Ear Anatomy and Function

• EENT stands for Ear, Nose, and Throat
• Ear conditions are the focus

Anatomy of the Ear

• Ears transduce sound waves into electrical signals, enabling hearing and balance
• The ear comprises the outer, middle, and inner sections:

Outer Ear

• Includes the auricle/pinna and external auditory canal

Auricle

• Also known as the pinna
• Attached to the head via skin
• Primarily made of cartilage
• Earlobe consist of fat and subcutaneous tissue
• Collects and directs sound waves into the external auditory canal

External Auditory Canal

• Measures 2 to 3 cm in length
• The lateral third contains elastic cartilaginous and dense fibrous tissue with attached skin
• The medial two-thirds consist of bone lined with thin skin
• Terminates at the tympanic membrane
• Skin contains hair, sebaceous & ceruminous glands which produce cerumen
• Self-cleaning mechanisms move old skin cells and cerumen outward
• The temporomandibular joint is anterior to the external auditory canal

Middle Ear structures

• Includes the tympanic membrane, eustachian tube, and ossicles

Middle Ear

• Has an air-filled cavity
• Connects to the nasopharynx via the Eustachian tube
• Continuous with air-filled cells in the mastoid portion of the temporal bone

Eustachian Tube

• Approximately 35mm long and 1mm wide
• Connects the middle ear to the nasopharynx
• Typically closed, but opens via the tensor veli palatini muscle
• Actions such as Valsalva maneuvers, yawning, and swallowing can open it

Eustachian Tube Functions

• Drains normal and abnormal secretions from the middle ear
• Equalizes pressure in the middle ear with atmospheric pressure

Tympanic Membrane

• Also known as the eardrum
• 1cm in diameter
• Very thin
• Pearly gray and translucent in appearance
• Has 3 layers of tissue:
  • Outer layer is continuous with the skin of the ear canal.
  • Middle layer is fibrous.
  • Inner layer is mucosal and continuous with the middle ear cavity lining.
• 80% has all 3 layers, referred to as pars tensa
• 20% lacks a middle layer, referred to as pars flaccida
• Absence of the middle layer makes the pars flaccida more vulnerable to pathologic disorders.
• Protects the middle ear
• Conducts sound vibrations from the external canal to the ossicles
• Sound pressure is magnified 22x because of transmission from a larger to smaller area

Ossicles

• The three smallest bones in the body
• Held in place by joints, muscles, and ligaments
• Assist in transmission of sound

Inner Ear houses

• Temporal Bone

Inner Ear Structures include

• Cochlea
• Semicircular Canals
• Cranial Nerve VII (facial nerve)
• Cranial Nerve VIII (vestibulocochlear nerve) which is balance and hearing

Parts of the inner ear

• Bony Labyrinth
• Membranous labyrinth

Membranous Labyrinth

• Housed inside the bony labyrinth
• Bathed in endolymph -Composed of the:
  • Utricle
  • Saccule
  • Cochlear duct
  • Semicircular canals
  • Organ of corti
    • linear movement
    • linear movement
    • rotational movement
    • end organ for hearing

Functions of the Ears

• Hearing (AC > BC)
• Balance and Equilibrium

Hearing functions in these steps

1. Sound travels through the external auditory canal
2. Tympanic membrane vibrates (healthy)
3. Ossicles vibrate (Malleus, incus → stapes rock → footplate)
4. Stapes rock
5. Fluid waves are made.
6. Movement of basilar membrane occurs.
7. Stimulates hair cells of organ of Corti (in cochlea)
8. Electrical current formed stimulates cochlear areas.
9. Hair cells stimulated:
   • Impulses sent to auditory cortex in the brain.
   • Brain decodes into sound messages.

Assessment of the Ear includes

• Inspection of the External Ear
• Otoscopic Examination
• Evaluation of Gross Auditory Acuity

Inspection of External Ear

• Inspection and direct palpation
• Note the auricle and surrounding tissues
• Look for deformities, lesions, and discharge
• Note the size, symmetry, and angle of attachment to the head

Otoscopic Examination

• Inspect the tympanic membrane and external auditory canal

Evaluation of Gross Auditory Acuity

• Whisper Test
  • One ear at a time
  • Examiner covers untested ear with palm then whispers into tested ear 1-2 ft away.
  • Normal acuity test: Patient correctly repeats whispered word
• Weber Test
• Rinne Test

Summary Table with Weber and Rinne Tests

• Normal hearing: Weber - Sound is heard equally in both ears / Rinne - Air conduction is audible longer than bone conduction in both ears
• Conductive hearing loss: Weber - Sound is heard best in affected ear (hearing loss) / Rinne - Sound is heard as long or longer in affected ear (hearing loss)
• Sensorineural hearing loss: Weber - Sound is heard best in normal hearing ear / Rinne - Air conduction is audible longer than bone conduction in affected ear

