Ear Examination

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 produce conductive hearing loss, and inner ear abnormalities produce sensorineural hearing loss.

External Ear

The external ear comprises the auricle (pinna), the 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 fusion 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, cysts, or sinuses.[1] The entire external ear can be visualized directly during an ear examination. 

Middle Ear

This is a complex air-filled cavity found within the skull's temporal bone. 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 the malleus, incus, and stapes (from lateral to medial).[2] 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 cochlear promontory. The compliance of the middle ear can be measured with tympanometry, which is not part of the standard ear physical examination. Tympanometry measures the impedance to soundwave transmission through the middle ear. Several pathologies result in an abnormal tympanogram, such as fluid within the middle ear or disruption of the ossicular chain. Pneumatic otoscopy can be used to grossly assess the tympanic membrane's mobility and compliance if tympanometry is unavailable. 

Inner Ear

The inner ear comprises the vestibular system and the cochlea, both of which have a bony and membranous portion. Its function is to convert acoustic vibrations into neural impulses for hearing and to detect and transmit cranial movement for balance. No parts of the inner ear can be directly visualized during an ear examination. However, signs of inner ear disease, such as sensorineural hearing loss or vestibular dysfunction, can be elicited.

Indications

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, and the astute historian must elicit more specific symptom descriptions. 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. The presence of CSF otorrhoea or CT scan evidence of temporal bone fracture may prompt this. A formal ear examination must follow if any hearing impairment is identified during routine hearing screening (such as during the NHS Newborn Hearing Screening Program in the UK).[3]

Contraindications

A lack of patient consent in a patient with the capacity to make such a decision precludes an ear examination. Caution must be taken in patients with otalgia as the examination can be uncomfortable.

Equipment

An otoscope allows for assessing the pinna, external auditory canal, and tympanic membrane. The light also enables the examiner to examine the pre- and postauricular areas closely. Disposable specula of varying sizes are required for the otoscope. A pneumatic otoscopy can be performed to assess the mobility of the tympanic membrane. This requires an otoscope with a pneumatic bulb and speculae with rubber rings to create an air-tight seal within the canal.[4] A tuning fork is required to differentiate between conductive and sensorineural hearing loss. The ideal tuning fork 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.

Personnel

An effective ear examination requires only the examiner and patient. If the examination is of a child, then the child's parent and an experienced nurse or play specialist can be useful to maximize patient compliance.

Preparation

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 ask the patient if they are in 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. The convention states that one first examines the better ear. A clear and courteous description of what is required of the patient during the examination reduces 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 and any relevant referral letters and review any investigations such as clinical imaging or hearing tests. The WHO recommended that 5 moments of hand hygiene be adhered to throughout the examination to reduce the risk of cross-contamination of pathogens.[5]

Technique or Treatment

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 "4 F's": the 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 with ear pathology are usually 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.[6]

Inspection and Palpation

The ears are first visualized with the patient seated 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 requires a detailed inspection for congenital malformations, scars, erythema, edema, masses, or exudate from the external auditory canal. If there are 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, post-auricular sulcus loss, palpation tenderness, 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.

Otoscopy

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 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, and 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.[7] 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, 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 and releasing the pneumatic bulb. In a normal ear, the tympanic membrane should move briskly. If there is fluid in the middle ear, such as acute otitis media, mobility is restricted.[4]

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 is valuable as a screening tool for hearing impairment. The test can reveal whether any gross hearing impairment is present and estimate the degree of the impairment. Firstly, explain to the patient that they must repeat words or phrases they hear to the examiner. To eliminate the possibility of lip-reading, stand behind the patient and say a test word to be repeated. 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 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

Fistula Test

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. Perilymphatic fistula can also be idiopathic. 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. 

Before 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.[8]

(Tuning) Fork Tests

Many otological pathologies result in hearing loss, either conductive or sensorineural. Conductive loss is due to a blockage of the vibrations reaching the cochlea, such as ossicular disruption or tympanic membrane perforation. Sensorineural hearing loss is due to damage to the cochlea itself or 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 whether they can hear it loudest in the left, right, or center.

Interpretation of Weber's Test

1. Normal hearing or symmetrical hearing loss: heard in the center.
2. Asymmetrical sensorineural hearing loss: heard loudest in the normal ear.
3. Asymmetrical conductive hearing loss: heard loudest in the affected ear.[9]

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

1. Air conduction is heard louder than bone conduction [Rinne's positive]: normal hearing or sensorineural hearing loss.
2. Bone conduction heard louder than air conduction [Rinne's negative]: conductive hearing loss.[10]

Therefore, Weber's lateralizes to the right in left sensorineural hearing loss, and Rinne's is positive on both sides. In left conductive hearing loss, Weber's lateralizes to the left, and Rinne's is negative on the left and positive on the right.

Facial Nerve Function Testing

The facial nerve has a complex infratemporal course running through the middle ear.[11] Therefore, several 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.[12]

Clinical Significance

The examiner can identify a large number of pathologies 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 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. Identifying 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 for many ear diseases should involve an interprofessional team, where possible. This may include otolaryngologists, audiologists, neurologists, neurosurgeons, radiologists, pediatricians, or infectious disease specialists. Specialist ENT nurses are, in many countries, playing a wider role in providing 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.