The history should include an account of the onset and progression of any deafness, noise exposure, drug history, a history of swimming or diving, air travel and head injury and family history. A recent or past episode of a generalised infection would be relevant and the presence of associated aural symptoms, such as ear pain, discharge, tinnitus and vertigo. Vertigo may be a symptom of Ménière syndrome, multiple sclerosis, acoustic neuroma or syphilis.
Several important clues can be obtained from the history. The often sudden onset of hearing loss in an ear following swimming or showering is suggestive of wax, which swells to block the ear canal completely.
Patients with conductive loss may hear better in noisy conditions (paracusis) because we raise our voices when there is background noise. Conversely, people with sensorineural deafness (SND) usually have more difficulty hearing in noise as voices become unintelligible.
Inspect the facial structures, skull and ears. The ears are inspected with an otoscope to visualise the external meatus and the tympanic membrane (TM) and the presence of obstructions such as wax, inflammation or osteomata.
The examination requires a clean external auditory canal. Gentle suction is useful for cleaning pus debris. Syringing is reserved for wax in people with an intact TM and a known healthy middle ear.
It is an advantage to have a pneumatic attachment to test drum mobility. Reduction of TM mobility is an important sign in secretory otitis media.
There are several simple hearing tests. The distance at which a ticking watch can be heard can be used but the advent of the digital watch has affected this traditional method.
Occlude far ear. Have the patient cover near eye with one hand to prevent lip reading. Place your mouth at the near side. Strongly whisper ‘68’ then ‘100’ from a distance of 50 cm. Ask the patient to repeat the words. Then repeat using a normal speaking voice.
In children and in adults with a reasonable amount of hair grab several hairs close to the external auditory canal between the thumb and index finger. Rub the hairs lightly together at 5 cm (high sensitivity) to produce a relatively high-pitched ‘crackling’ sound (see FIG. 43.3). If this sound cannot be heard, a moderate hearing loss is likely (usually about 40 dB or greater). Like the whisper test, this test is a rough guide only.
Simple hair-rubbing method of testing possible deafness
If deafness is present, its type (conduction or sensorineural) should be determined by tuning fork testing. The most suitable tuning fork for preliminary testing is the C2 (512 cps) fork. The fork is best activated by striking it firmly on the bent elbow.
The vibrating tuning fork is applied firmly to the midpoint of the skull or to the central forehead or to the teeth.
This test is of value only if the deafness is unilateral or bilateral and unequal (see FIG. 43.4). Normally the sound is heard equally in both ears in the centre of the forehead. With sensorineural deafness the sound is transmitted to the normal ear, while with conduction deafness it is heard better in the abnormal ear.
Lateralisation of the sound to one ear indicates a conductive loss on that side, or a sensorineural loss on the other side.
It therefore compares air and bone conduction in the same ear (see FIG. 43.5). A variation of the test includes placing the tuning fork on the mastoid process and the patient indicates when it can no longer be heard. The fork is then placed at the external auditory meatus and the patient indicates whether the sound is now audible. Normally air conduction is better than bone conduction and the sound will again be heard.
Rinne test comparing air conduction (a) with bone conduction (b)
A comparison of the interpretation of these tests is summarised in TABLE 43.3.
Table 43.3A comparison of the Rinne and Weber tests |Favorite Table|Download (.pdf) Table 43.3 A comparison of the Rinne and Weber tests
|State of the hearing ||Rinne test ||Weber test |
|Normal ||Positive: AC >BC ||Equal in both ears |
|Conduction deafness ||Negative: BC >AC ||Louder in the deaf ear |
|Very severe conduction deafness || |
Negative: BC >AC
May hear BC only
|Louder in the deaf ear |
|Sensorineural deafness ||Positive: AC >BC ||Louder in the better ear |
|Very severe sensorineural deafness ||‘False’ negative (without masking) ||Louder in the better ear |
Audiometric assessment includes the following:
Pure tone audiometry is a graph of frequency expressed in hertz versus loudness expressed in decibels. The tone is presented either through the ear canal (a test of the conduction and the cochlear function of the ear) or through the bone (a test of cochlear function).
FIGURES 43.6 and 43.7 are typical examples of pure tone audiograms.
Pure tone audiogram for severe conductive deafness in left ear
Source: After Black4
Pure tone audiogram for unilateral (left) sensorineural deafness. Suspect a viral or congenital origin in children; check adults for acoustic neuroma.
The difference between the two is a measure of conductance. If the two ears have different thresholds, a white noise masking sound is applied to the better ear to prevent it hearing sound presented to the test ear. The normal speech range occurs between 0 and 20 dB in soundproof conditions across the frequency spectrum.
Tympanometry measures the mobility of the tympanic membrane, the dynamics of the ossicular chain and the middle-ear air cushion. The test consists of a sound applied at the external auditory meatus, otherwise sealed by the soft probe tip.