Introduction: The endoscopic transorbital approach (ETOA) is being established as a new corridor
for the lateral portion of the anterior and middle skull base. One of the main concerns
of the approach is the risk of ophthalmological complications due to the retraction
on the orbit. Removal of the lateral orbital rim (LOR) is a simple measure that widens
the corridor and can potentially diminish injuries secondary to orbital retraction.
The aim of the present study is to analyze the impact of removal of the LOR on the
intraorbital pressure (IORP) during the various stages of ETOA.
Methods: In this prospective cadaveric study, standard ETOA to the anterior and middle fossae
were performed via a superior eyelid crease incision ([Fig. 1]). On one side of the specimen, the LOR was preserved and one the other side LOR
was removed. IORP was recorded with an intracranial pressure (ICP) probe during the
entirety of the procedures ([Fig. 2]). All specimens underwent a pre and post procedure CT scan to measure the volume
of bone removal.
Fig. 1: First steps of the procedure: (A) superior eyelid incision; (B) orbicularis oculi muscle fibers (dotted black line); (C) superolateral orbital rim (black asterisk) from the periorbita (red asterisk) with
ICP probe (arrow); (D) lateral orbital rim (asterisk); (E) frontozygomatic suture (asterisk); (F) removed LOR (circle), temporal muscle (white asterisk), lateral GSW (arrow), and
periorbita (black asterisk).
Fig. 2 Endoscopic dissection: (A) peeling of the periorbita, (B) drilling of the GSW, (C) exposure of temporal dura, (C) peeling of lateral wall of cavernous sinus. SOF, superior orbital fissure; MOB, meningoorbital
band; GG, gasserian ganglion.
Results: Four specimens were used (8 sides, 4 with LOR removal, 4 without). Mean IORP was
not statistically different between the two groups during the periorbita detachment
step, which was prior to LOR removal (117.4 vs. 91.5 mm Hg, for the LOR removal group
and LOR intact group, respectively, p = 0.217). IORP was then consistently reduced in the LOR removal group in every subsequent
step ([Fig. 3]): meningo-orbital band cutting (from 105.5 to 38.9 mm Hg, p = 0.002), temporal fossa drilling (from 85.3 to 69.5 mm Hg, p = 0.232), lateral greater sphenoid wing (GSW) drilling (from 99.8 to 49.9 mm Hg,
p < 0.001), medial GSW drilling (from 85.6 to 17.2 mm Hg, p < 0.001), and cavernous sinus peeling (from 85.6 to 3.0 mm Hg, p < 0.001). LOR removal led to an increase in the total volume of bone removed: 6.2
to 9.4 cc (p = 0.05).
Fig. 3 IORP with and without LOR removal (statistically significant results marked with
black asterisks).
Conclusion: We observed a decrease in IORP with LOR removal, especially when working on the GSW
and cavernous sinus and a significant increase in bone removal. These results support
LOR removal to help decrease the retraction stress on the orbit and increase working
corridor during ETOA.
