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concavity of the membrane (umbo), situated a little below its centre (Fig. 1071); passing downwards and forwards from the umbo is the triangular cone of reflected light, to which too much importance must not be attached, since its appearances vary considerably in healthy ears. Normally, the long crus of the incus is but faintly visible, and still less so are the promontory and fenestra cochleæ; in the condition of obstruction of the auditory tube (Eustachian), however, in which the membrane is indrawn, these structures, along with the folds of the drum-head, become more distinct.
In performing the operation of paracentesis of the tympanic membrane the posteroinferior quadrant is the site chosen for making the puncture, as, in addition to providing good drainage, it is farthest removed from important structures, especially the chorda tympani nerve.
In order to understand the clinical importance of the parts seen through the translucent membrane, it is necessary to study the relative position of the structure of the "mesotympanum," that is to say, that part of the tympanum which lies opposite the tympanic membrane. If the tympanic plate and the tympanic membrane be carefully removed so as to leave the ossicles and chorda tympani nerve in position, it will be seen
Roof of tympanic antrum
Groove for transverse sinus
Portion of lateral semicircular canal
Elevation caused by canalis facialis
Posterior margin of jugular foramen
FIG. 1074.-SECTION THROUGH PETROUS PORTION OF TEMPORAL BONE OF ADULT.
that the head of the malleus and the body and short crus of the incus are altogether above the tympanic membrane, and that they occupy the tympanic attic or epitympanic recess (Fig. 1074). At the junction of the two upper quadrants of the membrane is the handle of the malleus, which is directed downwards, backwards, and medially. The lateral process of the malleus is directed laterally a little below the deepest part of the roof of the osseous external acoustic canal. Opposite the postero-superior quadrant are the long crus of the incus, which descends behind and almost parallel to the handle of the malleus, and the stapes, which is directed medially and slightly backwards to the fenestra vestibuli. The chorda tympani nerve runs from behind forwards between the lateral surface of the superior part of the long crus of the incus and the medial surface of the neck of the malleus. At the deepest part of the roof of the osseous canal, above the chorda tympani nerve and the lateral process of the malleus, is a notch (notch of Rivinus), which is occupied by the flaccid and highest portion of the membrana tympani (Shrapnell's membrane). Opposite the postero-inferior quadrant of the drum-head is the promontory caused by the first part of the cochlea, below and behind which is the fenestra cochleæ. Opposite the antero-superior quadrant are the processus cochleariformis, the tendon of the tensor tympani, and the passage leading towards the auditory tube.
The labyrinthine wall of the tympanic cavity is related to the internal ear. The tegmental wall is separated from the middle fossa of the skull and the under surface of the temporal lobe of the brain by the tegmen tympani-a thin plate of bone, which is continued
o form the roof of the osseous portion of the auditory tube, while posteriorly the tympanic antrum. Laterally the tegmen is limited by the petrouture, which may remain unossified for some years after birth, thus hannel along which pyogenic infection may spread from the middle ear to the d brain. Infection may also spread along the small veins which convey blood mpanum to the superior petrosal and transverse sinuses.
lar wall of the tympanum is formed mainly by the bone forming the jugular is occupied by the bulb of the internal jugular vein. When the transverse sinus unusually far forward the bulb is likewise large, and the fossa, which is coneper, may arch up into the jugular wall of the tympanic cavity, from which it rated merely by a thin and translucent plate of bone which occasionally shows deficiency. In cases where this condition existed the jugular bulb has been the operation of paracentesis of the tympanic membrane. rly the tympanic cavity leads into the auditory tube, which brings it into tion with the nasal part of the pharynx. In the child the auditory tube is ider, and more horizontal than in the adult, hence inflammations are more pread along it to the tympanum.
