Peer-Review ReportWhat Bone Part Is Important to Remove in Accessing the Suprachiasmatic Region with Less Frontal Lobe Retraction in Frontotemporal Craniotomies
Introduction
Microsurgery for suprachiasmatic lesions, including anterior communicating artery (AComA) aneurysms and tuberculum sellae meningiomas extending into the suprachiasma, remains challenging. The complex anatomy of the region comprising the AComA, chiasma, and optic nerves, and the poorly accessible, deep-seated location of the suprachiasmatic lesions impede the treatment.
One of the main surgical trajectories to access the suprachiasmatic region is the anterolateral, transsylvian approach. With this approach, the classic, commonly used craniotomy is the standard frontotemporal pterional (PT) craniotomy (23). However, the recent development of surgical tools such as the high-power drill and a more detailed understanding of the clinical anatomy of the skull base have led to the clinical introduction of craniotomy techniques alternative to PT craniotomy to attain a greater area of exposure (AOE) and multidirectional access. Orbitozygomatic (OZ) and orbitopterional (OPT) craniotomies are representative procedures alternative to PT craniotomy (1, 10, 11, 18, 20, 21, 25). Furthermore, mini-supraorbital (mini-SO) craniotomy has been used because of its advantages of a sufficient AOE, less invasiveness, and a short operative time (8, 9). However, there has been no report detailing the specific area of the bone to be removed for maximizing the AOE over the suprachiasmatic region in these craniotomies. In the present study, we evaluate how the specific region of the bone removed affects the AOE over the suprachiasmatic region in craniotomies with an anterolateral trajectory; special attention is paid to the differences between the removal of the supraorbital bar and lateral orbital wall.
In addition to the particular region of bone removed, another major factor influencing the AOE is the retraction of the frontal lobe. Although greater retraction can produce a greater AOE, excessive stress during the retraction may injure the frontal lobe, especially its frontobasal area (4). Unfortunately, detailed descriptions on the relationship between brain retraction and surgical exposure are not available in anatomical reports on the recently introduced craniotomies, including OZ, OPT, and mini-SO craniotomies. In the present study, the effect of brain retraction on the AOE was quantitatively analyzed in relation to tailored craniotomies; guiding this analysis was the goal of minimizing frontal lobe retraction.
Section snippets
Craniotomies
Six sides of three formalin-fixed cadaver heads were used in the study. Colored silicon, red in artery and blue in vein, was injected. Before dissection, the heads were rigidly fixed with a three-pin head holder. The skin flap was retracted by the interfascial method, and the temporal muscle was retracted inferior-posteriorly, so as to not obstruct the microscope trajectory in the anterior-to-posterior and inferior upward direction (Figure 1A, inset). Craniotomies were performed using a
AOE
At the 5-mm level of frontal lobe retraction, the AComA complex in the suprachiasmatic region was visible with the PT-LO-SW craniotomy but not with the PT or PT-SO craniotomies. The AOEs obtained with each craniotomy and level of retraction are presented in Table 1.
Statistical Analyses
The differences of AOEs among all craniotomies were gradually decreased along with increased brain retractions, and there was an interaction between craniotomies and brain retractions (Figure 3).
Effects of Retraction Level
The statistical results of comparing
Discussion
Among the lesions occurring in the suprachiasmatic region, AComA aneurysm is one of the most common, accounting for as many as 36% of cerebral aneurysms (5); its treatment remains one of the most challenging too. Among the various surgeries for different types of anterior circulation aneurysms, surgery for AComA aneurysms gives rise to the highest incidence of postoperative morbidity and neuropsychological deficits (12). Subarachnoid hematoma, parenchymal resection, and injury to the
Conclusion
To minimize frontal lobe retraction when accessing the suprachiasmatic region via an anterolateral trajectory, it is important that the craniotomy involves the removal of the lateral orbital wall and the greater sphenoid wing, i.e., the frontal process of the zygomatic bone and the orbital and cerebral faces of the greater sphenoid wing. This valuable procedure could be applied not only to PT and alternative craniotomies, including OZ, OPT, and mini-SO craniotomies, but also to smaller
Acknowledgement
The authors thank Prof. Dr. Hiroyuki Nakamura, Department of Environmental and Preventive Medicine, Kanazawa University, for his meaningful suggestions about the statistical analyses, and Ms. Akino Kinoshita for her skillful medical illustrations.
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Cited by (11)
Three-step anterolateral approaches to the skull base
2014, Journal of Clinical NeuroscienceCitation Excerpt :Where the disease process so requires it, a third step can be added to the procedure described above, turning the transzygomatic approach into a three-step orbitozygomatic approach. Section of the lateral orbital wall improves the angle of horizontal access, which is particularly useful when a transsylvian route is used, for instance, in the management of craniopharyngioma or hypothalamic hamartoma [15,16]. On the basis of the previously mentioned description, bone removal stops before reaching the superior orbital fissure and does not extend anteriorly to the zygomatic arch.
From above or below: The controversy and historical evolution of tuberculum sellae meningioma resection from open to endoscopic skull base approaches
2014, Journal of Clinical NeuroscienceCitation Excerpt :However, because the underside of the ipsilateral optic nerve and chiasm are not as well visualized with the pterional approach, studies have reported that anywhere from 10 to 20% of patients may have postoperative visual deterioration [4,13,15,48–50]. Given these limitations of the traditional pterional craniotomy, various modifications were described as alternatives to increase the area of surgical exposure and minimize the degree of frontal lobe retraction [24,51]. These included the supraorbital (Fig. 3) [52,53], orbitozygomatic [22,23,26,51], and orbitopterional [24,27–29,51], craniotomies.
Comparative Anatomical Study of Fronto-Orbito-Zygomatic and Fronto-Temporal Approach to the Central Skull Base
2021, Journal of Craniofacial Surgery
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.