OTITIS AND ITS CONSEQUENCES.
in the child is a common disease, and may lead to very serious con sequences on account of the facility with which inflammation can extend from the tympanic cavity to the interior of the skull. During the first few years of life the mastoid process is in a rudimentary state. In the young chikl, therefore, the mastoid cells are limited to the horizontal portion which lies behind the tympanic cavity, and above and slightly posterior to the auditory meatus. It is only at a later period that they extend down wards and backwards to form the hollow of the mastoid process. These cells communicate with the tympanum, and share in any catarrhal process of which that cavity may be the seat The tympanum itself is separated from the interior of the skull by a thin layer of bone, which is often a mere translucent shell. This, according to Toynbee, may even be deficient in places, so that the mucous lining of the tympanum is sometimes here and there in actual contact with the dura mater covering the temporal bone. It is then easy to understand how, without any disorganisation of the bony layer itself, inflammation may extend from the tympanic cavity to the in terior of the cranium, and give rise to serious disease of the brain and its membranes.
The inflammation may spread from the ear to the skull-cavity through either the roof of the tympanum or that of the mastoid cells. It may also pass through the upper wall of the external auditory canal, or be conveyed inwards by means of the internal auditory meatus, which is lined by a prolongation of the brain membranes. The petrous bone may or may not participate in the disease. Sometimes it becomes carious. In other cases serious disease of the brain and its membranes may be set up, although the bony layer separating the ear cavities from the interior of the cranium seems in no way affected by the inflammation around it.
childhood there appears to be a special tendency to catarrh of the mucous membrane lining the middle ear. Von Triasch has commented upon the frequency with which in young persons this con dition is discovered after death, without any symptom of the derangement having been observed during the life of the patient. The tendency is
heightened by the scrofulous diathesis, and in the subjects of this consti tutional state the catarrh has a special proneness to become a serious sup puration. Diseases which have an influence in provoking the manifesta tions of the scrofulous cachexia are very apt to be followed by suppurative otitis, as scarlatina, measles, and small-poX. Besides these causes, cold or slight injuries to the ear may set up the same condition, and sometimes the tympanum becomes affected as a consequence of similar disease in parts around. Thus inflammation may spread to the middle ear from the external auditory meatus or from the pharynx. Dr. Knapp, of New York, states that in the majority of cases the occurrence of suppurative catarrh of the middle ear is clue to cold, which affects first the naso-pha ryngeal cavity, and then spreads up the Eustachian tube. In 8.78 per cent. of his cases he attributes the immediate cause of the otitis to sea bathing ; in 7.74 per cent. to scarlatina. The extension of the inflamma tion further inwards to the skull-cavity may be determined by any agency capable of setting up acute inflammation in the ear. Cold is a frequent cause of this disaster, and blows upon the head may produce the same result. It is an occasional complication of dentition (see page 560).
Morbid Anatomy.—When the mucous membrane lining the tympanum becomes acutely inflamed, it is of a deep red colour, and its vessels are full and distended. In the chronic stage the mucous membrane becomes thickened and pours out a copious purulent secretion which usually per forates the tympanic membrane and issues from the external meatus as a yellowish-white discharge. A chronic otitis may continue for months, or even years, without producing much inconvenience. But sometimes the inflammation extends to the bony wall, which becomes carious and soft ened ; or the inflammation suddenly assumes an acute character. In either case violent symptoms may be all at once noticed from implication of the brain and its membranes. The consequences of spreading of the inflam mation to the skull cavity are the occurrence of purulent meningitis, and of encephalitis with abscess of the brain.