The ear, nose and throat

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 focus on to the smaller oval window on which the stapes sits (see 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, resulting 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:

• The lateral, superior and posterior semicircular canals: these lie at right angles to detect rotational motion of their fluid (endolymph) in three planes.

• 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.

Pain and itching

Ask about:

• quality of the pain

• preceding trauma, upper respiratory tract infection (URTI)

• 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 .

Ear discharge

Ask about:

• purulent, mucoid or blood-stained discharge (otorrhoea)

• 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:

• sudden or gradual onset

• precipitating factors: trauma, URTI, noise exposure, antibiotics

• impact of the hearing loss on the patient’s function.

Hearing loss can be a result of 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.

Tinnitus

Tinnitus is an awareness of a noise in the absence of an external stimulus.

Ask about:

• quality of tinnitus: high-pitched, ringing, pulsatile

• intermittent or constant nature

• whether it is unilateral or bilateral

• 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:

• duration and frequency of episodes

• aggravating or provoking factors (position, head movement)

• associated ‘fullness in the ear’ during the episode (Ménière’s disease)

• associated focal neurology (cerebrovascular event)

• fluctuating hearing loss or tinnitus

• associated headaches, nausea or aura (migraine)

• 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 .

  9.3

  Diagnosing vertigo

  MS, Multiple sclerosis.

  	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
  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, paroxysmal, or evoked by manoeuvres 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.

Whispered voice test

Examination sequence ( Video 19A )

• Stand behind the patient.

• Start testing with your mouth about 15 cm from the ear you are assessing.

• Mask hearing in the patient’s other ear by rubbing the tragus (‘masking’).

• Ask the patient to repeat a combination of numbers and letters (e.g. 3-B-7). Start with a normal speaking voice to confirm that the patient understands the test. Then, lower your voice to a clear whisper.

• Repeat the test but this time at arm’s length from the patient’s ear. People with normal hearing can repeat the sequence correctly when whispered at 60 cm.

• If the patient responds incorrectly, the test is repeated using a different number/letter combination.

• If 50% or more of the items in the two triplets are incorrect, the test is abnormal.

Tuning fork tests

A 512-Hz tuning fork can be used to help differentiate between conductive and sensorineural hearing loss.

Weber’s test

Examination sequence ( Video 19B )

• Strike the prongs of the tuning fork against a padded surface to make it vibrate.

• Place the base of the vibrating tuning fork in the middle of the patient’s forehead ( Fig. 9.8 ).

  

• Ask the patient, ‘Where do you hear the sound?’

• Record which side Weber’s test lateralises to if not central.

In a patient with normal hearing, the sound would be expected to be heard in the middle, or equally in both ears; however, up to 40% of people with normal hearing will lateralise on Weber’s test. Therefore, Weber's test should only be interpreted in patients with hearing loss.

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

Examination sequence ( Video 19C )

• Strike the prongs of the tuning fork against a padded surface to make it vibrate.

• Place the vibrating tuning fork on the mastoid process ( Fig. 9.9A ) and ask, ‘Can you hear this?’ Then ask the patient to ‘tell me when you hear it stop’.

  

• Now place the tuning fork at the external auditory meatus and ask, ‘Can you still hear it’ (see Fig. 9.9B ). In a patient with normal hearing, they will still hear it.

To maximise the sound for the patient, the "U" of the tuning fork should face forward.

Alternative technique: loudness comparison

• Strike the prongs of the tuning fork against a padded surface to make it vibrate.

• Place the vibrating tuning fork on the mastoid process for about 2 seconds.

• Now place the still-vibrating tuning fork at the external auditory meatus and ask, ‘Is it louder in front of your ear or behind?’

With normal hearing, sound is heard louder or longer 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, sound is heard louder when the tuning fork is on the mastoid process (‘Rinne-negative’). This finding is associated with a high likelihood that the patient has a conductive hearing loss of at least 20 dB. 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 can detect a hearing loss of just 5 dB; 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 .

9.5

Tuning fork tests

	Weber’s test	Rinne’s 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

AC, Air conduction; BC, bone conduction.

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's test).