A patient presents to your clinic with the problem of hearing loss. While some cases do not present with any other symptoms, some may have associated otalgia, otorrhoea, blocked ear sensation or tinnitus. What are some differentials that go through your mind? Here, Singapore General Hospital presents a systematic approach for general practitioners (GPs) in the work-up of such patients.  

EAR ANATOMY AND PHYSIOLOGY

The ear is divided into three parts – the external ear, middle ear and inner ear.

When sound energy is channelled from the external environment to the ear, it first travels through the ear canal. Sound energy then vibrates the tympanic membrane (eardrum), which then vibrates the three ossicles (malleus, incus and stapes) sequentially.

The energy is then sent to the cochlea (the hearing organ), which then converts the sound energy into electrical signals which are sent to the brain via the auditory nerve.

Therefore, any pathology along the external ear and middle ear that blocks the conduction of sound energy to the cochlear can cause CHL.

CONDUCTIVE HEARING LOSS: EVALUATION AND WORK-UP IN PRIMARY CARE

Patients with ear pathologies present with any permutation of the following symptoms:

• Hearing loss
  

• Tinnitus

• Otalgia

• Otorrhoea

• Blocked ear sensation

• Ear itch

• Imbalance

• Vertigo
  

A good history taking and physical examination almost always reveals the diagnosis. This article will focus on otoscopic examination and tuning fork examination.

A. Otoscopic examination

Understand that the ear canal is curvilinear. Thus, when performing the otoscopic examination, pull the ear upward and outwards to straighten the ear canal for a better view of the tympanic membrane. Be systematic as you perform the otoscopic examination.

1. First, inspect the external ear canal

• Is there any wax, and if so, is it impacted?

• Is there any foreign body?

• Is the ear canal red and oedematous to suggest an infection?

• If there is an infection, what is the quality of the debris within the ear canal?

• A fungal infection (otomycosis) would have a wet tissue paper-like debris, and often you may even see fungal spores.
  

2. Next, focus your attention on the tympanic membrane

• Determine if there is a perforation. If so, is there associated infection?

• Is there a retraction of the tympanic membrane with associated squames to suggest cholesteatoma?

• Is the tympanic membrane red and bulging to suggest acute otitis media?
  

3. Finally, determine the middle ear status

• Is it air-filled or fluid-filled? Sometimes, one may even see air bubbles or an air-fluid level.

• It is not uncommon for the tympanic membrane to have sclerotic plaque, making the middle ear status difficult to determine.

• If so, use other clues from the history taking and physical examination to build the case for the diagnosis.

B. Tuning fork examination

Learning to use the tuning fork in your GP clinic is important, especially as there are no audiology services available.

In a patient who presents with hearing loss, a tuning fork examination is necessary to determine if it is a conductive or sensorineural type of hearing loss.

There is a range of tuning forks with different frequencies. For the purposes of testing for hearing, the 512 Hz tuning fork would be the best.

The two most commonly performed tuning fork tests are the Weber test and Rinne test.

1. Weber test

In the Weber test, strike the tuning fork and place it on the patient's forehead. An important tip is to apply counter pressure at the back of their head with your other hand as you press the tuning fork against their forehead.

Ask the patient where he hears the sound localise to – the middle, the right ear or the left ear.

• If hearing were normal (or equal) in both ears, the patient would report hearing the sound in the middle

• If the sound is localised to the right ear, there are two possibilities:

• Either a right CHL,
  

• Or that the right sensorineural hearing is better than the left
  

2. Rinne test

Then, perform a Rinne test. Strike the 512 Hz tuning fork and place it in front of the patient's ear, and then place it behind the ear against the mastoid prominence.

At this point, ask the patient if they hear it louder when the tuning fork is placed in front of the ear (air conduction) or when it is applied to the mastoid prominence (bone conduction).

• If air conduction is louder than bone conduction, the test is said to be positive. This is a normal response.

• If the bone conduction is louder than air conduction, the test is said to be negative. This suggests that there is CHL.

