Chapter 21 The special senses
The outer ear has a skin-lined tube 2.5 cm long leading down to the tympanic membrane (the ear drum). Its outer third is cartilaginous and contains hair, sebaceous and ceruminous glands, but the walls of the inner two-thirds are bony. The outer ear is self-cleaning as the skin is migratory and there are no indications to use cotton wool buds. Wax should only be seen in the outer third.
The middle ear is an air-containing cavity derived from the branchial clefts. It communicates with the mastoid air cells superiorly, and the Eustachian tube connects it to the nasopharynx medially. The Eustachian tube ventilates the middle ear and maintains equal air pressure across the tympanic membrane. It is normally closed but opens via the action of the palatal muscles to allow air entry when swallowing or yawning. A defect in this mechanism, such as with a cleft palate, will prevent air entering the middle ear cleft which may then fill with fluid. Lying within the middle ear cavity are the three ossicles (malleus, incus and stapes) that transmit sound from the tympanic membrane to the inner ear. On the medial wall of the cavity is the horizontal segment of the facial nerve, which can be damaged during surgery or by direct extension of infection in the middle ear.
The inner ear contains the cochlea for hearing and the vestibule and semicircular canals for balance. There is a semicircular canal arranged in each body plane and these are stimulated by rotatory movement. The facial, cochlear and vestibular nerves emerge from the inner ear and run through the internal acoustic meatus to the brainstem (see Fig. 22.7, p. 1076).
The ossicles, in the middle ear, transmit sound waves from the tympanic membrane to the cochlea. They amplify the waves by about 18-fold to compensate for the loss of sound waves moving from the air-filled middle ear to the fluid-filled cochlea. Hair cells in the basilar membrane of the cochlea detect the vibrations and transduce these into nerve impulses which pass to the cochlear nucleus and then eventually to the superior olivary nuclei of both sides; thus lesions central to the cochlear nucleus do not cause unilateral hearing loss.
The pinna and postauricular region should first be examined for scars or swellings. An auroscope is used to examine the external ear canal whilst the pinna is retracted backwards and upwards to straighten the canal. Look for wax, discharge or foreign bodies. The tympanic membrane should always be seen with a light reflex anteroinferiorly. Previous repeated infections may cause a thickened, whitish drum but fluid in the middle ear may show as dullness of the drum. Perforations are marginal or central.
This is a diffuse inflammation of the skin of the ear canal. The cause is bacterial, viral or fungal and the patient usually complains of severe pain. Gentle pulling of the pinna is tender and there may be lymphadenopathy of the preauricular nodes.
Examination often reveals debris in the canal which needs to be removed either by gentle mopping or preferably by suction viewed directly under a microscope. In severe cases the canal may be swollen and a view of the tympanic membrane impossible. Any foreign body seen should be removed with great care by trained personnel.
Treatment is with topical antibiotics in the first instance (drops such as dexamethasone 0.05%, framycetin sulphate 0.5%, gramicidin 0.005% drops or hydrocortisone acetate 1%, gentamicin 0.3%, or a spray such as dexamethasone 0.1%, neomycin sulphate 3250 units). If it does not resolve in 3–4 days then microsuction in an ENT department is necessary.
Otitis media can also present with discharge from the middle ear through a perforation of the tympanic membrane. There are no mucous glands in the external ear canal, however; if the discharge is serous, then middle ear pathology is unlikely.
Cholesteatoma is defined as keratinizing squamous epithelium within the middle ear cleft and can present with foul-smelling otorrhoea. Examination shows a defect in the tympanic membrane full of white cheesy material. Mastoid surgery is required to remove this sac of squamous debris as it can erode local structures such as the facial nerve or even extend intracranially.
Deafness can be conductive or sensorineural and these can be differentiated at the bedside by the Rinne and the Weber tests (Box 21.1) or with pure-tone audiometry. Conductive hearing loss has many causes (Table 21.1) but wax is the commonest.
