Ear
Anatomy and physiology
The ear is the specialised sensory organ of hearing and balance. It is divided anatomically into the external, middle and inner ear.
External ear
The external ear consists of the cartilaginous pinna, the external auditory canal (cartilage in the lateral one-third, bone in the medial two-thirds) and the lateral surface of the tympanic membrane ( Fig. 9.1 ). Sound is collected and channelled by the pinna and transmitted via the external auditory canal to the tympanic membrane. The external auditory canal has an elongated S-shaped curve; hence it is important to retract the pinna when examining the ear to see the tympanic membrane clearly. The outer portion of the canal has hair, and glands that produce ear wax, which forms a protective barrier.
Middle ear
The middle ear is an air-filled space that contains the three bony, articulated ossicles: the malleus, incus and stapes. The Eustachian tube opens into the middle ear inferiorly and allows equalisation of pressure and ventilation. Vibrations of the tympanic membrane are transmitted and amplified through the ossicular chain and focused on to the smaller oval window on which the stapes sits ( Fig. 9.1B ). The malleus is attached to the tympanic membrane and can be seen clearly on otoscopy ( Fig. 9.2 ). The long process of the incus can also be visible occasionally. The tympanic membrane has a flaccid upper part (pars flaccida) and it is important to look carefully in this area, as this is where a cholesteatoma (an invasive collection of keratinising squamous epithelium) can form. The chorda tympani nerve runs through the middle ear carrying taste fibres from the anterior two-thirds of the tongue; these ‘hitch a ride’ with the facial nerve, which runs through the mastoid bone in the wall of the middle ear.
Inner ear
The inner ear contains the organs of hearing (cochlea) and balance (vestibular system). The vibration of the stapes footplate stimulates fluid within the cochlea. This results in the movement of hair cells in the cochlea, which are converted to electrical impulses along the vestibulocochlear nerve (VIII).
The vestibular system helps maintain balance, along with visual input and proprioception. The vestibular part of the inner ear contains:
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The lateral, superior and posterior semicircular canals: these lie at right angles to detect rotational motion of their fluid (endolymph) in three planes.
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The utricle and the saccule: their hair cells are embedded in a gel layer containing small crystals (otoliths), which are subject to gravity and enable detection of head tilt and linear acceleration.
The history
Common presenting symptoms
Pain and itching
Ask about:
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quality of the pain
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preceding trauma, upper respiratory tract infection (URTI)
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associated symptoms: dysphagia/voice change (suggesting possible referred pain from a throat lesion).
Otalgia (ear pain) associated with pruritus (itching) is often due to otitis externa. Acute otitis media is common in children and otalgia often follows an URTI. Other causes of otalgia are described in Box 9.1 .
| Cause | Clinical features |
|---|---|
| Otological | |
| Acute otitis externa | Pain worse on touching outer ear, tragus Swelling of ear canal Purulent discharge and itching |
| Acute otitis media | Severe pain, red, bulging tympanic membrane, purulent discharge if tympanic membrane perforation present |
| Perichondritis | Erythematous, swollen pinna |
| Trauma | Pinna haematoma, pinna laceration, haemotympanum (blood behind tympanic membrane); cerebrospinal fluid leak or facial nerve palsy may be present |
| Herpes zoster (Ramsay Hunt syndrome) | Vesicles in ear canal, facial nerve palsy may be present; vertigo is common |
| Malignancy | Mass in ear canal or on pinna |
| Non-otological | |
| Tonsillitis Peritonsillar abscess | Sore throat, tonsil inflammation Trismus, soft-palate swelling in peritonsillar abscess |
| Temporomandibular joint dysfunction | Tenderness, clicking of joint on jaw opening |
| Dental disease | Toothache, e.g. due to dental abscess |
| Cervical spine disease | Neck pain/tenderness |
| Cancer of the pharynx or larynx | Associated sore throat, hoarseness, dysphagia, weight loss, neck lump |
Ear discharge
Ask about:
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purulent, mucoid or blood-stained discharge (otorrhoea)
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associated pain.