Table 1 AC: air conduction, BC: bone conduction

COMMON CONDITIONS CAUSING CHL AND HOW TO MANAGE THEM

1. Impacted ear wax

These patients may present with otalgia and blocked ear sensation. If there is secondary infection, there may be otorrhoea. Impacted ear wax often comes about when patients clean or dig their ears, often with a cotton bud, which pushes the wax further and further in.

However, do note that having a significant amount of ear wax does not necessarily mean it is due to CHL from impacted wax. The patient could have an underlying sudden sensorineural hearing loss, and happen to have a lot of ear wax. A tuning fork examination would help to differentiate between the two.

Management

Do give the patients either topical olive oil or cerumenolytics like docusate sodium. A tragal massage immediately after application of drops helps to dissolve the wax.

When to refer

Refer to a specialist when topical drops do not help to get rid of the wax and do not provide symptom relief. These patients would need help with a professional aural toilet. An important but not so common differential is keratosis obturans.

2. External ear infection (otitis externa)

Otitis externa may be bacterial or fungal. Bacterial infections can cause otalgia, otorrhoea and hearing loss (from blockage from the debris).

Examination often reveals tragal tenderness and a red and oedematous ear canal with pus. A tell-tale sign of otomycosis would be an intense itch. Otoscopic examination shows a wet tissue paper-like debris, and you may even see fungal spores.

Management

Treatment is with topical ear drops. As pseudomonas is the most common bacteria implication, ciprofloxacin ear drops are effective. Antifungal ear drops are indicated for otomycosis.

When to refer

Refer when there is recurrent infection or if infection persists despite a trial of treatment. If the patient reports severe otalgia that disturbs sleep and has a background of diabetes or other immunocompromised states, please refer to ENT in a timely manner as malignant otitis externa (MOE) is a consideration.

Granulation tissue in the ear canal between the medial two-thirds and lateral one-third is pathognomonic of MOE.

3. Tympanic membrane perforation / chronic suppurative otitis media

Often you would see mucoid discharge in the external ear due to infection of the middle ear. The middle ear mucosa may be inflamed.

Management

Treatment would include topical ear drops. In persistent or recurrent infections, we would often take cultures from the ear and treat with appropriate culture-directed antibiotics.  

Figure 1

When to refer

Refer the patient to ENT should they be keen on surgery to reconstruct the tympanic membrane, or if there is a recurrent infection. A recurrent infection sometimes means that there may be a concomitant middle ear pathology like cholesteatoma.

4. Cholesteatoma

The patient typically presents with chronic otorrhoea and gradual hearing loss. Examination reveals a retracted pars flaccida (superior aspect of the tympanic membrane) with accumulated squames (Figure 2).

Cholesteatoma, though benign, can erode surrounding bony structures including the ossicles (causing CHL), facial nerve canal (causing facial nerve palsy), labyrinth (causing dizziness) and tegmen/skull base (causing intracranial spread), and can also be secondarily infected (causing pain).

Figure 2

When to refer

Do refer to a specialist as cholesteatoma is a surgical disease.

5. Otitis media with effusion

Patients with this condition often present with a blocked ear. It may occur commonly after an upper respiratory tract infection and typically resolves in a few weeks.

Management

Do check for blood-stained saliva and neck nodes as otitis media with effusion could be the first presenting symptom of nasopharyngeal carcinoma, especially if it was 'unprovoked'.

Figure 3

When to refer

This is often a first presenting symptom of nasopharyngeal carcinoma. Do refer to a specialist for a scope especially if non-resolving. A myringotomy and ventilation tube insertion may be offered to the patient once the scope is clear.

6. Normal tympanic membrane but CHL suggested on tuning fork examination

This may be due to otosclerosis, or ossicular chain fixation or discontinuity from bony bars, otomastoiditis, cholesteatoma, etc. An evaluation with a CT scan is often necessary to determine the aetiology.

When to refer

Do refer them to a specialist for further evaluation and management.

Dr Brenda Sim is a Consultant at the Department of Otorhinolaryngology – Head & Neck Surgery at Singapore General Hospital. She has a subspecialty interest in otology and neurotology and is passionate about helping patients improve their quality of life. 

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