Mild traumatic brain injury (MTBI) was first advocated by the American Association of Rehabilitation Medicine (ACRM) in 1993 and was defined as an alteration of brain function attributable to external forces with one or more of the following : loss of consciousness for 0-30 minutes, post-traumatic amnesia for less than 24 hours, focal neurologic deficits that may or may not be transient, and an alteration of mental state at the time of the accident, including any confusion, disorientation, or slowed thinking. Per ACRM definition, MTBI is defined mainly for subjective symptoms and does not consider objective findings, such as severity and diagnostic imaging. Because of this confusion, the World Health Organization Collaborating Centre for Neurotrauma Task Force on MTBI proposed its definition based on the review of the literature in 2004. Their criteria are similar to those proposed by ACRM, except they specify the use of a Glasgow Coma Scale score of 13-15 at the presentation time to a healthcare professional instead of restricting it to a score within 30 minutes. Further, a systematic review conducted in 2014 based on this definition reported frequent incidence of cognitive impairment of MTBI for 2 weeks after injury and consciousness disorder. However, MTBI-related cognitive deficits were found to recover within a year after injury, and most of them were cerebral concussions. A concussion is representative of mild head trauma, and a single concussion does not lead to brain dysfunction, such as permanent cognitive impairment. In Japan, the term “MTBI” does not exist as a disease name in neurosurgery, nor is it a medical term with a unified definition. However, MTBI is confused with “mild head injury,” and the term is easily used when claiming damage. Even if a brain injury is present in “mild head trauma,” mild trauma does not cause organic brain injury. In this review, we explain the term “MTBI” and focus on associated cognitive dysfunction from our case studies and literature review.

  Stem cell therapies for the central nervous system are rapidly progressing from basic research to clinical research. Some of them have proved their safety and efficacy in the early phase of clinical trials and are moving into the late phase focusing on drug approval. In this article, we report the mode of action of stem cell therapies in the central nervous system and our recent results of phase 2a trials using intraparenchymal transplantation of mesenchymal stromal cells for patients with chronic traumatic brain injury.

  The rapid aging of Japanese society has increased the importance of antithrombotic therapy due to increases in the prevalence of atrial fibrillation and in arteriosclerotic diseases such as myocardial infarction and cerebral infarction in elderly people. This situation requires physicians in all clinical departments to understand the correct usage of antithrombotic drugs. The effectiveness of these drugs for treatment and prevention of ischemic diseases is well established. In recent years, the range of choices has expanded in terms of the wide variety of antiplatelet drugs and anticoagulants, indications for optional treatments such as dual antiplatelet therapy (DAPT), and the timing and duration of administration. Aggressive antithrombotic therapy for ischemic disease is required, but this has a risk of bleeding complications. Proper usage is needed in consideration of efficacy and safety, and a wide range of knowledge about antithrombotic drugs is required. First, administration methods that reduce risk are important. In addition, when complications occur, these must be minimized by taking appropriate measures, including discontinuation of antithrombotic therapy and use of reversal therapy. However, there are many concerns about the indication and timing of reversal therapy, and subsequent resumption of antithrombotic drugs is not specified in guidelines, with each procedure currently performed based on experience. In this paper, we review the efficacy and safety of antithrombotic drugs, with a focus placed on evidence.

  In Japan, the number of dementia patients is increasing as the population ages. Neurosurgeons are required to be involved in the early diagnosis and treatment of dementia. Therefore, it is necessary to acquire the basic knowledge necessary for dementia treatment.

  Under the changing population composition and disease structure in an aging society, the National Health Insurance System in Japan is facing a major turning point due to the heavy medical cost restraint pressure, the imminent work style reforms of doctors, and the COVID-19 disaster. From the neurosurgery perspective, maximum efforts should continue on daily medical treatment and ensure the sustainability of the organization to reflect the progress of neuroscience and related fields at the forefront. Given the economic basis for such a purpose, the reimbursement of the National Health Insurance System can be considered an evaluation from society for neurosurgery.

  The current state and various issues of the National Health Insurance System in neurosurgery should be addressed by demonstrating high professional ethics and professional autonomy. Further, high attention should be paid to recognize its importance in postgraduate education.

  Chronic subdural hematoma (CSDH) is one of the most common neurosurgery diseases among elderly patients. This study aimed to investigate the past trends of CSDH in Yamagata Prefecture, comprising mostly the aging population compared to Japan as a whole, and predict the CSDH future aspects. In 2004-2018, 4,096 patients with CSDH were treated in hospitals in Yamagata prefecture, and their mean age was 76.5 years. The CSDH incidence increased from 17.3/100,000/year to 35.9/100,000/year, and the mean age at the onset increased from 74.2 years to 78.4 years between 2004 and 2018. A modified Rankin Scale (mRS) of 3-6 at discharge or 1 month later was presented by 18.4% of patients. Further, 0.7% of the patients presented an increase in mRS of 0-2 at admission to 3-6 at discharge, whereas 27.7% of patients presented an mRS of 3-6 both at admission and at discharge, indicating a significantly higher proportion of patients than the former. Therefore, this study revealed that the incidence and onset age increased over time and that mRS at admission was correlated with prognosis in CSDH patients.

  Papillary glioneuronal tumor (PGNT) is a new type of tumor proposed in 1998. According to the 2007 World Health Organization classification of the central nervous system, PGNT is classified as a mixed glioneuronal tumor. Only 100 cases have been reported worldwide, and its mechanism is still unclear.

  We report the case of a 28-year-old woman with a PGNT. Her symptoms were headache only. Magnetic resonance image of the head revealed a 74mm cystic mass in the right temporal lobe. A nodular lesion with contrast effects was observed. The tumor was completely resected. Histologically, a single layer of cells appeared to be lining around the hyalinized blood vessels, forming pseudopapillary structures, and immunostaining was positive for glial fibrillary acidic protein, S-100, and nestin. Proliferating cells were found between the pseudopapillary structures, and synaptophysin and neuron-specific enolase were positive. After surgery, the patient had no recurrence for 2 years. Patients with PGNT should be carefully followed because of previous reports of recurrence incidence.