WaxForeign bodyOtitis externaChronic suppurationDrum
Pendred’s syndrome (see p. 962)
Long QT syndrome
Björnstad’s syndrome (pili torti)
Advancing ageOccupational acoustic traumaMénière’s diseaseDrugs (e.g. gentamicin, furosemide)
Eighth nerve lesions
Brainstem lesions (rare)
This arises from trauma or chronic middle ear disease where recurrent infection results in a permanent defect. Surgical repair is only indicated if the patient is symptomatic with hearing loss or recurrent discharge.
This is an acute inflammation of the middle ear, causing severe pain (otalgia) and conductive hearing loss. This occurs because fluid accumulation in the middle ear impairs sound conduction to the cochlea. Otitis media is often viral in origin, e.g. following a cold, and will settle within 72 hours without antibacterial treatment. In people with systemic features or after 72 hours, a systemic antibiotic, e.g. amoxicillin, should be given, particularly in the under 2 year olds. Topical therapy is of no value. Complications include infection of the mastoid bone.
This is common in children because of Eustachian tube dysfunction. The effusion resolves naturally in the majority of cases but can persist giving hearing loss, and it predisposes to recurrent attacks of acute otitis media. A grommet (tympanostomy tube) is inserted into the tympanic membrane and ventilates the middle ear cavity, i.e. takes over the Eustachian tube’s function. Grommets are extruded from the tympanic membrane as it heals (over 6 months to 2 years). Developmental outcomes are not improved by grommet insertions. In most children the middle third of the face grows around the age of 7–14 years and Eustachian tube dysfunction is rare after this.
This is usually a hereditary disorder in which new bony deposits occur within the stapes footplate and the cochlea. Characteristically seen in the second and third decades, it is commoner in females and can become worse during pregnancy. The hearing loss may be mixed, and treatment includes a hearing aid or replacement of the fixed stapes with a prosthesis (stapedectomy). The choice of treatment is dependent on the patient. Surgery is an excellent option, with very good success rates in regular stapedectomists’ hands, but it always carries a small risk of a complete hearing loss. Hearing aids, whilst safe, require the patient’s compliance if they are to afford benefit.
This is the commonest cause of deafness. It is a degenerative disorder of the cochlea and is typically seen in old age. It can be due to the loss of outer hair cells (sensory), loss of the ganglion cells (neural), strial atrophy (metabolic) or it can be a mixed picture. Ageing itself does not cause outer hair cell loss but environmental noise toxicity over the years is a major factor. The onset is gradual and the higher frequencies are affected most (Fig. 21.2). Speech has two components: low frequencies (vowels) and high frequencies (consonants). When the consonants are lost, speech loses its intelligibility. Increasing the volume merely increases the low frequencies and the characteristic response of ‘Don’t shout. I’m not deaf!’
This is a slow-growing benign schwannoma of the vestibular nerve (see p. 1076) which can present with progressive sensorineural hearing loss. Any patient with an asymmetric sensorineural hearing loss or sudden sensorineural hearing loss should be investigated, e.g. with an MRI scan.
Vertigo is usually rotatory when it arises from the ear. The presence of otalgia, otorrhoea, tinnitus or hearing loss suggests an otologic aetiology. Vestibular causes can be classified according to the duration of the vertigo. Common causes are summarized below.
BPPV is thought to be due to loose otoliths in the semicircular canals, commonly the posterior canal. Positional vertigo is precipitated by head movements, usually to a particular position, and often occurs when turning in bed or on sitting up. The onset is typically sudden and distressing. The vertigo lasts seconds or minutes and the phenomenon becomes less severe on repeated movements (fatigue). There is no serious underlying cause but it sometimes follows vestibular neuronitis (see p. 1079), head injury or ear infection.
Diagnosis is made on the basis of the history and by the Hallpike manoeuvre (Fig 21.3). A positive Hallpike test confirms BPPV, which can be cured in over 90% of cases by the Epley manoeuvre. This involves gentle but specific manipulation and rotation of the patient’s head to shift the loose otoliths from the semicircular canals.
Figure 21.3 Hallpike manoeuvre for diagnosis of benign paroxysmal positional vertigo. This can be done in the outpatient department. (a) The patient sits on a couch, his head is turned towards one ear. (b) The head is supported by the examiner while the patient lies down so that his head is just below the horizontal. Nystagmus (following a latent interval of a few seconds) is commonly noted when the head has been turned towards the affected ear. This can be repeated with the patient’s head turned towards the other ear.
