Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4501_Библиотеки_им_академика_М_И_Перельмана
.pdf
40 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 11
Here we see the interesting condition in
which a second exostosis appears
to have formed on the surface of a
pre-existing exostosis (male, age 60 yr).
Figure 12
This high power magnification shows
the usual lamellar structure of a typical
exostosis punctuated by the normal
process of focal remodeling (male, age
61 yr). The number of laminations may
correlate with the number of cold water
insults to the external auditory canal.
THE TYMPANIC MEMBRANE
Chapter 3
The Middle Ear
The tympanic membrane is irregularly round and slightly conical in shape;
the apex of the cone is located at the umbo, which marks the tip of the
manubrium. In the adult, it is angulated approximately 140° with respect to
the superior wall of the external auditory canal. The vertical diameter of the
tympanic membrane as determined along the axis of the manubrium ranges
from 8.5 to 10mm, while the horizontal diameter varies from 8 to 9mm (8).
The malleal prominence (Fig. 1), a projection formed by the lateral process of
the malleus, is located at the superior end of the manubrium. The manubrium
is firmly attached to the tympanic membrane at the umbo and lateral process
and is clearly visible throughout its length (the stria mallearis). The anterior
and posterior tympanic striae extend from the lateral process of the malleus
to the anterior and posterior tympanic spines, respectively. These striae
divide the tympanic membrane into larger pars tensa below, and smaller triangular pars flaccida (or Shrapnell’s membrane) above.
The superior recess of the tympanic membrane is eponymically known
as Prussak’s space (9). The pars flaccida forms the lateral border of this space
as it attaches superiorly to the bony margins of the notch of Rivinus or tympanic incisura. The lateral malleal ligament limits this space anterosuperiorly as it extends from the union of the head and neck of the malleus to the
periphery of the notch of Rivinus. Posteriorly, Prussak’s space opens into the
epitympanum. The anterior and posterior malleal folds mark the inferior
limit of Prussak’s space.
The thickened periphery of the pars tensa, the tympanic annulus (limbus) (Fig. 2), anchors the tympanic membrane in a groove known as the tympanic sulcus. The tympanic annulus and sulcus are absent superiorly in the
area of the notch of Rivinus. The surgeon, when exposing the middle ear via
a tympanomeatal flap approach, must elevate the tympanic annulus from the
tympanic sulcus if perforation of the tympanic membrane is to be avoided.
The pars tensa and pars flaccida differ in structure. The pars tensa, as its
name suggests, is taut and consists of three layers: (1) a lateral epidermal layer,
(2) a medial mucosal layer, and (3) an intermediate fibrous layer, the pars propria. The epidermal layer is contiguous with the skin of the external auditory
canal (see chap. 2, p. 33) and the mucosal layer is contiguous with the mucous
membrane of the middle ear. The intermediate layer consists of fibrous tissue
arranged in inner circular and outer radial strata. Elastic fibers are rare in the
pars tensa (10).
With acute infections of the middle ear, the tympanic membrane
becomes acutely inflamed. It is not unusual for blebs or bullae to form at the
interface between the pars propria and epidermal layers. The surgeon
41
42 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
performing therapeutic myringotomy (incision of the ear drum) must not be
misled by such a bleb and fail to incise all three layers of the membrane.
The pars flaccida, although lax, is actually thicker than the pars tensa
(10). First described by Shrapnell (11), it also consists of epidermal, fibrous,
and mucosal layers. The epidermis is composed of 5 to 10 layers of epithelial cells, the fibrous layer consists of irregularly arranged collagen and
elastic fibers, and the mucosal layer is composed of simple squamous cells,
as in the pars tensa.
When the tympanic membrane is perforated by either trauma or
infection, the extent of fibrous tissue proliferation determines the thickness
of the healing membrane. The replacement membrane may develop a dense
intermediate fibrous layer or alternately may fail to develop a fibrous layer,
Figure 1
This diagrammatic sketch illustrates the
superior, anterior, and inferior boundaries of Prussak’s space. Shrapnell’s
membrane (not illustrated) constitutes
the lateral wall as it extends from the
anterior and posterior tympanic striae
to attach to the margins of the notch of
Rivinus. Source: After Proctor (76).
