Preoperative Prediction of the Necessity for Anterior Clinoidectomy During Microsurgical Clipping of Ruptured Posterior Communicating Artery Aneurysms

The Usefulness of Extradural Anterior Clinoidectomy for Lower-Lying Posterior Communicating Artery Aneurysms : A Cadaveric Study

OBJECTIVE

To confirm the usefulness of the extradural anterior clinoidectomy during the clipping of a lower riding posterior communicating artery (PCoA) aneurysm through cadaver dissection.

METHODS

Anatomic measurements of 12 adult cadaveric heads (24 sides total) were performed to compare the microsurgical exposure of the PCoA and internal carotid artery (ICA) before and after clinoidectomy. A standard pterional craniotomy and transsylvian approach were performed in all cadavers. The distance from the ICA bifurcation to the origin of PCoA (D1), pre-anterior clinoidectomy distance from the ICA bifurcation to tentorium (D2), post-anterior clinoidectomy distance from the ICA bifurcation to tentorium (D3), pre-anterior clinoidectomy distance from the tentorium to the origin of PCoA (D4) and post-anterior clinoidectomy distance from the tentorium to the origin of PCoA (D5) and the distance of the ICA obtained after anterior clinoidectomy (D6) were measured. We measured the precise thickness of the blade for the Yasargil clip with a digital precision ruler to confirm the usefulness of the extradural anterior clinoidectomy.

RESULTS

Twenty-four sites were dissected from 12 cadavers. The age of the cadavers was 79.83±6.25 years. The number of males was the same as the females. The space from the proximal origin of the PCoA to the preclinoid-tentorium (D4) was 1.45±1.08 mm (max, 4.01; min, 0.56). After the clinoidectomy, the space from the proximal origin of the PCoA to the postclinoid-tentorium (D5) was 3.612±1.15 mm (max, 6.14; min, 1.83). The length (D6) of the exposed proximal ICA after the extradural clinoididectomy was 2.17±1.04 mm on the lateral side and 2.16±0.89 mm on the medial side. The thickness of the Yasargil clip blade used during the clipping surgery was 1.35 mm measured with a digital precision ruler.

CONCLUSION

The proximal length obtained by performing an external anterior clinoidectomy is about 2 mm, sufficient for proximal control during PCoA aneurysm surgery, considering the thickness of the aneurysm clips. In a subarachnoid hemorrhage, performing an extradural anterior clinoidectomy could prevent a devastating situation during PCoA aneurysm clipping.

Anterior clinoidectomy in low lying internal carotid artery-posterior communicating artery aneurysm

BACKGROUND

At times, a regulation internal carotid artery-posterior communicating artery junction (ICA-P-Comm) aneurysm becomes a surgical hurdle owing to its close proximity to the anterior clinoid process, an immovable ICA and a concealed dominant P-Comm artery arising from the aneurysm neck.

METHOD

A 70 year old patient with a low lying ICA-P-Comm aneurysm underwent a "tailored" intradural clinoidectomy for aneurysm clipping.

CONCLUSION

A tailored anterior clinoidectomy to expose "just enough" allows a proximal ICA control in a suitable area, mobility of an atherosclerotic ICA and exposes the P-Comm artery origin which are essential in safe clipping of these aneurysms.

Enhance Safety in Aneurysm Surgery: Strategies for Prevention of Intraoperative Vascular Complications

Complications during surgery for intracranial aneurysms can be devastating. Notorious pitfalls include premature rupture, parent vessel occlusion, local cerebral injury and brain contusion, and incomplete neck obliteration. These unfavorable intraoperative events can result in major neurological deficits with permanent morbidity and even mortality. Herein, the author highlights the relevant surgical strategies used in his daily practice of aneurysm surgery (e.g., aneurysm clipping with adenosine-induced temporary cardiac arrest), application of which may help prevent vascular complications and enhance surgical safety through reduction of the associated risks, thus allowing improvement of postoperative outcomes. Overall, all described methods and techniques should be considered as small pieces in the complex puzzle of prevention of vascular complications during aneurysm surgery.

