Examination of the ear is a vital skill for various medical professionals, including otolaryngologists, primary care physicians, emergency care physicians, paramedics, and pediatricians. Pathologies that result in positive ear examination findings range from the common and benign, such as viral labyrinthitis, to the rare and potentially life-threatening, such as acute bacterial mastoiditis.
Anatomy and Physiology
Knowledge of the anatomy of the external, middle, and inner ear systems is vital to enable clinicians to interpret what may be vague or misleading symptoms. The interaction and anatomical proximity of the ear to the brain, skull-base, and cranial nerves must also be appreciated, as certain pathology may involve these structures. In general, abnormalities of the external and middle ears will produce conductive hearing loss, and the inner ear abnormalities will produce sensorineural hearing loss.
The external ear is made up of the auricle (pinna), the external auditory meatus and canal, and the external (lateral) layer of the tympanic membrane. The external ear's function is the funneling of acoustic waves to the tympanic membrane and, therefore, the middle ear. Embryologically the pinna is formed by the fusions of six mesenchymal proliferations, known as Hillocks of His, derivations of the first and second branchial arches. Incomplete fusion of these Hillocks can lead to the development of preauricular pits or sinuses. The entire external ear can be visualized directly during an ear examination.
This is a complex air-filled cavity found within the temporal bone of the skull. It contains the three ossicles, the internal (medial) layer of the tympanic membrane, and the Eustachian tube orifice. It is lined with respiratory epithelium, which is continuous with the lining of the Eustachian tube and the upper aerodigestive tract. The ossicles are termed malleus, incus, and stapes (lateral to medial). The middle ear's primary function is to transmit acoustic waves from the tympanic membrane of the external ear to the oval window of the inner ear via the ossicles. During the examination, certain parts of the middle ear can be viewed through the tympanic membrane: the lateral process of the malleus, the incudostapedial junction, and occasionally the promontory. The compliance of the middle ear can be measured with tympanometry, not part of the standard ear examination – this measures impedance to soundwave transmission through the middle ear. A number of pathologies will result in an abnormal tympanogram, such as fluid within the middle ear or disruption of the ossicular chain.
The inner ear is comprised of the vestibular system and cochlea, both of which have a bony and membranous portion. The function of the inner ear is both the conversion of acoustic vibrations into neural impulses for hearing, as well as the detection and transmission of cranial movement for balance. No parts of the inner ear can be directly visualized during the ear examination. However, signs of inner ear disease, such as sensorineural hearing loss or vestibular dysfunction, can be elicited.
Symptoms that mandate an ear examination include otalgia, otorrhea, vertigo, tinnitus, aural fullness, hearing loss, and facial weakness. Careful history taking should differentiate between true vertigo (sensation of the room spinning, indicating vestibular system dysfunction) and the sensations of faintness (usually due to a pre-syncopal episode), light-headedness (a non-specific symptom), or disequilibrium due to cerebellar or gait disturbances. Patients often use the word ‘dizzy’ to describe all of these sensations.
Less common prompts for ear examination include patients with postnasal space disease, such as nasopharyngeal carcinoma, to exclude sequela resulting from an occluded Eustachian tube orifice. Patients with sustained trauma to the head and neck may have reduced consciousness, and an ear examination may be required if there is any concern regarding the lateral basal skull injury. This may be prompted by the presence of CSF otorrhoea or CT scan evidence of temporal bone fracture.
If any hearing impairment is identified during routine hearing screening (such as during the NHS Newborn Hearing Screening Program in the UK), a formal ear examination must follow.
An otoscope will allow for the assessment of the pinna, external auditory canal, and tympanic membrane. The light also enables the examiner to perform a close examination of the pre- and postauricular areas. Disposable specula of varying sizes are required for the otoscope. To assess the mobility of the tympanic membrane, pneumatic otoscopy can be performed. This requires an otoscope with a pneumatic bulb and speculae with rubber rings to create an air-tight seal within the canal.
A tuning fork is required for the differentiation between conductive and sensorineural hearing loss. The ideal tuning fork of choice has a long period of tonal decay that also causes minimal vibration sense (to avoid the patient's sensing vibration and confusing this with sound). Otolaryngologists traditionally utilize a 512-Hz tuning fork as it provides the greatest balance between these two characteristics.
The patient should be sat on a chair suited to their habitus and comfort. The chair should ideally be in the center of the room, as part of the examination requires the examiner to stand behind the patient. Before the examination, one must first ask the patient if they are in any pain. The patient should also be asked whether they have any ear-related symptoms (specifically discharge, pain, hearing loss) – and which they think is their better hearing ear. Convention states that one first examines the better ear.
