Atlas of clinical and surgical orbital anatomy

253 Pages·2011·160.39 MB·English

by  Dutton, Jonathan J.

1
C H A P T E R
Cavernous Sinus
The cavernous sinus (CS) is a very important intracranial, channels develop from these to form the superior cerebral,
extradural anatomic region that contains many structures middle cerebral, and inferior cerebral veins. Most of each car-
vital for visual function. Numerous disease processes along dinal vein atrophies, except for a segment of each vein in the
the skull base and in the cavernous sinus can have a major region of the trigeminal ganglion which becomes the fore-
impact on vision or on ocular motility. Yet, this anatomic runner of the cavernous sinus, and another segment more
structure remains quite unfamiliar to most ophthalmolo- posteriorly which becomes the internal jugular vein.
gists and orbital surgeons. It serves as a critical venous drain- By the 8 mm (36-day) embryonic stage the primitive
age route for both the orbit and the cranial base.16 It also supraorbital vein arises in the superficial tissues dorsal to
transmits arterial and neural structures from the intracranial the developing eye. It initially drains backward between
compartment into the orbital apex. the trigeminal and trochlear nerves into an anterior dural
The term cavernous sinus has been in use for 275 years, plexus, which will become the superior sagittal and trans-
ever since Jacobus Winslow proposed it in 1734, reflecting verse sinuses. A new anastomosis appears from the supraor-
his concept of a single trabeculated venous cavern similar to bital vein that diverts blood over the incipient annulus of
the corpus cavernosus of the penis.42 His concept was incor- Zinn into the venous plexus of the future cavernous sinus.
rect, yet the term has persisted in the medical literature. It By the 11 mm (40-day) stage the initial formation of the
is clear from modern studies that the CS is neither cavern- chondrocranium is seen around the anterior notochord, sur-
ous nor is it an intradual sinus, but rather it is a plexus or rounded by primitive mesenchyme. At the 14.5 mm (44-day)
network of extremely thin-walled veins associated with adi- stage chondrification begins in the future greater and lesser
pose tissue. Parkinson27 emphasized the inappropriateness wings of the sphenoid bone and in the dorsum sellae.38 At the
of this term on anatomical grounds. Hashimoto12 recom- same time the trigeminal (gasserian) ganglion forms, along
mended following Parkinson’s lead in using the term “lat- with its three major peripheral divisions. In the 23–25 mm
eral sellar compartment” (LSC)26 for this structure in its (50-day) embryo the hypophysis and diaphragma sellae
broader sense, and restricting the term “cavernous sinus” to become differentiated in the region of the developing cavern-
the more limited venous pathways within the LSC. In 2003, ous sinus. The lateral wall of the cavernous sinus is partially
Tobenas-Dujardin et al.38 proposed the term “inter-periosto- developed as a meningeal layer enclosing several cranial
dural space” which they believed would better reflect the real nerves, but the medial wall is not yet formed. By the 31 mm
anatomic pattern. However, this has not gained widespread (56-day) embryo a well developed cavernous sinus with a
usage. While the term lateral sellar compartment might definitive cavernous carotid artery and sympathetic plexus is
be anatomically more accurate, the term cavernous sinus present, containing two venous compartments, one on each
remains in widespread use, especially outside the specialty side of the midline. Cranial nerves III, IV, VI, and the three
of neurosurgery. Furthermore, the International Federation branches of the trigeminal nerve are all differentiated and
of Associations of Anatomists (IFAA) did not adopt an alter- located in their approximate adult relationships.
native terminology for the cavernous sinus in its most recent In the 70–90 mm (13–15-week) fetal stage small ossifica-
edition of Terminologia Anatomica 1998.37 Therefore, for tion centers are seen in the body, greater wings, and lesser
the present chapter we will use the classic terminology, using wings of the sphenoid bone. At the same time ossification
the term cavernous sinus for both the neural and venous is beginning in the cartilaginous petrous portion of the tem-
components. poral bone.12 The primordium of the dura mater and suba-
rachnoid membrane are already seen lining the area of the
cavernous sinus on either side of the body of the sphenoid.
Embryology
The pituitary gland is lined by an inner capsule and an outer
meningeal layer, forming the definitive medial wall of the cav-
The early development of the cavernous sinus is complex. ernous sinus. Many small irregularly shaped lumens develop
Our current understanding is based on the seminal studies within the mesenchyme of the cavernous sinus region, and
of Padget23 as well as more recent works.9,18 By the 3 mm these venous channels gradually enlarge with further fetal
(28-day) embryonic stage two longitudinal venous channels, development. These channels meander and intertwine, and
the anterior cardinal veins, are laid down and extend along are lined only by an endothelial layer with no smooth mus-
the ventrolateral surface of the developing brain, on the cle. These venous channels communicate with other venous
medial side of the cranial nerve roots. Three pairs of venous channels. Posteriorly they drain to the basilar venous sinus
1
1 Cavernous Sinus
and then to the jugular bulb; posteroinferiorly with the infe- second month of embryonic development, Rathke’s pouch
rior petrosal sinus and then into the pterygoid venous plexus wraps around the infundibulum, and differentiates into
through the foramen lacerum; and posterosuperiorly with the anterior lobe, or adenohypophysis, of the pituitary gland.
the superior petrosal sinus and then into the sigmoid sinus. The infundibulum differentiates into the pituitary stalk
The cavernous sinuses on each side communicate with each and the posterior lobe, or neurohypophysis, of the gland.
other through one or more intercavernous sinuses situated Ultimately, the two portions grow together to form the defin-
between the dural layers, below the pituitary gland. itive pituitary gland. As the cavernous sinus continues to
The gasserian ganglion is situated posterior to the develop- develop, the enclosing dural and endosteal sheaths conform
ing cavernous sinus on either side, over the tip of the petrous to the body of the pituitary gland to form the medial walls of
bone and lateral to the dorsum sellae. The three branches the sinus, as well as the roof and the diaphragma sellae that
of the trigeminal nerve run forward from the gasserian gan- separates the gland from the optic chiasm.
glion. The ophthalmic branch (V1) and the maxillary branch
(V2) run anteriorly in the lateral wall of the cavernous sinus, Anatomy of the adult cavernous sinus
within the loose inner connective tissue endosteal layer.
