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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3643_Библиотеки_им_академика_М_И_Перельмана.pdf
20
e
Fig. 1.4 (continued)
H. Muresian
21
Fig. 1.5 Variations of the carotid bifurcation. Panel ( a ), hypoplastic
ICA. The caliber of the ICA is evidently more reduced as compared with
the ECA (ICA is about half of the ECA diameter). Note also that the
carotid bulb is not apparent. A long atherosclerotic plaque occupies most
of the carotid bifurcation and of the proximal segment of the
ICA. Intraoperative aspect of left carotid bifurcation and of the excised
plaque. Panel ( b ), hypoplastic, slender ICA terminating by giving off the
ophthalmic artery (Opht). Panel ( c ), hypoplastic CCA. The CCA has
almost the same caliber as the ICA. The right CCA, ICA, is of normal
diameter, and there is an important participation of the right carotid system to the vascularization of the brain, with ACA and MCA on the left
side fed from the right ICA. Panel ( d ), absence of the carotid bulb. There
is no carotid bulb, and the carotid bifurcation appears as a double-
barrelled gun with the ICA and ECA of almost even caliber. Panel ( e ),
inverted carotid bifurcation. Intraoperative aspect of the right carotid
bifurcation. The ECA is anterolateral, while the ICA is posteromedial.
Note that in this case also, there is no defi nite carotid bulb. Panel ( f ),
inverted carotid bifurcation: sagittally disposed ICA and ECA. The ECA
is superposed over the ICA. STA superior thyroid artery. Mobilization of
the carotid bifurcation allows a good exposure of the more deeply situated ICA. Panel ( g ), bilaterally inverted carotid bifurcations. On both
sides, the ICAs are located posterior and medial. The superior thyroid
artery ( STA ) crosses the bifurcation. Panel ( h ), kinking of the CCA and
lower bifurcation, approximately at the level of C
4
–C 5 . Panel ( i ), sagittal
bifurcation with ECA anterior and ICA posterior. The superior laryngeal
nerve (SLN) passes between the ICA and the ECA
ICA
ICA
CCA
ECA
ICA
CCA
CCA
ICA
ICA
Opht
ICA
a
b
1 The Cerebral Circulation
22
ICA
CCA
ICA
CCA
CCA
ICA
ECA
CCA
ICA
c
Fig. 1.5 (continued)
H. Muresian
23
CCA
CCA
ICA
ECA
ECA
ICA
CCA
ECA
ICA
IJV
XII
d
e
Fig. 1.5 (continued)
1 The Cerebral Circulation
24
CCA
ICA
ECA
STA
ICA
CCA
ECA
CCA
ECA
ICA
STA
CCA
ECA
ICA
f
g
Fig. 1.5 (continued)
H. Muresian
25
CCA
ICA
ECA
ICA
ECA
CCA
SLN
h
i
Fig. 1.5 (continued)
1 The Cerebral Circulation
26
X
XII
IX
XI
VII
JF
CF
SMF
Styl
C
1
C
2
C
3
D
Sym
X
Ling. Mm.
OH-i
OH-s
ST
TH
SH
GH
a
b
Fig. 1.6 Anatomical relationships at the cranial base. Panel ( a ), a sche-
matic reconstruction and demonstration of the main structures at the
cranial base. The ICA is depicted in red, while the IJV in blue. The ICA
enters the skull at the level of the carotid foramen ( CF ) accompanied by
the sympathetic fi bers (not shown). The IJV exits the skull at the level
of the jugular foramen ( JF ) sharing the same orifi ce with the glossopha-
ryngeal ( IX ), vagus ( X ), and the accessory nerve ( XI ). Nerves IX and X
are pre-jugular, while XI is retro-jugular in most of the cases. The hypoglossal nerve ( XII ) courses the anterior condylar (hypoglossal) canal
and passes posterior to the ICA, IX and X nerves, descending over the
ICA down to the level of the bifurcation which it eventually crosses
from lateral to medial. The facial nerve ( VII ) exits the stylomastoid
foramen ( SMF ) being separated from the ICA by the styloid process
( Styl ) and muscles. Panel ( b ), schematic drawing of the hypoglossal
nerve ( XII ) and of the cervical (hypoglossal ansa). The carotid vessels
are colored red and the IJV in blue. The hypoglossal nerve is colored in
white and the cervical anterior rami in yellow. The branches of the XII
nerve are D for dura mater, SYM communicating with the sympathetic
trunk, X communicating branch to the superior vagal ganglion. The ter-
minal branches are for the intrinsic lingual muscles (Ling. Mm.). The
superior root of the cervical ansa originates in the ventral ramus C1,
while the inferior root, from C2 and C2. Branches from the ansa innervate the hyoid muscles: OHi omohyoid inferior belly, OHs omohyoid
superior belly, ST sternothyroid, SH sternohyoid, TH thyrohyoid, and
GH geniohyoid. The ansa courses over the IJV although numerous
variations are encountered
H. Muresian
27
Fig. 1.7 The natural asymmetry of the internal jugular veins. The IJVs
are frequently found to be asymmetric, refl ecting the differences
between the dural transverse and sigmoid sinuses. The jugular foramina
(lodging the superior bulb of the IJVs) are also dissimilar. This discrepancy has clinical relevance in case of IJV thrombosis (if the dominant
IJV is occluded), central vein catheterization, and, not least, during surgery. At times, the superior IJV can be of small caliber, but after receiving larger tributaries in the upper neck (retromandibular vein,
thyro-linguo-facial trunk), it becomes conspicuous. The tract of the IJV
can also depict variations of surgical relevance (see Fig.
1.8 )
1 The Cerebral Circulation
28
ECA
ICA
CCA
IJV
Thyr.
Fig. 1.8 Further anatomical
variations of the internal jugular
veins. The IJV crosses the carotid
bifurcation from lateral to
medial. The IJV becomes
anterior and medial in position
relative to the CCA. This
variation has clinical relevance
for two reasons: First, the IJV
must be protected during surgical
exposure of the CCA, as the vein
crosses the artery. Additionally,
the anteriorly coursing IJV can
be mistaken for a collateral
branch and inadvertently ligated.
Second, there would be a diffi cult
catheterization of the IJV if it lies
anterior and medial to the CCA
or the CCA can be punctured
instead of the vein. For other
variations, see Fig.
1.10 b, c
H. Muresian
29
X
ECA
ICA
XI
XII
Dig
SH
VII
Mast
SubM
Parot
Fig. 1.9 The extracranial portion of the facial nerve and anatomical
relationships at cranial base. This aspect is also discussed with the
exposure of the ICA high in the neck. Intraoperative aspect. Right side.
Preauricular extension of the neck incision. The carotid bifurcation is
exposed ( ICA and ECA ). The vagus ( X ), accessory ( XI ), and hypoglos-
sal ( XII ) nerves are exposed and circled with elastic tapes. The posterior
belly of the digastric muscle ( DIG ) and the stylohyoid muscle ( SH ) are
dissected and gently mobilized (in this way, cutting of these two mus-
cles is not necessary). The facial nerve (VII – indicated by arrow) is
exposed upon its exit from the stylomastoid foramen, deep to the mastoid process ( Mast ). The facial nerve crosses the retromandibular space
to enter the parotid gland ( Pa ro t ). The submandibular salivary gland
( SubM ) is also visible. The main trunk of the facial nerve can be readily
identifi ed and protected. It will eventually divide in the very substance
of the parotid gland
1 The Cerebral Circulation