the level of the membrana tympani is the epitympanic recess, which communiteriorly by means of a triangular opening (aditus ad antrum) with the tympanic the base of the triangle, directed upwards, is formed by the tegmen tympani; , directed downwards, is formed by the meeting of the medial and lateral walls. ening will admit an instrument half a cm. in diameter. The epitympanic recess s from before backwards the head of the malleus, the body and short crus of cus, the latter projecting backwards into the aditus. When these structures overed with inflamed mucous membrane or granulations, drainage from the anic antrum into the tympanum proper is interfered with. The boundaries of the 48, important surgically, are as follows: superiorly, the tegmen tympani; medially, an ence of compact bone, containing the lateral semicircular canal, inferior and anterior to ch is a second smaller prominence, corresponding to that portion of the facial canal ich curves immediately above and behind the fenestra vestibuli. The wall of the facial nal is here thin and not infrequently deficient, in which case inflammation may readily read from the tympanum to the facial nerve. The lateral wall of the aditus is formed by e deepest part of the upper and lateral wall of the osseous external acoustic meatus. The posterior wall of the tympanum, below the aditus ad antrum, is formed by diploic bone which contains the descending portion of the facial canal.
The tympanic antrum is to be considered, developmentally as well as anatomically, as an extension upwards and posteriorly of the tympanum (Fig. 1073). Its anatomy and relations will be best understood by studying it in the child, in whom it is relatively larger than in the adult. Situated above and posterior to the tympanic cavity proper, its lateral wall is formed by a triangular plate of bone which descends, behind the external acoustic process, from the squamous portion. Posteriorly, this triangular plate is separated from the petro-mastoid element by the squamomastoid suture, which overlies the posterior part of the antrum and transmits small veins to the surface. The suture does not become completely ossified until a year or two after birth, and remains of it may frequently be detected in the adult bone. The anterior and superior portion of the triangular plate turns medially at an angle to form the upper and posterior wall of the rudimentary osseous canal, as well as the floor of the epitympanic recess.
In the adult the lateral wall of the tympanic antrum is formed by a plate of bone, from to in. in thickness, which occupies the triangular and somewhat depressed area between the ridge extending, posteriorly and slightly upwards, from the posterior root of the zygoma (supra-mastoid portion of temporal crest), and the superior and posterior quadrant of the osseous external acoustic meatus; upon the latter is the supra-meatal spine, immediately posterior to which, upon the floor of the above triangle, is a crescentic depression, the fossa mastoidea. wall of the antrum is felt through the skin as a slight depression immediately behind the auricle, and immediately inferior to the ridge formed by the supra-mastoid crest; below the depression is the prominence corresponding to the insertion of the sterno-mastoid muscle. Trautmann has pointed out, however, that the supramastoid crest, which varies considerably in its obliquity, is sometimes situated a little above the level of the roof of the antrum, and that it is safer, therefore, to
take the level of the superior border of the osseous meatus as the guide in order to inferior half of th avoid opening the middle fossa of the skull. In children the supra-mastoid crest and emerges thre is not developed, so that if the operator mistake the posterior root of the zygoma In the infant for the crest, he will open into the middle fossa of the skull immediately in front the facial nerve f of the epitympanic recess. The upper and posterior quadrant of the osseous meatus the lateral rather is therefore the only reliable guide to the antrum in the child. the skull, at The medial wall is formed by a thick plate of spongy bone which separates the posterior seg antrum from that portion of the posterior fossa lying between the aqueduct of: follows, the the vestibule and the groove for the sigmoid portion of the transverse sinus, and which contains the posterior semicircular canal.
expose the far downward serve may be the tympanic a the adult, bec All of the osse ertical plane in The lymph v raal meatus ope icular lymph e lymph from
sels from thos -sternomastoi
The roof, which slopes downwards and forwards, is formed by the posterior and thinnest part of the tegmen tympani.
The floor is on a lower level than the aditus, and is therefore unfavourably placed for natural drainage.