The oculomotor (III) and trochlear (IV) nerves enter the
The cavernous sinus is a paired structure located near the cen-
cavernous sinus near the posterior clinoid process and also
ter of the head on either side of the sella turcica and pituitary
run anteriorly within the lateral wall to the superior orbital
gland, and posterior to the sphenoid sinus. It is defined as
fissure. The abducens nerve (VI) runs through the basilar
the space between the superior orbital fissure anteriorly, the
venous plexus and then enters the cavernous sinus; it courses
posterior petroclinoid fold and clivus dura mater posteriorly,
forward within the venous channels of the sinus just lateral
and the inner surface of the middle cranial fossa inferolater-
to the internal carotid artery, and passes into the superior
ally, where the meningeal and periosteal layers of the dura
orbital fissure. Third order sympathetic nerve fibers enter the
meet and fuse.12 It measures 8 to 10 mm in antero-p osterior
cranium through the foramen lacerum and become associ-
length, and 5 to 7 mm in height.17 The lateral wall of the
ated with these cranial nerves and vascular elements. The
sinus is more complex, composed of a superficial (outer)
internal carotid artery (ICA) enters the skull base through the
meningeal layer of dura, and a deeper (inner) layer contain-
future carotid canal. It then penetrates the floor of the cavern-
ing several cranial nerves. The cavernous sinus is therefore
ous sinus inferolateral to the cartilaginous sphenoid bone.
surrounded by this dural envelope, and contains a venous
As the sella turcica develops, the ICA gradually assumes the
plexus, a short segment of the internal carotid artery, and the
S-shaped configuration seen in the adult.
abducens nerve (VI). The venous plexus is fed by veins drain-
During the 128–183 mm (18–23-week) stage of fetal
ing from the face, orbit, nasopharynx, cerebrum, cerebellum,
development further ossification occurs in the sphenoid bone
and brainstem. It empties into the basilar venous system as
as it expands in the anterolateral directions. By the 230 mm
well as into the petrosal venous sinuses. Within the lateral
(28-week) fetal stage a thick periosteum is seen over the
wall of the cavernous sinus run the oculomotor (III) and tro-
surface of sphenoid bone. Dura is distinguishable along the
chlear (IV) nerves, and the first two divisions (V1 and V2)
lateral wall of the cavernous sinus as a definite meningeal
of the trigemimal nerve. These latter structures, therefore,
layer separate from the overlying arachnoid membrane and
are not technically within the cavernous sinus, but are only
the inner endosteal layer that is continuous with the perios-
associated with its lateral wall.
teum of the sphenoid bone. Superiorly the meningeal layer
folds to contribute to the diaphragma sellae over the pitu-
The bony boundaries of the cavernous sinus
itary gland. Within the mesenchyme of the cavernous sinus
large well-defined venous lumens are now present. The mes- The cavernous sinus lies within the middle cranial base. The
enchymal tissue between lumens gradually thins to become latter is bounded anteriorly and laterally by the greater wing
membranes separating the individual vascular chan- of the sphenoid bone, and posteriorly by the clivus and the
nels. Small arteries and autonomic nerve fascicles are now anterior aspect of the petrous temporal bone. The body of
apparent within these membranous walls. the sphenoid bone makes up the floor of the middle cra-
In the 150–200 mm (21–25-week) fetal stage, blood flow nial fossa and contains the sella turcica, situated between
through the cavernous sinus rapidly increases, probably due the anterior and posterior clinoid processes. The sella tur-
to alterations in neighboring venous pathways. Nerve fasci- cica consists of the tuberculum sellae anteriorly between the
cles become surrounded by collagen fibers forming sheaths. cranial openings of the optic canal. Behind it is the pituitary
Simultaneous with formation of the cavernous sinus is fossa, and the posterior extent of the sella is bounded by the
development of the pituitary gland, which forms an important dorsum sellae.
element adjacent to and above the bilateral cavernous sinuses. The cavernous sinus lies lateral to the body of the sphe-
During the 2–3 mm (21-day) embryonic stage the gland noid bone, and over the top of the petrous apex of the tem-
originates from two distinct ectodermal tissues. A finger-like poral bone. The posterior portion of the sinus rests against
protrusion, called Rathke’s pouch, grows upward as a dorsal the lateral edge of the dorsum sellae, and its anterior portion
evagination from the stomodeum, or mouth, just anterior extends to the superior orbital fissure beneath the anterior
to the bucco-pharyngeal membrane. It differentiates into clinoid process and the lesser wing of the sphenoid. Laterally
glandular epithelium characteristic of endocrine glands. The the sinus extends to the junction of the sphenoid body and
infundibulum is a ventral evagination from the floor of the the greater wing, but does not include the foramen rotun-
third ventricle of the diencephalon just caudal to the develop- dum, foramen ovale, and the foramen spinosum. The latter
ing optic chiasm from the same tissue.1 It differentiates into three foramina are located just lateral to the lateral wall of
the exocrine component of the pituitary gland. During the the cavernous sinus. Inferiorly, the sinus extends to the lower
2
Anatomy of the Adult Cavernous Sinus
border of the carotid sulcus, a groove along the lateral aspect by a meningeal layer continuous with the diaphragma sellae
of the sphenoid body in which lies the intracavernous por- above. Controversy exists as to the existence of the endosteal
tion of the internal carotid artery. layer in this region. Songtao et al.34 recently reported a dis-
Lateral to the anterior clinoid process and extending supe- tinct inner layer (lamina propria), between the dural layer
rolaterally beneath the lesser sphenoid wing is the superior and the pituitary gland, that also contributed to the medial
orbital fissure (SOF) which marks the anterior most extent wall in two-thirds of specimens studied.
