Comprehensive Guide: Ear Anatomy & Hearing Disorders

1. Ear Anatomy (해부학)[Outer Ear]<ul><li>Auricle / Pinna: Shell-like, gathers sound waves.</li><li>External Auditory Canal (Meatus): S-shaped (Straighten by pulling up & back). Outer 1/3: Cartilage, Ceruminous(wax) & Sebaceous glands. Inner 2/3: Bony tissue.</li><li>Tympanic Membrane (Ear Drum): Origin: Ecto/Meso/Endoderm. Oval (H: 9-10mm, W: 8-9mm, T: 0.1mm). 55° angle with floor. Parts: Pars flaccida & tensa. Umbo in middle. Cone of light: anterioinferiorly.</li><li>Nerve Supply: Auriculotemporal (V3), Vagus (CN X - Arnold's), Glossopharyngeal (CN IX - Jackobson's).</li></ul>[Middle Ear]<ul><li>Cavity: Air-containing, Petrous part of temporal bone.</li><li>Ossicles: Malleus(attached to TM), Incus, Stapes(connects to oval window). Magnify/transmit vibrations.</li><li>Eustachian Tube: Connects ME to Nasopharynx. Length: 36mm. 45° angle. Medial 2/3: Cartilaginous, Lateral 1/3: Bony. Narrowest: Isthmus (<0.5mm). Children: shorter/horizontal (↑OM risk).</li><li>Muscles: Tensor tympani (V3, Handle of malleus), Stapedius (CN VII, Stapes bone).</li><li>Tympanic Cavity: Epitympanum, Mesotympanum, Hypotympanum. Contents: Ossicles, Muscles, Chorda tympani (Taste Ant 2/3), Tympanic plexus.</li></ul>[Inner Ear]<ul><li>Bony Labyrinth: Perilymph (High Na), Cochlea, Vestibule, 3 SC canals.</li><li>Membranous Labyrinth: Endolymph (High K), Cochlear duct, Utricle, Saccule, SC ducts.</li></ul>

2. Hearing Loss Classification[Etiology]<ul><li>Acquired / Congenital: Idiopathic, TORCHES infections, Genetic, Drugs, Jaundice, NF2.</li><li>CHL: External/Middle ear deformity.</li><li>SNHL: Inner ear / CNS pathology.</li></ul>[Conductive Hearing Loss (CHL)]<ul><li>Symptoms: Muffled hearing, pain, stuffy sensation, dizziness.</li><li>External Ear Causes: Wax impaction (MC), Foreign body, Otitis externa, Bony lesions, Microtia.</li><li>Middle Ear Causes: OME (MC in children), AOM, COM (Perforation), TM collapse, Cholesteatoma, Ossicle damage, Otosclerosis.</li></ul>

3. Sensorineural Hearing Loss (SNHL)[Main Causes]<ul><li>Presbycusis (Age-related): MC cause. Men >55, Women >65. High frequency loss (Base hair cells). Non-reversible.</li><li>Meniere's Disease: Fluctuating SNHL + Vertigo + Tinnitus + Aural fullness (Tetrad). Low frequency loss (Apex hair cells).</li><li>Noise Induced: Chronic exposure. Preventable.</li><li>Ototoxic Drugs: Aspirin, Aminoglycosides, Cisplatin, Furosemide, etc.</li><li>Others: Autoimmune (RA, SLE), Trauma, Infections (Meningitis), Acoustic Neuroma (Unilateral), MS.</li></ul>[Management]<ul><li>Corticosteroids (Oral/Injection), Hearing aids, Cochlear implants (Advanced SNHL), Surgery.</li></ul>

4. Otosclerosis (이경화증)<ul><li>Definition: Fibrous dystrophy of bony otic capsule. Stapedial fixation > CHL.</li><li>Epidemiology: 20-30 yrs (Rare <20, >40). Women:Men 2:1. ↑ Risk in pregnancy. Inherited (AD 50% family history). 80% Bilateral.</li><li>Types: 1) Fenestral (MC): Fissula ante fenestram. 2) Retro-fenestral: Cochlear involvement (SNHL/Mixed).</li><li>Symptoms: Slowly progressive CHL, Soft speech (hear own voice), Paracusis of willisi (Hear better in noise), Tinnitus (70%), Dizziness.</li><li>Diagnosis: PTA (Carhart notch at 2000Hz), Tympanometry (Type As), Absent Acoustic reflex. Definitive: Exploratory tympanotomy.</li><li>Treatment: 1) Sodium fluoride (Active disease), 2) Hearing aids, 3) Surgery (Stapedotomy/Stapedectomy).</li></ul>

5. Diagnostic Tests & Findings<table><tr><td>Test</td><td>Findings</td></tr><tr><td>Weber (512Hz)</td><td>Centralized: Normal. Lateralized to Affected Ear: CHL. Lateralized to Good Ear: SNHL.</td></tr><tr><td>Rinne</td><td>AC > BC (Positive): Normal/SNHL. BC > AC (Negative): CHL.</td></tr><tr><td>PTA Symbols</td><td>O: Right Air, X: Left Air, &lt;/[ : Right Bone, &gt;/] : Left Bone.</td></tr><tr><td>PTA Levels</td><td>Normal (0-25dB), Mild (25-40), Moderate (40-55), Mod-Severe (55-70), Severe (70-90), Profound (>90).</td></tr><tr><td>Tympanometry</td><td>Type A: Normal. Type As: Stiff (Otosclerosis). Type Ad: Disarticulation. Type B: Flat (Fluid/Perforation). Type C: Negative pressure (ETD).</td></tr></table>

6. Tinnitus & Final Management<ul><li>Tinnitus Types: 1) Subjective (Only PT hears): SNHL, Presbycusis, Noise trauma. 2) Objective (Pulsatile): Vascular tumors (Glomus), HTN, Aneurism, Muscle spasms.</li><li>Management: Treat underlying cause, Hearing aids with maskers, Sound therapy (White noise), CBT, Psychiatric consult.</li><li>Hearing Aids Types: CROS (for unilateral HL), Bone conduction aid (Atresia/Otorrhea).</li><li>Cochlear Implants: Profound SNHL, postlingually deaf adults.</li><li>Key Notes: Ear wax doesn't need periodic removal. Bell's palsy is MC cause of CN7 palsy. Organ of corti is in basilar membrane. Endolymph is in scala media & SC canals.</li></ul>

Test	Findings
Weber (512Hz)	Centralized: Normal. Lateralized to Affected Ear: CHL. Lateralized to Good Ear: SNHL.
Rinne	AC > BC (Positive): Normal/SNHL. BC > AC (Negative): CHL.
PTA Symbols	O: Right Air, X: Left Air, </[ : Right Bone, >/] : Left Bone.
PTA Levels	Normal (0-25dB), Mild (25-40), Moderate (40-55), Mod-Severe (55-70), Severe (70-90), Profound (>90).
Tympanometry	Type A: Normal. Type As: Stiff (Otosclerosis). Type Ad: Disarticulation. Type B: Flat (Fluid/Perforation). Type C: Negative pressure (ETD).