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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4501_Библиотеки_им_академика_М_И_Перельмана
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130 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 26
This photomicrograph shows the
posterosuperior cell tract as it extends
anteromedially from the mastoid
toward the internal auditory canal
in a course parallel to the posterior surface of the temporal bone. It lies
in close anatomic relationship to the
nonampullated limb of the superior
canal (female, age 81 yr).
Figure 27
In this case, a large posterosuperior cell
tract leads directly to a pneumatized
apical area (female, age 16 yr).
CHAPTER 4: PNEUMATIZATION ■ 131
Figure 28
This temporal bone has a welldeveloped posteromedial cell tract
(male, age 57 yr). Abbreviations: AICA,
anterior inferior cerebellar artery; EAC,
external auditory canal.
Figure 29
The posteromedial cell tract of this
79-yr-old female is composed of large
cells which bulge into the posterior cranial fossa.
132 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 31
The subarcuate tract extends anteriorly
through the arc of the superior canal.
The posterosuperior tract parallels the
posterior border of the temporal bone
(male, age 80 yr). The subarcuate
tract is one of the several surgical
routes to the petrous apex (see also
Fig. 45 on p. 27).
Figure 30
The subarcuate tract is seen passing
between the ampullated and nonampullated limbs of the superior canal as
it extends anteromedially from the
mastoid. The petromastoid canal is also
seen, passing posterolaterally from the
posterior cranial fossa (male, age 44 yr).
CHAPTER 4: PNEUMATIZATION ■ 133
Figure 32
This section shows a large pacchionian
body in the subdural area of the middle
cranial fossa (male, age 50 yr) (see Fig. 33
on p. 134).
PACCHIONIAN BODIES
Pacchionian bodies, also known as arachnoid granulations, are pseudopodial
projections of the pia-arachnoid which normally extend through the dura
into venous sinuses or venous lacunae. There is variability in the number and
location of these bodies. The largest number can generally be found adjacent
to the superior sagittal sinus, but they may also be found bordering the transverse, cavernous, and superior petrosal sinuses. With age, there is a tendency
for the bodies to increase in size and number, and to undergo calcification.
Each of these pacchionian bodies is composed of several arachnoid villi; each
of the villi consists of bundles of collagenous fibers interspersed with piaarachnoid-like cells surrounded by a thin, outer membrane with small, oval
epithelial cells on the surface. The space contained by the villi is a continuation of the subarachnoid space. The bodies are believed to serve principally
as one-way, pressure-dependent valves between the relatively high pressure
cerebrospinal fluid system to the low pressure venous sinus system.
Pacchionian bodies are also found extending from the arachnoid of the
middle cranial fossa (Figs. 32 and 33) and from the posterior fossa into the
adjacent mastoid cells (Figs. 34–36). In these locations, the bodies may be
encountered by the surgeon, particularly in noninfected ears. Exposing them
does not result in a cerebrospinal fluid leak. The function of these bodies in
areas not related to venous channels is not known.
134 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 34
In this case, there is a large pacchionian
body arising from the meninges of the
posterior cranial fossa. There is soft tissue continuity (osseous dehiscence)
between the cranial cavity and the mastoid at the site of this body. It has not
been demonstrated, however, that such
sites provide pathways for bacterial
spread or cerebrospinal fluid leak.
Figures 35 and 36 on p. 135 are highpower views of areas A and B respectively (female, age 74 yr).
Figure 33
This photomicrograph shows a highpower view of the outlined area of
Figure 32 (male, age 50 yr).
CHAPTER 4: PNEUMATIZATION ■ 135
Figure 35
Shown is a high-power view of area
A in Figure 34 (female, age 74 yr).
Figure 36
Shown is a high-power view of area
B in Figure 34 (female, age 74 yr).
136 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 37
This ear demonstrates a persisting subarcuate fossa. If such an ear also had a
well-pneumatized subarcuate tract,
mastoidectomy could readily be complicated by a cerebrospinal fluid leak
(male, age 1 yr, 9 mo).
THE SUBARCUATE FOSSA AND THE PETROMASTOID CANAL
In the adult, the subarcuate fossa is usually a small shallow depression on the
posterior surface of the petrous pyramid, posterosuperior to the meatus of
the internal auditory canal. In the fetus and the newborn, the fossa is
relatively larger than in the adult (100) (Figs. 2 and 37). It leads into the petromastoid canal, a channel for the subarcuate artery and its accompanying vein
as they course posteriorly through the arc of the superior canal (Figs. 23 and
30) (101). The mastoid aperture of the petromastoid canal is usually found in
a periantral cell anterior to the nonampullated end of the superior canal;
however, in 5% of cases it opens directly into the antrum (100).