Diagnostic Evaluations include

• Audiometry
• Typanogram
• Middle Ear Endoscopy

Audiometry

• Detects hearing loss
• Single most important diagnostic instrument
• Includes 2 kinds:
  • Pure-tone audiometry
  • Speech audiometry
• Evaluates the 3 following characteristics:
  • Frequency
  • Pitch
  • Intensity

Scale for Severity of Hearing Loss w/ decibels

• Normal hearing lies between 0-15 decibels
• Slight hearing loss lies between >15-25 decibels
• Mild hearing loss lies between >25-40 decibels
• Moderate hearing loss lies between >40-55 decibels
• Moderate to severe hearing loss lies between >55-70 decibels
• Severe hearing loss lies between >70-90 decibels
• Profound hearing loss lies above >90 decibels

Typanogram

• Known as Impedance audiometry
• Measures middle ear muscle reflex to sound stimulation
• Changes air pressure in sealed ear canal to assesses compliance of tympanic membrane
• Compliance is impaired with middle ear disease

Middle Ear Endoscopy

• Use of endoscopes for this minimally invasive procedure
• Evaluates for suspected perilymphatic fistula and new-onset hearing loss
• Assesses anatomy of round window and tympanic cavity

Auditory Disturbances include

• Otitis Externa
• Otitis Media

Otitis Externa

• Inflammation of external auditory canal
• Causes:
  • Water in ear canal (Swimmer's ear is another term)
  • Trauma to skin of ear canal
  • Systemic conditions (Vitamin deficiency and endocrine problems)
• Most frequently bacterial and fungal infections
• Common pathogens include bacterial (S. Aureus and Pseudomonas species)
• Common pathogens include fungal (Aspergillus)

Etiology contributing to Otitis Externa include

• Psoriasis
• Eczema
• Seborrheic dermatitis
• Allergic reactions (hair spray, dye, lotions)

Clinical Manifestations of Otitis Externa include

• Pain
• Discharge from external auditory canal
• Aural tenderness
• Fever
• Cellulitis
• Lymphadenopathy
• Pruritus
• Hearing loss or feeling of fullness

Otoscopic exam when diagnosing Otitis Externa will show

• Erythema
• Edema
• Yellow or green foul-smelling discharge
• Fungal infections (hair-like black spores)

Medical management of Otitis Externa will focus on

• Relieving discomfort
• Reducing swelling of ear canal
• Eradicating infection
• Includes Analgesics
• Antimicrobial or Antifungal and Corticosteroids medications

Nursing Management

• Instruct patient on:
  • How to treat otitis externa
  • Not to clean external auditory canal with cotton tipped applicator
  • Avoiding events that can traumatize the canal
  • Avoiding getting area wet
• Focused on Prevention of swimmer's ear

Preventative Measures on Otitis Externa involve

• Protecting the external canal when swimming, showering, or washing hair using ear plugs
• Placing petrolatum jelly on a cotton ball in the ear while swimming, showering or washing hair
• Use a swim cap
• Dry the external canal afterwards with a hair dryer on low heat
• Place alcohol drops in the external canal to act as an astringent to help prevent infection after water exposure
• Prevent trauma to the external canal such as procedures, foreign objects (e.g., bobby pin), scratching, or any other action that breaks the skin integrity
• Be aware that if otitis externa is diagnosed, refrain from any water sport activity for approximately 7 to 10 days to allow the canal to heal completely
• Recurrence is likely, unless you allow the external canal to heal completely

Malignant Otitis Externa

• More serious, rare, external ear infection
• Also known as Temporal bone osteomyelitis
• Progressive, debilitating, occasionally fatal infection external auditory canal, surrounding tissue, & base of skull
• Risk populations are patients with immune system deficiencies (AIDS/HIV)
• Causative agent is psuedomonas aeruginosa
• Treated with IV antibiotics and aggressive wound care
• Requires combination of antipseudomonal and aminoglycoside antibiotics

Otitis Media

• Acute infection of the middle ear (less than 6 weeks)

Can occur at any age, most commonly seen in

• Children

Risk Factors include

• Younger age

• Chronic URTI

• Infections

• Medical conditions such as Trisomy 21, cystic fibrosis, or cleft palate

• Second hand smoke exposure

• Can be bacterial and viral

The following are clinical manifestations of Otitis Media

• Vary with severity of infection
• Unilateral in adults w/ otalgia
• Pain relieved after a spontaneous perforation or therapeutic tympanic membrane incision
• Drainage from ear
• Fever
• Hearing loss

Acute Otitis Externa and Acute Otitis Media share the following characterictics

• Otorrhea: AOE - May or may not be present / AOM - Present if tympanic membrane perforates; discharge is profuse
• Otalgia: AOE - Persistent; may awaken patient / AOM - Relieved if tympanic membrane ruptures
• Aural tenderness: AOE - Present on palpation of auricle / AOM - Usually absent
• Systemic symptoms: AOE - Absent / AOM - Fever, upper respiratory infection, rhinitis
• Edema of external auditory canal: AOE - Present / AOM - Absent
• Tympanic membrane: AOE - May appear normal / AOM - Erythema, bulging, may be perforated
• Hearing loss: AOE - Conductive type / AOM - Conductive type

