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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4399_Библиотеки_им_академика_М_И_Перельмана
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Temporal Bone Histology and Radiology Atlas56
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Figure 5-3. Normal facial nerve on horizontal temporal bone section. The white arrow demarcates the labyrinthine segment of
the nerve as it leaves the IAC laterally. The black arrow points to the geniculate ganglion. The green arrow shows the horizontal
(tympanic) section of the facial nerve. Note the malleus and incus in the epitympanum lateral to the Fallopian canal.
congenital, inflammatory, infectious, traumatic, and
neoplastic etiologies. Computed tomography (CT) is
use ful for identifying bony abnormalities of the intratemporal facial nerve, which can occur with congenital
malformations, trauma, and cholesteatoma. Magnetic
res onance imaging (MRI) is useful for identifying soft
tis sue abnormalities around the facial nerve, as seen
in inflammatory disorders, neoplasms, and hemifacial
spasm.
Imaging technique must be tailored to the clinical presentation, site-of-lesion testing results, and sus-
pected pathology. High-resolution temporal bone CT
is preferable for imaging the lateral course of the facial
nerve from the porus acusticus to the stylomastoid foramen. Temporal bone CT is particularly useful in the
evaluation of the caliber and the course of the IAC and
bony facial nerve canal in the temporal bone. When using CT to evaluate the facial nerve, pathology often can
only be inferred by the presence of erosion or destruction of the adjacent bony facial nerve canal. CT images
of the facial nerve (fallopian) canal in the temporal
bone are shown in Figures 5–2, 5–4, and 5–7, and cor-
Figure 5-4. Normal facial nerve canal on axial temporal bone CT scan. This image is inferior to the one in Figure 5-2. The
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double-lined arrow points to the geniculate ganglion. The solid white arrow points to the horizontal (tympanic) facial nerve.
Note that on this image are also seen, from medial to lateral, the IAC, the cochlea, the vestibule, the malleus and incus, and the
lateral epitympanic wall (scutum). (Image reprinted with permission from Reference 4.)
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Figure 5-5. Horizontal histology section shows the facial nerve in the anterior portion of the
IAC (single white arrow), at the geniculate ganglion (double black arrow), and in its proximal
horizontal (tympanic) segment (single green arrow). The ‘ice cream cone’ of the malleus head
and incus body and short process are seen in the epitympanum. This section is comparable to the
radiographic image in Figure 5-4.
responding horizontal temporal bone sections are seen
in Figures 5–3, 5–5, 5–6, and 5–8. The reader will note
that the black arrow in Figure 5–2 points to the anterior
portion of the IAC, as the facial nerve is an anterosuperior IAC structure.
CT imaging does not provide the resolution to
identify individual nerves; only the bony canal that
houses them. In contrast, MRI is better suited for evaluating soft tissue facial nerve abnormalities. MRI can
be used to image the facial nerve from the brainstem to
the fundus of the internal auditory canal, as shown in
Figure 5–9, and to determine the presence of perineural spread from parotid malignancies, which are out of
the scope of this Atlas.
Figure 5-6. Normal facial nerve canal on horizontal temporal bone section. Further inferiorly, the black arrow points to the
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horizontal (tympanic) facial nerve. From medial to lateral in the bone (lower left to upper right on the image), can be seen the
internal auditory canal with some nervous structures, the cochlea anteriorly to the IAC, the vestibule posterior to the IAC, the malleusand the incus, and the scutum (lateral epitympanic wall).
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Figure 5-7. Normal facial nerve canal on axial temporal bone CT scan. This image is further in-
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ferior to the one in Figure 5-4. The white arrow points to the vertical (mastoid) facial nerve canal,
which is surrounded by mastoid air cells. Anteriorly in this image is seen the carotid artery and
lateral to that, air in the Eustachian tube. (Image reprinted with permission from Reference 4.)
Figure 5-8. Normal facial nerve canal on horizontal temporal bone section, further inferiorly to
Figure 5-6. The black arrow points to the vertical (mastoid) facial nerve. It lies just posterior to the
stapedius muscle at the pyramidal process. Also seen are the carotid artery anteriorly, the basal
turn of the cochlea ending at the round window membrane, the posterior semicircular canal, and,
laterally, the inferior tympanic membrane and external auditory canal.
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Figure 5-9. Normal facial nerve on MRI. Axial CISS image at the level of the pons demonstrates the facial colliculus (arrow)
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seen as a small bump along the anterior wall of the fourth ventricle. This is formed by the motor tracts of the facial nerve
(purple curved line) coursing around the abducens nucleus (yellow dot). (Reproduced, with permission, from Reference 4.)
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REFERENCES
1. Facial Nerve, Anatomy, Regional and Applied. RJ Last, ed.
4th ed., J&A Churchill Ltd, London, UK, 1966.
2. Facial Nerve, Gray’s Anatomy. Susan Standring, ed. 41st ed.,
Elsevier, Illinois, 2015.
3. Hitselberger WE, House WF. Acoustic neuroma diagnosis.
External auditory canal hypesthesia as an early sign, Ar-
chives of Otolaryngology, 1966;83( 3): 218–221.
4. Gupta S, Mends F, Hagiwara M, Fatterpekar G, and
Roehm PC, Imaging the facial nerve: A contemporary
review, Radiology Research and Practice, 2013;2013. Article
ID 248039.
CHAPTER 6
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Horizontal Temporal Bone Sections with
Corresponding Computed Tomography Images
Hosakere K. Chandrasekhar and Sujana S. Chandrasekhar
Over the following horizontal temporal bone histology sections, the reader will be able to see detailed
anatomy and follow structures in the same plane as is
seen on axial CT images. We ask you to look at the unmarked pictures first and try to identify the structures
on both histology and radiograph, and then turn your
eye to the marked pictures as a form of self-guided
learning and assessment. Along the way, you will find
some clinical caveats of interest to the ear surgeon as
well as the radiologist interpreting these studies for the
otolaryngologist.
The reader is admonished to bear in mind that the
histology sections are 20 µm (0.02 mm) thick while the
CT images are 1 mm thick. The CT images are presented in bone windows as these are the most effective
for temporal bone assessment.
For these horizontal sections, the images will begin superiorly at the arcuate eminence, or the loop of
the superior (anterior) semicircular canal and go inferiorly. The histologic sections are 20 µm thick and every
10th section is stained, so that each successive figure is
0.2 mm from the previous one. The orientation of the
images is as if for a left axial CT scan, with the petrous
apex off to the left, the posterior fossa dura inferiorly,
and the mastoid cortex to the right.
The horizontal histologic sections and the axial
computed tomography images are oriented for maximal viewability such that the reader is encouraged to
turn this Atlas 90 degrees to the right. The pertinent
histologic section will be on the even-numbered page
above and its corresponding radiographic image will
be on the odd-numbered page below, and labeled images will follow on the next two pages. This will allow
for self-guided learning and self-assessment.
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HORIZONTAL SECTION 1
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