The mastoid process begins to develop in the second year. As development advances the diplöe surrounding the antrum in the child becomes excavated to
FIG. 1075.-FRONTAL SINUSES OF AVERAGE
FIG. 1076. A LARGE RIGHT FRONTAL
raps of glands eased secondar ; and care mu scess in one o nosteal mastoi Mle-ear diseas To open the ty achment of the And the postero saddle fossa o uterte sinus, by the surface in o aded by not enc
e osseous cana
s into the ep
al nerve, which must be prote the antrum t
The frontal a nose betweez
form the mastoid cells, which radiate from the antrum, and either directly or indirectly communicate with it by small openings. In the pneumatic type of
upwards into the squamous portion, forwards to the posterior wall of the osseoush the middle : mastoid the whole of the process is excavated by these cells, which extendendent part the "border-cells" may bulge into, and rupture through, the posterior wall of the ally mediar meatus (border-cells), and backwards into the occipital bone. Pus retained within dibulum.
osseous meatus. Less frequently the mastoid cells are absent, the bone consisting
either of osseous tissue similar to that of the diplöe, or of dense bone (sclerosed type) The sinuses
The mastoid portion of the temporal bone is grooved, upon its medial surface, by the sigmoid portion of the transverse sinus. The average distance of the foremost part of the sinus from the supra-meatal spine is 1 cm. The right sinus usually receives the superior sagittal sinus, and when this is the case it is larger and farther forward than the left; in extreme cases it may reach to within 2 or 3 mm. of the meatus. The average minimum distance of the transverse sinus
from the outer surface of the mastoid is about 1 cm., but when the sinus is large ad for more th
and far forward the thickness may be reduced to 1 or 2 mm.
acoustic meatus, lies immediately above and behind the fenestra vestibuli, between floor is the
The facial nerve, after entering the facial canal at the bottom of the internal
ends to point on may ar
it and the prominence of the lateral semicircular canal; thence it descends almost vertically in the mastoid wall of the tympanum in. posterior and medial to the
gree of develop Logan Turner, lower end of the median wards along
1 small area of
e temporal foss anterior wa
half of the deepest part of the posterior wall of the external osseous canal erges through the stylo-mastoid foramen (Fig. 1073).
he infant, in consequence of the absence of the mastoid process, the exit of al nerve from the stylo-mastoid foramen is unprotected and exposed upon ral rather than upon the basal surface of ll, at a point immediately behind the r segment of the tympanic horse-shoe. vs, therefore, that, in infancy, the incision se the antrum should not be curved too nwards and forwards, otherwise the facial may be divided. In the infant the position tympanic antrum is relatively higher than e adult, because in the former the upper of the osseous canal inclines towards the ical plane instead of being horizontal. The lymph vessels from the auricle and exnal meatus open into the posterior and anterior ricular lymph glands, the latter receiving also he lymph from the middle ear. The efferent essels from those glands open into the superior sub-sternomastoid glands; hence it is that those groups of glands are so frequently found to be diseased secondary to tuberculosis of the middle ear; and care must be taken not to mistake an
abscess in one of the mastoid glands for sub- FIG. 1077. ― RIGHT FRONTAL SINUS OF periosteal mastoid suppuration associated with VERY LARGE DIMENSIONS; LEFT SINUS middle-ear disease. UNOPENED (Logan Turner).
open the tympanic antrum the surgeon makes a curved incision a little behind the attachment of the auricle, and chisels or drills away the bone immediately above and behind the postero-superior quadrant of the external osseous meatus. In this operation the middle fossa of the skull is avoided by keeping below the supra-mastoid crest; the transverse sinus, by keeping close to the external acoustic canal and by chiselling obliquely to the surface in opening the mastoid cells; the descending portion of the facial nerve is avoided by not encroaching upon the inferior half of the deepest part of the posterior wall of the osseous canal. In extending the operation from the tympanic antrum through the aditus into the epitympanic recess, the lateral semicircular canal and the curve of the facial nerve, which lie in relation to the medial wall of the aditus, are liable to injury, and must be protected either by a curved probe, or, better, by a Stacke's protector, passed from the antrum through the aditus into the tympanic cavity.
The frontal air sinuses are two cavities situated immediately above the root of the nose between the two tables of the frontal bone. Each sinus at its most dependent part communicates, by means of the naso-frontal duct, either directly with the middle meatus of the nose, or indirectly with that channel through its infundibulum. A bony septum, rarely incomplete, separates the two sinuses; it is usually median in position below, but it may deviate to one or other side above (Figs. 1075 and 1076).