Figure 2
In the region of the umbo, the manubrium is enveloped by the lamina propria
of the tympanic membrane (see Fig. 19
on p. 50). The tympanic (fibrous) annulus is seen lodged within the tympanic
sulcus. The nerves of the tympanic
plexus ascend the promontory region in
grooves (male, age 63yr).
CHAPTER 3: THE MIDDLE EAR ■ 43
resulting in a thin membrane composed only of epidermal and mucosal
layers (Fig. 3). It may vary in thickness in different areas and may have areas
of hyalinization (Fig. 4). The replacement membrane when invaginated into
the middle ear space forms a retraction pocket (Figs. 5 and 6). These pockets
may be fixed by adhesions to structures in the middle ear. If not adherent,
positive middle ear pressures can cause them to evert into the external
auditory canal (Fig. 7).
For a successful functional result in myringoplasty operations (closure
of perforations of the tympanic membrane), it is important to avoid postoperative fibrous obliteration (blunting) of the anterior tympanomeatal angle.
Figures 8 and 9 show examples of malleus fixation caused by fibrous proliferation in this angle following myringoplasty.
Figure 3
This tympanic membrane shows histologic alterations caused by chronic
otitis media. Although intact, there is
an anterior marginal area of fibrous
thickening and a large area of replacement membrane (neomembrane). The
latter area represents a site of previous
perforation and is characterized by
the absence of the lamina propria
(the fibrous layer of the tympanic
membrane). The inset shows a higher
magnification of the outlined area
(male, age 54yr). Thin replacement
membranes are frequently seen during
routine otoscopic examination and,
unless very large, have no effect on
hearing.
Figure 4
A tympanosclerotic (hyalin) plaque
is seen in the anterior part of the
tympanic membrane. Otoscopically such
plaques have a whitish appearance and
are often erroneously termed “calcium
plaques.” They are the consequence of
otitis media (male, age 45yr). These
plaques cause no hearing loss unless they
are large enough to stiffen the tympanic
membrane or fix the manubrium.
44 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 5
The tympanic membrane shows a
posterior retraction pocket and an
anterior replacement membrane. The
long process of the incus has been
resorbed. Additionally, there is a
healed fistulous tract leading from the
mastoid to the external auditory canal.
These alterations are the result of
chronic otitis media and mastoiditis
(female, age 48yr).
Figure 6
There is a deep retraction pocket in the
posterior part of the tympanic membrane. The long process of the incus has
been resorbed and the central mastoid
tract is surrounded by sclerotic bone.
These changes are the result of previous otitis media and mastoiditis (male,
age 67yr).
CHAPTER 3: THE MIDDLE EAR ■ 45
Figure 7
Retraction pockets, if not fixed to
middle ear structures by adhesions,
may evert or invert depending upon
the state of middle ear pressure
(female, age 65yr).
Figure 8
There is fibrous fixation of the malleus
and hearing loss following surgical closure (myringoplasty) of an anterior
perforation of the tympanic membrane
with fascia from the temporalis muscle
(male, age 19yr; see Fig. 9 below).
Figure 9
The opposite ear of the subject shown
in Figure 8 demonstrates fibrous thickening of the entire tympanic membrane
with hearing loss following myringoplasty for an anterior perforation
(male, age 19yr). Such untoward
results can be avoided by the proper
use of skin grafts.
46 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
THE OSSICLES
The ossicles serve to transmit sound energy from the tympanic membrane to
the inner ear. The general size, shape, and configuration of the malleus,
incus, and stapes are shown in Figure 10.