Clear and courteous description of what is required of the patient during the examination will reduce the possibility of discomfort or confusion, especially during tests that require patient cooperation, such as the tuning fork tests.
As with all clinical encounters, the examiner should review clinical notes of previous encounters, any relevant referral letters, and review any investigations such as clinical imaging or hearing tests.
To reduce the risk of cross-contamination of pathogens, the WHO recommended ‘5 moments of hand hygiene’ should be adhered to throughout the examination.
The examiner must develop their system when approaching the ear examination; this instills fluency and structure and ensures nothing is missed. Most examiners first perform a general inspection before focused inspection of the ears, palpation, and otoscopy. This is then followed by what is known as the "four F's": free-field hearing test, the fistula test, (tuning) forks, and the facial nerve. Depending on the clinical scenario, examinations of the other cranial nerves, vestibular system, nose, throat, neck, or cerebellar systems may follow.
Patients that present with ear pathology usually are well and assessed in the outpatient clinic. However, any suspicion that the patient is unwell should prompt assessment according to the Advanced Life Support 'ABCDE' algorithm.
Inspection and Palpation
The ears are first visualized with the patient in a seated position facing the examiner. The examiner should note any asymmetry of the ears or any prominence, and a note should be made of any resting facial asymmetry. Starting with the 'better' ear and using the otoscope as a light source, the examiner should inspect the preauricular area for any surgical or traumatic scars, masses, evidence of pits or sinuses, or skin changes such as erythema or desquamation. The pinna itself requires a detailed inspection for congenital malformations, scars, erythema, edema, masses, or exudate from the external auditory canal. If there are any piercings, a note should be made of any signs of infection, and the examiner should be vigilant for signs of perichondritis. Finally, the postauricular area should be inspected for scars and erythema. Mastoid erythema, swelling, loss of the post-auricular sulcus, and anteroinferior displacement of the pinna are all signs of mastoiditis. The 'worse' ear should then be inspected in turn.
Following this inspection, the mastoid and tragus should be palpated for tenderness, indicating mastoiditis and otitis externa, respectively. Pre- and post-auricular lymphadenopathy should also be noted.
The pinna should be gently pulled in a posterosuperior direction, having warned the patient. This results in the straightening of the external auditory canal and subsequent alignment of the canal's cartilaginous and bony portions. The otoscope should be gently inserted into the external auditory canal. Any discomfort doing so should be noted. The canal should be assessed for any edema, exudate, wax, foreign bodies, and the presence or absence of a mastoid cavity (from a previous 'canal-wall-down' mastoidectomy). The tympanic membrane, if visible, should be assessed for perforation, sclerosis, retraction. The presence or absence of a normal light reflex should be noted. The attic area, immediately superior to the tympanic membrane, should be carefully inspected for signs of cholesteatoma. In cases of middle ear effusion, fluid levels or bubbles may be seen behind the tympanic membrane.
Pneumatic otoscopy is a simple test to assess the mobility of the tympanic membrane. The combined features of a bulging tympanic membrane and reduced mobility of pneumatic otoscopy are highly suspicious for acute otitis media. The speculum tip is inserted into the canal as with routine otoscopy, ensuring an airtight seal is formed. If there is any concern about an air leak, then a speculum with a rubber seal should be utilized, although this is not always required. Paying careful attention to the light reflex, positive pressure is introduced into the ear canal by gently squeezing the pneumatic bulb and releasing it. In a normal ear, the tympanic membrane should move briskly. If there is fluid in the middle ear, such as in the presence of acute otitis media, then mobility will be restricted.
Free-field Hearing Test
This is a bedside test of hearing. It is not as reliable as formal audiometry and is highly examiner-dependent. However, it has value as a screening tool for hearing impairment. The test can reveal whether any hearing impairment is present and estimate the degree of the impairment.
Firstly, explain to the patient that they will be required to repeat words or phrases they hear back to the examiner. To eliminate the possibility of lip-reading, stand behind the patient, and say a test word to be repeated back. The examiner then stands to the side of the test ear (conventionally the better hearing ear) and gently presses on the tragus of the non-test ear to mask it. The examiner then speaks several test words at arm's length and then half arm's length. At each distance, the test words are spoken at three volumes: whispered, conversational, and loud.
