Developing a Method to Precisely Locate the Keypoint During Craniotomy Using the Retrosigmoid Keyhole Approach: Surgical Anatomy and Technical Nuances.

Zhi-Heng Jian,Min-Feng Sheng,Gang Chen,Zhi-Jian Weng,De-Zhu An,Jia-Yan Li

doi:10.3389/fsurg.2021.700777

Abstract

Objective: To explore the precise location of the keypoint during craniotomy using the retrosigmoid keyhole approach.Methods: This study included 20 dry skulls and 10 wet cadaveric specimens. On the inner surface of dry skulls, the junction between the inferior margin of the transverse sinus (ITS) and the posterior margin of the sigmoid sinus (TSJ) was marked. The keypoint (D) was identified as the TSJ's corresponding point on the external surface of the temporal mastoid process (MP). The distance from the keypoint to the top point of the digastric groove, mastoidale, and asterion were noted (AD, BD, CD, respectively). A method to accurately locate the keypoint was developed based on these relationships. The developed method was used on the wet cadaveric specimens to evaluate its accuracy, safety, rapidity, and minimal invasion.Results: No significant difference was found between the AD, BD, and CD of the left and right sides. The drilling point was oriented on a straight line 12 mm above the top point of digastric groove, perpendicular to the Frankfort horizontal plane (FHP). In the cadaveric specimens, the operative area was clearly exposed. No venous sinus rupture occurred. The average craniotomy time was 28.74 ± 3.89 min.Conclusions: A potentially safe, accurate, and rapid craniotomy procedure was developed with the added advantage of preserving the visibility of the operating field and preventing venous sinus injury.

Highlights

The suboccipital retrosigmoid approach commonly used in the management of lesions of the cerebellopontine angle including vestibular schwannoma, choleostoma, trigeminal neuralgia, and facial spasm [1,2,3,4,5,6,7]
The development of minimal invasive surgery has led to an increased application of the retrosigmoid keyhole approach; this approach emphasizes a proximity between the superior and anterior margins of the bond window with the inferior margin of the transverse sinus (ITS) and the posterior margin of the sigmoid sinus, respectively [6, 8,9,10,11]
The top point of the digastric groove, the mastoid foramen, and the superior nuchal line (SNL) were identified on the surface of the skulls (Figure 2B). [4] According to previous observations in the dry skulls, the drilling point was confirmed: 12 mm above the top point of the digastric groove on a straight line perpendicular to the base line (E) (Figure 2C). [5] A burr hole was grounded with the drilling point serving as the central point

Summary

Introduction

The suboccipital retrosigmoid approach commonly used in the management of lesions of the cerebellopontine angle including vestibular schwannoma, choleostoma, trigeminal neuralgia, and facial spasm [1,2,3,4,5,6,7]. It is characterized by a minimal incisions and bone flaps measuring 4 cm and 20 × 25 cm, respectively. This study aimed to the develop a new method of orientation to the keypoint and burr hole on the external surface of the mastoid process (MP)

Methods

Results

Conclusion