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_4453_Библиотеки_им_академика_М_И_Перельмана
.pdf
4 Postauricular Approach
https://t.me/medicina_free
79
A. Posterior wall of the EAC
B. Mastoid roof
C. Sinodural angle
D. Sigmoid sinus
E. Lateral semicircular canal
F. Aditus ad antrum
G. Incus
Fig. 4.4 Fashion the upper part of the mastoid cavity (right)
To create the upper part of the mastoid cavity, thin the posterior wall of
the EAC to enlarge the aditus ad antrum. The posterior epitympanum,
short process of the incus, incudal fossa (located below the aditus ad
antrum), and the eminence of the lateral semicircular canal (located
medial to the aditus ad antrum) can be seen. The tegmen tympani (bone
plate above the tympanic cavity) and mastoid roof (tegmen mastoi-
deum) (bone plate above the mastoid) are also seen. The angle between
the sigmoid sinus and mastoid roof is called the sinodural angle. The
superior petrosal sinus is located deep and within the dura of the sinodural angle. The triangle formed by the sigmoid sinus, superior petrosal
sinus, and the bony labyrinth is called Trautmann’s triangle. The dura
mater over the cerebellum is located deep to this triangular bony plate
Instruments: medium-sized diamond burs
80
https://t.me/medicina_free
Y. Su et al.
A. Posterior wall of the EAC
B. Mastoid roof
C. Sigmoid sinus
D. Posterior semicircular canal
E. Lateral semicircular canal
F. Superior semicircular canal
Fig. 4.5 Skeletonization of the upper part of the mastoid cavity (right)
Thin the posterior wall of the EAC in the front of the cavity, and expose
the mastoid roof (tegmen mastoideum), sinodural angle, sigmoid sinus,
and posterior cranial fossa dura. Remove the air cells covering the bony
A. Posterior wall of the EAC
B. Mastoid tip
C. Sigmoid sinus
D. Digastric ridge
E. Junction of digastric ridge
and facial nerve canal
labyrinth to expose its lateral surface. Hint: A low-lying mastoid roof
and anterior sigmoid sinus are common, so identication and drilling
must be done carefully when close to the tegmen and sigmoid sinus
Instruments: medium-sized diamond burs
Fig. 4.6 Skeletonization of the lower part of the mastoid cavity (right)
Develop the lower half of the mastoid cavity in the same way. The anterior wall of the cavity is the thinned-down posterior wall of the EAC;
the bony canal of the vertical segment of the facial nerve can be seen at
its inner edge. The digastric ridge can be seen inferiorly. The stylomastoid foramen is located at the junction of the anterior end of the digas-
tric ridge and the vertical segment of the facial nerve canal. The
posterior wall of the cavity is formed by the sigmoid sinus, which runs
from above down to join the jugular bulb, medial to the mastoid tip,
then continues on as the internal jugular vein
Instruments: large-sized cutting burs, medium- sized diamond burs
4 Postauricular Approach
https://t.me/medicina_free
A. Skin flap of the EAC
B. Posterior wall of the EAC
C. Partly opened
epitympanum
D. Sigmoid sinus
E. Digastric ridge
F. Lateral semicircular canal
81
Fig. 4.7 The operative eld after mastoid skeletonization (right)
The operative cavity after mastoid skeletonization should be smooth,
with anatomical landmarks clearly visible. These include the thinned
posterior wall of the EAC, contoured tegmen of the epitympanum, mastoid roof, sinodural angle, sigmoid sinus, vertical segment of the facial
nerve canal, digastric ridge, epitympanum, incus, and bony labyrinth
82
https://t.me/medicina_free
Y. Su et al.
Anatomy oftheFacial Recess
Hui-bingWang
The facial recess and the sinus tympani are located lateral
and medial to the pyramidal eminence, respectively, in the
posterior tympanum, and they are often hidden locations for
cholesteatoma. The posterior tympanum can be revealed
through the posterior tympanotomy approach; the mesotympanum and epitympanum junction area can be revealed if the
incudal fossa is opened in continuity with the facial recess
approach; and the hypotympanum can be better revealed if
the lower part of the recess is enlarged.
The facial recess is shaped like an inverted triangle. The
anterior boundary of the facial recess is the medial part of the
posterior wall of the EAC and the chorda tympani (ca.
9.3mm in length); the posterior boundary is the mastoid segment of the facial nerve (ca. 8.8mm in length); and the upper
boundary is the incudal fossa (ca. 2.9mm wide). The transverse width of the middle of the facial recess is 2.65 mm.
The procedure to reveal the facial recess is to skeletonize the mastoid cavity, expose the aditus ad antrum and the
prominence of the lateral semicircular canal, expand the
aditus ad antrum to reveal the short process of the incus,
and thin the lateral part of the posterior wall of the EAC in
the plane of the mastoid segment of the facial nerve, while
keeping these structures intact. At this point, the three
boundaries of the facial recess can be approximately
located.
Choose diamond burs of appropriate size (usually smaller
than 2mm) to open the facial recess according to the specic
anatomy. Start to open the facial recess just below the short
process of the incus where it is widest, then expand the recess
gradually until the required exposure is achieved.
Hints: (1) The structure and function of the facial nerve
must be protected when opening the facial recess. (2) The
chorda tympani can be freed, displaced, or removed in special circumstances. (3) The incus buttress must be preserved
to support the short process of the incus if the ossicular chain
is to be kept intact. (4) The drill must not touch the incus.