of the cavernous sinus. It opens into the orbital apex, and The roof of the cavernous sinus is formed by dural folds
transmits cranial nerves III, IV, VI, and branches of the oph- extending from the petrous apex to the anterior clinoid
thalmic division of the trigeminal nerve (V1). Just posterior process (anterior petroclinoid ligament), from the petrous
and slightly inferior to the SOF, in the floor of the middle apex to the posterior clinoid process (posterior petroclinoid
cranial fossa, is the foramen rotundum, lateral to the sphe- ligament), and between the anterior and posterior clinoid
noid sinus. It lies lateral to the cavernous sinus and trans- processes (interclinoid ligament). The diaphragma sellae
mits the maxillary division (V2) of the trigeminal nerve completes the roof. The latter is composed of two layers, an
into the pterygopalatine fossa. The foramen ovale lies about outer superficial meningeal layer, and a deep layer of endos-
1 cm posterior and lateral to the foramen rotundum and car- teum.4 These layers form the dura, and are continuous ante-
ries the mandibular branch (V3) of the trigeminal nerve into riorly with dura that covers the planum sphenoidale over the
the infratemporal fossa. The foramen lacerum is an irregular body of the sphenoid bone, and posteriorly with the dura
opening posteromedial to the f. ovale and transmits the inter- that covers the dorsum sellae and clivus. The meningeal layer
nal jugular vein as it exits the cranium. In the petrous apex, is also continuous with the outer lateral wall of the cavern-
near its junction with the sphenoid and occipital bones, lies ous sinus, the upper dural ring of the carotid artery, and the
the carotid canal which continues anteromedially to open optic sheath. 6,15,35,39,41 The endosteal layer is continuous with
into the f. lacerum. the inner lateral wall of the cavernous sinus, the periosteum
Anteriorly, the anterior clinoid process is a rounded projec- of the middle cranial fossa, the lower dural ring of the carotid
tion extending from the lesser wing of the sphenoid bone. It artery, and periorbita of the orbital cavity. The junction of the
extends above the anterior roof of the cavernous sinus, and superior and medial walls of the cavernous forms the medial
forms the lateral wall of the optic canal. Inferomedially, the edge of the diaphragma over the pituitary gland. In the cen-
lesser sphenoid wing and clinoid process are joined by the ter of the diaphragma sellae is an opening through which
optic strut to the body of the sphenoid bone. The strut sepa- the pituitary stalk passes. The size of this opening varies from
rates the optic canal from the superior orbital fissure. It also <4 mm to >8 mm, and Campero et al.4 proposed the result-
forms the floor of the optic canal and the anterior roof of the ing differences in resistance could play a role in determining
cavernous sinus. The posterior face of the optic strut has a the direction of growth of pituitary adenomas.
depression to accommodate the anterior bend of the intra- The lateral wall of the cavernous sinus is the most com-
cavernous carotid artery beneath the anterior clinoid process. plex. Posteriorly it forms the medial edge of Meckel’s cave
along the petrous apex, and extends anteriorly to the lat-
eral edge of the superior orbital fissure. The vertical extent
The dural folds
of the lateral wall is from the petroclinoid dural fold supe-
The cavernous sinus has four walls that mark its boundar- riorly to the carotid sulcus inferiorly along the body of the
ies and delimit its anatomic extent. Dural folds help define sphenoid bone.5 The lateral wall is bounded by a multilay-
boundaries of the cavernous sinus and provide important ered membrane consisting of several inner endosteal layers
landmarks for surgery in this anatomic location. Anteriorly, that are continuous with the endosteum of the sinus floor
dural structures extend from the upper and lower portions where it adheres to the sphenoid bone, and an outer men-
of the anterior clinoid process and surround the internal ingeal layer that also covers the medial side of the temporal
carotid artery, forming upper and lower rings in the region lobe of the brain.43,44 From superior to inferior, cranial nerves
where the artery forms a sharp anterior bend. The segment III, IV, V1 and V2 lie within the inner endosteal layers of the
of the carotid artery that lies between the upper and lower lateral wall. These nerves, therefore, are anatomically sepa-
dural rings is the clinoid portion and lies within the anterior- rated from the venous channels that form the vascular com-
most portion of the cavernous sinus. The floor of the sinus is ponent of the cavernous sinus. Marinkovic et al.19 reported
composed of endosteum (periosteum) which also covers the the inner layers of the lateral wall to consist of three layers of
body of the sphenoid bone, and is continuous with perios- endosteum in the human fetus; an outer layer of dense con-
teum of the middle cranial fossa. nective tissue containing the trochlear nerve (IV), and a mid-
The medial wall of the sinus is divided into a lower sphe- dle layer containing loose connective tissue in which runs
noidal portion and an upper sellar portion. The lower the oculomotor nerve (III), as well as the ophthalmic (V1)
sphenoidal part of the medial wall overlies the body of and maxillary (V2) divisions of the trigeminal nerve. They
the sphenoid bone and a horizontal groove for the carotid reported an inner layer of endosteum running in the venous
artery, the carotid sulcus. It is covered by endosteum con- channels containing the abducens nerve (VI). Umansky et
tinuous with periosteum of the floor of the middle cranial al.40,41 found that in the adult the oculomotor, trochlear, and
fossa. The bone separating the sphenoid sinus from the cav- trigeminal nerves were included within a single irregular
ernous sinus is very thin in this region, less than 0.5 mm in deep lateral wall layer. This possibly represents the fused sec-
most individuals,17 and may even have spontaneous dehis- ond and third layers of Marinkovic et al.19
cences so that the sphenoid sinus may be separated from The broad posterior dural wall of the cavernous sinus
the cavernous sinus only by layers of endosteum and sinus extends from the posterior clinoid process and upper clivus
mucosa. The upper sellar portion of the medial wall is lined medially, to the petrous apex laterally along the upper edge
3
1 Cavernous Sinus
of the petroclival fissure. The upper edge of the posterior wall the anterior clinoid process, the trochlear nerve moves
extends to the posterior petroclinoid dural fold, which passes upward along the lateral surface of the oculomotor nerve
from the petrous apex to the posterior clinoid process. The and crosses over it to enter the orbit through the superior
lateral edge of the posterior wall is situated just medial to orbital fissure above the annulus of Zinn. It continues medi-
the opening of Meckel’s cave, which contains the trigeminal ally in the superior orbit to provide motor innervation to the
nerve and ganglion. Just lateral to the dorsum sellae, the pos- superior oblique muscle.
terior cavernous sinus opens into the basilar sinus, and com-
The abducens nerve
municates with the superior and inferior petrosal sinuses.
