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_4399_Библиотеки_им_академика_М_И_Перельмана
.pdf
Temporal Bone Histology and Radiology Atlas76
https://t.me/med1917
HORIZONTAL SECTION 4
https://t.me/med1917
77
78
https://t.me/med1917
https://t.me/med1917
79
Temporal Bone Histology and Radiology Atlas80
https://t.me/med1917
SUBARCUATE FOSSA
The subarcuate fossa is a prominent feature of the temporal bone during fetal life and infancy. It begins as a
plug of dural connective tissue invaginating 4 to 5 mm
into the fetal cartilage in the arch of the superior semicircular canal. It later extends into the trabeculated
bone and marrow of the infant mastoid. Histological
and radiographic evidence shows that it is still welldeveloped at age 8 months, narrowed by 11 months,
and completely obliterated by 18 to 24 months. As the
mastoid air cells develop during the first year of life,
they approach the subarcuate fossa and in some infants there is little or no bony separation of the mastoid
antrum from the fossa. During the second year of life,
the fossa is obliterated as the petrous bone grows to its
adult configuration and the fossa becomes a shallow
depression or narrow slit.
1
OTIC CAPSULE BONE
The otic capsule refers to the dense osseous labyrinth
of the inner ear that surrounds the cochlea, the vestibule, and the semicircular canals. In the fetus, the membranous labyrinth is embedded in mesenchyme, and
at some distance from the membranous labyrinth, the
peripheral mesenchyme becomes organized into cartilage at about week 5, and begins to form bone, or the
so-called otic capsule, after week 8. Gradually, the entire membranous labyrinth is encased in a bony shell.
In life, the otic capsule is the densest bone in the body
and there is very little inter-individual difference in otic
capsule density on radiographic studies.5 The student
may appreciate the particular density of the otic capsule
bone surrounding the superior semicircular canal on
both histologic and radiographic images in Horizontal
Sections 1 and 2, and in later images. In Chapter 9, the
changes seen in otic capsule density in otosclerosis are
apparent.
CLINICAL CAVEAT: The subarcuate fossa transmits the subarcuate artery, which often involutes
after childhood. In childhood, the subarcuate fossa
is an important preformed pathway for direct extension of infection from otitis media into the meninges2 and is the reason for aggressive treatment of
otitis media in children aged 2 and younger.
CLINICAL CAVEAT: The subarcuate artery is a
valuable surgical landmark in labyrinthectomy. It
bleeds predictably and is helpful for orientation in
the dense otic capsule bone as it is always under
the arc of the superior semicircular canal. It can be
sacrificed without danger to the anterior inferior
cerebellar artery or supplied structures.3 Likewise,
it is a potential site for cerebrospinal fluid leak following labyrinthine surgery.
CLINICAL CAVEAT: Gradinego’s syndrome4 of
otorrhea, severe retro-orbital pain, and diplopia (sixth
cranial nerve palsy) usually results from extension
of frequently indolent/chronic suppurative otitis media into the petrous apex with involvement of the
Gasserian (trigeminal nerve) ganglion in Meckel’s
cave and the abducens nerve along Dorello’s canal
between the petrous apex and the sphenoid sinus.
6. Horizontal Temporal Bone Sections with Corresponding Computed Tomography Images 81
https://t.me/med1917
THE INTERNAL AUDITORY CANAL
The internal auditory canal (IAC), also called the internal auditory meatus (IAM), is a canal within the
petrous part of the temporal bone between the posterior cranial fossa and the inner ear. It transmits the
eighth cranial nerve (vestibulocochlear nerve), the seventh cra nial nerve (facial nerve), and the labyrinthine
artery which is a branch of the basilar artery. The medial opening of the IAC in the posterior cranial fossa
is called the porus acousticus. The length of the IAC is
approximately 1 cm, and its lateral end is called the
fundus. At the fundal end of the IAM are three openings separated by the transverse or falciform crest, a
complete horizontal separation between the superior
and inferior part of the fundus, and the vertical crest,
known as “Bill’s bar,” which separates the superior
portion into an anterior and a posterior segment. Bill’s
bar is named after William F. House, DDS, MD, the
“father of neurotology,” who described its anatomical
significance.
6
Anterior to Bill’s bar, in the anterior superior quadrant of the IAC, are the facial nerve (CN VII) and nervus
intermedius (the sensory portion of the facial nerve).
Posterior to it in the posterior superior quadrant of
the IAM is the superior vestibular nerve. The inferior
portion of the IAC contains the cochlear nerve anteriorly and the inferior vestibular nerve posteriorly
(Fig ure 6–17).
CLINICAL CAVEAT: The vertical crest of the IAC
is an important surgical landmark used to avoid injury to the facial nerve when approaching the IAC
laterally via a translabyrinthine approach for either
vestibular nerve section or removal of vestibular
schwannoma (acoustic neuroma). Drilling through
the vestibule, the surgeon encounters the superior
vestibular nerve at the fundus and can use a microhook to separate the vestibular nerve at Bill’s bar
and begin peeling the rest of the vestibular nerve
away from the meatal portion of the facial nerve.
Figure 6–17. This cartoon depiction of a cross section through the Internal Auditory Canal
shows the transverse and vertical crests, and the relationships between the nerves of the IAC.
Temporal Bone Histology and Radiology Atlas82
https://t.me/med1917
HORIZONTAL SECTION 5
https://t.me/med1917
83
Temporal Bone Histology and Radiology Atlas84
https://t.me/med1917
HORIZONTAL SECTION 6
https://t.me/med1917
85
Соседние файлы в папке Библиотека им академика М.И. Перельмана