The outer ear consists of the visible part, called the pinna, which is composed of skin and cartilage, and the ear canal, the channel that leads to the eardrum. Behind the eardrum is the air-filled middle ear, which contains three tiny, delicate bones. The middle ear is directly linked to the respiratory system by the eustachian tube, the passage connecting the ear to the nose and throat.
This section covers disorders of the visible parts of the ear and of the ear canal, followed by conditions that affect the eardrum and middle ear. Outer- and middle-ear disorders have a number of causes, including injury, infections, obstruction, damage from atmospheric pressure changes, and inherited disease. The symptoms of these disorders include irritation, discomfort, pain, and, in some cases, partial hearing loss.
Most outer- and middle-ear problems are more easily treatable than those affecting the inner ear and are less likely to lead to permanent loss of hearing. Most causes of hearing loss are covered elsewhere (see Hearing and inner-ear disorders), as are disorders of the middle ear that particularly affect children (see Acute otitis media in children, and Chronic secretory otitis media).
For more information on the structure and the function of the ear, see Ears, Hearing, and Balance.
Disorders of hearing are very common and, in severe cases, they may interfere with communication, causing significant disability. In some cases, hearing loss is due to a disorder of the ear canal or the middle ear, but inner-ear disorders can also cause hearing problems. The inner ear also contains the vestibular apparatus, which helps to maintain the sense of balance. Inner-ear disorders may therefore lead to other symptoms such as dizziness.
This section starts by discussing all types of hearing loss from partial loss of hearing to total deafness. Hearing defects that are due to disorders of the inner ear, including noise-induced hearing loss and tinnitus (various sounds heard in one or both ears in the absence of an external source), are then covered in greater detail.
Problems in other parts of the ear that may cause hearing loss or deafness are covered elsewhere in the guide (see Outer- and middle-ear disorders), as is hearing loss or deafness that is present from birth (see Congenital deafness).
Inner-ear disorders do not only affect hearing; if the vestibular apparatus is disturbed, the sense of balance may be disrupted. Three common inner-ear disorders that affect balance – motion sickness, labyrinthitis, and Ménière’s disease – are described in this section. All of these disorders may cause symptoms such as dizziness and nausea. Ménière’s disease can also lead to hearing loss. The final article in this section discusses acoustic neuroma, a rare, noncancerous tumour affecting the vestibulocochlear nerve, which connects the inner ear to the brain.
For further information on the structure and function of the ear, see Ears, Hearing, and Balance.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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