Otology: Ear Anatomy, Physiology and Common Conditions

DCM 2203 · Ear, Nose and Throat Care · LWA 2: Otology

Ear anatomy and physiology explain how sound becomes a signal the brain can interpret and how inner-ear organs contribute to balance. This guide follows the DCM 2203 Otology outline: the external, middle and inner ear; hearing and balance; congenital ear differences; otitis externa, otitis media and mastoiditis; and traumatic conditions including foreign bodies, tympanic membrane perforation and temporal bone injury.

Core principle: Ask what the symptom is, inspect the pinna and canal, visualise the tympanic membrane when safe, assess hearing and balance, and look for complications before deciding on treatment or referral.

1. Otology: scope and clinical approach

Otology is the study of the ear and its disorders. Ear symptoms may arise from the external canal, middle ear, inner ear, adjacent structures or referred pain from the teeth, jaw, pharynx and neck. The first task is to localise the likely site and determine whether the problem is urgent.

Common presenting symptoms

• Otalgia: ear pain. Pain on pressing the tragus or moving the pinna suggests canal inflammation; deep pain after a cold may point toward middle-ear disease. Also consider referred dental, temporomandibular, throat or cervical pain.
• Otorrhoea: discharge from the ear. Ask about duration, smell, blood, recurrence, swimming, instrumentation, previous surgery and whether pain preceded discharge.
• Hearing difficulty: establish onset, one or both ears, progression, noise exposure, medicines, infections, trauma, speech or school impact and associated tinnitus or vertigo.
• Vertigo or imbalance: clarify spinning versus faintness, onset, duration, triggers, falls, headache, neurologic symptoms, hearing change and medication use.
• Itch, fullness or tinnitus: may occur with wax, dermatitis, infection, middle-ear fluid or hearing loss; the history and examination distinguish them.

2. Anatomy of the ear

External ear: pinna, canal and tympanic membrane

The pinna is the visible cartilaginous part of the ear; the lobule contains no cartilage. The external auditory canal runs inward to the tympanic membrane. Its lateral portion is cartilaginous and contains hair and ceruminous glands; the deeper portion is bony and has very thin skin. This explains why minor trauma from cotton buds or other objects can be painful and may cause bleeding. Cerumen is protective; it traps particles and supports the canal’s acidic environment.

The tympanic membrane separates the external canal from the middle-ear cavity. During otoscopy, describe whether it is intact, perforated, retracted, bulging, scarred or obscured, and whether landmarks and light reflex can be seen. Do not infer middle-ear infection from redness alone; crying, fever or irritation can make a membrane look red.

Middle ear and mastoid

The middle ear contains the auditory ossicles: malleus, incus and stapes. The stapes footplate acts at the oval window, transferring vibration to inner-ear fluid. The Eustachian tube connects the middle ear to the nasopharynx and helps ventilation and drainage. The mastoid process lies behind the ear and contains air cells connected to the middle-ear system; infection can spread there and cause mastoiditis.

Inner ear

The cochlea is a fluid-filled, coiled organ with sensory hair cells. The vestibule contains the utricle and saccule. The semicircular canals are arranged in different planes. Sensory signals travel through the vestibulocochlear nerve to brainstem and higher auditory and vestibular pathways.

3. Physiology of hearing and balance

How hearing works

1. The pinna collects sound waves and directs them through the external auditory canal.
2. Sound makes the tympanic membrane vibrate.
3. The malleus, incus and stapes transmit and amplify vibration across the middle ear.
4. Movement at the oval window produces fluid waves in the cochlea.
5. Movement of the basilar membrane bends cochlear hair-cell stereocilia, converting mechanical movement into electrical activity.
6. The cochlear division of cranial nerve VIII carries signals to the brain, where sound is interpreted.

Conductive hearing loss results when sound transmission through the outer or middle ear is reduced, for example by canal obstruction, effusion or ossicular disease. Sensorineural hearing loss results from cochlear hair-cell, auditory-nerve or related neural pathway injury. Some patients have mixed hearing loss. Sudden sensorineural loss is time-sensitive and should be urgently assessed rather than treated as simple wax or infection.

