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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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120 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 9
In contrast to the large external
auditory canal (EAC), the mastoid is
narrow, although well-pneumatized.
The large tip cell abuts the bony EAC
(male, age 73 yr).
Figure 10
This temporal bone shows a well-pneumatized narrow mastoid. The peritubal
area is well-pneumatized. The bony
dehiscence of the anterior wall of
the external auditory canal is an
occasionally occurring anatomic variant
(male, age 22 yr).
The anterolateral portion of the mastoid arises from the squamous part
of the temporal bone; the posteromedial portion, including the mastoid tip,
arises from the petrous part. The delineation of these areas is indicated on
the outer surface by the petromastoid fissure, which is usually obliterated in
early adult life. In most mastoids, the plane of junction of these two parts is
marked internally by an incomplete plate of bone, the petrosquamosal
septum, also known as Koerner’s septum (91). This bony partition is of variable thickness and descends to variable depths; in extensively pneumatized
bones it may be missing altogether. Proctor (61) proposes that Koerner’s
septum is the consequence of the “persistence and further development of
the mucosal fold between saccus superior and saccus medius in the antrum
and mastoid of the adult.”
CHAPTER 4: PNEUMATIZATION ■ 121
Figure 11
The temporal bone of this 8-mo-old
infant shows advanced pneumatization of the mastoid but inhibited
perilabyrinthine pneumatization; thus,
the internal auditory canal is short and
wide and the posterior canal bulges
into the posterior fossa. Anteriorly, the
pars tensa has been artifactually separated from the tympanic annulus.
When encountered during surgical procedures, Koerner’s septum may
be confused with the medial wall of the antrum (Figs. 12–14). The identity of
Koerner’s septum becomes obvious when it is realized that the usual
anatomic landmarks such as the tegmen of the mastoid, the prominence of
the lateral canal, the lateral venous sinus, and the antrum are not in view.
The mastoid region can be divided into three areas (Fig. 15): (1) The
mastoid antrum area is a large superior central space which communicates
with the epitympanic space of the middle ear via the aditus. The lateral wall
is formed by the squamous part of the temporal bone. (2) The central
mastoid tract area extends inferiorly from the mastoid antrum (Fig. 16). It
may consist of a single space of varying size or of a series of cells and may
Figure 12
The division of the mastoid into an
anterolateral squamous portion and
a posteromedial petrous portion by
Koerner’s septum is demonstrated in
this photograph (female, age 65 yr).
122 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 13
Koerner’s septum delineates a normally
smaller squamous part from the larger
petrous part of the mastoid. In this
specimen, the anterior epitympanic
recess protrudes into the middle cranial
fossa (male, age 76 yr).
Figure 14
This more inferior view of the same ear
shown in Figure 12 demonstrates the
smaller size of the anterolateral squamous part when compared to
the larger posteromedial part of the
mastoid. Because of the differing
origins of their pneumatization, the
facial recess and mastoid are always
separated by a bony partition (female,
age 65 yr).
be partly divided by the petrosquamosal (Koerner’s) septum. (3) The peripheral mastoid area has five cell groups consisting of (i) the tegmental cells
bordering the tegmen and lying superiorly in the mastoid bone, (ii) the
sinodural cells occupying the posterosuperior angle of the mastoid bone and
bounded superiorly by the dural plate of bone as well as posteroinferiorly by
the sinus plate of bone, (iii) the sinal cells lying lateral, medial, and posterior
to the sigmoid sinus, (iv) the facial cells lying in relation to the mastoid
segment of the facial nerve, and (v) the tip cells occupying the inferior projection of the mastoid bone and divided by the digastric ridge into medial
and lateral groups.
CHAPTER 4: PNEUMATIZATION ■ 123
Figure 15
This diagrammatic sketch illustrates
the areas of pneumatization of the mastoid region and accessory regions of the
temporal bone.
Figure 16
The central mastoid tract extends
inferiorly from the antrum and is
surrounded by smaller air cells, some
of which may extend into the cortex
of the posterior wall of the external
auditory canal (female, age 58 yr).
124 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 17
This photomicrograph shows extensive
pneumatization of the infralabyrinthine
area (female, age 16 yr).
THE PERILABYRINTHINE REGION
The perilabyrinthine region is subdivided into: (1) the supralabyrinthine
area (Fig. 24) and (2) the infralabyrinthine area (Fig. 17) which lie superior
and inferior to the labyrinth, respectively.
THE PETROUS APEX REGION
The petrous apex region is divided into: (1) the peritubal area (Figs. 18 and 19)
which surrounds the osseous portion of the eustachian tube and lies anterolateral to the carotid canal, and (2) the apical area (Figs. 20–24) which lies
anteromedial to the carotid canal. Peritubal pneumatization is common;
however, the apical area is not usually pneumatized (Fig. 25).
