E. Seoane et al., MICROSURGICAL ANATOMY OF THE DURAL COLLAR (CAROTID COLLAR) AND RINGS AROUND THE CLINOID SEGMENT OF THE INTERNAL CAROTID-ARTERY, Neurosurgery, 42(4), 1998, pp. 869-884
OBJECTIVE: To examine the relationship of the clinoid segment of the i
nternal carotid artery to the structures in the roof of the cavernous
sinus and to determine whether this segment is neither intradural nor
intracavernous, as recently proposed. METHODS: The region of the roof
of the cavernous sinus was dissected and examined using 3 to 40 x magn
ification and micro-operative techniques. RESULTS: The clinoid segment
was located within a collar formed by the dura lining the medial surf
ace of the anterior clinoid process, the posterior surface of the opti
c strut, and the upper part of the carotid sulcus. The clinoid segment
and the collar were defined above by the upper ring formed by the dur
a extending medially from the upper surface of the anterior clinoid pr
ocess to surround the artery and below by the lower ring formed by the
dura extending medially from the lower surface of the anterior clinoi
d process. The upper ring was adherent to the wall of the artery, but
the lower dural ring was separated from the lower margin of the clinoi
d segment by a narrow space that admitted venous tributaries of the ca
vernous sinus, called the clinoid venous plexus. This venous plexus na
rrowed as the upper ring was approached and became wider at the lower
ring, where the plexus communicated with the venous channels of the ca
vernous sinus. The upper and lower dural rings were best defined along
the lateral and anterior margins of the artery, were less distinct me
dially, and disappeared posteriorly, where the dura forming the upper
and lower rings came together. CONCLUSION: The clinoid segment is intr
acavernous, being located within a collar of dura in which venous trib
utaries of the cavernous sinus course. The implications of these findi
ngs for surgery are reviewed.