How balance works

The vestibular apparatus works with vision and position-sense from muscles and joints. The three semicircular canals respond mainly to angular head rotation. The utricle and saccule respond to gravity, head tilt and linear acceleration. The brain compares these inputs to stabilise posture and keep vision steady as the head moves. Dizziness is not automatically an ear disorder: cardiovascular, neurologic, medication-related and other causes must also be considered.

4. Assessment of ear symptoms

Focused history

• Onset, duration, progression, side and severity of pain, discharge, hearing change, tinnitus or dizziness.
• Fever, recent upper-respiratory infection, swimming, water exposure, eczema, cotton-bud use, foreign-body insertion, barotrauma, head injury or loud-noise exposure.
• Previous ear disease, perforation, grommets, operations, hearing aids, recurrent infections, diabetes, immunosuppression, medicines and drug allergies.
• Effects on sleep, communication, school or work; in children, speech and developmental concerns.

Examination and basic hearing assessment

1. Observe general appearance and vital signs if unwell. Compare both ears; inspect the pinnae, canal openings and surrounding skin.
2. Look for pinna displacement, postauricular redness or swelling, mastoid tenderness, discharge, scars, vesicles, trauma and facial asymmetry.
3. Use a suitable otoscope and speculum size. Examine the canal and tympanic membrane gently; stop if there is severe pain, bleeding, poor view or an uncooperative patient. Do not push wax or an object deeper.
4. Assess hearing in each ear. A whispered-voice screen and tuning-fork tests may help localise a suspected conductive or sensorineural deficit but do not replace formal audiometry.
5. When indicated, request audiology, tympanometry, cultures or imaging according to local pathway and clinical question. Imaging is not routine for uncomplicated ear pain; it is considered when trauma, complication, mass or another specific concern is present.

Rinne test: compare air conduction with bone conduction. Air conduction is normally perceived longer than bone conduction; a negative Rinne (bone at least as long as air) may support conductive loss in that ear. Weber test: sound usually lateralises toward the ear with conductive loss, and away from an ear with significant sensorineural loss. Interpret these tests with the history, otoscopy and examiner technique.

5. Congenital conditions of the ear

• Anotia: absence of the external pinna; severe forms may coexist with external canal atresia.
• Microtia: an underdeveloped or unusually small pinna. The external appearance ranges in severity and may be associated with abnormalities of the canal and middle ear.
• Aural atresia or stenosis: a missing or narrowed external auditory canal. Conductive hearing loss can occur because sound cannot reach the eardrum normally.

These differences are usually recognised at birth or in childhood. Check hearing early, consider whether one or both ears are affected, and refer for ENT and audiology assessment. Support communication, speech-language development and family counselling. Hearing rehabilitation and reconstructive options require individual specialist planning; do not attempt to open or instrument a narrowed canal.

6. Otitis externa

Otitis externa is inflammation of the external auditory canal, sometimes extending to the pinna. Acute diffuse disease is often infectious; chronic or recurrent symptoms may also involve dermatitis or fungal infection. Water exposure, scratching, cotton buds and loss of protective wax can damage the canal’s skin barrier.

Clinical features and diagnosis

• Ear pain, often worse when the tragus is pressed or the pinna is moved; itching, canal swelling, redness and discharge are common.
• The canal may be narrowed or contain debris, making the tympanic membrane difficult to see. Hearing can feel blocked when swelling or debris occludes the canal.
• Consider acute otitis media with discharge through a perforation, eczema/contact dermatitis, furuncle, foreign body, referred pain and, in high-risk patients, necrotising otitis externa.

Management principles

Management generally includes pain relief, keeping the ear dry and appropriate topical therapy chosen under current local guidance. Correct drop administration matters. If the canal is blocked, a trained clinician may need to improve delivery with careful aural toilet or a wick. When perforation or a tympanostomy tube is known or suspected, a non-ototoxic preparation should be selected according to the guideline. Routine systemic antibiotics are not appropriate for every uncomplicated case; use them only when indicated by the clinical picture and local protocol. Reassess failure to improve within the expected interval and revisit the diagnosis.

