Background: Exact preoperative confirmation of the distal dural ring and intradural location
of a paraclinoid internal carotid aneurysm has been an age old dilemma. This study
was aimed at identifying anatomical landmarks in cases of paraclinoid aneurysms, which
were relatively consistent, and would help in predicting the possibility of an extradural
inaccessible location of these aneurysms for surgical clipping. Methods: Ninety surgically managed unruptured paraclinoid aneurysms were retrospectively analyzed
with preoperative computerized tomography. Axial relation of the aneurysm neck to
the ophthalmic artery (OA), optic strut (OS), and anterior clinoid process (ACP) in
terms of vertical distance and the direction of projection were analyzed and tabulated
for all 90 cases. Intradural and extradural (inaccessible) aneurysms were compared.
Results: Seven out of the 8 inaccessible necks were medially directed and 1 was ventrally
placed (P = 0.053). The OA level when compared to the neck had a positive correlation
with inaccessible aneurysms for clipping (P = 0.002) The OS location above the level
of the neck had significant correlation with inaccessibility of clipping and extradural
location (P < 0.001). The tip of the ACP had no statistical significance with inaccessibility
(P = 0.351). Conclusions: Medially projecting aneurysms with necks below the level of the OS and origin of
the OA should be managed with a high index of suspicion and an alternate method of
treatment should be sought. The relation of the neck to the ACP does not seem to have
significant statistical bearing with decision making.
Key-words:
Anterior clinoid process - distal dural ring - extradural aneurysm - ophthalmic artery
- optic strut - paraclinoid aneurysm