Microsurgical Anatomy of the Anterior Circulation of the Brain Adjusted to the Neurosurgeon's Daily Practice

The study of cerebrovascular anatomy can be difficult and may take time due to its intrinsic complexity. However, it can also be difficult for the following reasons: the excessive description of neuroanatomy making articles hard to read, the unclear clinical application of what is written, the use of simplified or intricate schematic drawings that are not always appropriate for effective teaching, the poor quality of neuroanatomy dissections and the use of unusual views of figures that are not strictly related to the most frequent neuroimages to be interpreted in daily practice. Because of this, we designed an article that incorporates original and accurate anatomical dissections in an attempt to improve its comprehensibility. Five formalin-fixed adult cadaveric heads, whose vessels were injected with a colored silicone mixture (red for arteries and blue for veins), were dissected and examined under a microscope with magnifications from 3× to 40×. Special emphasis has been placed on correlating topographic anatomy with routine neuroimaging studies from computed tomographic angiography (CTA) and digital subtraction angiography (DSA). The essential surgical anatomy in a neurosurgeon’s daily practice is also described. The cadaveric dissections included in this study contribute to the understanding of the cerebrovascular anatomy necessary for the neurosurgeon’s daily practice.

Anterior Temporal Approach for Clipping Posterior-Projecting Supraclinoid Carotid Artery Aneurysms: A More Lateral Corridor to Better Visualize the Aneurysm Neck and Related Branches

BACKGROUND

Direct visualization of the aneurysm neck and its related branches during microsurgical clipping of supraclinoid internal carotid artery (SICA) aneurysms using a standard pterional approach may be difficult, especially when aneurysms are posteriorly projected. We evaluated the efficacy and safety of an anterior temporal approach for clipping posterior-projecting SICA aneurysms.

METHODS

Between December 2017 and March 2020, 26 patients with posterior-projecting SICA aneurysms who received microsurgical clipping via an anterior temporal approach were retrospectively reviewed. The percentage of complete aneurysm obliteration, intraoperative visualization, and preservation of related branches were evaluated.

RESULTS

Aneurysm locations were the posterior communicating artery (PCoA) (internal carotid artery [ICA]-PCoA) in 22 patients (84.6%), the anterior choroidal artery (AChA) (ICA-AChA) in 3 patients (11.5%), and both locations in 1 patient (3.9%). Complete aneurysm obliteration was achieved in all patients. For ICA-PCoA aneurysms in which the PCoA was preoperatively identified, the artery was intraoperatively identified in all cases and preserved 100% after surgery. For ICA-AChA aneurysms, AChAs were intraoperatively identified and preserved in all cases after surgery. Procedural-related infarction was 8.7% for ICA-PCoA aneurysms and 7.7% for all SICA aneurysms. Transient oculomotor nerve palsy was found in 2 patients (7.7%). No postoperative temporal contusion was detected. A good outcome at 3 months after surgery was achieved in 90% of patients for good clinical-grade subarachnoid hemorrhage and unruptured cases.

CONCLUSIONS

The anterior temporal approach is safe and effective for clipping SICA aneurysms with posterior projection, with a high preservation rate of the related branches.

Morphometric Comparison of the Pterional Trans-Sylvian and the Pretemporal Trans-Clinoidal Approaches to the Posterior Communicating Artery

BACKGROUND

Posterior communicating (Pcom) aneurysms in the modern era have tended toward increased complexity and technical difficulties. The pretemporal approach is a valuable extension to the pterional approach for basilar apex aneurysms, but its advantages for Pcom aneurysms have not been previously elucidated.

OBJECTIVE

To quantify characteristics of the pretemporal approach to the Pcom.

METHODS

We dissected 6 cadaveric heads (12 sides) with a pretemporal transclinoidal approach and measured the following variables: (1) exposed length of internal carotid artery (ICA) proximal to the Pcom artery; (2) exposed circumference of ICA at the origin of Pcom; (3) deep working area between the optic nerve and tentorium/oculomotor nerve; (4) superficial working area; (5) exposure depth; and (6) the frontotemporal (superior posterolateral) and (7) orbito-sphenoidal (inferior anterolateral) angles of exposure.

