Hearing Preservation During Anterior Petrosectomy: the “Cochlear Safety Line”

• Published in: World neurosurgery 2017-03, Vol.99, p.618-622
• Main Authors: Guo, Xiaoming, MD, Tabani, Halima, MD, Griswold, Dylan, Tayebi Meybodi, Ali, MD, Sanchez, Jose Juan Gonzalez, MD, PhD, Lawton, Michael T., MD, Benet, Arnau, MD
• Format: Article
• Language: English
• Subjects: Anatomic Landmarks; Anterior petrosectomy; Cadaver; Cochlea; Cochlea - injuries; Craniotomy - methods; Foramen ovale; Foramen spinosum; Hearing Loss - prevention & control; Humans; Internal acoustic canal; Kawase approach; Neurosurgery; Neurosurgical Procedures - methods; Petrous Bone - surgery; Postoperative Complications - prevention & control
• ISSN: 1878-8750; 1878-8769
• DOI: 10.1016/j.wneu.2016.11.019

Abstract Background Identification and protection of the cochlea during anterior petrosectomy is key to prevent hearing loss. Currently, there is no optimal method to infer the position of the cochlea in relation to the Kawase quadrangle, therefore damage to the cochlea during anterior petrosectomy remains a substantial risk. Objectives To identify and define landmarks available during anterior petrosectomy to locate the cochlea and prevent its damage. Methods Kawase approach was simulated in eleven specimens. After a subtemporal craniotomy, foramen spinosum and ovale were identified. Anterior petrosectomy was performed and the upper dural transitional fold (UDTF) was identified. Two virtual lines, from foramen spinosum (Line A), and the lateral rim of the foramen ovale (Line B), were projected to intersect the UDTF perpendicularly. The cochlea was exposed and the distances between Lines A and B and the closest point of the outer rim and membranous part of the cochlea were measured. Results The average distance between Line A to the bony and membranous edges of the anteromedial cochlea was -0.62±1.38 mm and 0.38±1.63 mm, respectively. The average distance between Line B to the bony and membranous edges of the cochlea was 1.82±0.99 mm and 2.78±1.29 mm, respectively. Line B (cochlear safety line) never intersected the cochlea. Conclusions The cochlear safety line is a reliable landmark to avoid the cochlea during the Kawase approach. When expanding the anterior petrosectomy posteriorly, the “cochlear safety line” may be used as a reliable landmark to prevent exposure of the cochlea, therefore preventing hearing loss.