Shock Waves DOI 10.1007/s00193-017-0753-5 REVIEW Primary blast-induced traumatic brain injury: lessons from lithotripsy A. Nakagawa 1 · K. Ohtani 2 · R. Armonda 3 · H. Tomita 4 · A. Sakuma 5 · S. Mugikura 6 · K. Takayama 7 · S. Kushimoto 8 · T. Tominaga 1 Received: 31 December 2016 / Revised: 11 July 2017 / Accepted: 16 August 2017 © Springer-Verlag GmbH Germany 2017 Abstract Traumatic injury caused by explosive or blast events is traditionally divided into four mechanisms: pri- mary, secondary, tertiary, and quaternary blast injury. The mechanisms of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury mecha- nism is associated with the response of brain tissue to the initial blast wave. Among the four mechanisms of bTBI, Communicated by O. Petel and S. Ouellet. B A. Nakagawa nakagawa@nsg.med.tohoku.ac.jp 1 Department of Neurosurgery, Tohoku University Graduate School of Medicine, 1-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan 2 Interdisciplinary Shock Wave Application Research Division, Institute of Fluid Science, Tohoku University, Sendai, Miyagi, Japan 3 Neuroendovascular Surgery, Neurotrauma, NeuroICU, MedStar, Washington Hospital Center, Georgetown University Hospital, Washington, DC, USA 4 Department of Disaster Psychiatry, International Research Institute of Disaster Science, Tohoku University, Sendai, Japan 5 Department of Psychiatry, Tohoku University Graduate School of Medicine, Tohoku University Hospital, Sendai, Japan 6 Department of Diagnostic Radiology, Tohoku University Graduate School of Medicine, Sendai, Japan 7 Department of Cardiology, Tohoku University Graduate School of Medicine, Sendai, Japan 8 Division of Emergency and Critical Care Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan there is a remarkable lack of information regarding the mech- anism of primary bTBI. On the other hand, 30 years of research on the medical application of shock waves (SWs) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and under- water SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by shock- accelerated flow. The resultant tissue injury includes several features observed in primary bTBI, such as hemorrhage, edema, pseudo-aneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathologi- cal findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interac- tion, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation are all important factors in determining the extent of SW-induced tissue and cellular injury. In addition, neuropsychiatric aspects of blast events need to be taken into account, as evidenced by reports of comorbidity and of some similar symptoms between physi- cal injury resulting in bTBI and the psychiatric sequelae of post-traumatic stress. Research into blast injury biophysics is important to elucidate specific pathophysiologic mechanisms of blast injury, which enable accurate differential diagno- sis, as well as development of effective treatments. Herein we describe the requirements for an adequate experimental setup when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measure- ment/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mecha- nisms of primary bTBI. Keywords Traumatic brain injury · Blast injury · Animal model · Emergency medicine · Neurocritical care · Neurosurgery · Shock waves · Translational research 123