The following descriptors of hearing can then be noted if the patient correctly identifies 50% or more words at each level:
Arm's Length Test Words:
- Whispered: normal hearing
- Conversational: mild-moderate hearing loss
- Loud: severe hearing loss
Half-arm's Length Test Words:
- Whispered: mild hearing loss
- Conversational: moderate hearing loss
- Loud: profound hearing loss
A perilymphatic fistula is an abnormal connection between the inner and middle ear, allowing perilymph to leak into the middle ear. This can be secondary to dehiscence at the oval or round windows or otic capsule. Etiologies include trauma, cholesteatoma, otological surgery, or barotrauma. The pressure of the middle ear is transiently increased during the test. If a perilymphatic fistula is present, this pressure may be directly transmitted to the inner ear.
Prior to performing the test, the patient is warned that it may make them feel dizzy. The test is, therefore, performed sitting down. The patient's tragus is firmly palpated, and the examiner assesses the patient's eyes: nystagmus toward the test ear implies a perilymphatic fistula.
(Tuning) Fork Tests
Many otological pathologies result in hearing loss, either conductive, sensorineural, or both. Conductive loss is due to a blockage of the vibrations reaching the cochlea, due to ossicular disruption or tympanic membrane perforation, for example. Sensorineural hearing loss is due to damage to the cochlear itself or due to damage to the vestibulocochlear nerve.
Weber's and Rinne's tuning fork tests allow the differentiation between these two types of hearing loss. Weber's test is performed first. The examiner strikes the tuning fork and places it in the center of the patient's forehead, with the examiner's other hand providing counter-pressure on the back of the patient's head. The patient is then asked to state whether they can hear it loudest in the left, right, or center.
Interpretation of Weber's Test:
- Normal hearing or symmetrical hearing loss: heard in the center.
- Asymmetrical sensorineural hearing loss: heard loudest in the normal ear.
- Asymmetrical conductive hearing loss: heard loudest in the affected ear.
Rinne's test is then performed by striking the tuning fork and holding it 2 cm away from the external acoustic meatus (air conduction). After 2 to 3 seconds, the base of the fork should then be firmly pressed on the mastoid, using the examiner's other hand to provide contralateral counter-pressure (bone conduction). The patient is then asked which sound was heard loudest.
Interpretation of Rinne's Test:
- Air conduction is heard louder than bone conduction [Rinne's positive]: either normal hearing or sensorineural hearing loss.
- Bone conduction heard louder than air conduction [Rinne's negative]: conductive hearing loss.
Therefore in left sensorineural hearing loss, Weber's will lateralize to the right, and Rinne's will be positive on both sides. In the left conductive hearing loss, Weber's will lateralize to the left, Rinne's will be negative on the left and positive on the right.
Facial Nerve Function Testing
The facial nerve has a complex intratemporal course, running through the middle ear. Therefore, a number of otological pathologies, including cholesteatoma, surgery, trauma, and middle ear infection, can cause facial nerve palsy. Examining for this is most commonly performed by assessing the branchiomotor component of the nerve, which innervates the muscles of facial expression. The examiner should ask the patient to lift their eyebrows, squeeze their eyes shut, resist forceful eye-opening, puff out their cheeks, and show their teeth. Any weakness should be graded using the House-Brackmann grading system.
A large number of pathologies can be identified by the examiner and their clinical team based purely on the findings of this examination. Foreign bodies in the external auditory canal can be retrieved in the clinic. Topical antibiotics and steroid therapy can be prescribed to treat otitis externa, and oral antibiotics can be prescribed to treat otitis media.
Findings may prompt further investigation. Computed tomography of the temporal bone may be indicated in the presence of signs of acute middle ear infection, trauma, or cholesteatoma. Magnetic resonance imaging may be warranted in findings of facial nerve palsy or unilateral sensorineural deafness. The identification of any hearing loss can guide further formalized hearing tests such as pure-tone audiometry and tympanometry.
Findings may also prompt surgical planning; for example, in the presence of cholesteatoma, large tympanic membrane perforation, or pinna abnormalities.
Enhancing Healthcare Team Outcomes
Treatment planning of many ear diseases should involve the wider interprofessional team, where possible. This may consist of otolaryngologists, audiologists, neurologists, neurosurgeons, radiologists, pediatricians, or infectious disease specialists. Specialist ENT nurses are, in many countries, playing a wider role in the provision of ENT care - especially in tasks such as micro suctioning of the external auditory canal. The audiological department has an especially significant role in assessing a patient's hearing, both pre- and post-surgically, as well as with the provision of hearing aid devices.