The sinuses vary considerably in their size and shape, independently of the degree of development of the glabella and superciliary arches (Fig. 1077). According to Logan Turner, the dimensions of an average-sized sinus are: height, 11 in., from the lower end of the fronto-maxillary suture vertically upwards; breadth, 1 in., from the median septum horizontally laterally; depth, in., from the anterior wall backwards along the orbital roof. The sinus may exist merely as recesses limited to a small area of bone above the nose, or it may extend upwards on to the forehead for more than two inches; laterally it may be limited by the bony wall of the temporal fossa, while posteriorly it may reach as far back as the optic foramen. The anterior wall is thickest, but the thickness may vary from 1 to 5 mm. The floor is the thinnest wall, hence when pus is retained within the cavity, it tends to point at the superior and medial angle of the orbit. Intra-cranial suppuration may arise in connexion with sinus disease by extension through the roo
or the posterior wall. The muco-periosteal lining, which readily strips from the bone, is thin and pale, and provided with mucus-secreting glands.
In many individuals, by the aid of trans-illumination, the extent of the sinuses and the position of the intervening septum may be mapped out upon the forehead. For this
FIG. 1078.-VERTICAL FRONTAL SECTION THROUGH THE NOSE AND FRONTAL SINUSES.
purpose a small electric lamp is placed against the floor of the sinus, beneath the medial third of the supra-orbital margin.
In an antero-
In a profile s process of the ma Thich they are c Sadow caused b Berefore, the lig etind it are th Osterior ethmoi
before back ortion of the cr be possibility o ving subject. The spheno form apertu nero-posterior Sagram is tak al black shade the piriform
ansverse curv m. medial to In a profile us is seen im shaped shac sinus area ense shadow w
The skiagraphic appearances of the frontal sinuses are of importance clinically and give more information than trans-illumination. Antero-posterior skiagrams show the vertical extent of the sinus, the degree of asymmetry, and the presence or absence of recesses, with their intervening septum. An orbital expansion is indicated by a welldefined shadow with a sharply-defined upper margin, extending laterally parallel to and immediately above the medial half or more of the supra-orbital margin. A profile skiagram shows not only the height of the sinuses but also their antero-posterior diameter, as well as the degree to which they extend backwards between the roof of the orbit and the
of the mid eteriorly, with ne. Anterio
floor of the anterior fossa of the skull. While it is exceptional to meet with frontal sinuses duced by before the age of five years, they are almost invariably present by the seventh or eighth year. teriorly it is
In exploring the sinus, the opening in the bone should be made close to the median henoid which
plane, immediately above the root of the nose. In marked cases of deviation of the septum one sinus may extend so far across the median plane of the forehead as to reduce the other to a mere slit; in such cases the surgeon may fail to open the diseased sinus when the operation is performed through the anterior wall. The sinus frequently contains incomplete partitions, which give rise to the formation of pockets and recesses usually found towards the lateral angle of the sinus; when dealing with chronic suppuration of the sinuses, special attention should be paid to these recesses as well as to the backward extension of the cavity along the orbital roof. The anterior ethmoidal cells are closely related to the thin medial or nasal portion of the floor of the sinus and its duct of exit; hence suppuration very frequently co-exists in both cavities. In some cases pus flows directly from the frontal sinus and infundibulum along the hiatus semilunaris into the maxillary sinus, which opens into the back part of the hiatus. Killian's operation for the cure of chronic suppuration in the sinus consists in the removal of its anterior and inferior walls, the supra-orbital margin being left to prevent the falling in of the eyebrow. By removing the frontal process of the maxilla good access may at the same time be obtained to the ethmoidal cells and free drainage established between the frontal sinus and the nasal cavity. (Skiagraphs of Frontal Sinuses, see Plates I. and II.)
e of importaz mours and ediately beh ittal section That would ce the sphenoidal the plate o a of the b hand, the sphe alla turcica, pophysis sur he damage P