Hearing Loss Etiology and Impact

• Module 3 covers the structure of the ear and disorders that can affect it.

Outer Ear Disorders

• Microtia is a condition where the external ear (pinna) is underdeveloped or absent, usually unilateral but can be bilateral.
• Microtia is associated with atresia, leading to conductive hearing loss, and can be caused by genetic mutations, environmental factors during fetal development, syndromic conditions like Treacher Collins Syndrome or Goldenhar Syndrome, and vascular disruption.
• Atresia is the absence or underdevelopment of the external auditory meatus, leading to conductive hearing loss.
• Atresia is caused by congenital factors like Treacher Collins Syndrome, Goldenhar Syndrome, genetic mutations, environmental factors, and vascular disruption.
• Exostosis, also known as "Surfer's Ear," is the development of bone growths in the ear canal, caused by repeated exposure to cold water and wind.
• Exostosis can lead to conductive hearing loss when the bony growths become large enough to block the ear canal.
• Earplugs or swim caps can help with prevention, but surgery resolves existing exostosis.
• Cerumen impaction is the accumulation of earwax in the ear canal, blocking sound transmission and causing conductive hearing loss, tinnitus, ear pain, dizziness, or a feeling of fullness.
• Avoid cotton swabs to prevent cerumen impaction; instead, use earwax-softening drops and allow earwax to drain naturally.
• Microtia and cerumen impaction affect the collection, defection and direction of sound, while atresia and exostosis affect direction and resonance.

Middle Ear Disorders

• Tympanic membrane perforation involves a tear or hole in the eardrum, caused by pressure from effusion, foreign objects, or trauma, and usually heals unless tympanoplasty is needed.
• Otitis media is an infection or inflammation of the middle ear, often caused by fluid buildup due to Eustachian tube dysfunction, treated with decongestants, antihistamines, or antibiotics.
• Eustachian tube dysfunction arises when the tube does not open, causing negative middle ear pressure, fluid buildup, retracted eardrum, and potential hearing loss, triggered by altitude changes, infections, or allergies, and treated with decongestants, antihistamines, or antibiotics.
• Cholesteatoma involves a buildup of dead skin cells in the middle ear, causing erosion of the ossicular chain and hearing loss.
• Cholesteatoma is caused by chronic ear infections and Eustachian tube dysfunction, surgical removal and antibiotics treat the issue.
• Tympanic membrane perforation affects vibration while otitis media affects

Inner Ear Disorders

• Connexin 26 involves a mutation of GJB2, affecting the gap junction protein critical for hair cell activity and is the most common recessive gene.
• Noise-induced hearing loss is due to prolonged or sudden exposure to loud noise, damaging hair cells in the cochlea.
• Noise-induced hearing loss affects high frequencies first, especially from music or noise. Acoustic trauma is loud and impactful, bilateral, and symmetrical.
• Presbycusis is progressive age-related hearing loss that is bilateral and symmetrical.
• Cochlear aplasia involves the absence of the cochlea, with possible presence of semicircular canals, resulting in total hearing loss due to arrested development during the end of the 3rd week.
• Connexin 26 affects the amplification and encoding of sound signals, while presbycusis, noise-induced hearing loss, and cochlear aplasia affect encoding.

Auditory Pathways Disorders

• Cochlear nerve aplasia is the absence or underdevelopment of the cochlear nerve, resulting in total hearing loss and end of the 3rd week of arrested development.
• Cochlear nerve aplasia Is due to genetic mutations, developmental arrest, lack of blood supply to the nerve, infections during pregnancy (e.g., Cytomegalovirus, Rubella), maternal drug exposure, CHARGE Syndrome, or Waardenburg Syndrome.
• Acoustic neuroma is a non-cancerous Schwannoma growing on the vestibular nerve, affecting hearing, balance, and facial nerves due to cell overgrowth, NF2, or radiation exposure, causing unilateral hearing loss, tinnitus, dizziness, and facial numbness, and requires surgery and monitoring.
• Cochlear nerve aplasia and acoustic neuroma both affect encoding.

Disorders of the Vestibular System

• Meniere's Disease, Acoustic Neuroma, and Labyrinthitis commonly affect both hearing and balance.
• Genetic conditions like Usher and Pendred Syndrome can cause lifelong hearing loss and vestibular deficits.
• BPPV (Benign Paroxysmal Positional Vertigo) involves brief vertigo episodes triggered by head movements and can be treated with Canalith repositioning maneuvers (Epley maneuver).
• Age-related dizziness may arise as semicircular canals don't work as well.
• Determining the cause and treatment of vestibular system disorders is challenging because multiple systems effect this.

Syndromes

• Down Syndrome affects eustachian tube disfunction and structural ear anomalies related to skull formation, trisomy 21, and low small set ears.
• Waardenburg Syndrome is autosomal dominant and associated with wide set eyes, possible congenital hearing loss, severe to profound hearing loss.
• Usher Syndrome is linked to congenital or childhood hearing and vision loss, vestibular difficulties, autosomal recessive.
• Treacher-Collins Syndrome causes malformation of cheeks, jaw, face, outer and middle ear malformations (autosomal dominant), and moderate conductive hearing loss.
• Goldenhar Syndrome is unilateral ears, nose, lip, soft palate, mandible, strabismus or cross eyed, scoliosis, and is autosomal dominant.
• Long QT Syndrome is autosomal recessive and is linked to congenital or early onset hearing loss.
• Pendred Syndrome is autosomal recessive, EVA, possible cochlear malformation and thyroid dysfunction.
• Charge syndrome is a spontaneous mutation that is autosomal dominant, coloboma, heart disorders, choanal atresia, retarded growth, genitourinary abnormalities, and ear anomalies.
• Syndromic hearing loss occurs due to effects on multiple body parts.
• Non-syndromic hearing loss doesn't have other signs or symptoms.
• Recessive genes require two copies for expression trait/disorder, while dominant genes require one copy, unless the trait/disorder resulted from a spontaneous mutation.

Other important details

• Auditory nerve and pathway disorders affect: Neural encoding of sound transmission of information to brain, brain decoding of sound processing time
• Auditory Functions, localization, understanding speech, understanding speech in noise
• Inner ear disorders, infections, and other issues impact auditory functions. Effects Sensory reception of sound waves, amplification of sound,neural encoding of sound rubella, cmv, effects encoding
• OXOTOSIS MEDS EFFECT ENCODING

The lesson covers various etiologies, including genetic inheritance patterns (dominant and recessive genes) and congenital malformations. Additionally, it explores the impact of conditions like Eustachian tube dysfunction and TM perforation on auditory function and hearing loss.