Sinus kavernozusun lateral duvarında seyreden kraniyal sinirlerin radyolojik ve anatomik olarak değerlendirilmesi

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Introduction
The cavernous sinus (CS), located in a space between endosteal and meningeal dura, is a vascular
channel of great importance and its contents show
great variation (1,2). The CS extending from the tip
of the petrous bone to the medial part of the superior orbital fissure, has a parasellar position (3,4).
The CS contains the venous plexus, internal carotid
artery (ICA) and abducent nerve, and on the its lateral wall cranial nerves (CNs) III (oculomotor nerve),
IV (trochlear nerve), V1 (ophthalmic nerve) and V2
(maxillary nerve) (4,5). With the increasing frequency of surgical procedures to the CS, knowledge of
the microanatomy of the CS has become essential.
The most frequent complication seen during the CS
surgery is the injury of cranial nerves. In addition,
the contents of this sinus may be affected by trauma, tumors or infections (6). For these reasons, the
knowledge of the anatomy of the cranial nerves on
the lateral wall of this sinus is important. Imaging
of CNs III, IV, V1, V2, and VI in the CS has been
reported with both magnetic resonance imaging
(MRI) and computed tomography (CT) (7-9). But a
precise evaluation of these CNs in the CS is difficult by these methods. The three dimensional (3D)
constructive interference in steady state (CISS) sequence depicts the small structures surrounded by
the cerebrospinal fluid with high contrast and high
spatial resolution (10), therefore, we assumed that
contrast enhanced 3D-CISS MRI is more suitable for
the evaluation of CNs in the sinus. In this study,
we evaluated the normal structures (dimension and
shape) in the CS with the 3D-CISS MRI and dissection. In addition, the trabeculated venous space of
the sinus was studied.
The anatomy of the CS is still being investigated
and different approaches to the region are given,
which are of significant importance in guiding surgi-
* Department of Anatomy, Gulhane Military Medical Faculty
** Department of Radiology, Gulhane Military Medical Faculty
Reprint request: Yalçın Kırıcı, Department of Anatomy, Gulhane Military
Medical Faculty, Etlik-06018, Ankara, Turkey
E-mail: ykirici@gata.edu.tr
Date submitted: January 08, 2010 • Date accepted: May 17, 2010Volume 52 • Issue 3 Cranial nerves and cavernous sinus • 163
cal intervention. This study presents many different
topographic aspects and measurements of the region.
Material and Methods
This study examined 15 formalin-fixed human cadavers (30 sides) without detectable malformations.
These cadavers were from 5 adults (3 males and 2 females), ranging from 45 to 70 years old (average 56
years) and 10 spontaneously aborted fetuses (6 males
and 4 females), ranging from 22 to 36 weeks of gestation (average 29 weeks). Permission had been obtained
from the local ethics committee of Ankara Maternity
and Health Academic and Research Hospital (Ref.
No:5/16.10.03). In addition, 50 3D-CISS MRI with
normal pituitary gland were chosen for radiological
study. Patients, who were scanned with MRI, were 18
males and 32 females, ranging from 9 to 58 years old
of age (average 28 years).
Following the removal to the calvaria and exposure
of the brain, 15 CS were macroscopically examined.
The sites of entrance for the oculomotor and trochlear nerves into the tentorial notch and roof of the
sinus were identified before starting the dissection. A
longitudinal incision was made throughout the entire
length of the lateral surface of the sinus. The roof and
the upper part of the lateral wall were removed, afterwards the anterior clinoid process was removed to
give a better exposure of the structures of the superior
part of the CS, and the CS region was microdissected
under the stereoscopic microscope (Stemi 2000; Carl
Zeiss, Jena, Germany). After removing the trabeculae
and blood remnants, exposured the entire CS, the routes neural structures could easily be identified.
The important landmarks of the CS are CNs III, IV,
V1 and V2 on the lateral wall of this sinus. Shape, location and dimension of the CS, courses of the nerves
on the lateral wall of the CS wall were investigated. In
addition, the trabeculated venous space of the sinus
was studied.
We incorporated the contrast enhanced 3D-CISS
sequence into the pituitary gland MRI protocol.
Following the T2 and T1-weighted coronal, and T1-
weighted sagittal sequence, we obtained postcontrast
CISS and T1-weighted scans. Postcontrast coronal
3D-CISS images were obtained using the following
parameters: TR/TE 11.7/5.8 ms; 180×180 matrix;
160×180 mm FOV; 0.5 mm slice thickness and two
acquisitions. This sequence added only extra 2-3 minutes to total examination time. The intra cavernous segments of cranial nerves were retrospectively
evaluated in midcoronal postcontrast CISS and T1-
weighted image through the pituitary gland-stalk
junction by one radiologist.
Results
The CS was observed between the petrous apex of
the temporal bone and the superior orbital fissure.
The width of the CS was 6-12 mm (mean 10.08) in
the right side and 5-12 mm (mean 8.42) in the left
side. The CS appeared symmetric in 13 cases, while it
appeared asymmetric in 36 cases. The CS was not measured in one case, because Meckel’s cave lay within
the CS. The CNs III, IV, V1 and V2 were observed over
lateral wall of the CS (Figure 1). The CN III pierced
the roof of the sinus lateral to the posterior clinoid
process and ran in the upper part of the lateral wall.
The CN III travels superolateral to the ICA. The CN III
was identified in all cases on both 3D CISS MRIs and
dissection of the cadavers. However, significant differences were noted in all other CNs between the two
techniques. The CN IV generally runs paralel, inferior
and close to the CN III on the lateral wall of the sinus.