THE BONY LABYRINTH
Chapter 5
The Inner Ear
The bony labyrinth develops from the otic capsule. Its matrix is trilamellar,
consisting of the internal periosteal (or endosteal) layer, the middle mixed
layer of intrachondrial and enchondral bone, and the external periosteal layer.
The internal and external periosteal layers are derived, respectively, from the
embryonic internal and external perichondrium (see the section on ossification, chap. 9, p. 287). Scattered within the middle layer is intrachondrial bone
(globuli interossei) (Figs. 1 and 2) which consists of islands of cartilage, the
lacunae of which develop a thin layer of bone from invading osteoblasts. The
amount of intrachondrial bone decreases with the age of the individual (102).
Following fracture, this middle layer of bone fails to heal by osteoid or callus
formation. The endosteal (inner periosteal) layer also demonstrates poor
reparative capability. Fractures of the temporal bone heal predominantly with
fibrous tissue and some bone from the external periosteal layer.
The long axis of the bony labyrinth, measuring 20mm in length (4),
roughly parallels the posterior surface of the petrous pyramid. Its components are the vestibule, the semicircular canals, and the cochlea (Fig. 3).
The Vestibule
The vestibule is the central chamber, measuring 4 mm in diameter; the irregular
topography of its walls corresponds to the contained elements of the
membranous labyrinth. At the posterosuperior aspect of its medial wall is a
depression known as the elliptical recess which accommodates part of the utricular macula. The spherical recess is a similar depression for the saccular macula,
located anteroinferiorly. The vestibular crest, an oblique elevation between these
two recesses, bifurcates posteriorly into two wings which delimit the cochlear
recess for the vestibular cecum (basal end) of the cochlear duct.
There are discrete openings in the bony walls of the vestibule. The opening for the cochlea lies anteriorly, while the openings for the semicircular
canals are located posteriorly. The cribriform (or cribrose) areas are clustered
tiny openings through which the vestibular and cochlear nerve bundles gain
access to the inner ear. The oval window is an opening on the lateral wall,
adjoining the tympanic cavity. The vestibular aqueduct with its contained
endolymphatic duct opens into the posteroinferior aspect of the vestibule.
The Cochlea
The osseous cochlea (Figs. 4–6) derives its name from its resemblance to a
snail shell; it consists of a 32-mm spiral canal which winds two and one-half
137
138 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 1
The three layers of the adult bony
labyrinth are shown. The globuli
interossei (intrachondrial bone) are
islands of modified cartilage in the
enchondral layer of bone. Grenzscheiden
are to be distinguished from the blue
mantles of Manasse (male, age 59yr).
Figure 2
Shown here are the three layers of
the bony labyrinth of a newborn infant
with osteogenesis imperfecta. The
endosteal layer of bone is normal. The
enchondral layer shows an increase in
the fibrous tissue component. The delicate trabeculae of the enchondral layer
are separated by moderately cellular
fibrous tissue with some blood vessels.
The periosteal bone is denser than the
enchondral layer, and is also composed
of thin trabeculae separated by fibrous
tissue.
turns about a central bony axis, the modiolus. The base of the spiral is
located at the anterolateral aspect of the internal auditory canal, corresponding to the cochlear cribrose area for the transmission of nerves supplying
the cochlea; the apex points inferiorly, laterally, and anteriorly. The height of
the cochlea is 5mm. The osseous spiral lamina is a slender bony projection
which circles the modiolus to partially subdivide the cochlear canal into the
scala vestibuli anteriorly and the scala tympani posteriorly; it terminates
apically at the hamulus. The helicotrema is the apical communication of the
two scalae. The secondary osseous spiral lamina is a thin, narrow, curved
shelf of bone located on the external wall of the basal end of the cochlea,
hugging the posterior surface of the spiral ligament. Defects in the
CHAPTER 5: THE INNER EAR ■ 139
Figure 3
This sketch of the bony labyrinth
in effect shows the configuration of the
endosteal layer of bone. Source: After
Sobotta (186).
Figure 4
This photograph shows the microscopic
anatomy of a normal cochlea. Note that
from base to apex there is progressive
narrowing of the spiral ligament and
widening of the basilar membrane
(female, age 63yr). Same ear as in
Figures 5 and 6.
interscalar septum between the middle and apical turns (scala communis)
are common and of no functional significance (Fig. 7).
The Canals
The osseous semicircular canals (here referred to as the lateral, posterior, and
superior canals) are situated posteriorly relative to the vestibule. Each canal
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