The intercavernous sinuses that connect the cavernous The abducens nerve (VI) leaves the pontomedullary sulcus
sinuses on each side pass between the dural and endosteal and courses anterosuperiorly in the prepontine cistern. It
layers along the floor of the sella turcica, between the pitu- pierces dura overlying the basilar venous plexus on the clivus
itary gland and the body of the sphenoid bone. and enters a dural channel called Dorello’s canal. The nerve
continues superiorly and medially over the clivus and passes
Nerves of the cavernous sinus beneath the posterior petroclinoid ligament where it enters
the posterior cavernous sinus. It then passes around the lateral
Five cranial nerves or branches pass through the cavern-
side of the intracavernous carotid artery, within the endosteal
ous sinus or travel in its walls en route from their origin in
layer that surrounds it. As the abducens nerve passes forward
the brain stem to their orbital and extraorbital targets. The
it is joined by sympathetic fibers from the carotid autonomic
oculomotor, trochlear, and the first two divisions of the
plexus.29 It then continues forward between and medial to
trigeminal nerve lie in the lateral wall of the sinus between
the oculomotor and ophthalmic nerves (V1). Anteriorly, the
the superficial dural and deep reticular endosteal layers. The
abducens nerve gradually assumes a more inferior position
abducens nerve runs within the sinus in a reticular layer that
relative to the ophthalmic nerve, so that as it enters the supe-
may be separate or part of that investing the ICA. In addi-
rior orbital fissure it lies medial and inferior to V1. Near the
tion, a plexus of sympathetic nerve fibers accompanies the
SOF the abducens nerve divides into as many as five separate
carotid artery and several nerve branches along their course
rootlets.11 These pass through the annulus of Zinn to provide
through the sinus.13
motor innervation to the lateral rectus muscle.
The oculomotor nerve
The trigeminal nerve
The oculomotor nerve (III) exits the brain and runs in the
The trigeminal nerve (V) is the largest cranial nerve, and
interpeduncular fossa between the superior cerebellar and
arises from the lateral pons. It is a mixed nerve providing
posterior cerebral arteries. It pierces the roof of the cavernous
sensory innervation, proprioceptive, and nociceptive infor-
sinus posteriorly through the center of the oculomotor trig-
mation from the head and face, as well as motor function to
one, lateral to the posterior clinoid process. As it penetrates
the muscles of mastication. A small motor and larger sensory
the lateral portion of the posterior petroclinoid ligament it
root run anterolaterally, superior to the petrous apex. These
acquires its own dural sheath. The nerve continues anteri-
roots enter a subarachnoid and dural outpouching known
orly within the deep endosteal layer of the lateral sinus wall.
as Meckel’s cave located in a small depression on the apex of
The oculomotor nerve continues forward, passes beneath the
the petrous portion of the temporal bone, just at the poste-
base of the anterior clinoid process, and branches into its
rior edge of the cavernous sinus. The sensory nerve fascicles
superior and inferior divisions just before passing through
are joined by preganglionic parasympathetic fibers from the
the superior orbital fissure into the orbital apex. As it runs
greater superficial petrosal nerve, and gradually coalesce to
through the SOF, the oculomotor nerve is covered by a
form the gasserian ganglion. The motor root passes beneath
perineurium and a thin connective tissue sheath that blends
the ganglion and exits the cranium through the foramen
with the superolateral margin of the annulus of Zinn. The
ovale where it immediately joins the mandibular branch of
nerve carries motor fibers to the superior rectus and levator
the trigeminal nerve (V3) en route to muscles of mastication.
palpebrae superioris muscles (superior division), and to the
The gasserian ganglion also receives sympathetic filaments
medial and inferior rectus muscles, and the inferior oblique
from the carotid plexus, and gives off sensory fibers to the
muscles (inferior division). It also carries preganglionic para-
tentorium and dura of the middle cranial fossa.
sympathetic visceral efferent fibers to the ciliary ganglion
Three nerve trunks emerge anteriorly from the gasserian
(see Chapter 4).
ganglion; the ophthalmic, maxillary, and mandibular nerves,
each exiting the cranium via a separate foramen or fissure.
