The special senses

Chapter 21 The special senses

Disorders of the ear, nose and throat

The Ear

Anatomy and physiology

The ear can be divided into three parts: outer, middle and inner (Fig. 21.1).

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).

Common disorders

The discharging ear (otorrhoea)

Discharge from the ear is usually due to infection of the outer or middle ear.

Hearing loss

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.

Table 21.1 Deafness

Conductive Sensorineural

External meatus


WaxForeign bodyOtitis externaChronic suppurationDrum

Pendred’s syndrome (see p. 962)

Long QT syndrome

Björnstad’s syndrome (pili torti)

End organ

Advancing ageOccupational acoustic traumaMénière’s diseaseDrugs (e.g. gentamicin, furosemide)


Middle ear

Ossicular bone problems
Suppuration (otitis media)

Eighth nerve lesions

Acoustic neuroma


Cranial trauma


Inflammatory lesions:


Tuberculous meningitis






Carcinomatous meningitis


Brainstem lesions (rare)


Multiple sclerosis



Acoustic neuroma

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.

Benign paroxysmal positional vertigo (BPPV)

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.

The nose

Anatomy and physiology (Fig. 21.4)

The function of the nose is to facilitate smell and respiration:

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).

Common disorders

Nasal obstruction

Nasal obstruction is a symptom and not a diagnosis. It can significantly affect a patient’s quality of life. Causes include:


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.

The throat

Anatomy and physiology

The throat can be considered as the oral cavity, the pharynx and the larynx (Fig. 21.6). The oral cavity extends from the lips to the tonsils. The pharynx can be divided into three areas:

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.

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Mar 31, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on The special senses

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