Necrotising otitis externa: suspect invasive disease in an older adult, a person with diabetes or immunosuppression who has severe persistent or night pain, granulation tissue, spreading infection or cranial-nerve findings. This is an urgent ENT condition requiring specialist assessment.

7. Otitis media

Otitis media affects the middle ear. It is important to separate acute infection, middle-ear fluid without acute infection and chronic suppurative disease because their examination findings and management differ.

Acute otitis media (AOM)

AOM often follows an upper-respiratory infection, particularly in children. Symptoms can include rapid-onset ear pain, fever, irritability and reduced hearing. Otoscopy may show a bulging, inflamed tympanic membrane with reduced mobility or a new perforation with discharge. Diagnosis depends on acute symptoms and evidence of middle-ear inflammation/effusion; a red membrane by itself is not enough.

Give appropriate pain relief and assess severity, age, general condition, complications and risk factors. Antibiotic decisions should follow the current Uganda Clinical Guidelines and facility protocol; international antimicrobial guidance such as NICE NG91 illustrates the importance of selective prescribing and safety-net advice but should not replace local policy. Explain when and where reassessment is needed if symptoms worsen, persist or new warning signs develop.

Otitis media with effusion (OME)

OME is fluid behind an intact tympanic membrane without the acute features of bacterial infection. It may cause muffled hearing, aural fullness or delayed speech-language progress in a child. Assess hearing and development, provide follow-up, and refer persistent or functionally significant problems according to local services. Avoid assuming that every middle-ear fluid collection needs antibiotics.

Chronic suppurative otitis media (CSOM)

CSOM involves persistent or recurrent discharge through a perforated tympanic membrane, often with conductive hearing loss. Ask how long the ear has been discharging and about previous treatment, water entry, pain, smell, hearing and dizziness. Examine gently and assess hearing; persistent disease, granulation tissue, a retraction pocket or suspected cholesteatoma needs ENT review. Keep the ear dry and use ear cleaning or medicines only as advised by a trained clinician and local protocol. Where the eardrum is perforated, avoid potentially ototoxic drops unless a clinician has selected a safe agent.

8. Mastoiditis

Mastoiditis is infection and inflammation of the mastoid air-cell system, commonly associated with middle-ear infection. It is potentially serious because infection can spread to nearby structures.

Features to recognise

• Pain, redness, tenderness or swelling behind the ear.
• The pinna may be pushed outward or forward; there may be persistent discharge, fever, headache, malaise or hearing change.
• Severe headache, vomiting, neck stiffness, altered consciousness, facial weakness or other neurologic signs suggest possible complications.

Suspected mastoiditis needs urgent hospital/ENT assessment. The patient may require investigations, intravenous antibiotics and, if needed, drainage or mastoid surgery under specialist care. Do not manage suspected mastoiditis as uncomplicated otitis media or delay escalation while waiting for outpatient treatment to work.

9. Traumatic conditions

Foreign body in the ear

Ask what was inserted, when, whether it is painful and whether any attempt has already been made to remove it. Inspect for injury and check hearing if possible. Avoid blind instrumentation and irrigation when the object is a battery, vegetable matter, deeply impacted, against the tympanic membrane, or when perforation is possible. Repeated attempts increase swelling, canal injury and the chance of pushing the object deeper. A button battery, severe pain, bleeding, an uncooperative child or a deeply lodged object needs urgent trained removal or referral.

Tympanic membrane perforation

Perforation can follow infection, a slap, blast, diving/barotrauma, head injury or instrumentation. Symptoms may include sudden pain, blood or discharge, tinnitus and reduced hearing; pain may lessen after a perforation occurs. Keep the ear dry, do not probe or irrigate it, and arrange clinical assessment. Vertigo, severe or sudden hearing loss, facial weakness, significant bleeding, suspected CSF leak or head trauma requires urgent evaluation. Follow-up should confirm healing and address persistent perforation or hearing loss.