The trochlear nerve
The ophthalmic nerve (V1, or first division of the trigeminal
The trochlear nerve (IV) exits the dorsal surface of the nerve) is the smallest of the three trunks and contains only
midbrain just below the inferior colliculus in the cerebello- sensory fibers. It carries sensory innervation from the cor-
mesencephalic fissure. It curves anteriorly in the ambient nea, ciliary body and iris, the lacrimal gland, the conjunctiva,
cistern around the lateral aspect of the tectum and tegmen- and from the skin of the upper eyelid, forehead, scalp and
tum, and proceeds in an anterolateral and slightly inferior nose. Tracing this branch forward, it arises from the upper
direction to penetrate the tentorium. The nerve runs forward part of the gasserian ganglion as a short flattened band. It
following the edge of the anterior petroclinoid ligament and enters the cavernous sinus posteriorly where it passes for-
pierces the lower part of the posterior wall of the cavern- ward within the deep endosteal layer of the lateral cavernous
ous sinus posterolateral to the oculomotor nerve. The tro- sinus wall, below the oculomotor and abducens nerves. Near
chlear nerve courses just inferior to the third nerve within the the anterior end of the cavernous sinus the ophthalmic nerve
endosteal layer of the lateral sinus wall. As it passes beneath gives off a small recurrent branch which passes between the
4
Anatomy of the Adult Cavernous Sinus
layers of the tentorium. The main trunk then divides into runs a complex course from the bifurcation of the common
three branches, the frontal, lacrimal, and nasociliary nerves carotid artery in the neck, into the cranium, and then takes
that pass into the orbit through the superior orbital fissure. a serpinginous path through the cranial base and cavernous
The nasociliary nerve enters the orbit through the oculomo- sinus before terminating at the anterior and middle cere-
tor foramen of the annulus of Zinn, into the intraconal com- bral arteries. In 1938, Fischer7 published a seminal paper in
partment between the superior and inferior branches of the which he described five segments of the carotid artery based
oculomotor nerve (see Chapter 4). The frontal and lacrimal on its angiographic course and its displacement by various
nerves enter the orbit above the annulus into the superior intracranial anomalies. While this nomenclature became
extraconal orbital space. Occasionally the lacrimal nerve widely used, it did not relate the segments of the ICA to spe-
is absent, and sensory fibers reach the lacrimal gland and cific anatomic compartments and it numbered the segments
superolateral eyelid via the zygomaticotemporal branch of in the opposite direction of blood flow. In recent decades,
the maxillary nerve (V2). Sympathetic fibers from the cav- many attempts have been made to correct these inaccuracies,
ernous plexus accompany the ophthalmic nerve into the but they often introduced unnecessary complexity. In 1996,
orbital apex. Bouthillier et al.3 proposed a classification that described seg-
The maxillary nerve (V2) carries sensory information from ments of the ICA with a numerical scale following the direc-
the lower eyelid and cheek, the upper lip, the gums above the tion of blood flow, and identified segments according to
incisor and canine teeth, the nasal mucosa, palate and roof of surrounding anatomy and the compartments through which
the pharynx, and from the maxillary, ethmoid, and sphenoid the artery travels. These segments were as follows: cervical,
sinuses. Tracing it forward, it arises from the central portion petrous, lacerum-cavernous, clinoid, ophthalmic, and com-
of the gasserian ganglion and enters the cavernous sinus municating segments. More recently, Ziyal et al.46 proposed
where it runs for a short distance within the lateral wall. It a more simplified classification by omitting the lacerum seg-
exits the inferior sinus and penetrates the floor of the middle ment and combining the ophthalmic and communicating
cranial fossa through the foramen rotundum, which is situ- segments. While a final classification system is still a matter
ated on a line between the superior orbital fissure and the of debate, for the present chapter we have chosen to use a
foramen ovale. The nerve then crosses the pterygopalatine more simplified modified anatomic description.
fossa, passes over the back of the maxillary bone, and enters The cervical segment (C1) of the ICA begins at the com-
the orbit though the inferior orbital fissure to become the mon carotid artery bifurcation in the neck. It runs superiorly
infraorbital nerve. The maxillary nerve gives off a number of within the carotid sheath, in company with the internal jug-
branches. The middle meningeal nerve is given off immedi- ular vein, the vagus nerve, a venous plexus, and sympathetic
ately after the maxillary nerve leaves the gasserian ganglion; nerves. Where the ICA enters the carotid canal, this sheath
it accompanies the middle meningeal artery and supplies the divides into an inner layer that becomes periosteum of the
dura mater of the middle cranial fossa. Within the pterygo- bony canal, and an outer layer that becomes periosteum of
palatine fossa the maxillary nerve gives off two sphenopal- the external cranial surface.
atine branches that course to the sphenopalatine ganglion. The petrous segment (C2) of the ICA begins at the
The latter is a sympathetic ganglion receiving sensory, motor entrance of the exocranial osteum of the carotid canal on
and sympathetic fibers distributed to the region of the phar- the ventral surface of the petrous portion of the temporal
ynx, palate, and mouth. The alveolar branches emerge just bone. It ascends vertically within the periosteum of the canal
before the maxillary nerve enters the inferior orbital fissure. for a distance of about 10 mm and then turns anteromedi-
They supply the upper gums and adjacent portions of the ally as a horizontal segment for about 20 mm anterior to the
oral mucosa, nasal mucosa, and the maxillary sinus, and cochlea. Inside the carotid canal the ICA is surrounded by
communicate with the alveolar nerves to supply the upper a venous plexus extension from the cavernous sinus, and a
teeth. network of sympathetic fibers from the cervical sympathetic
The mandibular nerve (V3) does not pass through the trunk. The ICA may give off one or two small inconsistent
cavernous sinus but exits the cranium lateral to the sinus branches from these initial segments. The caroticotympanic
through the foramen ovale. It carries sensory information branch arises from the vertical segment and enters the tym-
from the lower lip, the lower gums and teeth, the chin and panic cavity through a small foramen in the canal. The vid-
jaw, and parts of the external ear. The motor branches of the ian branch (artery of the pterygoid canal) may sometimes
trigeminal nerve are distributed in the mandibular nerve and arise from the horizontal segment and provides an anasto-
innervate the masseter, temporalis, medial and lateral ptery- motic connection with the external carotid system through
goid muscles, as well as the tensor veli palatini, mylohyoid, the pterygopalatine fossa. The petrous segment of the ICA
anterior belly of the digastric, and tensor tympani muscles. ends at the distal (intracranial) osteum of the carotid canal
Numerous small sympathetic nerve fibers surrounding the as it opens into the canalicular portion of the foramen lace-
ICA coalesce within the cavernous sinus into discreet fiber rum (see Chapter 2).
bundles. These leave the ICA and join the abducens nerve The lacerum segment (C3) is not recognized in all classi-
for a few millimeters before crossing over to the ophthalmic fication schemes of the ICA. When recognized, the lacerum
nerve. They accompany the ophthalmic nerve into the orbit segment begins at the cranial end of the carotid canal on
(see Chapter 4). the posterior side of the cannalicular portion of the foramen
lacerum. The artery passes across (over) the foramen lace-
rum and then turns vertically along the body of the sphenoid
Internal carotid artery and its branches
bone just lateral to the dorsum sellae. At this point the ICA
The internal carotid artery (ICA) is the only artery in the lays inferomedial to the posterior surface of the gasserian
body that travels completely through a venous structure. It ganglion within Meckel’s cave. As it ascends onto the
5
1 Cavernous Sinus
sphenoid bone, the vessel passes beneath a connective tis- the OA may enter the orbit through the superior orbital fis-
sue band, the petrolingual ligament. This is an extension of sure instead of the optic canal.
periosteum bridging between the petrous apex posteriorly and The communicating segment (C7) of the ICA begins just
the lingual process of the sphenoid bone at the anterior edge before the origin of the posterior communicating artery and
of the foramen lacerum. The transition between the lacerum ends at the bifurcation into the anterior and middle cerebral
and cavernous segments occurs at the upper end of this liga- arteries. In some classification schemes the ophthalmic and
ment. As with other segments of the ICA, the artery is accom- communicating segments are combined into a single supra-
panied by a venous plexus and sympathetic nerve fibers. clinoid segment.