The Malleus
The most lateral of the ossicles is the malleus. It has a head, neck, lateral
process, anterior process, and manubrium. The anterior process (processus
gracilis or processus Folianus) is a thin projection of bone which extends from
the neck of the malleus into the petrotympanic (Glaserian) fissure, accompanied by the chorda tympani nerve (Figs. 11–13). It seems doubtful that the
anterior process of the malleus has any important function, for in adult ears
it is often found to be fractured (Fig. 14) or partially resorbed (Fig. 15) without causing hearing loss. It is held to the walls of the petrotympanic fissure
by the anterior malleal ligament which, with the posterior incudal ligament,
serves to establish the axis of rotation of the ossicles (Fig. 16). The anterior
malleal ligament must not be confused with the anterior suspensory ligament
of the malleus.
The dense fibrous tissue of the anterior malleal ligament is in contiguity with the periosteum of the malleus (12) and traverses the petrotympanic
fissure to reach as far as the angular spine of the sphenoid bone. On its
thinner, medial aspect runs the chorda tympani nerve as it passes anteriorly
to enter the iter chordae anterius at the Glaserian fissure.
Figure 10
This sketch shows the articulated
ossicles and the form and dimensions
of the stapes. Source: After Anson and
Donaldson (77).
CHAPTER 3: THE MIDDLE EAR ■ 47
Figure 11
Mesenchyme is still present in the
middle ear cavity. The long anterior
process of the malleus (processus gracilis or Folianus) is demonstrated in its
normal configuration (male, age 5mo).
Figure 12
The anterior process of the malleus is
believed to develop in membrane bone
and to fuse secondarily with the
enchondral bone of the remainder of
the malleus (male, age 39yr).
Figure 13
The anterior process of the malleus and
the anterior malleal ligament constitute
the anterior pole of the axis of ossicular
rotation. The anterior malleal ligament
may reach as far as the angular spine of
the sphenoid bone (male, age 65yr).
48 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
The lateral process of the malleus contains a cartilaginous cap attached
to the pars tensa of the tympanic membrane (Figs. 17 and 18). The inferior
end of the manubrium is firmly attached to the tympanic membrane as the
pars propria splits to envelop it (the umbo) (Fig. 19). In surgical procedures,
the tympanic membrane can be readily separated from the malleus except at
the umbo.
Midway between the lateral process and umbo, the manubrium,
because of its gentle medial curvature, may separate slightly from the pars
propria so that its only attachment is a fold of mucous membrane, the plica
mallearis (Fig. 20). Prostheses clamped to the manubrium in the region
midway between the lateral process and umbo therefore may have little or
no contact with the pars propria of a normal tympanic membrane.
Figure 14
In the adult temporal bone, the anterior
process of the malleus frequently
shows fractures (female, age 85yr).
Figure 15
In this ear, the anterior process of the
malleus has undergone partial resorption. The chorda tympani nerve frequently lies in a groove on the medial
surface of the malleus near the base of
the anterior process (female, age 85yr).
CHAPTER 3: THE MIDDLE EAR ■ 49
Usually the manubrium lies midway between the anterior and posterior borders of the tympanic membrane (Fig. 21), but may occupy a more
anterior position (Fig. 22). The surgical significance of an anteriorly located
manubrium is the difficulty it may cause in the repair of an anterior perforation of the tympanic membrane, as well as in the removal of exostoses and
stenoses of the external auditory canal. Surgical procedures on the tympanic
membrane and exter nal auditory canal are especially difficult when an anteriorly located malleus is associated with convexity of the anterior canal wall.
The cross-sectional ovoid configuration of the manubrium (Figs. 23
and 24) is an important determinant in the design of prostheses that attach
to it (Figs. 25 and 26).
Figure 16
The anterior suspensory ligament,
shown here, lies superior to the anterior malleal ligament seen in Figures 13
to 15. Apparently, the suspensory ligaments do not interfere with the process
of sound transmission even though
they are outside the axis of rotation
(male, age 47yr).
Figure 17
Although the lateral process of the
malleus is firmly adherent to the tympanic membrane, surgical separation
without perforation is readily accomplished (male, age 28yr).
Соседние файлы в папке Библиотека им академика М.И. Перельмана