Medical Management

• Broad-spectrum antibiotics
• Antibiotic otic preparation if drainage is present
• Condition may become subacute with purulent discharge
• Rarely causes hearing loss
• If secondary complications, may involve with the mastoid Meningitis or brain abscess which are all very rare

Surgical Management:

• Myringotomy/Tympanotomy is performed if pain persists
• Is a painless, short, outpatient procedure of less than 15 minutes
• Allows drainage and analysis of discharge
• Healing takes 24 – 74 hours ONLY

Serous Otitis Media

• Accumulation of middle ear effusion
• There is a presence of fluid, even without evidence of active infection
• Stemmed from negative pressure in middle ear caused by Eustachian tube obstruction
• Can be seen in those undergoing post-radiation therapy d/t barotrauma, eustachian tube dysfunction with concurrent URTI, or with allergies

Clinical Manifestations includes

• Hearing loss
• Fullness in the ear or congestion
• Popping and crackling noises when eustachian tube opens
• Dull tympanic membrane with air bubbles on otoscopy
• Conductive hearing loss on audiogram

Management requires Medical Intervention

• Unless the infection recurs
• Myringotomy is considered if hearing loss is significant
• Corticosteroid to decrease edema
• Valsalva maneuver cautiously. There is a risk it may perforate the tympanic membrane or worsen pain

Chronic Otitis Media

• Recurrent AOM that causes irreversible tissue pathology
• Damage to tympanic membrane
• Involves the ossicles and mastoid
• Rare in developed countries

Clinical Manifestations

• May be minimal
• Varying degrees of hearing loss
• Persistent or intermittent foul smelling otorrhea
• No pain unless acute mastoiditis
• May cause mastoiditis
• Otoscope shows a perforation and cholesteatoma

Cholesteatoma

• Cyst-like lesion of external layer of tympanic membrane into middle ear
• Caused by chronic retraction pocket of tympanic membrane
• Skin forms sac that fills with dead skin cells and sebaceous materials
• Can attach to structures of middle ear, mastoid, or both

Symptoms may include

• May be asymptomatic
• Hearing loss
• Facial pain
• Paralysis
• Tinnitus
• Vertigo
• Conductive or mixed hearing loss

Medical management utilizes

• Local treatment (suctioning under otoscopic guidance)
• Antibiotic drops or powder
• Systemic antibiotics (only in ACUTE INFECTIONS)

Surgical Management involves

• Tympanoplasty
• Ossiculoplasty
• Mastoidectomy

Tympanoplasty

• The most common surgical procedure for COM
• Surgical reconstruction of the tympanic membrane
• May require reconstruction of the ossicles
• Reestablishes middle ear function
• Closes perforation
• Prevents recurrent infection
• Improves hearing
• Approach is done through trans canal or post auricular incision

Occiculoplasty

• Surgical reconstruction of ossicles with use of prostheses (teflon, stainless steel, or hypoxyapatite)
• The greater the damage will mean less success rate to restore normal hearing

Mastoidectomy

• Performed to remove cholesteatoma, gain access to diseased structure, & create dry.
• A noninfected and healthy ear
• Ossicles may be reconstructed
• Extensive disease/damage may need 2-stage operation
• Post-auricular approach
• 1st stage is to eliminate infection by removing mastoid air cells
• 2nd stage is to check for recurrent cholesteatoma & reconstruction of ossicles
• The success rate for correcting conductive hearing loss is 75%
• There is risk of facial nerve damage

Otosclerosis

• A condition where portions of the dense enchondral layer of the bony labyrinth remodel into lesions of irregularly-laid spongy bone in the middle ear

Otosclerosis Involves

• Stages
• Formation of new, abnormal spongy bone, especially around oval window, causing fixation of stapes
• Sound transmission prevented because stapes cannot vibrate
• Can progress to complete deafness
• Women
• Familial condition

Clinical Management

• May involve one or both ears
• Progressive conductive or mixed hearing loss
• Tinnitus
• Normal tympanic membrane
• Rinne Test shows BC > AC
• Audiogram confirms conductive or mixed hearing loss

Surgical Management

• Stapedectomy removes stapes superstructure
• Inserts tissue graft & suitable prosthesis
• Majority experince resolution of hearing loss
• Sodium fluoride give post op to success rate
• Balance disturbance and vertigo may occur post op for several days
• Balance disturbances are RARE long term

Home Work

• Trace impacted cerumen, and aural foreign bodies, along with their corresponding signs/symptoms, method of diagnosis, and medical/surgical management

Activity

• Create a comparative table of Meniere's Disease vs. Benign Paroxysmal Positional Vertigo, outlining mechanism to diagnose, plus their factors, factors, potential complications, medical and surgical management

Explore the ear's anatomy, including the Eustachian tube, tensor veli palatini, and organ of Corti. Learn about the tympanic membrane, auricle, and external auditory canal. Understand how these structures contribute to hearing and balance.