This article describes the intricate anatomy of the cavernous sinus and the MR appearances of normal anatomy and relevant disease processes, as well as CT and angiographic correlation. While patients’ initial signs and symptoms may appear mundane, early recognition and identification of cavernous sinus pathology may avert significant morbidity and mortality.
is an Associate Professor,
is a Fellow,
is an Assistant Professor, and
is a Professor in the Department of Radiology;
Dr. Mandava is
an Assistant Professor in the Department of Neurology; and
o is a Resident in the Department of Surgery, Section of
Neurosurgery, and a Professor of Radiology, University of Texas
Medical Branch, Galveston, TX.
is a Radiologist in private practice in Virginia.
is an Associate Professor in the Department of Otolaryngology,
Baylor College of Medicine, Neurosensory Center of Houston,
Several vascular structures, the cranial nerves, the pituitary
gland, and osseous structures sit in close proximity to each other
in the cavernous sinus. Vascular, infectious, inflammatory,
metastatic, and traumatic lesions in one of these structures can
quickly spread to the other contiguous elements. Proper clinical
recognition, appropriate imaging, and expeditious medical and/or
surgical intervention can reduce morbidity and mortality. Undue
delay in any aspect of this multimodality care could lead to
The carotid arteries and their intracavernous branches account
for most of the pathology that leads to morbidity and mortality.
The cranial nerves, on the other hand, may give the first clinical
indication that something is amiss.
The carotid arteries, cavernous sinus, and the minimally
blood-brain-barrierinvested pituitary gland together lend
themselves to be studied via different imaging modalities, each
with its strengths and limitations.
Magnetic resonance (MR) imaging has supplanted computed
tomography (CT) and cerebral arteriography for evaluating potential
cavernous sinus lesions.
The noninvasive multiplanar capabilities of MR imaging along with
superb soft-tissue contrast and MR angiography (MRA) enable MR to
diagnose most cavernous sinus pathology. However, certain cavernous
sinus vascular syndromes still benefit from traditional angiography
for diagnosis, as well as multidisciplinary intervention.
Discussion in this article will be limited to vascular issues,
such as carotid-cavernous (C-C) fistulas, cavernous sinus
aneurysms, cavernous sinus thrombosis, and granulomatous
inflammation of the cavernous sinus. The purpose of this pictorial
essay is to describe the intricate anatomy of the cavernous sinus
and the MR appearances of the normal anatomy and disease processes
afflicting it. CT and angiographic correlation is provided where
appropriate. Surgical considerations and approaches will be briefly
discussed. All MR studies were performed on 1.5T units. Suggested
MR protocols will be described.
The cavernous sinus is a venous space of the central skull base
encased by a dural envelope. The superior dural wall extends from
the planum sphenoidale to the clivus in conjunction with the
diaphragm sellae. The medial wall is formed by the dura investing
the pituitary gland. Dura from the floor of the middle cranial
fossa and lateral wall of the sphenoid forms the inferior medial
border. The lateral wall extends from the anterior and posterior
clinoid processes to the middle cranial fossa. The anterior limit
of the sinus is the superior orbital fissure, and the posterior
border is the clivus. The interior of the sinus contains multiple
septations. Blood flow is predominantly from the ophthalmic veins
and pterygoid plexus. Intercavernous flow occurs through the
connections anterior and posterior to the pituitary gland. Egress
from the sinus is through the superior and inferior petrosal
sinuses into the jugular system.
The carotid artery traverses the sinus from inferior lateral to
superior anterior. There are several arterial branches within the
sinus, including the meningohypophyseal artery, inferolateral
artery of the cavernous sinus, capsular artery, and, often, the
Cranial nerves III, IV, VI and VII are located within the
lateral wall of the cavernous sinus. The abducens nerve (VI) enters
the cavernous sinus through Dorello's canal and traverses the sinus
within the lumen (Figure 1). The oculomotor (III) and trochlear
(IV) nerves are located near the superior border, while the
ophthalmic division of the trigeminal nerve occupies the inferior
aspect. The maxillary division is more lateral and inferior to VI
and exits this dural lining at the foramen rotundum. Many of these
structures can be seen with MR or contrast-enhanced CT (Figure
The cavernous sinus is best evaluated with contrast-enhanced MRI
in the axial and coronal planes (Table 1). The cavernous sinus is
concave medially and shows homogeneous enhancement other than the
normal filling defects posteriorly and laterally secondary to the
gasserian ganglion in Meckel's cave. MR imaging is superior to CT
in evaluating disease afflicting the cavernous sinus except in the
rare cases in which bony involvement is present, rendering both CT
and MR imaging complementary. MR angiography is a noninvasive
alternative to angiography to evaluate the cavernous carotid
arteries. Angiography is reserved for diagnostic dilemmas and for
minimally invasive endovascular procedures (only briefly discussed
in this manuscript).
Carotid cavernous fistulae can be spontaneous or traumatic,
direct or dural and high-flow or low-flow.
A few of the spontaneous C-C fistula are believed to be secondary
to connective tissue disorders.
A distant history of trauma cannot be totally discounted in the
spontaneous variety. The direct variety results from tears in the
meningeal branches of the internal carotid artery (ICA) or the
external carotid artery (ECA).
The triad of chemosis, orbital bruit, and pulsatile exopthalmos
has been classically associated with a C-C fistula.
Radiologic diagnosis can be made by CT or MR showing the triad of
exophthalmos, an enlarged and tortuous superior ophthalmic vein,
and lateral bowing of the cavernous sinus (Figure 3). Conventional
angiography may still be necessary to diagnose the etiology of the
C-C fistula and, secondarily, to thrombose the fistula via coil or
Treatment options and appropriate selection of these options remain
controversial because spontaneous thrombosis of C-C fistula with
resolution of symptoms often occurs.
