External ear

The pinna (Fig. 26.1) is made of fibroelastic cartilage. The external auditory meatus has an outer cartilage portion; the inner part is formed by the tympanic bone (Fig. 26.2). It is lined by squamous epithelium and contains ceruminous glands that produce wax. There is very little subcutaneous tissue and soft tissue swelling is very painful.

Fig. 26.1 Anatomy of the pinna.

Fig. 26.2 Anatomy of the ear.

Middle ear

The vibrating tympanic membrane is conical and attached to the margin of the bony ear canal laterally and to the handle of the malleus, the first of the three ossicles, medially (Fig. 26.2). The head of the malleus is attached to the body of the incus in the space superior to the middle ear known as the attic. The long process of the incus attaches to the head of the stapes via its lenticular process. The stapes is joined to the oval window margin by the annular ligament. The middle ear is lined by simple cuboidal epithelium containing some mucus-secreting cells. The middle ear space is connected to the nasopharynx by the Eustachian tube, which maintains the middle ear at atmospheric pressure.

The inner ear

The inner ear membrane encloses a labyrinth filled by a fluid called endolymph. This is surrounded by a bony labyrinth, the otic capsule, which is filled with perilymph. The cochlea, the hearing component of the inner ear, is a tube linking the oval and round windows, coiled up like a shell. The vestibular (balance) portion of the inner ear consists of three semicircular canals, together with their vestibule, which contains the saccule and utricle, medial to the stapes footplate. The cochlear and vestibular nerves combine in the internal auditory meatus and pass medially to the brainstem. The facial nerve enters the temporal bone through the internal auditory meatus and passes laterally to the geniculate ganglion, where it turns posteriorly (the first genu). It passes through the middle ear above the oval window and turns inferiorly (the second genu) to exit at the stylomastoid foramen.

Clinical features

Disorders of the external or middle ear can impair sound transmission to the inner ear and cause conductive deafness. Sensorineural deafness results from lesions of the cochlea or its nerve. Deafness is often associated with a noise in the ear (tinnitus). Ear pain (otalgia) may be due to ear disease but may also be referred from other sites (Table 26.1). Ear-related disorders of balance usually cause a sensation of movement (vertigo), most often rotation. ‘Unsteadiness’ however, typically has a non-otological cause. Patients with ear disease occasionally fall to the ground but never lose consciousness.

Table 26.1 Causes of referred otalgia

Examination

The ear canal and tympanic membrane are inspected with an otoscope, a rigid telescope or a microscope. Microscopy can assist in wax or discharge removal. Tuning fork tests differentiate between conductive and sensorineural hearing loss (Rinne’s test). In health or sensorineural deafness, a tuning fork is heard better via the ear canal (air conduction) than via the mastoid process (bone conduction). When there is a conductive hearing loss, the tuning fork is heard better by bone conduction. When hearing is symmetrical, a tuning fork placed in the centre of the forehead is heard equally well in both ears (Weber’s test). If a conductive hearing loss is present in one ear, the tuning fork is heard better in the deaf ear if the loss is conductive which can be easily shown by occluding one ear and applying the fork to your own head. Conversely, in a unilateral sensorineural deafness, the sound is louder in the good ear.

Audiometry

Hearing by air conduction can be assessed by pure tone audiometry, in which sounds of known pitch and loudness are presented to each ear in turn via headphones. Bone conduction (cochlear function) can be separately tested by applying sounds to the mastoid process. A masking tone is needed if the two cochleae are to be tested separately. The difference between the air and bone conduction gives the level of conductive hearing loss (Figures 26.4 and 26.5). The patient’s ability to hear speech can be tested by presenting lists of words via headphones. The percentage correctly identified at different loudness levels allows derivation of a speech reception threshold (50% of words correct) and a discrimination score. Middle ear function (compliance) can be assessed by tympanometry. The amount of sound from a probe reflected back from the drum is measured while the pressure in the ear canal is made to vary. The compliance is maximal when the pressure in the ear canal equals the pressure in the middle ear, because when pressure is the same on both sides of the drum it is maximally mobile. Tympanometry is most often used to confirm the presence of fluid in the middle ear.