A purulent discharge can be caused by otitis externa or acute otitis media with a perforation. A chronic offensive discharge may be a sign of cholesteatoma.
Blood-stained discharge may suggest the presence of granulation tissue from infection or can be a result of trauma, with or without an associated cerebrospinal fluid (CSF) leak.
Hearing loss
Ask about:
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sudden or gradual onset
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precipitating factors: trauma, URTI, noise exposure, antibiotics
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impact of the hearing loss on the patient’s function.
Hearing loss can be due to disruption in the conduction mechanism or may have sensorineural causes, such as failure of the VIII nerve or cochlea ( Box 9.2 ). Profound loss before speech acquisition affects speech development and quality.
| Conductive a | |
|
|
| Sensorineural b | |
|
|
a Disruption to the mechanical transfer of sound in the outer ear, eardrum or ossicles.
Tinnitus
Tinnitus is an awareness of a noise in the absence of an external stimulus.
Ask about:
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quality of tinnitus: high-pitched, ringing, pulsatile
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intermittent or constant nature
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whether it is unilateral or bilateral
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associated hearing loss or other ear symptoms.
Tinnitus is usually associated with hearing loss. An acoustic neuroma (a tumour of the vestibulocochlear nerve, cranial nerve VIII) needs to be considered in unilateral tinnitus or tinnitus with an asymmetrical sensorineural hearing loss.
Vertigo
Vertigo is a sensation of movement relative to one’s surroundings. Rotational movements are most common and patients often have associated nausea, vomiting and postural or gait instability. Vertigo can originate peripherally or, less often, centrally (brainstem, cerebellum). Patients will often say they are ‘dizzy’ when describing the illusion of movement: that is, vertigo. It is very important to clarify exactly what they mean by this. Lightheadedness is not a vestibular symptom, but unsteadiness may be.
Ask about:
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duration and frequency of episodes
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aggravating or provoking factors (position, head movement)
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associated ‘fullness in the ear’ during the episode (Ménière’s disease)
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associated focal neurology (cerebrovascular event)
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fluctuating hearing loss or tinnitus
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associated headaches, nausea or aura (migraine)
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previous significant head injury; previous URTI.
The most common causes of vertigo include benign paroxysmal positional vertigo (attributed to debris within the posterior semicircular canal), vestibular neuritis (also known as vestibular neuronitis, a viral or postviral inflammatory disorder) and Ménière’s disease (caused by excess endolymphatic fluid pressure). Other causes include migraine, cerebral ischaemia, drugs and head trauma. Discriminating features are described in Box 9.3 .
| Benign paroxysmal positional vertigo | Vestibular neuritis | Ménière’s disease | Central vertigo (migraine, MS, brainstem ischaemia, drugs) | |
|---|---|---|---|---|
| Duration | Seconds | Days | Hours | Hours – migraine Days and weeks – MS Long-term – cerebrovascular accident |
| Hearing loss | – | – | ++ | – |
| Tinnitus | – | – | ++ | – |
| Aural fullness | – | – | ++ | – |
| Episodic | Yes | Rarely | Recurrent vertigo; persistent tinnitus and progressive sensorineural deafness | Migraine – recurs Central nervous system damage – usually some recovery but often persistent |
| Triggers | Lying on affected ear | Possible presence of upper respiratory symptoms | None | Drugs (e.g. aminoglycosides) Cardiovascular disease |
Nystagmus
Nystagmus is an involuntary rhythmic oscillation of the eyes, which can be horizontal, vertical, rotatory or multidirectional. It may be continuous or paroxysmal, or evoked by manœuvres such as gaze or head position. The most common form, ‘jerk nystagmus’, consists of alternating phases of a slow drift in one direction with a corrective saccadic ‘jerk’ in the opposite direction. The direction of the fast jerk is used to define the direction of nystagmus ( Box 9.4 ). Pendular nystagmus, in which there is a sinusoidal oscillation without a fast phase, is less common. Nystagmus may be caused by disorders of the vestibular, visual or cerebellar pathway.
