Tinnitus Causes and Mechanisms

What is tinnitus?

A subjective phantom perception of sound in head or in the ears without any external source

What is somatosensory tinnitus?

This is an objective, evoked acoustic event that is generated in the head or neck regions due to blood flow, myogenic activity, vascular pulsation, myoclonus, a patulous eustachian tube, etc.

Can somatosensory tinnitus be changed by body movements?

Yes

What percentage of tinnitus is subjective?

95% of all cases (meaning it’s only heard by the patients)

Where does subjective tinnitus originate in?

It originates in the peripheral and/or central auditory pathway

What percentage of tinnitus is objective?

5% of cases (meaning it can be heard by others)

What is evoked tinnitus?

This is a type of somatosensory tinnitus where a patient can hear/stop hearing it on their own decision

List types of tinnitus sounds from most often heard to least often heard (6)

1. Ringing 37.5%

2. Buzzing 11.2%

3. Cricket-like 8.5%

4. Hissing 7.8%

5. Whistling 6.6%

6. Humming 5.3%

What percentage of tinnitus is bilateral?

60%

What percentage of tinnitus is unilateral?

30%

What percentage of tinnitus is in someone’s head?

10%

While hearing loss increases with age, the prevalence of bothersome tinnitus _______________ after the age of 70 years

levels off/decreases

Is there any clear source of tinnitus?

No

What are 6 potential causes/mechanisms of tinnitus?

1. Central origin

2. Vascular lesion

3. Muscular lesion

4. Auditory nerve lesions

5. Cochlear lesions

6. Outer/middle ear lesions

What are 3 evidences that we have for a central origin of tinnitus?

1. Hyperactive CNS

2. Central gain

3. PET and fMRI scans

What is central gain?

When hearing loss “uncovers” the internal noise

The brain compensates for hearing loss by becoming more sensitive (central gain)

What are a few examples of vascular etiologies of tinnitus?

1. Vascular tumor

2. Aneurysm/stenosis of carotid artery

3. Cardiac murmur

4. Persistent stapedial artery

How does a vascular lesion cause tinnitus?

Well, usually, in most blood vessels, blood flow is inaudible.

When the blood loses this quality, it assumes a random pattern and causes a vibration of the vessel wall, which is then audible to the patient

A vascular lesion causes pulsatile tinnitus which can be either….

Bruit (artery lesion) or Hum (venous lesion)

What is bruit tinnitus?

Turbulent blood flow in vessels close to temporal bone

What are 4 bruit pulsatile tinnitus etiologies?

1. Vascular tumors

2. Aneurysm/stenosis of carotid artery

3. Cardiac murmurs

4. Persistent stapedial artery

What is a venous hum tinnitus?

Basically, blood flow disturbances in the region of the ear

What are 7 examples of venous hum conditions?

1. Dehiscent jugular bulb

2. Transverse sinus stenosis

3. Anemia

4. Thyrotoxicosis

5. Pregnancy

6. Benign intracranial hypertension

7. Arteriovenous malformation

How do we decrease venous hum in a physical assessment?

1. Gentle anterior neck pressure

2. Head toward uninvolved side

How do we increase venous hum in a physical assessment?

1. Head toward involved side

2. Deep breathing and valsalva

How do we treat venous hum tinnitus?

Through reassurance and correcting underlying cause

A glomus patient can be “heard” by patient as what 3 sounds?

1. Murmur

2. Venous hum

3. Pulsating sound

What would a glomus tumor look like on otoscopy?

1. Bluish/reddish mass

2. Possible pulsation/ TM movement

3. Paling with positive pressure

What imaging would we get done on a vascular lesion?

MRI and arteriography

How do we treat vascular lesions?

Surgically

What type of lesion can be associated with clicking tinnitus?

Muscular lesions

What are 2 types of objective tinnitus?

1. Vascular lesions

2. Muscle lesions

What is palatal myoclonus?

It is a rhythmic, involuntary contraction of the muscles in the soft palate (roof of the mouth)

What two muscles is palatal myoclonus associated with?

It can be associated with tensor tympani or stapedius muscle myoclonus which can result in abnormal rhythmic activity of muscles, and can be transient

What are symptoms of palatal myoclonus cause of tinnitus?

