Thiel’s embalming method with additional intra-cerebral ventricular formalin injection (TEIF) for cadaver training of head and brain surgery

Anatomical Science International https://doi.org/10.1007/s12565-020-00545-z METHOD PAPER Thiel’s embalming method with additional intra‑cerebral ventricular formalin injection (TEIF) for cadaver training of head and brain surgery Shigeta Miyake1 · Jun Suenaga1 · Ryohei Miyazaki1 · Jo Sasame1 · Taisuke Akimoto1 · Takahiro Tanaka1 · Makoto Ohtake1 · Hajime Takase1 · Kensuke Tateishi1 · Nobuyuki Shimizu1 · Hidetoshi Murata1 · Kengo Funakoshi2 · Tetsuya Yamamoto1 Received: 23 December 2019 / Accepted: 17 April 2020 © The Author(s) 2020 Abstract Thiel’s embalming method provides natural coloration, flexibility, and tissue plasticity, and is used widely to prepare specimens for cadaver surgical training. However, this method causes brain softening, thereby restricting the cadaver surgical training of intra-cranial procedures. In this study, three cadavers were embalmed using formalin fixation, Thiel’s embalming method, and Thiel’s embalming method with additional intra-cerebral ventricular formalin injection, respectively. We also established rat models of the three embalming methods to develop and determine the best method for retaining adequate brain elasticity. The intra-ventricular formalin injection in the cadaver was performed through the Kocher’s point, as in the classical external ventricular drain procedure. Both, the cadaver brains and rat models yielded consistent shear wave measurements and brain surface stiffness data. Notably, the Thiel’s embalming method with additional intra-cerebral ventricular formalin injection yielded suitable elasticity for brain cadaver surgical training in terms of brain mobilization and surgical field deployment, and also discharged formaldehyde in undetectable quantities. To our knowledge, this is the first report in which a fixed quality, namely, brain elasticity for the performance of head and brain cadaver surgical training, has been evaluated in a cadaver subjected to the Thiel’s embalming method with immersion fixation in the cerebrospinal fluid space. We conclude that the Thiel’s embalming method with additional intra-cerebral ventricular formalin injection can maintain the brain elasticity, and may therefore improve the quality of head and brain cadaver surgical training safely and easily. Keywords Brain · Cadaver · Elasticity imaging techniques · Embalming · Neurosurgery Introduction The performance of surgical procedures requires equivalent levels of knowledge of anatomy and dissection techniques. Traditionally, anatomical studies have provided essential structural and morphological knowledge. In recent years, the introduction of various novel devices has increased the complexity of surgical procedures, and surgeons must take precautions to reduce the incidence of adverse events. Therefore, in addition to knowledge from textbooks, surgeons aim to gain practical experience with surgical maneuvers. To * Shigeta Miyake shige_m@yokohama‑cu.ac.jp 1 Department of Neurosurgery, Yokohama City University, 3‑9 Fukuura, Kanazawa, Yokohama 2360004, Japan 2 Department of Neuroanatomy, Yokohama City University, 3‑9 Fukuura, Kanazawa, Yokohama 2360004, Japan meet this demand, cadaver surgical training (CST) has been introduced worldwide to enable improvements in surgical techniques and outcomes (Hayashi et al. 2016). Although CST has been performed using both, fresh and conventional formalin-fixed cadavers, certain problems have been identified (Hayashi et al. 2014). Embalming is generally required to ensure safe and reliable fixation, and to ensure a life-like tissue quality for CST, which aims to reproduce surgical techniques and views. Fresh cadavers exhibit excellent tissue preservation; however, special freezing facilities are required to prevent bacterial infection and decomposition. Traditional formalin fixation provides excellent tissue fixation and disinfection; however, it increases both the stiffness of tissues and the exposure of trainees to formaldehyde. Previous reports have described the embalming method first introduced by Walter Thiel in 1992 as among the most suitable for CST, as it provides reliable fixation and 13 Vol.:(0123456789) S. Miyake et al. disinfection, thereby retaining the color, flexibility, and plasticity of tissues (Thiel 2002; Liao et al. 2015; Ottone et al. 2016). The literature published up to 2016 includes 82 reports that discuss the life-like tissue, organ flexibility, and plasticity provided by this method (Ottone et al. 2016). Using shear wave echo elastography, Joy et al. (2015) found that cervical organs and muscles fixed using Thiel’s embalming method retained a life-like level of elasticity (Eisma et al. 2011, 2013; Verstraete et al. 2015). Despite its advantages, Thiel’s embalming method causes softening of the brain (Benkhadra et al. 2011), which leads to major issues of crumbling and melting of the tissues during neurosurgical CST. Although Thiel’s embalming method enables reproducible extra-dural surgical views owing to tissue flexibility, intra-cranial surgical procedures have not been reproducible in these specimens. Here, we report the use of Thiel’s embalming method with additional intra-cerebral ventricular formalin injection (TEIF), which aimed to improve brain plasticity and tissue flexibility. Materials and methods All cadavers used in this study were donated in accordance with living wills and the informed consent of bereaved family members, and this manuscript complies with Japanese acts and guidelines (the Postmortem Examination and Corpse Preservation Act, Act on Body Donation for Medical and Dental Education, and Guidelines for Cadaver Dissection in Education and Research of Clinical Medicine). Ethical approval for this study was granted by the Yokohama City University Human Ethics Committee (A1802000002) in accordance with the Guidelines for Cadaver Dissection in Education and Research of Clinical Medicine. All cadavers used in this study were prepared for a CST course intended for neurosurgeons. Anatomical photographs were obtained during CST procedures using a surgical microscope (KINEVO 900 and OPMI PENTERO 800) leased from Carl Zeiss Meditech (Jena, Germany). Table 1  Characteristics of the three cadavers Three cadavers were embalmed using formalin fixation, Thiel’s embalming method, and TEIF, respectively (Table 1). Formalin embalming was performed using 10% formaldehyde and a reflux fixation procedure via the femoral artery. Thiel’s embalming (Hayashi et al. 2014) was performed using solutions A, B, C, and 40% formaldehyde (the final concentration of formaldehyde was adjusted to 2%), with a reflux fixation procedure via the common carotid artery (Fig. 1a). Thiel’s embalming solution was purchased from A.S. Chemical (Osaka, Japan). TEIF was initially performed as described for Thiel’s embalming, with the addition of an intra-cerebral ventricular injection of formalin 2 days before decapitation (Fig. 1b–e). The intra-cerebral ventricular injection of formal (...truncated)