The low flow dural C-C fistulae were considered to be more likely
to spontaneously thrombose. However, note should be made that a
delay in addressing the C-C fistula and its complications in a
timely manner may compromise the function of the eye.
Embolization via the arterial system for the direct C-C fistulas or
the venous system for the dural fistulas has been advocated.
Cavernous sinus aneurysms
Cavernous sinus aneurysms of the carotid artery make up nearly
5% of all intracerebral aneurysms.
For an unknown reason, women account for a great majority of the
cases of cavernous carotid aneurysms.
Etiologically, these aneurysms are catego-rized into idiopathic,
traumatic, mycotic, secondary to radiation injury, and connective
tissue disorders groups. Size-based classification has also been
adopted: small (<1 cm), large (1 to 2.5 cm), and giant (>2.5
Ophthalmoplegia secondary to compression of cranial nerves III,
IV, and VI, and retro-orbital pain and loss of sensation in V1 and
V2 are common findings due to mass effect of the aneurysm.
Embolic strokes emanating from intraluminal thrombus may give rise
to symptoms corresponding to distal arterial territories. If the
intrasinus aneurysm should rupture, a C-C fistula may result. On
the other hand, if a giant aneurysm were to erode through or grow
beyond the cavernous dura, rare progression to subarachnoid
hemorrhage with concomitant sudden worsening of the neurological
status can be seen. A flow void or heterogenous mass with flow
voids by MR or rounded contrast enhancement by CT suggests the
diagnosis (Figures 4 and 5). MR imaging with or without contrast
can also suggest the diagnosis by showing a saccular mixed signal
region secondary to slow flow and/or partial thrombosis along the
cavernous carotid arteries. The cavernous carotid arteries are
normally seen as round or tubular signal void regions. MR
angiography can add complimentary information.
Conservative therapy may suffice for small carotid cavernous
aneurysms. Large and giant aneurysms or patients with embolic
events, mass effect on cranial nerves, and subarachnoid hemorrhage
unquestionably require a joint neurosurgical/interventional
approach. Drastic surgery (such as ligation of the proximal carotid
artery, reconstruction of the carotid artery, and embolization of
the aneurysm) has been suggested.
Cavernous sinus thrombosis
Cavernous sinus thrombosis usually occurs as a complication of
facial cellulitis or sinusitis. An immune compromised state and
diabetic ketoacidosis are common risk factors for this condition.
Rare cases of malignancy and trauma have also been associated with
cavernous sinus thrombosis.
Classic presenting findings include pain, chemosis, proptosis,
and ophthalmoplegia. Involvement of the cavernous sinus is via
thrombophlebitic spread of infection from both the superior and
inferior ophthalmic veins, though direct extension from the
sphenoid sinus is possible. Fungi of the mucor or the aspergillus
classes are the common etiologic agents.
A few bacterial cases such as staphylococcus aureus and pseudomonas
aeruginosa have also been reported.
MR imaging or CT with contrast can usually detect filling
defects with the cavernous sinus (Figure 6) to suggest the
If strong clinical suspicion exists, repeat imaging may sometimes
be necessary, since early in the disease process both CT and MR may
miss the diagnosis. Emergent initiation of medical therapy or
surgical debridement may prevent lethal sequelae, such as formation
of a brain abscess, stroke, and death. However, despite aggressive
management, mortality continues to be high.
Delay in obtaining confirmatory imaging studies or delivery of
medical therapy and/or surgical intervention has traditionally
resulted in high morbidity and mortality. While a brain abscess is
due to contiguous spread, strokes are due to the involvement and
thrombosis of one or both of the carotid arteries.
Orbital pseudotumor is an encompassing inflammatory condition,
which when limited to the cavernous sinus is known by the eponym
Tolosa-Hunt syndrome is generally accepted as granulomatous
periarteritis of the carotid artery and its intracavernous
branches. Patients describe steady unilateral orbital pain of
several weeks' duration, followed by opthalmoplegia due to
involvement of cranial nerves III, IV, and VI (Figure 7).
Intravenous or oral steroids can abate symptoms within 24 hours.
Resolution of radiologically evident arteritis has also been
Radiologic studies in the form of CT, MRI/MRA, and, in rare
instances, angiography, may be useful in differentiating orbital
pseudotumor from other causes of orbital pain and opthalmoplegia.
Mass lesions such as lymphoma, meningioma, chordoma, and other
inflammatory conditions, such as sarcoid, have to be excluded
Obtaining the correct radiologic study with an accurate clinical
history may prevent unnecessary biopsies or other surgical
interventions. The importance of radiologic studies in narrowing
the differential diagnosis cannot be overstated, since lymphoid
tumors, sarcoid, and inflammatory conditions can also be
steroid-sensitive. Enhancement of the intraconal structures
extending into the orbital apex and cavernous sinus can be easily
detected by the multiplanar capabilities of MR, but may be
difficult to differentiate from infection, metastasis, or lymphoma.
Obtaining the pertinent medical history and correlating the
clinical and radiographic findings is paramount in limiting and
narrowing the diagnosis.
Nowhere is the adage The eye is the window into the brain more
applicable than with cavernous sinus lesions. Although the
patient's initial signs and symptoms may appear mundane, early
recognition and identification of cavernous sinus pathology may
avert significant morbidity and mortality. Treatment options vary
from watchful waiting to aggressive combined medical, surgical, and