The CN IV (which is much thinner than CN III) courses lateral to the ICA. The CN IV is inferior to the CN
Figure 1. A. Coronal CISS image at the level of the pituitary gland
(star) demonstrates that left 6th cranial nerve (arrow) is close to
the lateral wall of the cavernous sinus at the level of the V2 branch
(arrowhead) of the 5th nerve. B. The schematic drawing of the image.
The pituitary gland (star), internal carotid artery (C), 3rd nerve (III),
4th nerve (IV), 6th nerve (arrow) and, V1 (V1) and V2 branches
(arrowhead) of the 5th nerve164 • September 2010 • Gulhane Med J Kırıcı et al.
III. We also observed two CN IV (4%) lying very close
to V1 for its whole course on the lateral wall of the
CS. The V1 courses inferolateral to the upper portion
of the ICA siphon, and V2 runs in the inferolateral aspect of the CS (Figure 2). In all fetuses, the CNs III, IV,
V1 and V2 travels from medial to lateral, respectively.
Figure 2. A. The structures running lateral wall of the cavernous
sinus in adult cadaver. B. The schematic drawing of the structures.
The internal carotid artery (C), 3rd nerve (III), 4th nerve (IV), 6th
nerve (arrow) and, V1 (V1) and V2 branches (arrowhead) of the 5th
nerve
We found that all CN III were thick and all CN IV
were thin. Also, the CN III and IV were very close in
two cases (Figure 3). Intracavernous segments of CNs
III, IV, V1 and V2 were identified on 3D CISS MRIs in
50 (100%), 49 (98%), 47 (94%) and 41 (82%) of the
50 CS, respectively. In 35 (70%) of 50 patients, all
CNs in the CS were identified (Figure 1). We showed
no apparent trabeculation in the fetal material but
all of the adult sinuses had a few trabeculae running
inferiorly from the medial side of the internal carotid
artery to the floor of the CS (Figure 4).
Figure 3. A. The structures running lateral wall of the cavernous
sinus in fetal cadaver. B. The schematic drawing of the structures.
The internal carotid artery (C), 2nd nerve (II), 3rd nerve (III), 4th nerve
(IV), 6th nerve (arrow) and, V1 (V1) and V2 branches (arrowhead) of
the 5th nerve
Figure 4. The trabeculation structures in the cavernous sinus in adult
cadaver. Trabeculations are showed (arrow)Volume 52 • Issue 3 Cranial nerves and cavernous sinus • 165
Discussion
The CS is of particular importance due to its particular location, contents and relations. Many studies
have been made on this region and its contents, but
the exact nature of the CS has not yet been clearly defined. The anatomy of the CS has been studied both
on the adult and fetal cadaveric studies (2,5,6,11-14).
Many researchers have reported the CS structures on
MRI (7-10) and on CT (15). The contrast-enhanced 3D
CISS sequence has been used to demonstrate various
other CNs detectability rates for CNs III, IV, V1, and
V2 on the CS were 100%, 61%, 92% and 88% respectively (10). We identified intracavernous segments of
CNs III, IV, V1 and V2 on contrast-enhanced 3D CISS
MRI in 50 (100%), 49 (98%), 47 (94%) and 41 (82%)
of the 50 the CS, respectively. These rates are higher
than those of the previous studies (9,10). Cranial nerves III and IV, V1 and VI, and V2 were seen on 75%
of dynamic images each; they were seen, respectively,
on 62%, 30%, and 28% of conventional postcontrast
images (9). The images depicted the intracavernous
segments of CNs III, IV, V1, V2, and VI in 76 (100%),
46 (61%), 70 (92%), 67 (88%), and 73 (96%) of the 76
sinuses, respectively (10).
We found that CN IV sometimes ran close to CN
V1. Tuccar et al. noticed two trochlear nerves (5%)
curving along the lateral wall at a distance from nerve
III (14).
CN III was identified in all cases on both contrastenhanced 3D CISS and contrast-enhanced T1-
weighted MR imaging. However, significant differences were noted in all other CNs between the two imaging techniques (10). MR demonstrates the cranial
nerves effectively. Cranial nerves III, V1, V2, and VI
on the lateral wall of the CS also can be shown with
MR because they are surrounded by low-intensity signal from flowing blood (7). Unfortunately, we were
unable to image cranial nerve IV on the CS, probably
because of its small size and close proximity to cranial nerve III. Many authors have included the V2 component of the trigeminal nerve as a component of the
CS (3,16). Most authors have considered the V2 as a
component of the CS (4,16). Korogi et al. reported
that V1 and V2 were seen on 75% of dynamic MR
images but on only 28% of conventional post contrasted MRI (9). Yagi et al. reported that V2 was seen
in the CS in 88% of the patients (10). The finding of
this author is similar to our results (82%). The presence of the trabeculae of the adult sinuses have been
demonstrated in many studies (3,4,12). In the literature, we found very little to work with the fetus. The
trabeculae were virtually non-existent in fetal materials by Bedford (1). The result of this is similar to
our present study. Many researchers have expressed
that 3D-CISS MRI is more useful than other methods
(10,17,18). This imaging technique is useful for the
differentiation between paraclinoid and cavernous
sinus aneurysms. The CS has a very complex structure and important vascular and neural contents. It
is extremely difficult for the surgeon to reach and
operate on the sinus. Understanding of the microsurgical anatomy of the region is essential for the surgeon operating in and around the CS for neoplastic
and vascular lesions. This study and other anatomic
and morphometric studies of the region performed
on cadavers and radiological materials will provide
a great benefit in minimizing the rate of complications which may occur during the resection of tumors
of the cavernous sinus and the hypophysis, or other
surgical procedures at this region