Hearing Disorders

By understanding how things go right, we understand how they go wrong

• So we've already covered a number of hearing disorders

  • There's a bit more to mop up, though!

• Today, we're going to focus on causes of hearing loss, deafness, and weirdness in hearing!

Today's Plan

• Causes of acquired hearing loss

• Presbycusis

• Causes of congenital hearing loss

• Tinnitus

Causes of acquired hearing loss

'Acquired' hearing loss means the person could hear at some point

• As opposed to congenital (also 'pre-lingual') deafness, which is from birth

Trauma

• Barotrauma

  • Can cause rupture or fistula of the TM, round window, or cochlear membranes

• Skull fractures

  • You can imagine how that might mess things up

• Middle ear damage

  • Insertion trauma

Noise Related Hearing Loss

• This is the big one

• We've talked about it a bunch

• Protect your ears!

Disorders of the Outer Ear

• Cerumen Impaction

  • Wax blockage causes hearing loss

• Foreign Objects

  • Plz do not insert objects into your ear

• Otitis Externa

  • Infection of the ear canal leading to swelling and pain

Disorders of the Middle Ear

• Otitis Media

  • Infection of fluid in the middle ear

• Ossicular Dislocation

  • The Ossicles aren't properly attached

• Eustachian tube dysfunction

  • When pressure cannot equalize and fluid cannot drain

Cholesteatoma

• A non-cancerous growth in the middle ear

  • Usually associated with repeated OM, but not always

• Grows, eventually involving the ossicles, TM, and more

• Diagnosable from otoscopy or MRI

• Removed surgically

Ménière's disease

• Overpressure of endolymph affecting hearing and balance

• Causes are unclear

• Often has strong vestibular and hearing effects

Ototoxicity

• Medications or chemicals which affect (generally) the organ of corti

• Mechanism can be cell death, blocking the endocochlear potential, and more!

  • Quinine compounds, loop diuretics, aminoglycoside antibiotics (for some), and many more

• Opioid painkiller (ab)use can causing hearing loss

  • Rush Limbaugh's hearing loss is widely attributed to painkiller abuse

• Alcohol is vestibulotoxic, in the short term

  • Hence drunk people not being able to balance

Disease Related Hearing Loss

• Many diseases can affect hearing

• Chicken Pox, Cytomegalovirus, Mumps, Meningitis, and lots more

• These have various effects on the organ of corti

• The exact mechanisms here are often frustratingly vague!

Autoimmune Diseases and Hearing loss

• When your body attacks the structures needed for hearing, you lose hearing

Acoustic Neuroma and Otosclerosis

• More on this in 'Surgical Interventions'!

... but the hearing disorder most people are familiar with is...

Presbycusis

Presbycusis

• Also known as 'age-related hearing loss'

• Also known as

Physiopathology of Presbycusis

• We're not 100% sure of the exact pathology

• There appears to be a genetic component which influences the degree of it

• Different people have different characteristics of loss

• These fit into different 'types'

Some potential causes of presbycusis

• Mechanical: Stiffening of the basilar membrane

• Neural: Degeneration of the auditory nerves and spiral ganglion

• Metabolic: Loss of bloodflow and atrophy of the stria vascularis

• Sensory: Degradation of OHCs

• These can be mixed together, and people can be unique

One nice way to put it

Presbycusis is likely caused by the accumulation of various auditory insults over years.

• Roehm C.E., Marino J., Parham K. (2013) Presbycusis. In: Kountakis S.E. (eds) Encyclopedia of Otolaryngology, Head and Neck Surgery. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-23499-6_551

Presbycusis is the check at the end of the meal

• "No, I can go shooting without hearing protection, it's fine the next morning"

• "Going to that concert without protection was fine, I didn't even notice anything!"

• "Oh, luckily that medication didn't affect me"

• "Smoking doesn't cause hearing loss, I hear things just fine"

• Your cochlea remembers!

Even if you're not losing hearing now, take care!

• Because sooner or later, you'll be paying the bill

There is no treatment for presbycusis

• Particularly given that there's no one cause

• Patients are generally 'treated' with amplification or CIs

• ... but that's all we can do

OK, so that's how people lose hearing

• What about people who never started with it?

