Original Japanese devices and ingenious techniques discovered during the last quarter of a century has impacted the development of neuroendoscopic surgery.

  First, the refinement of the neuroendoscope in Japan. The world-leading flexible endoscope has evolved from a fiberscope to a videoscope with a CCD at the tip. It has been used for removing intraventricular hematoma, ventricular lavage, and choroid plexus coagulation, which are frequently indicated in low- and middle-income countries to avoid cerebral spinal fluid shunt. A unique holder for a rigid endoscope with a passive robotic arm system has been designed in collaboration with neurosurgeons and Japanese companies. This enables the surgeons to effortlessly release and fix the scope with nitrogen gas pressure. Currently, it is widely used for keyhole and skull base surgeries in foreign countries. Second, transparent sheath is a simple and world-famous device. This sheath transformed the hematoma removal surgery into an endoscope solo procedure in Japan. The procedure has been disseminated worldwide and applied to the biopsy or excision of intraparenchymal lesions. Finally, the novel concept of cylinder neurosurgery was developed.

  Along with the development of equipment and techniques, the first certified system for neuroendoscopy was established in Japan. Some training courses using simulation models were designed simultaneously to standardize basic procedures and guarantee safety. This serves as a useful reference for education and training in foreign countries.

  Pioneers in Japan encouraged ‘glocalization’ of some equipments and techniques ridiculed as Galápagos syndrome. Next generation should take pride in this history and continue best original inventions.

  Stereotactic and functional neurosurgery (SFN) is one of the oldest subspecialties of neurosurgery. In Japan, functional epilepsy surgery was performed in the Meiji era, and general surgeons operated on patients with intractable cancer pain with open myelotomy and cordotomy even before World War Ⅱ. The knowledge gained from such old procedures contributed to the understanding of neurophysiology. Therefore, functional neurosurgery was known as “applied neurophysiology”. Human stereotactic surgery started in 1947, and many Japanese neurosurgeons, particularly Hirotaro Narabayashi, Keiji Sano, and Chihiro Ohye, have contributed to the development of this field. We also have to remember that common procedures currently used in neurosurgery, such as neuroendoscopy, navigation surgery, intraoperative monitoring, and the concept of exo-scope, are taken from SFN, which pursue less invasive and accurate surgery. Research on the Forel H field in the 1960s in Japan is now being revived for the treatment of epilepsy, Parkinson's disease, and dystonia. Young doctors should learn from the history and understand where we come from, where we are now, and where we are going. This is very important for Japan's contribution to many untreated patients.

  While the middle and long-term essential tremor outcome after magnetic resonance-guided focused ultrasound (MRgFUS) is well documented, the immediate and early postoperative tremor outcome is less documented. We aimed to characterize the clinical significance of the immediate and early post-MRgFUS tremor fluctuation in patients with essential tremor.

  We retrospectively analyzed the consecutive 23 patients with essential tremor who underwent MRgFUS of thalamic ventral intermediate nucleus in our institute. Therapeutic outcomes were scored using clinical rating scale for tremor (CRST) part A and B (part A＋B). We also measured the areas of MR T2-weighted hypointense (zone 1) and peripheral hyperintense (zone 2) on the immediately postoperative MR images. The clinical characteristics, MRgFUS parameters, CRST part A＋B score, and zone 1＋2 area were compared between the group with more than 50% improvement and the group with 50% or less improvement immediately after the MRgFUS. The CRST part A＋B scores were examined from the preoperative to 6-12-month postoperative period using repeated measure analysis of variance (ANOVA). The odds ratio between the early postoperative tremor fluctuation and the 6-12-month postoperative tremor improvement was calculated.

  Immediately postopertive CRST part A＋B scores improved by more than 50% in 18 patients (78%) and by 50% or less in five patients (22%). The area for the zone 1＋2 was 13.1±4.2mm² in the patients with improvement and 21.7±8.9mm² in the patients without immediate improvement (p=0.037). A repeated measure ANOVA demonstrated that the CRST part A＋B scores improved significantly in each postoperative period compared to the preoperative baseline score (p＜0.001). Among the 20 patients with 6-12-month follow-up, eight patients (36%) had deterioration of tremor within the first three months and five of them had ineffective outcome in the postoperative 6-12 months. The odds ratio between tremor fluctuation in 1-3 months and ineffective tremor control in 6-12 months was 8.33 (p=0.046).

  Patients with ineffective essential tremor control after MRgFUS tend to have a large zone 1＋2 area. Early tremor fluctuation may indicate ineffective tremor control in the middle and long term. Further targeting accuracy is necessary to improve the long-term tremor outcome for patients with essential tremor.

  Diploic veins sometime develops into collateral venous pathways in patients with superior sagittal sinus (SSS) thrombosis due to a large parasagittal meningioma. Preserving the diploic venous system is essential for preventing bleeding and venous infarcts. However, few reports have described methods for avoiding damage to the diploic venous system. Herein, we report successful tumor resection while preserving the diploic venous system. Three-dimensional multislice computed tomographic angiography was used for preoperatively determining the positional relations between the tumor, SSS, and diploic venous system. Catheter angiography helped in understanding the detailed perfusion dynamics of the veins. Based on this preoperative information, it is important to design a craniotomy to preserve veins during surgery.

  This report presents a case of skin reconstruction using a rotation flap for a medium-sized scalp defect after resection of a metastatic skull tumor. Although skin defects exceeding 20cm² are preferred for treatment with various types of free flaps, these procedures result in poor aesthetic outcomes.

  A 37-year-old female patient undergoing chemotherapy for breast cancer presented with a protruding lesion on the skull. Magnetic resonance imaging (MRI) and biopsy performed in the department of plastic surgery revealed a metastatic skull tumor. After six months of follow-up, MRI showed rapid growth of the lesion, with invasion into the superior sagittal sinus and subcutaneous tissue. Surgical resection was indicated with suspension of chemotherapy. The tumor was completely resected, with a 1cm negative margin, followed by scalp reconstruction for a skin defect of approximately 30cm² using a large unilateral rotation flap to achieve a satisfactory cosmetic outcome. The patient was discharged one week after surgery to resume chemotherapy.

  A 76-year-old man who had undergone total bladder cancer resection one and a half year ago without recurrence or metastasis was presented. He started experiencing right lower limb pain two months prior accompanied by a right foot drop two weeks ago. On admission, severe right lower limb pain, weakness of the right anterior tibialis muscle, and toe dorsiflexion were noted. Routinely performed lumbar magnetic resonance imaging (MRI) revealed slight lumbar spinal stenosis at the L3/4 and L4/5 levels, which could not explain the exact mechanism of the patient's complaints and neurological deficits. Considering the severe leg pain and rapidly progressing foot drop, we suspected malignant lesions despite the former doctor's comments. Positron emission tomography scan was performed to rule out malignant disorders, which revealed a pelvic metastatic tumor in the right lumbosacral nerve trunk and plexus. The passage of the L5 and S1 nerves through the mass lesion at the lumbosacral plexus was clearly described by the MR neurography.

  In this report, the authors gained vast knowledge about medical history taking, and meticulously performed neurological and image examination depending on the targeted lesion. The authors discussed lumbosacral plexus lesion as a cause of foot drop.