This condition is characterized by recurring episodic rotatory vertigo lasting 30 minutes to a few hours; attacks are recurrent over months or years. Classically, it is associated with a low frequency sensorineural hearing loss, feeling of fullness in the affected ear, loss of balance, tinnitus and vomiting. There is a build-up of endolymphatic fluid in the inner ear, although its precise aetiology is still unclear.
Vestibular sedatives, e.g. cinnarizine, are used in the acute phase. Preventative measures, such as a low-salt diet, betahistine and avoidance of caffeine, are useful. If the disease cannot be controlled, then a chemical labyrinthectomy, perfusing the round window orifice with ototoxic drugs such as gentamicin, is used. Gentamicin destroys the vestibular epithelium; therefore the patient has severe vertigo for around 2 weeks until the body compensates for the lack of vestibular input on that side. The patient will happily trade occasional mild vertigo when the balance system is challenged to the unpredictable, severe and disabling attacks of vertigo of Ménière’s disease.
These are managed with vestibular sedatives in the acute phase. Most patients will settle over a few days but continuous true vertigo with nystagmus suggests a central lesion. A patient with a deficit of vestibular function due to viral labyrinthitis or neuronitis should be able to cease vestibular sedatives within 2 weeks; long-term use can give parkinsonian side-effects, delay central compensation and thus prolong the vertigo. Vestibular rehabilitation by a physiotherapist or audiological scientist can speed up the compensation process, although most patients will be able to do this themselves with time.
This is a sensation of a sound when there is no auditory stimulus. It can occur without hearing loss and results from heightened awareness of neural activity in the auditory pathways. Patients describe a hissing or ringing in their ears and this can cause much distress. It usually does not have a serious cause but vascular malformation, e.g. aneurysms, or vascular tumours can be associated. Tinnitus occurs due to awareness of neural activity in the auditory pathways that our brains are made more conscious of.
The external portion of the nose consists of two nasal bones attached to the rest of the facial skeleton and to the upper and lower lateral cartilages. The internal nose is divided by a midline septum that comprises both cartilage and bone. This divides the internal nose in two, from the external nostril to the posterior choanae. The posterior choanae are in continuity with the nasopharynx posteriorly. The paranasal sinuses open into the lateral wall of the nose and are a system of aerated chambers within the facial skeleton.
The blood supply of the nose is derived from branches of both the internal and external carotid arteries. The internal carotid artery supplies the upper nose via the anterior and posterior ethmoidal arteries. The external carotid artery supplies the posterior and inferior portion of the nose via the superior labial artery, greater palatine artery and sphenopalatine artery. On the anterior nasal septum is an area of confluence of these vessels (Little’s area) (Fig. 21.5a).
Nose bleeds vary in severity from minor to life-threatening. Little’s area (Fig. 21.5a) is a frequent site of nasal haemorrhage. First aid measures should be administered immediately, including external digital compression of the anterior lower portion of the external nose, ice packs and leaning forward. The patient should be asked to avoid swallowing any blood running posteriorly as this causes gastric irritation and then nausea and vomiting.
Not infrequently, small recurrent epistaxes occur and these may require a visit to the emergency clinic for an examination and simple local anaesthetic cautery with a silver nitrate stick. If the bleeding continues profusely then resuscitation in the form of intravenous access, fluid replacement or blood, and oxygen can be administered. If further intervention is necessary, consideration should be given to intranasal cautery of the bleeding vessel, or intranasal packing using a variety of commercially available nasal packs (Fig. 21.5b). In addition to direct treatment of the epistaxis, a cause and appropriate treatment of a cause should be sought (Table 21.2).
Trauma – foreign bodies, nose-picking and nasal fractures
Iatrogenic – surgery, intranasal steroids
Neoplasm – nasal, paranasal sinus and nasopharyngeal tumours
Osler–Weber–Rendu syndrome (familial haemorrhagic telangiectasia)
Rhinitis (see p. 808). If an allergen is identified, then allergen avoidance is the mainstay of treatment. Topical steroids and/or antihistamines can be tried. If severe, then oral antihistamines or referral to an allergy clinic for immunotherapy is warranted.
