A Comparison of Approaches and Comprehensive Guide for a Complete Cadaveric Central Nervous System Extraction

Abstract

The opportunity to learn anatomy through the examination and dissection of human tissue is a valuable experience that allows students the opportunity to visualize complex spatial relationships between various anatomical structures. This is equally true in neuroanatomy education. However, due to time and tissue limitations, nervous system dissections are limited. In particular, the extraction of the full central nervous system (CNS) is rarely if ever performed in part due to time constraints, difficulty, and lack of instructions. In fact, there are no instructions, nor are there comparisons of different approaches in the anatomy literature or in textbooks for performing a complete CNS extraction. The goals of this project were 1) to provide a comprehensive, detailed, step‐by‐step guide for performing a human cadaver CNS extraction and 2) to compare and contrast various approaches for major steps of the dissection. Three human cadavers without apparent cranial/vertebral deformity or neurodegeneration were acquired from the State Anatomical Board of Colorado and used in anatomy courses in at the University of Colorado Anschutz Medical Campus. Full CNS extractions were performed in which the brain, brainstem, spinal cord, cauda equina, dorsal root ganglia, eyes, and extraocular muscles were removed in one piece from each cadaver. Steps of the extraction were documented and photo/video footage was recorded. We compared different methods and approaches for major steps across the three dissections according to: 1) time, 2) tools, and 3) preservation of (i.e. minimal damage to) the tissue. By comparing methods and approaches across three dissections, we determined the best order to proceed through the dissection, the optimal tools, and the most efficient approaches. Highlights of these findings include the following: a traditional bone saw (ThermoShandon Model #10000) was superior to a SONOPET (Stryker Model #UST‐2001) ultrasonic surgical bone for performing a laminectomy caudal to the C1 vertebra. In addition, the C1 vertebra was best removed with a chisel rather than a bone saw. Moreover, the timing of the C1 removal was critical; its preservation until after the craniotomy and occipital wedge removal minimized risk for spinal cord damage. Additionally, removal of the frontal bone in three pieces improved accessibility to the orbit and optic canal. Based on our results we developed a comprehensive written and video guide for this dissection in the following order: 1) cleaning and preparation, 2) laminectomy, 3) craniotomy, 4) occipital wedge, 5) C1 removal, 6) removal of dura mater, 7) cutting of spinal and cranial nerves, 8) orbit exposure and eye removal, 9) final extraction, and 10) cleaning. By refining techniques in each dissection, we reduced the time required for one prosector to perform the CNS extraction (steps #1–9) from 20 hours to 5 hours; Step #10 (cleaning) required approximately 10 hours in all three dissections. We anticipate that this dissection guide will be a valuable resource for anatomists to more efficiently and precisely perform a full cadaveric CNS extraction. In the future, this guide may be used to build curriculum for advanced dissection courses, to prepare special prosections for traditional anatomy courses, or to develop unique educational displays in plastinated tissue libraries or exhibits.