiogram should be ordered if it is suspected that the patient has severe cardiac or valvular disease.  If the patient has isolated carotid bruits, a carotid ultrasound should be ordered before CT angiography of the head and neck.

Radiologic evaluation of patients with pulsatile tinnitus:  A radiologic evaluation should be based on the otoscopic findings and characteristics of the tinnitus.  In patients with normal otoscopy and venous pulsatile tinnitus, a CT of the temporal bones is usually the most valuable test.  It may identify sigmoid sinus dehiscence or diverticula, a superior canal dehiscence, and thinning of the temporal squamosa and tegmen dehiscence which can be associated with increased intracranial pressure and benign intracranial hypertension.  The MRI, MRangiogram and MR venogram are also valuable in these patients if the CT of the temporal bones is negative.  MRI may identify jugular bulb and dural venous sinus abnormalities, and signs of increased intracranial pressures such as empty cella, small ventricles and flattened posterior globes.  If the patient has arterial pulsatile tinnitus and has normal otoscopy, a CT angiogram including the upper neck is valuable.  It may identify cervical vascular pathology including carotid body tumor, any tortuosity of the carotid vessels, arterial venous fistula and AVM, carotid artery dissections or aneurysms, cervical or intracranial atherosclerotic disease and fibromuscular dysplasia.

In patients who have abnormal otoscopy a CT angiogram of the temporal bones may be done first and supply valuable information.  This will identify ectopic carotid artery, jugular bulb abnormalities, glomus tumor and associated carotid body tumors.  Carotid angiography is suggested only if a strong suspicion of arterial venous malformation or AVM is present, as these patients may often be managed endo vascularly.

OTHER TESTING

Patients with benign intracranial hypertension or any suspicion of increased intracranial pressure may undergo a lumbar puncture for opening pressures, as this may guide treatment.

MANAGEMENT OF PULSATILE TINNITUS

The management of pulsatile tinnitus is directed at the underlying cause. In benign intracranial hypertension education of the patient on the association of symptoms with obesity is important and focus on weight reduction is of paramount importance.  Acetazolamide may reduce symptoms but rarely eliminate the tinnitus completely.  Some patients may benefit from shunting if their tinnitus is disabling, or if there are vision changes.  Patients may respond to bariatric surgery.  These patients should be followed by ophthalmology and neurology as well.

Patients with advanced cardiac and vascular disease should consider surgical intervention if pulsatile tinnitus is severely bothersome.  Carotid endarterectomy and angioplasty with stenting may be beneficial, especially if carotid stenosis is 70% or greater.  Patients with glomus tympanicum or hypotympanic tumor will benefit from surgery.  Patients with glomus jugulare tumors will benefit from either surgery or focused radiation.  Patients with carotid artery dissection may benefit from anticoagulation to prevent embolism.  If a dehiscent jugular bulb is present a surgical repair with bone dust, perichondrium or a cartilage graft is beneficial.  If myoclonus of the tensor tympani or stapedes muscle is present and migraine is present, migraine management should occur first before surgical section of the tensor tympani or stapedes muscles.  Patients with levator veli palatini myoclonus may benefit from Botox, although temporary palatal insufficiency may become a limiting consequence of therapy that prevents long term use of this treatment.  Patients who have a dural arteriovenous fistula may benefit from coiling or embolization. When patients have semicircular canal dehiscence at the superior petrosal sinus the dehiscence is unable to be visualized through a middle fossa approach, and a transmastoid surgical repair can be successful.

Many surgeons have tried to ligate the ipsilateral internal jugular vein when pulsatile tinnitus is present.  This generally has poor results as collateral pathways of blood flow maintain turbulence at the symptomatic point and symptoms tend to return very quickly after surgery.