The cavernous segment (C4) of the ICA begins at the supe- Within the cavernous sinus the ICA gives origin to several
rior margin of the petroligual ligament. As it ascends onto arterial branches.13 The most proximal branch is the menin-
the sphenoid body, the vessel penetrates dura to enter the gohypophyseal trunk, arising lateral to the dorsum sellae
posterior cavernous sinus just lateral to the posterior clonoid close to the first bend in the ICA and just above the foramen
process. The artery makes an anterior-ward bend (the pos- lacerum. Although there is some variability in branching pat-
terior bend of the ICA) and runs horizontally forward in a tern,14 this trunk usually gives rise to three further branches,
horizontal groove, the carotid sulcus, along the sphenoid the tentorial (Bernasconi Cassinari artery), inferior hypos-
bone. The ICA continues forward to the anterior clinoid physeal, and dorsal meningeal (or clival) arteries. In about
process where it bends sharply upward as the anterior loop 30% of individuals, one or another of these branches can
(anterior bend of the ICA), medial to the anterior clinoid arise directly from the ICA. These branches supply portions
process. Anteriorly, the two layers of the lateral cavernous of the oculomotor, trochlear, and abducens nerves.15 These
sinus wall separate as they rotate into a horizontal position to vessels also supply blood to the roof of the cavernous sinus,
envelop the anterior clinoid process and part of the anterior the tentorium, the dura of the clivus, the capsule of the pitu-
ICA loop. The deep fibrous layer of the lateral wall forms an itary gland, and the floor of the sella turcica.
incomplete dural ring around the carotid artery forming the The inferolateral trunk (ILT) arises from the horizon-
proximal or lower ring. This marks the actual anterior roof tal segment of the intracavernous ICA and gives rise to four
of the cavernous sinus and the end of the cavernous segment branches. The tentorial branch supplies blood to the oculo-
of the ICA. motor and trochlear nerves, whereas small twigs from the
The vertical upward loop of the clinoid segment (C5) of ILT supply the abducens nerve. The orbital branch provides
the ICA begins at the proximal dural ring and ends a short blood to the ophthalmic division of the trigeminal nerve,
distance above this at the distal or upper dural ring. The lat- and to the orbital portions of cranial nerves III, IV, and VI.
ter is a complete ring of dura extending from the superficial The maxillary branch nourishes the maxillary division of the
layer of the lateral wall of the cavernous sinus as it passes trigeminal nerve, and the mandibular branch perfuses
over the anterior clinoid process and surrounds the ICA. This the mandibular division and portions of the gasserian
upper ring is fused with the adventitia of the ICA laterally. It ganglion.19
is continuous with the falciform ligament superiorly, with McConnell’s capsular artery is the third, variably present
the roof of the cavernous sinus and the anterior clinoid pro- branch from the ICA and supplies the capsule of the pituitary
cess laterally, and with the diaphragma sellae medially.32 The gland and walls of the sella turcica.20 Arteriovenous fistulae
clinoid segment of the ICA between the two dural rings is may occur from rupture of the ICA or any of these intracaver-
not intracavernous, but a venous plexus, continuous with the ous arterial branches.
anterior sinus channels, often extends through the incom-
plete lower dural ring and surrounds the ICA to the level of
Venous relationships
the upper ring.
Above the upper ring, the ICA becomes intradural as it The cavernous sinus contains four major venous spaces,31
enters the subarachnoid space and is situated between the with a variable amount of fatty connective tissue distributed
anterior clinoid process laterally and the carotid sulcus of between the channels. These serve as major venous drain-
the basisphenoid bone medially, just posterior to the optic age routes for the orbit and skull base. The orbital ophthal-
canal. The ophthalmic segment (C6) of the ICA begins at mic veins drain into the anteroinferior venous space, situated
the upper dural ring and ends just before the origin of the just behind the superior orbital fissure in a concavity within
posterior communicating artery. Two arterial branches arise front of the anterior loop of the carotid artery.11 This space
from this segment, the superior hypophyseal artery and the extends anteriorly to the confluence of the superior and infe-
ophthalmic artery (OA). The former supplies portions of the rior ophthalmic veins just within the cavernous sinus. The
pituitary gland. The OA emerges from the anterior surface of posterosuperior venous space is located between the poste-
the ophthalmic segment of the ICA immediately beneath the rior half of the sinus roof and the posterior ascending part of
optic nerve. It runs anteriorly and slightly laterally below the the intracavernous carotid artery. It drains posteriorly into a
optic nerve and on the upper surface of the optic strut, and confluence composed of the basilar sinus, the inferior petro-
then forward into the optic canal inferolateral to the nerve. As sal sinus, and the superior petrosal sinus. The larger inferior
it passes through the optic canal along with the optic nerve, petrosal sinus is the most important of these, draining blood
the ophthalmic artery pierces dura so that when it emerges from the cavernous sinus to the jugular bulb or to the lower
at the orbital apex the artery is extradural in location, infero- sigmoid sinus. The medial venous space is situated between
lateral to the optic nerve and sheath. In 10% of individuals, the carotid artery and the pituitary gland, and the very nar-
the ophthalmic artery may arise from the clinoid or even the row lateral venous space lies between the carotid artery and
cavernous segments,31 or more rarely from the inferolateral the lateral wall of the cavernous sinus. The latter is often so
trunk from the cavernous segment of the ICA.46 In such cases, narrow as to only accommodate the abducens (VI) nerve
6
Clinical Correlations: Orbital Apex/Cavernous Sinus Syndromes
that runs through it. Small tributaries interconnect the lateral has not achieved widespread usage, and here we will use the
venous spaces with the pterygoid venous plexus via variable classic terms orbital apex, superior orbital fissure, and ante-
emissary veins that pass through foramina in the skull base rior cavernous sinus, since these are well entrenched in the
(e.g. the foramen Vasalius). A venous plexus surrounds the medical literature.
