Advantages of Extradural Anterior Clinoidectomy and Extradural Approach with Dural Incision for Blood Blister Aneurysm or Pseudoaneurysm in the Internal Carotid Artery: Two Case Reports

Blood blister aneurysms (BBAs) or pseudoaneurysms (PAs) in the internal carotid artery (ICA) have fragile necks; therefore, conventional neck clipping is difficult. The standard treatment for BBAs or PAs is trapping with high or low flow bypass. However, there is no consensus on whether or not anterior clinoidectomy should be performed together. Two patients with ruptured ICA PA (anterior protrusion) or BBA (posterior protrusion) were presented to our hospital. Complete trapping was safely performed for both types of aneurysms via extradural anterior clinoidectomy and the extradural approach with dural incision. The advantages of the procedure are 1) safe proximal clipping, 2) early identification of the ICA C3 portion, 3) minimized frontal lobe retraction, 4) optic canal opening to allow mobility of the optic nerve, and 5) dural ring incision to allow mobility of the ICA.

Interdural course of the ophthalmic artery in the optic canal

OBJECTIVE

In the current neurosurgical and anatomical literature, the intracanalicular segment of the ophthalmic artery (OphA) is usually described to be within the optic nerve dural sheath (ONDS), implying direct contact between the nerve and the artery inside the optic canal. In the present study, the authors sought to clarify the exact relationship between the OphA and ONDS.

METHODS

Ten cadaveric heads were subjected to endoscopic endonasal and transcranial exposures of the OphA in the optic canal (5 for each approach). The relationship between the OphA and ONDS was assessed. Histological examination of one specimen of the optic nerve and the accompanying OphA was also performed to confirm the relationship with the ONDS.

RESULTS

In all specimens, the OphA coursed between the two layers of the dura (endosteal and meningeal) and was not in direct contact with the optic nerve, except for the first few millimeters of the proximal optic canal before it pierced the ONDS. Upon reaching the orbit, the two layers of the dura separated and allowed the OphA to literally float within the orbital fat. The meningeal dura continued as the ONDS, whereas the endosteal dura became the periorbita.

CONCLUSIONS

This study clarifies the interdural course of the OphA within the optic canal. This anatomical nuance has important neurosurgical implications regarding safe exposure and manipulation of the OphA.

Junctional Internal Carotid Artery Aneurysms: The Schrödinger's Cat of Vascular Neurosurgery

Objectives Despite advances in neuroimaging, it is not always definitive whether a paraclinoid aneurysm is intradural or entirely extradural. We illustrate the potential use of surgical exploration in these aneurysms that we refer to as "junctional" aneurysms. Methods Retrospective review of eight patients with unruptured aneurysms who underwent a planned surgical exploration of a junctional aneurysm. Results Of the eight patients, three underwent exploration of the aneurysm during surgery for a different aneurysm. All three of these were found to be extradural. Five patients underwent a craniotomy for the exclusive purpose of clarifying the location of the aneurysm. Two of these cases were found to be intradural and were clipped. Two cases were found to be extradural. In one patient, the initially extradural aneurysm was converted into an intradural aneurysm during removal of the anterior clinoid process, necessitating surgical clipping. One transient third nerve palsy was observed. Discussion Until further progress in neuroimaging allows clinicians to determine unequivocally the exact anatomical location of a paraclinoid aneurysm, we advocate the use of the term junctional aneurysm to reflect the clinical uncertainty inherent in management decisions made regarding these aneurysms. We have illustrated a strategy of surgical exploration in select patients.