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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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220 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
The utricle as well as the ampullae of the superior and lateral canals are
drained by the anterior vestibular vein (289). The posterior vestibular vein
receives blood from the saccule, the ampulla of the posterior canal, and the
basal end of the cochlea. The vein of the round window joins with the confluence of the anterior and posterior vestibular veins to form the vestibulocochlear vein. The latter vessel unites with the common modiolar vein to
become the inferior cochlear vein; it then traverses the bony canal of
Cotugno (Cotunnio), located near the cochlear aqueduct, to empty into the
inferior petrosal sinus. The membranous ducts are drained by channels
Figure 38
This schematic drawing shows the
venous drainage of the human membranous labyrinth.
Figure 39
The venous drainage of the cochlea is
provided by the anterior and posterior
spiral veins which join near the basal
end to form the common modiolar vein
(female, age 77yr).
CHAPTER 7: VASCULAR ANATOMY ■ 221
which course toward their nonampullated ends to form the vein of the
vestibular aqueduct; this vessel travels within the vestibular aqueduct or a
paravestibular canaliculus to drain into the lateral venous sinus. A variably
present vessel is the internal auditory vein (274). When present, it collects
blood from the apical and middle turns of the cochlea and drains into the
inferior petrosal sinus via the internal auditory canal.
Stereoscopic Views of the Temporal Bone
SURGICAL DISSECTION OF THE TEMPORAL BONE
Familiarity with the macroscopic anatomy of the temporal bone can be
acquired by dissection of the fresh cadaver specimen with the aid of the
operating microscope and appropriate surgical instruments. The following
photographs (Figs. 1–28) present a logical approach to the step-by-step
dissection of a right temporal bone. The sequence of dissection has relevancy
for transmastoid surgical procedures only. It does not apply to transcanal
procedures such as exploratory tympanotomy, stapedotomy, transcanal
labyrinthectomy, ossiculoplasty, myringoplasty, etc. An organized sequence
of dissection enables the maximum educational yield to be obtained from
each specimen. The views are presented in surgical orientation with the
anterior aspect of the ear located superiorly in the photographs.
In order to appreciate the three-dimensional effect, it is important to
concentrate on the paired images and have them fully your field of
vision. In addition, the plane of your eyes must remain parallel to the plane
of the page. Then “defocus” your eyes and allow the images to fuse.
Alternatively, looking “through” or “beyond” the images without focusing
on them enables perception of the three-dimensional effect. We believe that
these stereo views will facilitate the comprehension of ear anatomy in its
three-dimensional aspect, and aid in understanding of the two-dimensional
photographs in this book.
Chapter 8
223
224 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 2
Initial drilling is done in the mastoid fossa
which overlies the mastoid antrum. Large cutting burs are preferable at this stage, where bone
removal is carried superiorly to identify the
mastoid tegman and posteriorly to identify the
eminence of the sigmoid sinus.
Figure 1
After the postauricular incision has been made,
the muscle and periosteum are elevated to
expose the mastoid cortex. The mastoid fossa
and spine of Henle are identified. The latter
landmark limits the anterior dissection in an
intact canal wall procedure.
CHAPTER 8: STEREOSCOPIC VIEWS OF THE TEMPORAL BONE ■ 225
Figure 3
Koerner’s septum, when present, is a plate of
bone that extends downward from the mastoid
tegmen for a variable distance. It represents the
junction of the petrous and squamous portions
of the mastoid. In this specimen it hides the
lateral canal.
Figure 4
Once Koerner’s septum has been removed, the
prominence of the lateral canal is visualized. It is
important to saucerize the edges to avoid
obscuring the view by the bony margins of the
mastoid cavity.
226 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 6
The bony wall of the lateral venous sinus
(sigmoid sinus) is seen as a protuberance of the
posterior wall of the mastoid cavity, passing
anteroinferiorly towards the jugular bulb. The
sinodural angle represents the junction of the
tegmen (roof) of the mastoid and the lateral
venous sinus.
Figure 5
The mastoid tip is divided into medial and
lateral compartments by the digastric ridge. The
anterior portion of this ridge is located near the
mastoid segment of the facial nerve.
CHAPTER 8: STEREOSCOPIC VIEWS OF THE TEMPORAL BONE ■ 227
Figure 7
As bone is exenterated superiorly and anteriorly
from the antrum toward the epitympanum, the
incus comes into view. If one places a small
amount of fluid in the epitympanum, light
refraction will often reveal the position of the
incus before it is exposed to direct view. It is
important to avoid striking the ossicles with the
rotating bur, to prevent acoustic trauma.
Figure 8
With diamond burs, the posterior fossa dura and
endolymphatic sac have been decorticated. The
endolymphatic sac has been opened and a tube
placed within its lumen. Note the anatomic relationship of the endolymphatic sac and the lateral
venous (sigmoid) sinus. Surgical procedures to
drain the endolymphatic sac into either the subarachnoid space or mastoid cavity are known as
endolymphatic sacotomy operations. Donaldson’s
line is a posterior extension of the plane of the
lateral canal bisecting the posterior canal; the
endolymphatic sac lies inferior to this line.
228 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 10
The extent of the mastoid exenteration shown
here is known as a simple mastoidectomy. The bone
of the lateral canal has been thinned to create a
blue line.
Figure 9
The bone of the posterior canal has been thinned
to create a blue line. The blueness is the result of
light resorption (instead of reflection) at the site
of the thinned bony wall.
CHAPTER 8: STEREOSCOPIC VIEWS OF THE TEMPORAL BONE ■ 229
Figure 12
Removal of epitympanic bone exposes the body of
the incus and head of the malleus. This surgical
approach is known as posterior atticotomy. The epitympanum is divided into medial and lateral
compartments by these ossicles. The posterior incudal ligament is seen.
Figure 11
The facial nerve has been partly uncovered by removing
bone with the largest diamond bur that can comfortably
be accommodated to avoid the risk of impaling the
facial nerve. Drilling is done parallel, not perpendicular,
to the expected course of the facial nerve, and liberal
irrigation is used. Exposing the trunk of the facial nerve
throughout its course is known as facial nerve exploration.
The facial recess, lateral to the facial nerve, is opened by
drilling with a small diamond bur, inferior to the short
process of the incus and lateral to the plane of the facial
nerve. The chorda tympani nerve is lateral and inferior
to the facial recess. This surgical approach to the middle
ear is known as a posterior tympanotomy and is frequently
used with intact canal wall procedures.
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