The Parietal Notch: A Surgical Landmark for Students Learning Mastoid Surgery

Mastoidectomy is a procedural skill that must be mastered by otolaryngology residents to perform otologic surgery. Surgical exposure of the middle and inner ear through the mastoid using cadaveric specimens is a standard simulation method to teach three-dimensional anatomy of the ear to residents. Neurovascular structures, sensory organs and minute components of the hearing apparatus are hidden inside dense bone, and therefore, exposing these delicate features is challenging. Landmarks on the mastoid surface guide the initial dissection, using a drill, allowing the operator to identify deeper landmarks. For novice surgeons, these landmarks are critical to perform safe otologic surgery. We asked whether the parietal notch, a bony suture line, is a reliable and accurate surface landmark that defines the posterior aspect if the mastoid process of the temporal bone. This posterior margin should be defined by the sinodural angle internally. If the parietal notch is demonstrated to provide a reliable approximation of the sinodural angle it will greatly help novice surgeons understand the the extent of their temporal bone dissections