# Hearing Disorders ### Will Styler - LIGN 113 --- ### 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 - 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](https://www.cdc.gov/ncbddd/hearingloss/freematerials/parentsguide508.pdf) --- ### 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](https://www.mayoclinichealthsystem.org/hometown-health/speaking-of-health/autism-vaccine-link-debunked) - 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](https://www.psychiatrictimes.com/view/auditory-hallucinations-psychiatric-illness) - 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' - Except maybe in audiograms! --- ### 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! --- ### 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](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4134889/) - 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!