How to Use an Otoscope
Clinical anatomy of the Ear
The pinna is composed of elastic cartilage covered with skin. In the middle is the conchal bowl, which funnels down towards the external auditory meatus.
The external ear canal is about 2-5 cm long in adults and extends from the conchal bowl to the tympanic membrane. It is not straight so you need to pull the pinna upwards and backwards to get a better view of the tympanic membrane. The membrane lies at an angle to the canal creating the anteroinferior recess of the canal, where debris or foreign bodies may collect.
The tympanic membrane consists of the pars tensa and the pars flaccida. The malleus handle lies in the middle layer of the pars tensa. At the superior end of the handle is the lateral process of the malleus, the most medial and easily recognisable structure in the drum. The tip of the handle is called the umbo, and a cone of light can usually be seen extending anteroinferiorly from the umbo - the light reflex.
The drum is surrounded by a fibrocartilaginous annulus, and the chorda tympani nerve (the branch of the facial nerve supplying taste to the anterior part of the tongue) crosses the junction between the pars flaccida and pars tensa. You can see the long process of the incus and the stapedius tendon through the posterosuperior quadrant of the drum, the promontory (the bone overlying the basal turn of the cochlea) and the round window niche through the posteroinferior quadrant, and the eustachian tube orifice anterosuperiorly.
Using an Otoscope
First explain to the patient that you are going to look in the ear and that it may be uncomfortable, although it should not be painful. Choose a speculum size that is appropriate for the patient's canals and fit it to the otoscope. Children have narrower canals and will require a narrower speculum than adults.
Always hold the otoscope in the hand of the same side as the ear you are about to examine. You can hold the otoscope in either a pencil grip or a hammer grip. The pencil grip allows the side of your hand to rest on the patient's temple, reducing the risk of trauma if the patient suddenly moves his or her head (this is common when examining young children or patients with tender canals). Many students prefer the hammer grip as it initially feels more natural. It is less satisfactory, however, because you have less control, which increases the risk of inflicting pain by pressing the speculum tip on to the skin of the canal wall. We recommend that you persevere with the pencil grip until you find it a more natural poise.
Examine the good ear first
Examine the good ear first. This has several advantages: it prevents the spread of infection into an unaffected ear, it usually allows you to see some normal anatomy with which to compare the other side, and also helps stop you relaxing once you have identified one abnormality, failing to see less obvious but often more important findings - a common problem of students. With the light source turned up full, use the otoscope as a torch to examine the pinna briefly for meatal abnormalities and previous surgical wounds.
The commonest scars around the ear are those from postaural and endaural incisions. Eczema around the meatus usually indicates the presence of otitis externa. With your free hand, gently pull the pinna upwards and backwards to straighten the external ear canal. This is not usually necessary in young children as the canal is straighter. While resting the side of your hand against the patient's temple introduce the speculum gently into the canal. The patient may cough as the cutaneous branch of the vagus is stimulated.
What to look for
Examine the external canal and the tympanic membrane systematically. Firstly, look at the external canal wall. Does the skin look normal or is it inflamed with debris in the canal (otitis externa)? Next identify the handle of the malleus. If it is not immediately obvious then look for its lateral process, which is rarely absent.
You should then inspect the pars tensa systematically, starting in the posterosuperior quadrant and then moving forwards, downwards, and backwards until all 360 degrees has been covered. Try to identify as many structures as you can. Finally, carefully inspect the pars flaccida - this is where abnormalities are often missed.
To make sure you do not miss anything, ask yourself the following questions.
Can I clearly see all the external auditory canal? - The canal may be absent, stenotic, oedematous, or filled with wax, debris, blood, or a foreign body. You may be able to remove material to obtain a better view, but if there is a strong possibility of a perforation in the tympanic membrane, the patient should be referred to an ear, nose, and throat surgeon as syringing can damage the middle ear structures in such patients.
Can I see the tympanic membrane or the handle of the malleus, or both? - The deeper part of the canal can again be obscured by wax or other material. Rarely the membrane and malleus may be completely absent - for example, after certain ear operations. The handle may be visible even if most of the pars tensa is absent; the handle gives you an indication of where the membrane should have been.
