Surgical Freedom Evaluation During Optic Nerve Decompression: Laboratory Investigation

OBJECTIVE The extended endoscopic endonasal transtuberculum transplanum approach is currently used for the surgical treatment of selected midline anterior skull base lesions. Nevertheless, the possibility of accessing the lateral aspects of the planum sphenoidale could represent a limitation for such an approach. To the authors' knowledge, a clear definition of the eventual anatomical boundaries has not been delineated. Hence, the present study aimed to detail and quantify the maximum amount of bone removal over the planum sphenoidale required via the endonasal pathway to achieve the most lateral extension of such a corridor and to evaluate the relative surgical freedom. METHODS Six human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. The laboratory rehearsals were run as follows: 1) preliminary predissection CT scans, 2) the endoscopic endonasal transtuberculum transplanum approach (lateral limit: medial optocarotid recess) followed by postdissection CT scans, 3) maximum lateral extension of the transtuberculum transplanum approach followed by postdissection CT scans, and 4) bone removal and surgical freedom analysis (a nonpaired Student t-test). A conventional subfrontal bilateral approach was used to evaluate, from above, the bone removal from the planum sphenoidale and the lateral limit of the endonasal route. RESULTS The endoscopic endonasal transtuberculum transplanum approach was extended at its maximum lateral aspect in the lateral portion of the anterior skull base, removing the bone above the optic prominence, that is, the medial portion of the lesser sphenoid wing, including the anterior clinoid process. As expected, a greater bone removal volume was obtained compared with the approach when bone removal is limited to the medial optocarotid recess (average 533.45 vs 296.07 mm; p < 0.01). The anteroposterior diameter was an average of 8.1 vs 15.78 mm, and the laterolateral diameter was an average of 18.77 vs 44.54 mm (p < 0.01). The neurovascular contents of this area were exposed up to the insular segment of the middle cerebral artery. The surgical freedom analysis revealed a possible increased lateral maneuverability of instruments inserted in the contralateral nostril compared with a midline target (average 384.11 vs 235.31 mm; p < 0.05). CONCLUSIONS Bone removal from the medial aspect of the lesser sphenoid wing, including the anterior clinoid process, may increase the exposure and surgical freedom of the extended endoscopic endonasal transtuberculum transplanum approach over the lateral segment of the anterior skull base. Although this study represents a preliminary anatomical investigation, it could be useful to refine the indications and limitations of the endoscopic endonasal corridor for the surgical management of skull base lesions involving the lateral portion of the planum sphenoidale.

Journal of Neurosurgery

Section: Quantitative Analysis Statistical Analysis 3d Reconstructimentioning

confidence: 99%

mentioning

confidence: 99%

Defining the lateral limits of the endoscopic endonasal transtuberculum transplanum approach: anatomical study with pertinent quantitative analysis

Somma

Torales

Cavallo

et al. 2019

Self Cite

“…Cadaveric specimens were processed based on previously described methods. [9] The retractor blade was withdrawn from 0.0 to 2.5 cm in 0.5 cm increments for orbital retraction from the orbital rim to the coronal plane. The average values of three IOP and IORP measurements were obtained.…”

Section: Cadaver Studiesmentioning

confidence: 99%

Optimization of orbital retraction during endoscopic transorbital approach via quantitative measurement of the intraocular pressure – SevEN 006

Moon

et al. 2020

Preprint

Background: Increased use of the transorbital approach (TOA) warrants greater understanding of the risk of increased intraocular pressure (IOP) and intraorbital pressure (IORP) due to orbital compression. We aimed to investigate the changes in IOP and IORP in response to orbital retraction in TOA and establish a method for the continuous measurement of intraoperative IORP.Methods: We assessed nine patients who underwent TOA surgery from January 2017 to December 2019, in addition to five cadavers. IORP and IOP were measured using a cannula needle monitor, tonometer, cuff manometer, and micro strain gauge monitor.Results: In all nine clinical cases and five cadavers, increased physical compression of the orbit increased the IOP and IORP in a curvilinear pattern. In clinical cases, when the orbit was compressed 1.5 cm from the lateral margin in the sagittal plane, the mean IOP and IORP were 25.4±5.2 mmHg and 14±9.2 mmH2O, respectively. The IORP satisfactorily reflected the IOP (Pearson correlation coefficient=0.824, p<0.001).Conclusion: We measured IOP and IORP simultaneously during orbital compression to gain basic information on pressure changes. In clinical cases, the change in the IOP could be conveniently and noninvasively monitored using continuous IORP measurements.

“…Cadaveric specimens were processed based on previously described methods. [9] The blade was withdrawn from 0 to 2.5 cm in 0.5 cm increments for orbital retraction from orbital rim to coronal plane, the average value of three IOP and IORP measurements were obtained.…”

Section: Cadaver Studiesmentioning

confidence: 99%

“…An oculoplastic surgeon performed the TOA protocol similar to previous cadaver studies. [9] An ophthalmologist measured IOP at the beginning of surgery. Pressure measurement was taken at intervals of 10 minutes.…”

Section: Clinical Casesmentioning

confidence: 99%

Optimization of Orbital Retraction During Endoscopic Transorbital Approach: Quantitative Measurement of Intraocular Pressure - SevEN 006

Moon

et al. 2020

Preprint

Background: Increased utilization of transorbital approach (TOA) necessitates study of the risk of increased intraocular pressure (IOP) and intraorbital pressure (IORP) due to orbital compression. We aimed to investigate the changes in IOP and IORP in response to orbital retraction in TOA and establish a method for continuous measurement of intraoperative IORP.Methods: We investigated nine patients who underwent TOA surgery from January 2017 to December 2019, and five cadavers. IORP and IOP were measured using a cannula needle monitor, tonometer, cuff manometer, and micro strain gauge monitor.Results: In all nine clinical cases and five cadavers, increased physical compression of the orbit increased the IOP and IORP in curvilinear pattern. In clinical cases, when the orbit was compressed 1.5 cm from the lateral margin in the sagittal plane, mean IOP and IORP levels were measured at 25.4±5.2 mmHg and 14±9.2 mmH2O, respectively. The IORP reflected the IOP satisfactorily (Pearson correlation coefficient=0.824, p<0.001).Conclusion: We measured IOP and IORP simultaneously during orbital compression offering the basic information of the pressure change. In clinical cases, we found that the change in IOP can be monitored conveniently and noninvasively using continuous IORP measurement.