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Full text of "Diseases Of The Nose Throat And Ear"

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In infancy, with the exception of the tympanic antrum and a layer of small
cells in its lateral wall, the mastoid process contains no cells, the bone being
diploeic. This acellular or infantile type of mastoid process persists through-
out life in about 20 per cent of people. It may be converted to a compact
acellular mastoid by the laying down of cancellous bone in the marrow
spaces (Fig. 170, B). In normal circumstances the infantile mastoid process
becomes pneumatized (Fig. 170, A), but between the acellular and pneumatic
types there are intermediate stages. Controversy still exists as to which
comes first, failure of pneumatization or infection, some otologists believing
that failed pneumatization is the result of infection and not the precursor.
Studies of the histopathology of acute mastoiditis have shown in some
cases that during the process of healing the lumen of the air cell is filled
with granulation tissue in which new bone is formed. There is then the
possibility that an originally pneumatic process may become sclerotic,
though such an occurrence is held by some to be rare.

Mastoiditis is a complication of otitis media in which infection spreads
from the tympanic antrum to involve the bony walls of the cells _of_,the
mastoid"i?focess."The infection mayj>e~ acute or; chronic.

AETIOLOGY, Acute mastoicfitfs~aflses from an acute otitis media by exten-
sion of infection from the mastoid antrum to the air cells and occurs there-
fore in a cellular temporal bone. In many cases of acute otitis media infec-
tion, although present in the cellular system, produces no bone destruction
but in. severe acute infections there is a greater inflammatory reaction result-
ing in pus formation, increased tension, resorption of bone with loss of
trabeculation and the formation of an empyema. Eventually the inflam-
matory process may erupt through the lateral surface to produce a subperi-
osteal abscess. An untreated abscess may spread in several directions:
(1) Through the periosteum and skin covering the mastoid process. (2) Into
the external meatus to simulate a discharging furuncle. (3) Through the
medial aspect of the mastoid tip into the digastric fossa (Bezold's mastoiditis).
(4) Through the posterior root of the zygoma beneath the temporal fascia
(zygomatic mastoiditis) causing slight oedema of the upper eyelid as an
early sign.- (5) Through the canal for the mastoid emissary vein or through
the temporo-occipital suture to form an abscess posterior to the mastoid
process. (6) Beyond the confines of the middle ear cleft giving rise to intra-
cranial complications.

SYMPTOMS. The symptomatology of the majority of cases of acute mastoid-
itis seen in hospital practice has been modified or obscured by previous
unsuitable or inadequate antibiotic therapy. In acute otitis media pain
behind the ear and tenderness over the area of the mastoid antrum are