Fig. 26.4 Audiogram showing conductive deafness.

Fig. 26.5 Audiogram showing sensorineural deafness.

Temporal bone imaging

In patients with unilateral sensorineural hearing loss, MRI is used to detect an acoustic neuroma (Fig. 26.6). MRI also demonstrates the presence of normal fluid in the cochlea before attempting cochlear implantation. CT scans can be used to demonstrate temporal bone anatomy, congenital abnormalities and fractures or unusual pathology.

Fig. 26.6 Magnetic resonance imaging (MRI) of the cerebellopontine angle.

A Normal MRI scan of cerebellopontine angle. Thin arrow = IAM (internal auditory meatus). B MRI showing an acoustic neuroma. Thick arrow = lesion compressing cerebellum.

Bat ears

A developmental abnormality results in absence of the antihelical fold (see Fig. 26.1). This produces prominent ears that cause embarrassment. The abnormality can be corrected surgically.

Trauma

Trauma to the ear may result in a haematoma, which strips the perichondrium off the underlying cartilage. Secondary infection may lead to loss of cartilage, resulting in a ‘cauliflower ear’. Haematomas should therefore be drained under strict aseptic conditions.

Tumours

Basal cell and squamous carcinomas may occur on the pinna and require excision (Fig. 26.7).

Fig. 26.7 Squamous carcinoma of the pinna.

Wax

Wax (cerumen) is normally found in the ear canal. The ear canal has a migratory epithelium that carries wax to the opening of the external auditory meatus. Wax seldom causes deafness, unless it becomes packed against the eardrum.

Otitis externa

This is an inflammatory condition of the ear canal skin. Secondary infection with bacteria or, less frequently, fungi may occur. It is managed by cleaning the ear, followed by local treatment with eardrops, sprays or ointment containing a steroid, with or without antiseptic, or a weak acid solution (which controls the typical causative anaerobic organisms). Adults tend to develop skin sensitivities to the components of topical antibiotic preparations – which are thus best avoided. Antibiotics also predispose to fungal superinfection. Both phenomena simply exacerbate the severity of this painful condition. Keeping water out of the ear with Vaseline-coated plugs helps prevent any recurrence. Uncommonly, chronic otitis externa causes stenosis of the ear canal.

Tumours

Squamous carcinoma of the ear canal occurs uncommonly. It is treated by a combination of surgery and radiotherapy.

Acute suppurative otitis media

This is a bacterial infection of the middle ear space, usually caused by Streptococcus pneumoniae or Haemophilus influenzae, most commonly occurring in young children (3 years of age and under). Children present with a combination of ear pain (otalgia), fever and malaise. On examination, dilated blood vessels are seen on the drum surface in the early stages. The drum then becomes red and begins to bulge. Perforation with discharge frequently occurs, usually followed by spontaneous healing. Antibiotic therapy remains controversial: the majority of cases resolve spontaneously in a few days (EBM 26.1). Antibiotics are useful in high risk patients (e.g. immunosuppression) as they shorten the episodes and reduce the rate of infective complications such as mastoiditis, facial palsy or meningitis.

Otitis media with effusion (OME), or ‘glue ear’

In this condition, fluid accumulates in the middle ear space, usually in children. A minority of adult cases are caused by nasopharyngeal tumours and systemic disease. Childhood OME causes hearing loss and may interfere with the acquisition of language and performance at school. Virtually all cases resolve spontaneously, but this may take as long as 10 years. Initial management involves documentation of the presence of effusion and the degree of hearing loss during a period of watchful waiting. If the effusions persist, hearing may be improved by drainage of the effusion (myringotomy) and insertion of a ventilation tube (Fig. 26.8). In children, removal of the adenoids leads to more effective resolution. Spontaneous resolution may also occur in adults, but often effusions persist. Ventilation tubes can also be of value, but some cases are better managed with a hearing aid.

Fig. 26.8 Surgical treatment of otitis media with effusion.