maxillary nerve within the foramen ovale as it exits Meckel’s The superior orbital fissure (SOF) is a bony open-
cave and drains through the lateral space to the pterygoid ing between the orbital apex and the middle cranial fossa.
plexus. The superficial middle cerebral veins also drain into The fissure is an apostrophe-shaped opening with a wider
the lateral venous space. A very small fifth venous space, rounded portion inferomedially, and a narrow elongated
called the clinoid space, extends upward from the anteroin- portion superolaterally. It lies in the sphenoid bone between
ferior space along the carotid artery between the lower and the body and lesser wing medially, and between the lesser
upper dural rings. and greater wings laterally. The bony fissure is divided into
The cavernous sinus venous channels collect blood from three anatomic regions by the annulus of Zinn.33 The upper
the orbit via the superior and inferior ophthalmic veins. It and lateral-most narrow portion of the fissure lies above the
also receives venous blood from the cerebral hemispheres annulus and is lined by dura of the middle cranial fossa.
via the middle and inferior cerebral veins, and from dura This dural layer continues on the orbital side of the fissure
through tributaries of the middle meningeal veins. The cav- where it blends into periorbita and fibers of the annulus of
ernous sinus drains posteriorly into the basilar sinus which Zinn. This portion of the superior orbital fissure transmits
extends posterior to the dorsum sellae and interconnects the the orbitomeningeal artery and dural veins that communi-
left and right cavernous sinuses. It also drains backward into cate between the middle cranial fossa and the orbital venous
the jugular bulb by way of the superior petrosal sinus, and network. It also transmits the superior ophthalmic vein in
into the transverse sinus via the inferior petrosal sinus. Under its lower portion.30 Neural elements passing through this seg-
some circumstances, the cavernous sinus can also drain for- ment of the SOF include the trochlear nerve, and the frontal
ward through the ophthalmic veins into the facial veins. In and lacrimal branches of the ophthalmic nerve.8 The trochlear
about one-third of individuals a tiny foramen Vesalius is pres- and frontal nerves ascend as they pass through the SOF, and
ent in the posterior part of the greater sphenoid wing, medial move medially so as to enter the orbit into the superior extra-
to the foramen ovale.10 This opening transmits an emissary conal space. The lacrimal nerve runs just above the superior
vessel, the vein of Vesalius, from the cavernous sinus to the ophthalmic vein and passes above the superolateral portion
pterygoid venous plexus. This vessel can transmit infection of the annulus.
from the pterygoid plexus into the cavernous sinus in cases The inferior portion of the SOF lies beneath the annulus
of facial cellulitis. and is continuous inferiorly with the inferior orbital fissure
The cavernous sinuses on each side are commonly con- (IOF), which separates the orbital apex from the pterygopal-
nected by one or more intercavernous sinuses. These con- atine fossa. The inferior orbital fissure is bridged by the infe-
nections lie within the sella turcica, anterior, posterior or rior smooth orbital muscle of Müller, and its lateral wall is
beneath the pituitary gland. They are lined inferiorly by covered by dura of the middle cranial fossa. This compart-
endosteum covering the sphenoid bone, and superiorly by ment transmits the inferior ophthalmic vein into the lower
meninges covering the pituitary gland. In some cases these portion of the cavernous sinus.
channels are absent, and in others the anterior and posterior The larger central portion of the SOF is situated just lateral
intercavernous sinuses, together with the cavernous sinuses to the sphenoid body, below the optic strut, and above the
proper, form a circular sinus around the pituitary gland.32 posterior maxillary strut. It is surrounded on the orbital side
There remains some controversy as to whether the cav- by the central opening of the annulus of Zinn (also known
ernous sinus is in reality a cavity of unbroken trabeculated as the common annular tendon). All structures passing
venous caverns, or a plexus of veins that merge and divide as through this segment will enter the intraconal orbital space,
they pass through the cavernous sinus space.2,24,36 However, and therefore mostly serve extraocular muscle or ocular func-
both concepts are, in part, correct.31 Some veins, such as the tions. These structures include the superior and inferior divi-
superior ophthalmic vein, maintain their integrity through sions of the oculomotor nerve, the nasociliary branch of the
part of the sinus, whereas in other areas large venous dural ophthalmic nerve, and the abducens nerve. Each of these
sinuses predominate. Here, the venous spaces are lined by neural elements is covered by a perineurium and is wrapped
a basal membrane surrounded by fibrous connective tissue, in a layer of connective tissue. These fuse to the superolateral
but without smooth muscle.16 margin of the central annulus as they pass through it.
