Hearing Loss; Audiometry Flashcards
(8 cards)
Describe the difference in meaning of Weber’s and Rinne’s Tests
Weber’s Test
* Strike the tuning fork to make it vibrate and hum (use the palm of your hand or your knee – not the patient!)
* Place it in the centre of the patient’s forehead
* Ask the patient if they can hear the sound and which ear it is loudest in
Results:
- A normal result is when the patient hears the sound equally in both ears.
- In sensorineural hearing loss, the sound will be louder in the normal ear (quieter in the affected ear). The normal ear is better at sensing the sound.
- In conductive hearing loss, the sound will be louder in the affected ear. This is because the affected ear “turns up the volume” and becomes more sensitive, as sound has not been reaching that side as well due to the conduction problem. When the tuning fork’s vibration is transmitted directly to the cochlea, rather than having to be conducted, the increased sensitivity makes it sound louder in the affected ear.
Rinne’s Test
* Strike the tuning fork to make it vibrate and hum
* Place the flat end on the mastoid process (the boney lump behind the ear) – this tests bone conduction
* Ask the patient to tell you when they can no longer hear the humming noise
* When they can no longer hear the noise, remove the tuning fork (still vibrating) and hover it 1cm from the same ear
* Ask the patient if they can hear the sound now – this tests air conduction
* Repeat the process on the other side
Results:
* A normal result is when the patient can hear the sound again when bone conduction ceases and the tuning fork is moved next to the ear rather than on the mastoid process. It is normal for air conduction to be better (more sensitive) than bone conduction. This is referred to as “Rinne’s positive”.
- An abnormal result (Rinne’s negative) is when bone conduction is better than air conduction. The sound is not heard after removing the tuning fork from the mastoid process and holding it near the ear canal. This suggests a conductive cause for the hearing loss. Sound is transmitted through the bones of the skull directly to the cochlea, meaning bone conduction is intact. However, the sound is less able to travel through the air, ear canal, tympanic membrane and middle ear to the cochlea due to a conductive problem.
TOM TIP: The way I remember which way round these tests are, is to picture Spiderman shooting a web (Weber’s) right in the middle of someone’s face.
The causes of adult-onset sensorineural hearing loss are [+]
Sudden sensorineural hearing loss (over less than 72 hours)
Presbycusis (age-related)
Noise exposure
Ménière’s disease
Labyrinthitis
Acoustic neuroma
Neurological conditions (e.g., stroke, multiple sclerosis or brain tumours)
Infections (e.g., meningitis)
Medications
There are a large number of medications that can cause sensorineural hearing loss. Some of the more common to remember are: [3]
Loop diuretics (e.g., furosemide)
Aminoglycoside antibiotics (e.g., gentamicin)
Chemotherapy drugs (e.g., cisplatin)
The causes of adult-onset conductive hearing loss are [+]
Ear wax (or something else blocking the canal)
Infection (e.g., otitis media or otitis externa)
Fluid in the middle ear (effusion)
Eustachian tube dysfunction
Perforated tympanic membrane
Otosclerosis
Cholesteatoma
Exostoses
Tumours
Describe a three step algorithm for interpreting audiograms [3]
1. is there anything below 20dB
yes = move to step 2
no = normal hearing
2. is there a gap? (b/w air and bone conduction)
yes = conductive or mixed hearing loss
no = sensorineural hearing loss
3. is one below or both below the 20dB line
one = conductive
both = mixed
Describe how you interpret an audiogram report like this [2]
Audiograms are usually the first-line investigation that is performed when a patient complains of hearing difficulties. They are relatively easy to interpret as long as some simple rules are followed:
* anything above the 20dB line is essentially normal (marked in green on the audiogram below)
* in sensorineural hearing loss both air and bone conduction are impaired
* in conductive hearing loss only air conduction is impaired
* in mixed hearing loss both air and bone conduction are impaired, with air conduction often being ‘worse’ than bone
This report:
- Right conductive hearing loss
What are causes for unilateral hearing loss?
It can be conductive, sensorineural, or mixed
- The cause of UHL can range from otitis media with effusion to acoustic neuroma.
Infrequent
Meniere’s disease
Stroke
Rare
Vestibular schwannoma
Head and neck cancer
What is a common and infrequent cause of bilateral hearing loss? [2]
Common
Presbycusis
Infrequent
Meniere’s disease
