Ear, Nose and Throat Flashcards
Categories of hearing loss
There are two main categories of hearing loss: conductive hearing loss and sensorineural hearing loss.
Conductive hearing loss relates to a problem with sound travelling from the environment to the inner ear. The sensory system may be working correctly, but the sound is not reaching it. Putting earplugs in your ears causes conductive hearing loss.
Sensorineural hearing loss is caused by a problem with the sensory system or vestibulocochlear nerve in the inner ear.
Basic ear anatomy
There are three sections of the ear are:
Outer ear
Middle ear
Inner ear
The basic structures, from outside in, are:
The pinna is the external portion of the ear
The external auditory canal is the tube into the ear
The tympanic membrane is the eardrum
The Eustachian tube connects the middle ear with the throat to equalise pressure
The malleus, incus and stapes are the small bones in the middle ear that connect the tympanic membrane to the structures of the inner ear
The semicircular canals are responsible for sensing head movement (the vestibular system)
The cochlea is responsible for converting the sound vibration into a nervous signal
The vestibulocochlear nerve transmits nerve signals from the semicircular canals and cochlea to the brain
Presentation of hearing loss
Hearing loss may be gradual and insidious. Patients may present because others have noticed they are not paying attention or missing details of conversations. Sometimes patients can present with concerns about dementia, when in fact, the issue is hearing loss.
Sudden onset hearing loss (over less than 72 hours) requires a thorough assessment to establish the cause.
There may be associated symptoms alongside hearing loss, which can give clues about the potential cause:
Tinnitus (ringing in the ears)
Vertigo (the sensation that the room is spinning)
Pain (may indicate infection)
Discharge (may indicate an outer or middle ear infection)
Neurological symptoms
It is worth noting patients with hearing loss are more likely to develop dementia, and treating the hearing loss (e.g., a hearing aid) may reduce the risk.
Weber’s and Rinne’s Tests
Weber’s test and Rinne’s test are used to differentiate between sensorineural and conductive hearing loss. A tuning fork is used to perform both tests.
Weber’s Test
To perform 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
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.
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.
Rinne’s Test
To perform 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
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.
Causes Of Sensorineural Hearing Loss
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:
Loop diuretics (e.g., furosemide)
Aminoglycoside antibiotics (e.g., gentamicin)
Chemotherapy drugs (e.g., cisplatin)
Causes Of Conductive Hearing Loss
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
Presbycusis
Presbycusis is described as age-related hearing loss. It is a type of sensorineural hearing loss that occurs as people get older. It tends to affect high-pitched sounds first and more notably than lower-pitched sounds. The hearing loss occurs gradually and symmetrically.
The causes of reduced hearing in presbycusis are complex. There are several different mechanisms, including loss of the hair cells in the cochlea, loss of neurones in the cochlea, atrophy of the stria vascularis and reduced endolymphatic potential.
Risk factors for presbycusis
Age
Male gender
Family history
Loud noise exposure
Diabetes
Hypertension
Ototoxic medications
Smoking
Exposure to loud noise over time is a key risk factor that can be addressed to potentially prevent or reduce the extent of presbycusis. Hearing protection should be worn in environments where there is exposure to loud noises for prolonged periods to reduce the risk of presbycusis, for example, in occupations such as woodworking or construction.
Presentation of presbycusis
Hearing loss in presbycusis is gradual and insidious. The gradual onset may mean patients do not notice the change in their hearing. The loss of high-pitched sounds can make speech difficult to hear and understand, particularly in loud environments. Male voices may be easier to hear than female voices (due to the generally lower pitch). Patients may present after others have noticed they are not paying attention or missing details of conversations. Sometimes patients can present with concerns about dementia, when in fact, the issue is hearing loss.
There may be associated tinnitus (ringing in the ears).
It is worth noting patients with hearing loss are more likely to develop dementia, and treating the hearing loss (e.g., a hearing aid) may reduce the risk.
Diagnosing presbycusis
Audiometry is the investigation of choice for establishing the diagnosis and extent of hearing loss. Presbycusis will give a sensorineural hearing loss pattern, with normal or near-normal hearing at lower frequencies and worsening hearing loss at higher frequencies.
Managing presbycusis
The effects of presbycusis cannot be reversed.
Management involves supporting the person to maintain normal functioning:
Optimising the environment, for example, reducing the ambient noise during conversations
Hearing aids
Cochlear implants (in patients where hearing aids are not sufficient)
Sudden sensorineural hearing loss
Sudden sensorineural hearing loss (SSNHL) is defined as hearing loss over less than 72 hours, unexplained by other causes. This is considered an otological emergency and requires an immediate referral to the on-call ENT team. The diagnosis is made when someone rapidly loses their hearing, and no conductive cause can be found.
With SSNHL, hearing loss is most often unilateral. It may be permanent or resolve over days to weeks.
Conductive causes of rapid-onset hearing loss (not classed as SSNHL) include:
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
Causes of sudden sensorineural hearing loss
Most cases (90%) of SSNHL are idiopathic, meaning no specific cause is found.
Other causes of SSNHL include:
Infection (e.g., meningitis, HIV and mumps)
Ménière’s disease
Ototoxic medications
Multiple sclerosis
Migraine
Stroke
Acoustic neuroma
Cogan’s syndrome (a rare autoimmune condition causing inflammation of the eyes and inner ear)
Investigating sudden sensorineural hearing loss
Audiometry is required to establish the diagnosis. A diagnosis of SSNHL requires a loss of at least 30 decibels in three consecutive frequencies on an audiogram.
MRI or CT head may be used if a stroke or acoustic neuroma are being considered.