Causes of 'Pre-Lingual' or Congenital Deafness

Hereditary Genetic Conditions

• Around 50% of deafness in children is genetic in nature

• GJB2-related Congenital Deafness is the most common

  • The Connexin 26 (CX26) protein is rendered non-functional, and it helps with K+ transport

• These are recessive mutations

  • People can carry the mutation without being Deaf

  • This is why many hearing people have Deaf children

• Here's a pamphlet on genetics of hearing loss

Genetic 'Syndromes'

• Here, deafness occurs alongside other developmental abnormalities

• Down Syndrome, Usher Syndrome, Treacher Collins Syndrome, and many more

• The source of the hearing loss varies

  • Down Syndrome is usually conductive loss

  • Usher syndrome is hair cell related and often causes balance issues too

  • Treacher Collins is due to...

Atresia, Microtia and Anotia

• The pinna or ear canal are small, ill-formed or missing

• Many different extents, with different effects

• Always a conductive loss

In-Utero Disease Exposure

• Rubella, Influenza, Mumps are the big ones

• Also Cytomegalovirus, toxoplasmosis, and herpes

• The mother may be relatively unaffected, but deafness may still occur

An aside: The MMR Vaccine is 'Measles, Mumps, and Rubella'

• Measles and Mumps causes hearing loss in children and adults

• Rubella causes deafness in utero

• The MMRV vaccine also covers Chicken Pox

  • Which is also linked to hearing loss

• There is no link between vaccines and autism, and the study this myth is based on was falsified

• If you care about hearing, vaccinate your kids

In-Utero Ototoxicity

• The same compounds which can cause deafness in adults can cause congenital hearing loss

• Methylmercury is more dangerous during development than to adult hearing!

• "Exposure to methylmercury most commonly occurs when people eat kinds of fish and shellfish that have high levels of methylmercury in their tissues"

There are more possible causes

• Hearing is very complex, and subtle changes during development can have non-subtle effects

• ... but those are some of the most common causes

... so that's why hearing goes away

• But do people ever hear MORE than they want to?

Tinnitus

Tinnitus is the sensation of sound which is not present

• "ringing", "buzzing", "static", "hissing", "roaring", "grasshoppers"

• Can be a single 'pitch' or broadband, at any pitch

• Can be 'quiet' or 'loud'

• Can be in one ear or both

Tinnitus is a phenomenon, not a disease

• It's caused by many different things

• Generally associated with hearing loss and noise exposure

  • ... but not always

Tinnitus is NOT the same as auditory hallucination

• Auditory hallucination is a common symptom of psychiatric disorders

• Tinnitus perceptions are very basic ('ringing' or 'hissing' or 'noise')

• Auditory hallucinations are the perception of complex sounds which aren't real

  • e.g. voices, footsteps, music, animal sounds

• Tinnitus is usually not interpretable or confusable with sounds originating in the real world

  • People 'know their tinnitus'

Tinnitus can be temporary or permanent

• "Ringing in your ears" after head, acoustic, or pressure trauma

  • 'My ears are still ringing from that concert'

• Some mildly ototoxic drugs cause tinnitus for the duration of use

Tinnitus can be subjective or objective

• Objective tinnitus is actual noise inside your head

  • Pulsatile bloodflow, whooshing from heart murmurs, etc

  • Somebody else can hear the noise with a stethoscope

• Subjective tinnitus is the sensation of noise which is not objectively present

  • This is the far more common version!

There are other interesting causes of sound perception

• Here's a nice video on 'The Hum' which discusses possible sources for it.

We don't understand how it works, exactly!

• We suspect it's more of a 'brain' thing than an 'ear' thing

• There's not a scientific consensus on the causes

Possible sources of tinnitus

• The brain trying to 'turn up sensitivity' due to missing or damaged hair cells

• Phantom hearing, along the lines of 'phantom pain' from a healed injury

• Neural connection imbalances or failures

• ... and many more!

Long term effects of tinnitus

• There is no 'damage' or 'harm' caused by tinnitus

• Hearing is not further 'reduced' by it, and it has no balance effects

• Many people live with it without troubles

• It's annoying as heck

Reducing the emotional and quality-of-life impact of tinnitus

• Counseling and Therapy (Cognitive behavioral therapy) to reduce the psychoemotional impact

• Masking the tinnitus (using music, background noise, or sound generators)

  • Wearable masking devices are a thing

• Acoustic Neural stimulus approaches

  • Feeding in a signal designed to compensate for the specific patient's hearing loss profile

  • The literature is unclear about effectiveness here

So, tinnitus is super common

• ... but not super understood

• and not really 'treatable' at this time!

Wrapping up

• There are many causes of adult hearing loss

• Age-related hearing loss is common, and steps you take today can reduce it

• Congenital deafness is often genetic, but can have other causes

• ... and tinnitus is as annoying as it is poorly understood

Next time

Audiology, from an Audiologist!

Thank you!