Temporal bone fracture and serious ear trauma

After a significant head injury, stabilise and manage the patient according to emergency trauma protocols. Warning signs include blood behind the tympanic membrane (haemotympanum), bruising behind the ear, clear fluid from the ear, facial-nerve weakness, hearing loss, vertigo, severe headache or neurologic change. Suspected skull-base or temporal-bone injury is an emergency: avoid packing or irrigating the ear, document findings without delaying resuscitation, and seek urgent senior, trauma and ENT care.

10. Red flags and referral

• Sudden sensorineural hearing loss or rapidly progressive hearing loss.
• Postauricular redness, swelling or tenderness; protruding pinna; suspected mastoiditis.
• Facial weakness, severe vertigo, gait inability, neurologic symptoms or severe headache with ear disease.
• Head injury with haemotympanum, Battle sign, suspected CSF otorrhoea, loss of consciousness or other skull-base signs.
• Severe persistent canal pain in a person with diabetes or immunosuppression; cranial-nerve deficit or spreading infection.
• Button battery, deep foreign body, uncontrolled bleeding, severe systemic illness or a very young/unwell child.
• Persistent or recurrent discharge, suspected cholesteatoma, repeated infections, speech delay or hearing difficulty affecting school, communication or development.

11. Worked examples and self-check

Self-check questions

1. Name the three auditory ossicles.
2. Which inner-ear structure converts sound vibration into neural activity?
3. Which vestibular organs mainly sense angular rotation, and which detect gravity/linear movement?
4. Give two findings that help distinguish otitis externa from acute otitis media.
5. What findings suggest mastoiditis?
6. State two reasons not to irrigate or probe an ear with a foreign body or trauma.

Answers: 1. Malleus, incus and stapes. 2. Cochlear hair cells. 3. Semicircular canals detect angular rotation; utricle and saccule detect head position relative to gravity and linear acceleration. 4. Tragal/pinna tenderness and inflamed canal suggest externa; middle-ear symptoms with a bulging/poorly mobile tympanic membrane support AOM. 5. Tender red postauricular swelling, pinna displacement, fever or discharge. 6. A battery, deep object, possible perforation, trauma, bleeding, severe pain or poor visualisation makes irrigation/probing unsafe.

12. Key points to remember

• The outer and middle ear conduct sound; the cochlea transduces it, while the vestibular apparatus contributes to balance.
• Localise ear symptoms with a focused history, pinna/canal examination, safe otoscopy and hearing assessment.
• Differentiate otitis externa, AOM, OME and CSOM; treatment is diagnosis-specific and guided by current local policy.
• Mastoiditis, sudden hearing loss, facial weakness, serious trauma, battery insertion and neurologic or vestibular red flags require urgent escalation.
• Protect the ear from trauma and avoid blind instrumentation, cotton-bud cleaning and unsafe irrigation.

References and further reading

1. Uganda Ministry of Health. Uganda Clinical Guidelines 2023. Use the current national and facility protocol for diagnosis, medicines, referral and follow-up.
2. National Institute on Deafness and Other Communication Disorders (NIDCD). How Do We Hear?
3. NIDCD. Balance Disorders.
4. World Health Organization. Deafness and hearing loss.
5. World Health Organization. Chronic suppurative otitis media: burden of illness and management options.
6. American Academy of Otolaryngology–Head and Neck Surgery Foundation. Clinical Practice Guideline: Acute Otitis Externa (Update).
7. National Institute for Health and Care Excellence. Otitis media (acute): antimicrobial prescribing, NG91. International reference; local Uganda guidance takes precedence for clinical decisions.
8. National Health Service. Mastoiditis.
9. Hartzell LD, et al. Contemporary diagnosis and management of congenital microtia and aural atresia: Part 1, principles and diagnosis. 2023.
10. NHS Borders. Temporal bone fractures: clinical guideline.

Class notes: Coming soon.