Managing sudden sensorineural hearing loss
The NICE clinical knowledge summaries (updated September 2019) recommend an immediate referral to ENT for assessment within 24 hours for patients presenting with sudden sensorineural hearing loss presenting within 30 days of onset.
Where an underlying cause is found (e.g., infection), treatment can be directed at this.
Idiopathic SSNHL may be treated with steroids under the guidance of the ENT team. Steroids may be:
Oral
Intra-tympanic (via an injection of steroids through the tympanic membrane)
Eustachian tube dysfunction
Eustachian tube dysfunction is when the tube between the middle ear and throat is not functioning properly. The Eustachian tube is present mainly to equalise the air pressure in the middle ear and drain fluid from the middle ear.
When the Eustachian tube is not functioning correctly or becomes blocked, the air pressure cannot equalise properly and fluid cannot drain freely from the middle ear. The air pressure between the middle ear and the environment can become unequal. The middle ear can fill with fluid.
Eustachian tube dysfunction may be related to a viral upper respiratory tract infection (URTI), allergies (e.g., hayfever) or smoking.
Presentation of Eustachian tube dysfunction
Eustachian tube dysfunction may present with:
Reduced or altered hearing
Popping noises or sensations in the ear
A fullness sensation in the ear
Pain or discomfort
Tinnitus
Symptoms tend to get worse when the external air pressure changes and the middle ear pressure cannot equalise to the outside pressure, for example, flying, climbing a mountain or scuba diving.
Otoscopy may appear normal, but it is important to exclude other causes (e.g., otitis media).
Investigating Eustachian tube dysfunction
Often Eustachian tube dysfunction gives a typical set of symptoms and is associated with a clear cause, for example, a recent viral upper respiratory tract infection or hayfever. In this situation, investigations are not required as the symptoms will resolve with time or simple treatments.
In persistent, problematic or severe symptoms, investigations to help establish the diagnosis and cause include:
Tympanometry
Audiometry
Nasopharyngoscopy (an endoscopic camera through the nose to the throat to inspect the Eustachian tube openings)
CT scan to assess for structural pathology
Tympanometry
Tympanometry involves:
Inserting a device into the external auditory canal (ear canal)
Creating different air pressures in the canal
Sending a sound in the direction of the tympanic membrane
Measuring the amount of sound reflected back off the tympanic membrane
Plotting a tympanogram (graph) of the sound absorbed (admittance) at different air pressures
The amount of sound absorbed by the tympanic membrane and middle ear (not reflected back to the device) is known as the admittance.
Normally, sound is absorbed best when the air pressure in the ear canal matches the ambient air pressure. The ambient air pressure is equal to the middle ear pressure in healthy ears.
When there is Eustachian tube dysfunction, the air pressure in the middle ear may be lower than the ambient air pressure because new air cannot get in through the tympanic membrane to equalise the pressures. As a result, the tympanogram will show a peak admittance (most sound absorbed) with negative ear canal pressures.
Managing Eustachian tube dysfunction
Treatment options for Eustachian tube dysfunction include:
No treatment, waiting for it to resolve spontaneously (e.g., recovering from the viral URTI)
Valsalva manoeuvre (holding the nose and blowing into it to inflate the Eustachian tube)
Decongestant nasal sprays (short term only)
Antihistamines and a steroid nasal spray for allergies or rhinitis
Surgery may be required in severe or persistent cases
Otovent is an over the counter device where the patient blows into a balloon using a single nostril, which can help inflate the Eustachian tube, clear blockages and equalise pressure.
Surgery for Eustachian tube dysfunction
There are three main surgical options:
Treating any other pathology that might be causing symptoms, for example, adenoidectomy (removal of the adenoids)
Grommets
Balloon dilatation Eustachian tuboplasty
Grommets are tiny tubes inserted into the tympanic membrane by an ENT surgeon. This allows air or fluid from the middle ear to drain through the tympanic membrane to the ear canal. Grommets are usually inserted using a local anaesthetic. The procedure is relatively safe with few complications. Grommets typically fall out within 18 months.
Balloon dilatation Eustachian tuboplasty involves inserting a deflated balloon into the Eustachian tube, inflating the balloon for a short period (i.e., 2 minutes) to stretch the Eustachian tube, then deflating and removing it. This is usually done under general anaesthetic.
Otosclerosis
Otosclerosis is a condition where there is remodelling of the small bones in the middle ear, leading to conductive hearing loss. Oto- refers to the ears, and -sclerosis means hardening. It usually presents before the age of 40 years.
The development of otosclerosis is thought to result from a combination of environmental and genetic factors, although the exact mechanism is not understood. It can be inherited in an autosomal dominant pattern. However, no specific genetic mutations have been identified. It is more common in women.
Pathophysiology of otosclerosis
The auditory ossicles are the tiny bones in the middle ear that transmit sound vibrations from the tympanic membrane to the cochlea. They are the malleus, incus and stapes. The stapes is connected to the oval window (fenestra ovalis) of the cochlea, where it transmits vibrations into the cochlea, which converts them into sensory signals.
In patients with otosclerosis, these tiny bones in the middle are affected by abnormal bone remodelling and formation. This mainly affects the base of the stapes, where it attaches to the oval window, causing stiffening and fixation and preventing it from transmitting sound effectively. It causes conductive hearing loss.
Presentation of otosclerosis
The typical presentation is a patient under 40 years presenting with unilateral or bilateral:
Hearing loss
Tinnitus
It tends to affect the hearing of lower-pitched sounds more than higher-pitched sounds. Female speech may be easier to hear than male speech (due to the generally higher pitch). This is the reverse of the pattern seen in presbycusis.
Due to conductive hearing loss with intact sensory hearing, the patient can experience their voice as being loud compared to the environment (due to bone conduction of their voice). This can lead to them talking quietly.