Intermittent tinnitus correlates with contractions of the soft palate and oropharyngeal muscles

What will the tympanogram show on palatal myoclonus?

Rhythmic jerks, synchronous contraction or clicking tinnitus

What would the MRI of palatal myoclonus show?

Degeneration of inferior olivary nucleus in the medulla oblongata underneath the superior olivary complex

How would we diagnose palatal myoclonus?

EMG of palatal muscles

What are the 3 symptoms of tensor tympani muscle spasms (myoclonus)?

1. repetitive, irregular contractions of muscles

2. Intermittent, rough cracking noise in the ear, triggered by noise

3. Sometimes ear fullness

What is another example of a muscle lesion etiology of tinnitus?

Patulous ET (the mucosa of the ET snaps together)

Which cochlear nuclei plays a pivotal role in somatic tinnitus perception?

Dorsal cochlear nuclei

T/F. Patients may be able to change the sounds of their tinnitus by forceful head and neck contractions

True

What is a vestibular schwannoma?

AKA an acoustic neuroma

A non-cancerous (benign) tumor that grows on the nerve connecting the inner ear to the brain (vestibulocochlear nerve)

What kind of hearing loss is indicative of vestibular schwannoma?

Unilateral tinnitus with or without SNHL (sudden or progressive)

What type of imaging is required in patients with unilateral tinnitus?

MRI

What are 2 auditory nerve lesion causes of tinnitus?

1. Vestibular schwannoma

2. Vascular loop

What is a vascular loop?

When there is a loop of the anterior inferior cerebellar artery (AICA) around the VII nerve causing a reduction of it’s diameter

What are 5 symptoms of vascular loop?

1. SNHL

2. Good WRS

3. Normal caloric testing

4. No tumor on MRI

What are 3 most common cochlear lesions?

1. Presbycusis

2. Noise trauma

3. Meniere’s disease

What type of tinnitus comes from presbycusis?

Constant, bilateral, high-frequency tinnitus

What tinnitus is more severe, presbycusis induced or noise trauma induced?

Noise trauma induced

What type of tinnitus comes from noise trauma?

Constant, high frequency tinnitus

What kind of tinnitus comes from Meniere’s disease?

Low-pitched roaring sound, very loud

What other symptoms are of meniere’s disease?

Low frequency SNHL

Vertigo

Aural fullness

Acute attacks

Can a patient with a non-functioning cochlea have tinnitus?

Yes!

What percentage of patients still had tinnitus after having their 8th nerve severed?

50% of patients

List 7 cochlear mechanisms of tinnitus

1. Discordant damage of OHC and IHC

2. Cross-talk between 8th nerve fibers

3. Ionic imbalance

4. Dysfunction of cochlear neurotransmitter systems

5. Stereocilia decoupling

6. Aberrant behavior of the efferent system

7. Central origin

What is a SOAE-related tinnitus?

When tinnitus is caused by spontaneous otoacousti emissions

What is the prevalence of SOAE-related tinnitus?

4%

What are 5 middle/outer ear lesions that can cause tinnitus?

1. Otosclerosis

2. Middle ear effusion

3. Tumors

4. Impacted wax

5. Otomycosis

How does otosclerosis, MEE< tumors, impacted wax, or otomycosis induce tinnitus?

The CHL masks out environmental noise and allows the background “body noise” to become apparent leading to tinnitus

What are 6 general causes of tinnitus?

1. Hormonal changes

2. Diabetes

3. Fibromyalgia

4. Lyme disease

5. Vitamin deficiency

6. Exposure to lead, chemicals

What are 5 triggers of tinnitus?

1. Red wine, grain-based spirits, alcohol

2. Nicotine, marijuana

3. Caffeine, cheese, chocolate, some spices

4. Monosodium glutamate (MSG)

5. Foods high in sugar

What are 5 reasons why tinnitus is so difficult to deal with?

1. Tinnitus is a phantom perception that cannot be measured objectively

2. Tinnitus is a symptom not a disease

3. Lack of proven mechanisms of tinnitus

4. tinnitus has a variety of causes

5. Perception of tinnitus has powerful connections with our emotional system