To the surgeon, the apical area is the most remote part of the temporal
bone. It may be pneumatized by the peritubal, perilabyrinthine, posterosuperior, posteromedial, and subarcuate cell tracts. Surgical access for drainage
of purulent accumulations (petrous apicitis) can usually be accomplished by
following one of these routes (92–95). An alternative route, proposed by
Ramadier (96), is to drill through the bony labyrinth between the cochlea
and carotid canal; most otologic surgeons, however, consider this approach
to be too difficult to be practical. The limited space available between the
cochlea posteriorly and the facial nerve and carotid artery anteriorly is
demonstrated in Figures 20, 21, and 22. Infections of the petrous apex have
become a rarity in most parts of the world.
CHAPTER 4: PNEUMATIZATION ■ 125
Figure 18
In this ear, peritubal air cells are located
both medial and lateral to the
eustachian tube. The internal carotid
artery is separated from the bony part
of the eustachian tube by a thin plate of
bone (male, age 74 yr).
Figure 19
There is a dehiscence of the anterior
wall of the external auditory canal. This
anatomic variant is of significance in
surgical procedures in this area (male,
age 53 yr).
126 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 20
This temporal bone shows extensive
pneumatization of the peritubal and
apical areas of the petrous apex region.
Peritubal cells frequently serve as a
route of pneumatization to the apical
area (female, age 89 yr).
Figure 21
The petrous apex is narrow but
extensively pneumatized. The aditus is
that constricted region posteromedial
and superior to the body and short
process of the incus leading from the
epitympanum to the mastoid antrum
(female, age 64 yr).
CHAPTER 4: PNEUMATIZATION ■ 127
Figure 22
In this ear, the petrous apex area is
highly pneumatized. Serial sections
show continuity with the peritubal
and posterosuperior cell tracts (female,
age 49 yr).
Figure 23
This temporal bone shows a single
large apical air cell (male, age 40 yr).
128 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 25
This temporal bone shows the usual
state of nonpneumatization of the
petrous apex. The carotid canal with its
vascular and neural plexuses is also
found in the petrous apex (male,
age 60 yr).
Figure 24
Two common pathways to the petrous
apex from the mastoid are the posterosuperior tract and the subarcuate tract
(female, age 16 yr).
CHAPTER 4: PNEUMATIZATION ■ 129
THE ACCESSORY REGIONS
Occasionally, pneumatization extends beyond the middle ear, mastoid, perilabyrinthine, and petrous apex regions to involve adjacent portions of the
temporal bone and even the adjacent cranial bones, thus forming the accessory cell areas (Fig. 15): (1) a zygomatic area that is an anterior extension
from either the epitympanic or tegmental cell areas and occupies the root
and sometimes the arch of the zygoma, (2) a squamous area which lies in the
squamous portion of the temporal bone above the level of the infratemporal
line as a superior extension from the tegmental cells, (3) an occipital area that
lies within the occipital bone as a posterior extension from the sinal cells, and
(4) a styloid area consisting of a rare accessory pneumatization occurring as
an extension of the tip cells into the base of the styloid process.
THE TRACTS OF PNEUMATIZATION
Pneumatization of the temporal bone is the result of a hollowing-out process
in which mesenchyme is resolved to leave spaces. Each space becomes aircontaining and is in free communication with all other pneumatized spaces.
The tracts of pneumatization are well-known to the otologic surgeon, for
they serve as routes which can be followed to approach diseased areas of the
temporal bone (86,97–99).
These tracts are as follows: (1) The posterosuperior cell tract extends
anteromedially from the superior part of the mastoid and lies in the angle
between the dural plates of bone of the middle and posterior cranial fossae
and the superior canal. This tract usually terminates near the internal auditory canal, but may pass superior to the internal auditory canal to reach the
supralabyrinthine and apical areas (Figs. 26 and 27). (2) The posteromedial
cell tract extends anteromedially from the mastoid along the posterior surface of the petrous bone at a level inferior to the posterosuperior cell tract
(Figs. 28 and 29). On one side it is bordered by the endolymphatic duct and
sac, and on the other by the bony wall of the posterior cranial fossa. It may
lead to the supralabyrinthine and infralabyrinthine areas. (3) The subarcuate
cell tract, occurring in 3% of temporal bones (100), extends from the mastoid
in an anteromedial direction through the arc of the superior semicircular
canal adjacent to the petromastoid canal. It may reach the apical area
(Figs. 30 and 31). (4) The perilabyrinthine tracts extend from the epitympanic
and hypotympanic areas of the middle ear into the supralabyrinthine and
infralabyrinthine areas, respectively. (5) The peritubal tract arises from the
protympanum or eustachian tube and takes a course anterior to the internal
carotid artery to reach the apical area (Fig. 20).
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