CHAPTER XXIV
THE EAR[5]

[5] We desire here to acknowledge our indebtedness to Dr. Logan Turner for again revising this chapter.

Surgical Anatomy.—The anatomical subdivision of the ear into three parts—the external, middle, and internal ear—forms a satisfactory basis for the study of ear lesions. The outer ear consists of the auricle and external auditory meatus, the latter being made up of an outer cartilaginous portion half an inch in length, and a deeper osseous portion three-quarters of an inch long. The canal forms a curved tube, which can be straightened to a considerable extent for purposes of examination by pulling the auricle upwards and backwards. It is closed internally by the tympanic membrane, which separates it from the tympanic cavity or middle ear. The middle ear includes the tympanum proper, which is crossed by the chain of ossicles—malleus, incus, and stapes—the Eustachian tube, which communicates with the naso-pharynx, and the tympanic antrum and mastoid cells. As these cavities lie in close relation to the middle and posterior cranial fossæ, infective conditions in the tympanum and mastoid cells are liable to spread to the interior of the skull. The internal ear or labyrinth lies in the petrous part of the temporal bone, its outer boundary being the inner wall of the middle ear.

Physiologically the different parts of the auditory mechanism may be divided into (1) the sound-conducting apparatus, which includes the outer and middle ears; and (2) the sound-perceiving apparatus—the internal ear and central nerve tracts. Impairment of hearing may be due to causes existing in one or other or both of these subdivisions. The condition of the sound-conducting apparatus can be investigated by direct inspection through the speculum, and by inflation of the Eustachian tube and tympanum, while that of the sound-perceiving apparatus is ascertained partly by testing the hearing, and partly by excluding affections of the outer and middle ear. When the sound-conducting apparatus is at fault, the resulting deafness is spoken of as “obstructive”; when the sound-perceiving apparatus is affected, the term “nerve deafness” is used. The semicircular canals, which are peripheral organs concerned in the maintenance of equilibration, form part of the inner ear apparatus.

Cardinal Symptoms of Ear Disease.—The most important symptom of ear disease is impairment of hearing, which varies in degree, and may be due to lesions either in the sound-conducting or in the sound-perceiving apparatus. The sudden onset of deafness may be due to impaction of wax in the external meatus or to hæmorrhage or effusion into the labyrinth. A gradual onset is more common. In children there is a great tendency for acute inflammatory conditions of the middle ear to arise in connection with the exanthemata and in association with adenoids. In adult life chronic catarrhal processes are more common causes of gradually increasing deafness, while in advanced age there is a tendency to acoustic nerve impairment. Certain anomalous conditions of hearing are occasionally met with, such as the “paracusis of Willis”—a condition in which the patient hears better in a noise; “diplacusis,” or double hearing; and “hyperæsthesia acustica,” or painful impressions of sound.

Tinnitus aurium, or subjective noises in the ear, may constitute a very annoying and persistent symptom. These sounds vary in their character, and may be described by the patient as ringing, hissing, or singing, or may be compared to the sound of running water or of a train. They are usually compared to some sound which, from his occupation or otherwise, the patient is accustomed to hear. They may be purely aural in origin, being due, for example, to increased pressure on the acoustic nerve endings from causes in the labyrinth itself or in the middle or external ear; or they may be due to certain reflex causes, such as naso-pharyngeal catarrh or gastric irritation. Vascular changes such as occur in anæmia, Bright's disease, and heart disease may also be concerned in their production.

Pain, or earache, varies in degree from a mere sense of discomfort to acute agony. The pain associated with a boil in the external meatus is usually aggravated by movements of the jaw, by pulling the auricle, and by pressure upon the tragus. The pain of acute middle-ear inflammation is deep-seated, intermittent in character, and worse at night, and is aggravated by blowing the nose, coughing, and sneezing—acts which increase middle-ear tension by forcing air along the Eustachian tube. Mastoid pain and tenderness are indicative of inflammation in the antrum or cells, and when these symptoms supervene in the course of a chronic middle-ear suppuration, they should always be regarded as of grave import. Severe neuralgia of the ear may simulate the pain of acute mastoiditis, and it must not be forgotten that earache may be traced to a diseased tooth. A careful examination, not only of the ear, but also of the throat and teeth, should therefore be made in all cases of earache.

Vertigo, or giddiness, may be produced by causes which alter the tension of the labyrinthine fluid, such, for example, as the pressure of wax upon the tympanic membrane, or exudation into the middle ear or into the labyrinth. Giddiness occurring in the course of chronic middle-ear suppuration may be significant of labyrinthine or of intra-cranial mischief, but is not necessarily so. Giddiness preceded by nausea suggests a gastric origin; if followed by nausea it points to an aural origin. In cases of suspected aural vertigo, the patient's “static sense” should be carefully tested. He should be asked (1) to stand with both feet together with the eyes closed, (2) to stand on one or other foot with eyes closed, (3) to walk in a straight line, (4) to hop backwards and forwards off both feet. His incapacity for performing such movements should be noted. As nystagmus may be associated with disturbance of equilibrium due to ear disease, the movements of the eyeballs must be carefully tested.

Labyrinthine nystagmus is of a rhythmic character, and consists of a slow and a rapid movement. Physiological nystagmus can be induced by stimulating the movement of the endolymph in the semicircular canals, by syringing the ear with hot and cold water (caloric test), by rotating the individual (rotation test), and by the galvanic current. Any departure from the normal reactions which these tests may produce, should raise the suspicion of a pathological condition of the semicircular canals.