A Myringotomy. B Grommet insertion.

Chronic suppurative otitis media

This causes aural discharge and deafness.

Otosclerosis

This is a condition in which the stapes becomes fixed by new bone formation. It is more common in females and sometimes runs in families. It can be treated by an operation called stapedectomy, in which the stapes is replaced by a piston attached to the incus. This produces excellent hearing improvement in the majority of patients, but a minority suffer surgically-induced, permanent inner ear damage. The hearing loss can be managed with a hearing aid.

Deafness

Deafness is most commonly due to changes in the cochlea. Ageing produces a gradual deterioration in hearing acuity (presbycusis). The cochlea may be damaged by chronic noise exposure, blast injuries and temporal bone fractures. Significant noise exposure may occur in heavy industry and agriculture, from playing in rock bands and shooting. Deafness may also be inherited or a manifestation of systemic disease. Some drugs, such as aminoglycosides and cytotoxic agents like cisplatinum, can damage the cochlea. Viral infections such as mumps and rubella can also cause sensorineural deafness. Unilateral hearing loss occurs in acoustic neuroma (Fig. 26.6B).

Most cases of inner ear deafness are managed with a hearing aid, but in cases of profound deafness, hearing may be restored by a cochlear implant. This consists of a series of electrodes surgically introduced into the cochlea. A speech processor converts sound into electrical energy, which stimulates the cochlear nerve.

Vertigo

In some cases, balance disorders may arise from abnormalities of the vestibular portion of the inner ear.

Benign paroxysmal positional vertigo is a very common condition in middle age and is due to debris floating in the posterior semicircular canal which stimulates the ampulla hair cells, producing vertigo. Episodes are triggered when the affected ear is down-most – as when the patient turns over in bed. Debris can be displaced therapeutically from the posterior canal by positioning the head so that it floats out of the canal into the vestibule (Epley’s particle repositioning manoeuvre). If this fails, division of the ampullary (singular) nerve or occlusion of the posterior semicircular canal is beneficial.

Vestibular neuronitis causes severe vertigo lasting for as long as several weeks. The hearing remains normal. It is due to severe temporary reduction of vestibular function in the affected ear. Patients are managed by bed rest and vestibular sedatives, such as prochlorperazine.

Abnormal fluctuations of fluid pressure within the inner ear (endolymphatic hydrops) produce a combination of fluctuating deafness, tinnitus and vertigo known as Ménière’s disease. This uncommon condition is initially treated medically, using either a vasodilator agent (e.g. betahistine) or a diuretic. If medical treatment fails, the vestibular portion of the labyrinth may be destroyed by a middle ear injection of gentamicin. Procedures of last resort are surgical destruction of the labyrinth, or section of the vestibular nerve.

Clinical features

Nasal obstruction is a common symptom with a number of causes. Sneezing and rhinorrhoea are generally due to chronic rhinitis. Purulent nasal discharge and facial pain occur in sinusitis. Loss of smell may be due either to nasal blockage that prevents odours reaching the olfactory epithelium or to damage of the olfactory nerves. Smell is an important part of taste and reduced taste is therefore usually also reported by patients with anosmia.

Examination

The nasal cavity can be inspected using a nasal speculum or an otoscope. More detailed examination, particularly of the posterior part of the nose, is carried out with a rigid telescope.

Imaging

Imaging is not required if nasendoscopy is normal. Images are useful preoperatively to give the surgeon a guide as to individual variations especially in the areas of potential hazard – orbital wall, floor of the anterior cranial fossa (skull base) and to minimize the risk of complications. Computed tomography (CT) is the best means of imaging the paranasal sinuses and also gives information about the middle meatus of the nose, where the sinus ostia are situated (Fig. 26.11). The sinuses can also be visualized by magnetic resonance imaging (MRI), but the bony anatomy is not shown and mucosal disease is exaggerated.

Fig. 26.11 Coronal CT scan sinuses.

The narrow maxillary ostia and uncinate processes are seen on this cut (arrow), lateral to the middle turbinate.

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