Minimally Invasive Spheno-orbital Craniectomy, Technique, and Nuance

Introduction: Historically in cranial surgery, large, “one-size fits all,” craniotomies were performed to gain wide access and surgical visualization. Over time, the influence of pioneers such as Perneczky, McCarty, and Yasargil has led to refined microsurgical-instruments, improvement in microsurgical techniques and modifications and development of “keyhole” craniotomies. These advancements have placed a greater emphasis on minimally invasive cranial approaches with variable incision lengths, size of the craniotomy, and several other modifications that focus on less trauma, better cosmesis, and shorter hospital stay. The aim of this study is to describe our tailored spheno-orbital craniectomy, its role in minimally invasive surgery, and compare the surgical view and access to traditional techniques.

Methods: Using 8, formalin fixed, latex injected cadaveric heads, 3D CT reconstruction was performed on all specimens prior to dissection. The spheno-orbital craniectomy was performed on the right side of 4 specimens and the standard pterional craniotomy performed on the left side. Several measurements were recorded during dissection. Ability to perform an anterior clinoidectomy and access to several key anatomical structures were recorded (i.e., optico-carotid window, oculomotor carotid window, ICA terminus, contra-lateral optic nerve, optic chiasm). Bone flap(s) were reconstructed with standard cranial plating system (Synthes MatrixNeuro). All specimens underwent post-dissection CT scan with 3D reconstruction. Volumetric analysis for total bone removed for each approach was performed on post-dissection specimens using 3D Slicer software.

Results: The measurements were recorded during each dissection; all specimens were dissected by a single person. The mean spheno-orbital craniectomy was 2.5 × 2.5 cm. The spheno-orbital craniectomy was covered with a 3.5 × 2.5 cm mesh. The number of burr hole(s) for the traditional fronto-temporal craniotomy was 3, and mean craniotomy size was 7.5 × 6.5 cm. Anterior clinoidectomy was performed with both approaches. Access to the optico-carotid window, oculomotor carotid window, ICA terminus, contralateral optic nerve, optic chiasm was achieved with both approaches. However, the modified spheno-orbital craniectomy, could not access the distal fissure, limited at the M2 bifurcation. Number of plates needed to secure traditional pterional flap: 4. The 3D volumetric analysis demonstrated a mean voxel number of 15,440 in the modified burr hole and 19,179 with the traditional. Mean volume of bone removed was 3.42 cm³ with the modified burr hole and 4.32 cm³ with the traditional.

Discussion: The spheno-orbital craniectomy is an excellent minimally invasive approach to access pathology around the proximal anterolateral skull base. However, it has limited application when approaching pathology that necessitates wide sylvian fissure dissection. As with any skull base approach, the key is to choose the best approach that facilitates optimal intraoperative orientation and maneuverability, without disruption of normal brain parenchyma and minimization of operative morbidity.

Publication History

Article published online:
01 February 2023