The cavernous sinus to orbit transition Clinical correlations: orbital apex/cavernous
sinus syndromes
While we usually consider the orbital apex and cavern-
ous sinus as separate anatomic entities, the anatomy of the
superior orbital fissure area is important as a continuous Lesions occurring at the cavernous sinus—orbital apex tran-
transition zone between the two regions. Parkinson25,27,28 sition zone frequently result in ocular or orbital dysfunction.
considered the orbital apex, superior orbital fissure, and the Symptoms are useful in defining the precise anatomic local-
cavernous sinus to be connected via a continuous venous ization of such lesions, and this can be valuable for diagno-
link bridging these structures. Since that time a number of sis and therapeutic planning. Several syndromes have been
anatomic studies have reaffirmed Parkinson’s concept.21,22,35 used to characterize the symptom complex associated with
Froelich et al.8 proposed the term lateral sellar orbital junc- lesions in this area.45 The term superior orbital fissure syndrome
tion (LSOJ) to define this transitional zone. However, this is often associated with lesions located just anterior to the
7
1 Cavernous Sinus
orbital apex, and involves structures passing through the in the surrounding tissues or secondary to distant malignan-
central annulus of Zinn, as well as those above the annulus. cies. Primary tumors include meningiomas, neurofibromas,
Symptoms involve multiple cranial nerve palsies involving gliomas, pituitary gland tumors, and tumors extending from
the oculomotor, trochlear, and abducens nerves, as well as parasellar regions such as nasopharyngeal malignancies, or
the ophthalmic division of the trigeminal nerve, but not the from the orbit as with lacrimal gland tumors. Metastatic
optic nerve. Orbital apex syndrome is associated with lesions tumors to the cavernous sinus are most often from the breast,
at the apex involving both the superior orbital fissure and prostate, or lung, and lymphomas can involve the orbit or
the optic canal. It involves dysfunctions of cranial nerves as the cavernous sinus and adjacent sinuses.
seen in the SOF syndrome, as well as the optic nerve. More Vascular lesions that can cause a cavernous sinus syn-
posterior lesions can produce a cavernous sinus syndrome, drome include aneurysms of the internal carotid artery or
and may include features of the orbital apex syndrome, as its intracavernous branches. Rupture of such an aneurysm
well as Horner’s syndrome, and possible involvement of the or a vascular tear following trauma can result in a carotid-
maxillary division of the trigeminal nerve. While these vari- cavernous fistula. Such fistulas can be direct, where there is
ous syndromes differ in their exact anatomic locations, the a direct communication between the carotid artery and the
pathologies causing them are similar. Therefore, we will fol- cavernous venous channels, or indirect where the communi-
low Yeh and Foroozan45 in applying the term orbital apex cation is with small branches of the carotid artery. The for-
syndrome to all of these syndromes for convenience of mer type has a higher blood flow, and presents with abrupt
discussion. onset of proptosis, chemosis, ophthalmoplegia, and possi-
Orbital apex syndrome can result from diseases involv- bly loss of vision. The latter type tends to have slower blood
ing the cavernous sinus and/or the orbital apex. Typical signs flow, progresses more slowly, is associated with less severe
and symptoms depend upon the specific anatomic structures symptoms, and may resolve spontaneously.
involved, but frequently include ophthalmoplegia, trigem- Localization of lesions affecting the cavernous sinus
inal sensory loss, Horner’s syndrome, proptosis, chemosis, is important in the differential diagnosis of cavernous
and facial pain. Etiologies are numerous and may be infec- sinus syndrome. From the above anatomic discussions, it
tious and non-infectious inflammatory conditions, vascular should be apparent that intracavernous neural structures
anomalies, neoplastic lesions, and trauma. can be affected differently in various parts of the sinus.
Inflammatory syndromes include Herpes zoster, Tolosa Sensory deficits are frequently seen with cavernous sinus
Hunt syndrome, sarcoidosis, Churg-Strauss syndrome, lesions. The maxillary nerve (V2) exits the sinus posteri-
Wegener’s granulomatosis, giant cell arteritis, and thyroid orb- orly, whereas the ophthalmic nerve (V1) courses through
itopathy. Orbital pseudotumor is a non-specific idiopathic the sinus to the superior orbital fissure. A lesion in the
inflammatory process that may involve any orbital struc- anterior or middle sinus would be expected to affect V1
ture including those of the orbital apex, cavernous sinus, and but not necessarily V2. Within the lateral sinus wall run
optic nerve. With inflammatory lesions, the onset of symp- from top to bottom the oculomotor nerve (III), the tro-
toms is frequently more abrupt than with other causes, and chlear nerve (IV), and V1, and in the posterior cavern-
often includes pain. Infectious etiologies include fungal infec- ous sinus, V2. With expanding lesions from above, the
tions such as Mucormycosis and Aspergillosis, bacterial infec- motor nerves will be affected before any sensory deficit.
tions, and tuberculosis. Cavernous sinus thrombophlebitis is a The abducens nerve (VI) does not run in the lateral wall
potentially lethal condition caused by bacterial or fungal inva- but within the sinus immediately lateral to the cavern-
sion complicating sinusitis in immunocompromized patients. ous ICA. Being relatively unprotected, isolated sixth nerve
Neoplastic tumors are a frequent cause of cavernous sinus palsies are seen earlier with ICA aneurysms or with other
and orbital apex syndromes, and may arise as primary lesions intracavernous lesions.
8
Clinical Correlations: Orbital Apex/Cavernous Sinus Syndromes
Anterior clinoid
process
Chiasmatic groove
Tuberculum sellae
Optic canal
Sella turcica
Superior orbital
fissure
Posterior clinoid
Carotid groove
process
Foramen rotundum
Clivus
Foramen lacerum
Foramen Vasalius
Petrous bone
Foramen
ovale
Internal acoustic
meatus
Figure 1-1 Bony sella turcica and clinoid processes limiting the cavernous sinus.
Carotid artery, Optic chiasm
intradural segment
CN III
Diaphragma sellae
CN IV
Pituitary gland
CN V1
Caverous sinus
CN VI
Carotid artery, horizontal
intracavernous segment
CN V2
Sphenoid sinus
CN V3
Figure 1-2 Cross section through the mid cavernous sinus.
9
1 Cavernous Sinus
Optic nerve
Carotid artery
Diaphragma
Pituitary gland
sellae
Posterior clinoid
process
CN III
CN IV
CN VI
CN V2
Meckel’s cave
CN V3
Figure 1-3 Dura mater of the cranial base and nerve roots entering the cavernous sinus.
Optic nerve
Carotid artery
Interclinoid
ligament
Superior orbital
fissure
Anterior petroclinoid Pituitary stalk
ligament
Cavernous
sinus Posterior
petroclinoid
CN V1 ligament
Gasserian ganglion
CN V2
Figure 1-4 Outer layer of the lateral wall of the cavernous sinus.
10