Peripheral nerve neuropathy due to nerve entrapment is not uncommon. Peripheral nerve entrapment (PN-EN) must be differentiated from brain and spinal cord diseases ; its treatment requires less invasive microsurgery. As many patients with numbness or paralysis of the extremities are seen in the neurosurgery outpatient clinic, we recommend that neurosurgeons incorporate the treatment of PN-EN into their daily practice and provide some suggestions.

  The diagnosis of PN-EN is performed in 5 steps. (1) Does the patient present with a single neuropathy. (2) Is the symptom exacerbated when a load is applied (the provocation test may be useful). (3) Is there a Tinel-like sign at the suspected entrapment site. (4) Nerve blocks may be diagnostic. (5) Electrophysiological and magnetic resonance studies may be useful.

  When patients report to the outpatient clinic complaining of hand numbness, carpal tunnel syndrome must first be ruled out. When they present with numbness of the lower limbs, 3 areas must be checked. (1) The anterior lateral thigh (lateral femoral cutaneous neuropathy), (2) the instep from the outside of the lower leg (common peroneal neuropathy), and (3) the sole of the foot (tarsal tunnel syndrome).

  Para-lumbar spine diseases are also often encountered in patients seen on an outpatient basis. We recommend that the neurosurgeon divide the pain area into 3 areas, (1) around the iliac crest (superior cluneal neuropathy), (2) the medial buttock (middle cluneal neuropathy), and (3) the lateral buttock (gluteus medius muscle pain and piriformis syndrome).

  The diagnosis and treatment of these diseases require the elucidation of the pathological background and the development of diagnostic tools. We encourage Japanese neurosurgeons to incorporate the diagnosis and treatment of PN-EN into their daily practice and suggest that PN-EN treatment be recognized as an area of Japanese neurosurgery.

  Currently, the gold standard for the surgical treatment of cervical degenerative diseases is anterior cervical discectomy and fusion (ACDF) and laminoplasty (or laminectomy). However, unresolved problems include adjacent segment disease after ACDF and kyphosis after laminoplasty (or laminectomy). As a recent topic for cervical degenerative diseases, the new anterior technique, which is anterior cervical disc replacement (ACDR), has become available in Japan. ACDR is a relatively new motion-preserving procedure and is expected to prevent adjacent segment disease. Although good surgical results have been reported in Western and Asian countries except for Japan, where it has been introduced in advance. The long-term results in Japan are unknown, and careful follow-up is required. Cervical laminoplasty (or laminectomy) is indicated for cases with the preoperative alignment of lordosis or mild kyphosis. Despite the maintenance of preoperative alignment, some patients have poor postoperative surgery results. Therefore, the concept of cervical spine sagittal balance was proposed, as well as the thoracolumbar spine sagittal balance. The C2-C7 sagittal vertical axis, which indicates the anterior deviation of the cervical spine ; the chin-brow to vertical angle, which is an index of horizontal vision ; the T1 Slope, which is an index of cervical lordosis ; and cervical lordosis are used as the parameters of cervical spine sagittal balance. It is becoming an index for selecting surgical procedures.

  With the increasing prevalence of spinal degenerative diseases, curative treatment is necessary. Here, we report diagnostic and minimally invasive treatment methods for lumbar degenerative diseases. We describe diffusion tensor imaging as a diagnostic modality and a minimally invasive percutaneous procedure for a herniated lumbar disc. Finally, we report the current status of endoscopic treatment and intraoperative imaging that are effective for spinal cord surgery.

  Lumbar magnetic resonance imaging can aid the qualitative evaluation and diagnosis of lesions using two-dimensional images but have limited application in three-dimensional and quantitative evaluations. Diffusion-weighted imaging is garnering attention as a method for quantitatively evaluating neural function. Diffusion tensor imaging could help quantify damage to the cauda equina and nerve roots. In recent years, percutaneous nucleotomy with high radiofrequency bipolar systems and chemonucleolysis with condoliase have been performed. Percutaneous nucleotomy uses combined intervertebral disc removal forceps and high-frequency bipolar modes for intradiscal manipulation. Condoliase reduces the water-retaining function of glycosaminoglycans in the nucleus pulposus and intradiscal pressure.

  Here, we explain the current status of endoscopes and intraoperative imaging devices that are effective for spinal cord surgery. Full endoscopic spine surgery is used for lumbar spinal stenosis.

  Hybrid or cone-beam and O-arm intraoperative computed tomography scans are useful. Advances in diagnostic imaging, improvements in surgical techniques, and development of new technologies have made spine surgery effective and safe.

  In the future, it will be possible to identify lesions causing pain and paralysis based on diagnostic imaging and perform nerve decompression using minimally invasive methods. Furthermore, multi-level and fusion surgeries will be reduced.

  Spinal cord tumors may be epidural, intradural extramedullary, and intramedullary. Histological diagnoses are diverse, as observed for brain tumor pathologies. However, the treatment strategies for spinal cord tumors have similarities.

  1. The diagnoses and surgical indications for spinal cord tumors should rely on neurological findings and imaging studies.

  2. Surgical treatment should be aimed at the maximum degree of tumor resection and the preservation of neurological function.

  In this paper, we discuss a few clinical cases to explain the important strategies for treating spinal cord tumors. It is difficult to remove intramedullary tumors while preserving neurological function in the small and fragile spinal cord.

  Patients with coronavirus disease 2019 (COVID-19) who receive extracorporeal membrane oxygenation (ECMO) tend to show extreme hypercoagulability and require intensive anticoagulant therapy. The prognosis is extremely poor in patients with intracranial hemorrhage. We report a case of COVID-19 complicated by acute subdural hematoma, which necessitated craniotomy for hematoma evacuation to improve the patient's prognosis. A 60-year-old man diagnosed with COVID-19 presented with severe respiratory failure and hypercoagulability and underwent ECMO along with intensive anticoagulant therapy with a large dose of heparin. Physical examination revealed anisocoria secondary to acute subdural hematoma. He denied a history of head injury, and computed tomography angiography revealed no vascular lesions. We diagnosed the patient with a non-traumatic, simple type hematoma. We discussed this case with the attending physician and reviewed the surgical indications and procedures. The attending physician recommended postoperative heparin withdrawal with ECMO. The hematoma was evacuated using a small craniotomy. Considering the risk of COVID-19, we cautiously performed all intraoperative procedures, especially those associated with aerosol generation, such as irrigation and the use of the craniotome. Heparin was discontinued postoperatively. The modified Rankin scale (mRS) score on postoperative day 90 was mRS 3. Optimal infection control measures prevented nosocomial infections in this patient despite the emergency surgical intervention.

  Cutaneous squamous cell carcinoma (cSCC) normally spreads to locations close to the primary lesion. We describe an extremely rare case of brain metastasis from cSCC in a 47-year-old female who had undergone removal of lower leg cSCC (T2N0M0) 2 years previously. She was admitted to our hospital with dizziness. Contrast-enhanced computed tomography imaging showed a cerebellar lesion with contrast effect. We performed surgical removal and histological examination revealed that the lesion was metastasis from lower leg cSCC. She was given radiotherapy for the residual tumor (39Gy). After the operation and radiotherapy, magnetic resonance imaging showed significant reduction in the size of the residual tumor and the posttreatment course was uneventful. No standard treatment strategy for brain metastasis from cSCC has been established. Therefore, further investigations are needed to establish an effective treatment for these tumors.