Is the tympanic membrane intact? - Be careful to note the difference between a retracted drum and a perforation. Usually the small blood vessels in the middle ear mucosa give you a clue. If there is any debris or white keratin around the edge of the pars tensa or, more commonly, over the pars flaccida the patient may have an occult cholesteatoma (skin debris within the middle ear cavity) and should be referred for a specialist opinion.
Is the tympanic membrane the right colour and transparency? - Although the normal appearance of the membrane varies greatly, a gold or blue colouration or a dull membrane usually indicates fluid in the middle ear. White patches in the membrane are called tympanosclerosis. Small chalk patches are extremely common. Thicker tympanosclerotic plaques are usually due to previous surgery. Both types usually have no clinical importance unless the results of tuning fork tests are abnormal.
I can't see properly - It is important to check the light is adequate and the battery is fully recharged. An undercharged unit will produce a poor light and subtle changes in the colour of the tympanic membrane may not be accurately detected.
All I can see is a red drum - What you are most likely to be looking at is the posterior canal wall. Try tilting the otoscope anteriorly and superiorly or pulling the pinna slightly further to straighten out the canal and assist your view.
The anatomy is so abnormal I can't work out what is what - Try looking for the lateral process of the malleus. Even if most other structures have been destroyed this is often visible. Once you can identify the lateral process, orientation will be much easier.
I'm not sure if there is a perforation or not - In most cases a perforation is obvious, but the sharp mouth of a deep retraction pocket can look remarkably similar. If you can see blood vessels in the middle ear mucosa these confirm the presence of a perforation. If it is difficult to tell, an ear, nose, and throat surgeon may use a pneumato-otoscope attachment, which fits into a socket in the head of more expensive otoscopes. This attachment can produce negative or positive pressure in the ear canal, producing visible movement in an intact drum.
Although this is not a comprehensive system, it should give you some idea of the likely abnormality. If you are in any doubt refer the patient to an ear, nose, and throat specialist.
Case 1: A 23 year old man had had intermittent odourless discharge from his right ear for two years since experiencing sudden earache while diving on holiday. He felt he was deaf in that ear and had recently noticed some high pitched tinnitus on the right, although his ear was currently dry.
- The man has a perforation of the posterosuperior quadrant of the tympanic membrane. No cholesteatoma is visible, and the intact long process of the incus and stapes head could be seen through the perforation.
Case 2: A 5 year old girl had multiple attacks of otitis media, was falling behind in her schoolwork, and was mispronouncing words. Her teacher felt she was not paying attention in class and her parents noticed that she turned up the television volume to unacceptably loud levels. What is the likely diagnosis?
- The tympanic membrane is intact but is dull and a golden colour. This child has otitis media with effusion (glue ear).
Case 3: A 28 year old woman had put up with an intermittent foul smelling discharge from her ear for over 10 years. Topical antibiotics controlled her symptoms for only a few weeks. She had suddenly become very deaf in the affected ear and had asked for a specialist opinion.
- There is a large mass of infected squamous epithelium and keratin behind the pars flaccida - a cholesteatoma. This can cause infective complications such as meningitis and may erode into the labyrinth or facial nerve. The cholesteatoma therefore needs to be removed. The operation entails exploring the mastoid to identify the fundus of the sac, removing the disease, and grafting the surgical defect.
Buying an Otoscope
An adequate dedicated otoscope can be purchased for around £150. The otoscopic attachments may either be included or can often be purchased for a small extra cost. It is worth checking the quality of the otoscopic parts because a poor otoscope will not allow an accurate assessment of the tympanic membrane, no matter how skilled you are.
It is not essential to have a vast knowledge of ear, nose, and throat surgery to detect most common complaints diagnosable with the otoscope, but your examination skills can deteriorate from lack of practice. If you continue practicing, otoscopy will soon become as routine as the rest of the physical examination. The more normal ears you look in, the easier it becomes to detect disease when you come across it.
Further reading: Hawke M, Keene M, Alberti PW. Clinical otoscopy: an introduction to ear disease. 2nd ed. Edinburgh: Churchill Livingstone, 1990.