4 Postauricular Approach
https://t.me/medicina_free
83
A. Short process of the incus
B. Incus buttress (posterior
buttress)
C. Posterior wall of the EAC
D. Prominence of the lateral
semicircular canal
E. Te gmen mastoideum
Fig. 4.8 Mastoid skeletonization (left)
Make a postauricular incision, open the mastoid cavity from the cribriform area, remove most of the mastoid cells, and mastoid skeletonization is completed. After determining the location of the mastoid antrum,
widen the aditus ad antrum anteriorly to show the short process of the
incus and the prominence of the lateral semicircular canal
Instruments: large- and medium-sized cutting burs, large- and mediumsized diamond burs
84
https://t.me/medicina_free
A. Short process of the incus
B. Incus buttress
C. Prominence of the lateral
semicircular canal
D. Posterior wall of the EAC
E. Unopened facial recess
Y. Su et al.
Fig. 4.9 Location of the facial recess (left)
Thin down the posterior wall of the EAC, and use the short process of
the incus and the lateral semicircular canal as anatomical landmarks to
locate the facial recess. The upper boundary of the facial recess is the
incus buttress, the anterior boundary is the medial part of the posterior
wall of the EAC and the chorda tympani, and the posterior boundary is
the mastoid segment of the facial nerve. To open the facial recess safely,
start to open it from just below the incus buttress, which is the widest
part of the recess. In the course of removing the bone of the facial
recess, note the following: (1) Remove the bone layer by layer to prevent injuring deeper structures. (2) Use liberal irrigation to clear bone
chips, to prevent heating, and to better observe color changes of the
bone surface. (3) The direction of movement of the drill must be along
the long axis of the facial nerve, so as not to damage it
Instruments: small-sized diamond burs
A.
B. Incus buttress
C. Prominence of the lateral
D. Posterior wall of the EAC
E. Posterior tympanic mucosa
F.
4 Postauricular Approach
https://t.me/medicina_free
Short process of the incus
semicircular canal
Posterior boundary of the
facial recess (bony facial
canal)
85
Fig. 4.10 Removal of bone of the facial recess (left)
After being located, open the facial recess layer by layer using small
diamond burs. Any soft tissue in this area should be carefully dissected
and the bone removed superiorly and inferiorly to identify whether it is
the facial nerve. Mastoid air cells are occasionally seen anterior to the
facial nerve and can be mistaken for the tympanum, so they must be
explored using a hook and correctly identied
Instruments: small-sized diamond burs, right- angled hook
A. Incus buttress
B. Anterior boundary of the
facial recess
C. Posterior boundary of the
facial recess
D. Posterior tympanic mucosa
Fig. 4.11 Exposure of the posterior tympanic mucosa (left)
Gradually open the facial recess until the tympanic mucosa is exposed.
The posterior tympanic mucosa is the last barrier to entering the poste-
rior tympanum. The mucosa should be opened using a hook, not a bur,
to prevent injury to the ossicular chain and inner ear
Instruments: small-sized diamond burs, right- angle hook
86
https://t.me/medicina_free
Y. Su et al.
A. Incudostapedial joint
B. Opened facial recess
Fig. 4.12 Open facial recess to expose the posterior tympanum (left)
Remove the posterior tympanic mucosa, and the posterior tympanum is
exposed. The incudostapedial joint and part of the tympanic medial
A. Incudostapedial joint
B. Round window niche
C. Enlarged facial recess
wall can be observed through the facial recess. The posterior tympanum
is explored using a hook, preparing to widen the recess exposure
Instruments: small-sized diamond burs, right- angle hook
Fig. 4.13 Enlarge the facial recess to reveal the round window niche
(left)
Enlarge the facial recess step by step, working parallel to the mastoid
segment of the facial nerve and the chorda tympani. In the course of
removing the bone of the facial recess, use a right-angle hook to keep
exploring the scope of the posterior tympanum. Use copious irrigation
and watch closely for any color change of the bone surface to distin-
guish any soft tissue early and identify whether the facial nerve sheath
is exposed. In most cases, the round window niche can be fully revealed
with adequate enlargement of the facial recess. To show the area of the
round window niche better, the chorda tympani can be freed, displaced,
or removed if the facial recess is extremely narrow
Instruments: small-sized diamond burs, right- angle hook
4 Postauricular Approach
https://t.me/medicina_free
A. Round window niche
B. Promontory
C. Incudostapedial joint
87
Fig. 4.14 Expose the promontory and round window niche (left)
The promontory and round window niche can be observed under a
microscope at high magnication. The window is located deep in the
round window niche. Generally, one can observe only the aperture of
the round window niche and the mucosal folds overlying it through the
facial recess. When the bone anterior to and above the round window
niche has been removed, the window and its closing membrane can be
seen
Instruments: small-sized diamond burs
A. Short process of the incus
B. Prominence of the lateral
semicircular canal
C. Mastoid segment of the
facial nerve
D. Thinned posterior wall of
the EAC
E. Mastoid cells anterior to
the facial nerve
Fig. 4.15 Mastoid cells anterior to facial nerve (right)
Mastoid cells may be present anterior to the facial nerve below the incus
buttress in some well-pneumatized cases. Generally, it is more convenient and safer to open the facial recess through these cells
Instruments: small-sized diamond burs
88
https://t.me/medicina_free
Y. Su et al.
A. Tympanic segment of the
facial nerve
B. Pyramidal segment of the
facial nerve
C. Mastoid segment of the
facial nerve
D. Round window niche
E. Pyramidal eminence and
stapedius tendon
F. Chorda tympani
Fig. 4.16 Fully opened facial recess (right)
The pyramidal eminence is used as an anatomical marker for the position of the mastoid segment of the facial nerve. Many structures can be
seen through the fully opened facial recess, such as the tympanic, pyra-
midal, and mastoid segments of the facial nerve, chorda tympani, pyramidal eminence, incudostapedial joint, oval window, promontory, and
the round window niche
Instruments: small-sized diamond burs
Соседние файлы в папке Библиотека им академика М.И. Перельмана