Nasal polyps. This condition occurs with inflammation and oedema of the sinus nasal mucosa. This oedematous mucosa prolapses into the nasal cavity and can cause significant nasal obstruction. In allergic rhinitis (see p. 798) the mucosa lining the nasal septum and inferior turbinates are swollen and a dark red or plum colour. Nasal polyps can be identified as glistening swellings which are not tender. Treatment with intranasal steroids helps but if polyps are large or unresponsive to medical treatment then surgery is necessary.
Foreign bodies. These are usually seen in children who present with unilateral nasal discharge. Clinical examination of the nose with a light source often reveals the foreign body, which requires removal either in clinic or in theatre with a general anaesthetic.
Sinonasal malignancy. This is extremely rare. The diagnosis must be considered if unusual unilateral symptoms are seen, including nasal obstruction, epistaxis, pain, epiphora, cheek swelling, paraesthesia of the cheek and proptosis of the orbit.
Sinusitis is an infection of the paranasal sinuses that either is bacterial (mainly Streptococcus pneumoniae and Haemophilus influenzae) or is occasionally fungal. It is most commonly associated with an upper respiratory tract infection and can occur with asthma. Symptoms include frontal headache, purulent rhinorrhoea, facial pain with tenderness and fever. It can be confused with a variety of other conditions such as migraine, trigeminal neuralgia and cranial arteritis.
Treatment for a bacterial sinusitis includes nasal decongestants, e.g. xylometazoline, broad-spectrum antibiotics, e.g. co-amoxiclav because H. influenzae can be resistant to amoxicillin, anti-inflammatory therapy with topical corticosteroids such as fluticasone propionate (nasal spray) to reduce mucosal swelling, and steam inhalations.
If the symptoms of sinusitis are recurrent (Box 21.2) or complications such as orbital cellulitis arise, then an ENT opinion is appropriate and a CT scan of the paranasal sinuses is undertaken. Plain sinus X-rays are now rarely used to image the sinuses.
Types of sinusitis
Symptoms lasting 1 week to 1 month
>4 episodes of acute sinusitis per year
Symptoms for 1–3 months
Symptoms for >3 months
Olfaction is mainly under the control of cranial nerve I, although irritant, unpleasant nasal sensations are carried by cranial nerves V, IX and X. Anosmia is a complete loss of the sense of smell and hyposmia is a decreased sense of smell:
The main cause of a loss of smell is nasal obstruction due to upper respiratory infection or nasal polyps. Other causes include sinonasal disease, old age, drug therapy and head injury/trauma. It is difficult to predict the speed and extent of recovery in the latter causes. In many patients anosmia is idiopathic, but before this diagnosis is accepted an assessment of the patient for the possibility of an intranasal tumour or intracranial mass should be undertaken.
People with a fractured nose present with epistaxis, bruising of the eyes and nasal bridge swelling. Initially, it is often difficult to assess if the bones are deviated, particularly if there is significant swelling. Reduction of the fracture should be undertaken in the first 2 weeks after injury and can be achieved by manipulation. However, if the fracture sets, a more formal rhinoplasty may have to be undertaken at a later stage. The patient should be examined for a head injury and the nose should also be checked for a septal haematoma. This is painful, can cause nasal obstruction, is fluctuant to touch on the nasal septum and requires immediate drainage.
Lying within the hypopharynx is the larynx. This consists of cartilaginous, ligamentous and muscular tissue with the primary function of protecting the distal airway. The pharynx is innervated from the pharyngeal plexus.
In the larynx, there are two vocal cords which abduct (open) during inspiration and adduct (close) to protect the airway and for voice production (phonation). The main nerve supply of the vocal cords comes from the recurrent laryngeal nerves (branches of the vagus nerve) which arise in the neck, but on the left side passes down around the aortic arch and then ascends in the tracheo-oesophageal groove to the larynx.
Normal vocal cords in phonation vibrate between 90 (male) and 180 (female) times per second, giving the voice its pitch or frequency. A healthy voice requires full closure of the vocal cords with a smooth, regular pattern of vibration, and any pathology that prevents full closure will result in air escaping between the vocal cords during phonation and a ‘breathy’ voice.