RESULTS

Compared with pterional craniotomy, the pretemporal transclinoidal approach increased the exposed length of the proximal ICA from 3.3 to 11.7 mm (P = .0001) and its circumference from 5.1 to 7.8 mm (P = .0003), allowing a 210° view of the ICA (vs 137.9°). The deep and superficial working areas also significantly widened from 53.7 to 92.4 mm2 (P = .0048) and 252.8 to 418.2 mm2 (P = .0001), respectively; the depth of the exposure was equivalent. The frontotemporal and spheno-Sylvian angles increased by 17° (P = .0006) and 10° (P = .0037), respectively.

CONCLUSION

The pretemporal approach can be useful for complex Pcom aneurysms by providing easier proximal control, wider working space, improved aneurysm visualization, and more versatile clipping angles. Enhanced exposure results in a potentially higher rate of complete aneurysm obliteration and complication avoidance.

Quantitative Anatomic Study of the Minipterional Craniotomy in the Paraclinoid Region: Benefits of Extradural Anterior Clinoidectomy

BACKGROUND

Extradural anterior clinoidectomy (eAC) via the minipterional craniotomy (MPT) approach (MPT+eAC) has been recently introduced to the neurosurgical armamentarium to improve access to anterior and middle fossa skull base structures using a minimally invasive approach. However, the effect of extradural clinoidectomy on surgical exposure with the minipterional approach has not been evaluated. Moreover, the effect of eAC on surgical maneuverability has not been established for either traditional pterional or minipterional craniotomy. We sought to illustrate the microsurgical anatomy of the MPT+eAC and to evaluate the effect of eAC on surgical exposure and maneuverability.

METHODS

The area of exposure, area of surgical freedom, and maneuverability score for the MPT approach and MPT+eAC were compared in 5 cadaveric heads.

RESULTS

Compared with the MPT approach, the MPT+eAC enlarged the area of exposure approximately twofold (93 cm² vs. 184 cm²; P < 0.001). All targets considered in the paraclinoid region, including the posterior communicating artery origin, prechiasmatic region, and ophthalmic artery origin, showed an increase in surgical freedom and maneuverability after performing eAC. Targets remote from the clinoid such as the internal carotid bifurcation were not affected.

CONCLUSIONS

MPT+eAC offers a larger area of exposure and greater surgical freedom and maneuverability at the paraclinoid region using this minimally invasive approach.

The carotico-clinoid bar: A systematic review and meta-analysis of its prevalence and potential implications in cerebrovascular and skull base surgery

BACKGROUND

The caroticoclinoid bar (CCB) is implicated in both transcranial and endonasal surgery. Its morphology reflects differences in the microsurgical anatomy of the parasellar area while its manipulation during an anterior or middle clinoidectomy can result in ICA injury. Although safe surgical access to the paraclinoidal region is related to adjustment of surgical technique according to CCB anatomical variants, a review of the literature indicates the lack of a systematic assortment of published data regarding the prevalence of this variable structure. As such the topic needs further investigation.

OBJECTIVE

To systematically review and document the prevalence of the CCB and its anatomic variations.

METHODS

3 Databases were systematically reviewed according to the PRISMA statement through August of 2018 for the identification of relevant studies.

RESULTS

A total of 27 articles (7,521 subjects/specimens, 14,449 sides) were included in this meta-analysis. The overall pooled prevalence of the CCB was 32.6% (95% CI 26.6% - 38.8%) when measured over subjects/specimens and 23.6% (95% CI 19.7% - 27.6%) when measured over sides. Overall prevalence of the CCB reported from imaging studies was 23.1% (95% CI 8.9% - 41.4%) when measured over subjects/specimens and 18.7% (95% CI 12.6% - 25.7%) when measured over sides. Moreover, the CCB was slightly more prevalent (p = 0.050), on the right side.

CONCLUSION

Our results indicate considerable CCB prevalence rates and that imaging studies report lower prevalence rates. Although meticulous preoperative investigation is mandatory, surgeons carrying for patients with parasellar pathologies should always be vigilant about this structure.