| Nystagmus type | Clinical pathology | Characteristics | |
|---|---|---|---|
| Fast phase | Maximal on looking | ||
| Jerk: | |||
| Peripheral | Semicircular canal, vestibular nerve | Unidirectional Not suppressed by optic fixation Patient too dizzy to walk Dix–Hallpike fatigues on repetition | Away from affected side |
| Central | Brainstem, cerebellum | Bidirectional (changes with direction of gaze) Suppressed by optic fixation Patient can walk (even with nystagmus) Dix–Hallpike persists | To either side |
| Dysconjugate (ataxic) | Interconnections of III, IV and VI nerves (medial longitudinal bundle) | Typically affects the abducting eye | To either side |
| Pendular | Eyes, e.g. congenital blindness | No fast phase | Straight ahead |
Past medical history
Ask about:
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previous ear surgery, trauma
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recurrent ear infections
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systemic conditions associated with hearing loss (such as granulomatosis with polyangiitis)
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any significant previous illnesses such as meningitis, which can result in significant sensorineural hearing loss.
Drug history
The aminoglycoside antibiotics (such as gentamicin), aspirin, furosemide and some chemotherapy agents (cisplatin) are ototoxic.
Family history
Some causes of sensorineural hearing loss and otosclerosis are congenital. Otosclerosis causes a conductive hearing loss due to fixation of the stapes footplate.
Social history
The patient’s occupation should be noted, as well as any significant previous exposure to loud noise.
The physical examination
Inspection
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Pinna skin, shape, size, position, scars from previous surgery/trauma, deformity.
Palpation
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Gently pull on the pinna and push on the tragus to check for pain.
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Gently palpate over the mastoid bone behind the ear to assess for pain or swelling.
Otoscopy
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Use the largest otoscope speculum that will comfortably fit the meatus.
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Explain to the patient what you are going to do.
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Hold the otoscope in your right hand for examining the right ear (left hand to examine left ear). Rest the ulnar border of your hand against the patient’s cheek to enable better control and to avoid trauma if the patient moves ( Fig. 9.3 ).
Fig. 9.3
Examination of the ear using an otoscope.
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Gently pull the pinna upwards and backwards to straighten the cartilaginous external auditory canal. Use the left hand to retract the right pinna ( Fig. 9.3 ).
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Inspect the external auditory canal through the speculum, noting wax, foreign bodies or discharge. You should identify the tympanic membrane and the light reflex anteroinferiorly (see Fig. 9.2 ).
Congenital deformities of the pinna, like microtia ( Fig. 9.4A ) or low-set ears, can be associated with other conditions such as hearing loss and Down’s syndrome. Children can also have protruding ears that occasionally require corrective surgery (pinnaplasty). Trauma can result in a pinna haematoma ( Fig. 9.4B ) and subsequent ‘cauliflower ear’ due to cartilage necrosis if untreated. Trauma may also cause mastoid bruising (‘Battle’s sign’), suggesting a possible skull-base fracture. Lesions on the pinna are relatively common and can be related to sun exposure; they include actinic keratosis, and basal cell and squamous cell cancers ( Fig. 9.4C ).
If discharge is noted on otoscopy and the tympanic membrane is intact, otitis externa is the likely cause ( Fig. 9.5A ). The canal can reveal exostoses, abnormal bone growth due to cold water exposure, often seen in surfers ( Fig. 9.5B ).
Scarring on the tympanic membrane (tympanosclerosis) can be caused by previous grommet insertion or infections. Tympanic membrane perforations can be central or marginal, and the position and size of the perforation should be noted as a percentage ( Fig. 9.6A ). A severe retraction pocket of the pars tensa can mimic a perforation ( Fig. 9.6B ). A retraction of the pars flaccida can contain a cholesteatoma, which may cause an offensive discharge and erode the bony ossicles, resulting in a conductive hearing loss ( Fig. 9.5C ). Fluid behind the tympanic membrane is called otitis media with effusion (OME or ‘glue ear’, Fig. 9.7A ), and a fluid level may be seen ( Fig. 9.7B ). This commonly affects children and can be treated surgically with insertion of a ventilation tube or grommet (see Fig. 9.6C ). If persistent OME is seen in adults, the postnasal space needs to be examined by a specialist to exclude a lesion in that site. Acute otitis media presents with pain; the tympanic membrane can become inflamed ( Fig. 9.7C ), and may bulge and eventually perforate.
Testing hearing
Whispered voice test
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Stand behind the patient.
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Start testing with your mouth about 15 cm from the ear you are assessing.
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Mask hearing in the patient’s other ear by rubbing the tragus (‘masking’).
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Ask the patient to repeat a combination of multisyllable numbers and words. Start with a normal speaking voice to confirm that the patient understands the test. Lower your voice to a clear whisper.
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Repeat the test but this time at arm’s length from the patient’s ear. People with normal hearing can repeat words whispered at 60 cm.
Tuning fork tests
A 512-Hz tuning fork can be used to help differentiate between conductive and sensorineural hearing loss.
Weber’s test
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Strike the prongs of the tuning fork against a hard surface to make it vibrate.
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Place the base of the vibrating tuning fork in the middle of the patient’s forehead ( Fig. 9.8 ).
Fig. 9.8
Weber’s test.
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Ask the patient, ‘Where do you hear the sound?’
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Record which side Weber’s test lateralises to if not central.
In a patient with normal hearing, the noise is heard in the middle, or equally in both ears.
In conductive hearing loss the sound is heard louder in the affected ear. In unilateral sensorineural hearing loss it is heard louder in the unaffected ear. If there is symmetrical hearing loss it will be heard in the middle.
Rinne’s test
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Strike the prongs of the tuning fork against a hard surface to make it vibrate.
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Place the vibrating tuning fork on the mastoid process ( Fig. 9.9A ).
Fig. 9.9
Rinne’s test.
A Testing bone conduction. B Testing air conduction.
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Now place the still-vibrating base at the external auditory meatus and ask, ‘Is it louder in front of your ear or behind?’ ( Fig. 9.9B ).
With normal hearing, the sound is heard louder when the tuning fork is at the external auditory meatus. That is, air conduction (AC) is better than bone conduction (BC), recorded as AC > BC. This normal result is recorded as ‘Rinne-positive’.
In conductive hearing loss, bone conduction is better than air conduction (BC > AC); thus the sound is heard louder when the tuning fork is on the mastoid process (‘Rinne-negative’). A false-negative Rinne’s test may occur if there is profound hearing loss on one side. This is due to sound being conducted through the bone of the skull to the other ‘good’ ear. Weber’s test is more sensitive and therefore the tuning fork will lateralise to the affected ear in conductive hearing loss before Rinne’s test becomes abnormal (negative). In sensorineural hearing loss, Rinne’s test will be positive, as air conduction is better than bone conduction.
Tuning fork test findings are summarised in Box 9.5 .
| Weber test | Rinne test | |
|---|---|---|
| Bilateral normal hearing | Central | AC > BC, bilateral |
| Bilateral symmetrical sensorineural loss | Central | AC > BC, bilateral |
| Unilateral or asymmetrical sensorineural loss LEFT | Louder right | AC > BC, bilateral a |
| Unilateral conductive loss LEFT | Louder left | BC > AC, left AC > BC, right |
| Bilateral conductive loss (worse on LEFT) | Louder left | BC > AC, bilateral |
a Patients with a severe sensorineural loss may have BC > AC due to BC crossing to the other better-hearing cochlea that is not being tested (false-negative Rinne test).
Testing vestibular function
Testing for nystagmus
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