Hemispherotomy is a radical treatment for drug-resistant epilepsy that targets developmental, acquired, and progressive diseases with widespread epileptogenic regions in one cerebral hemisphere. Currently, two main approaches are utilized after repeated improvements: lateral and vertical approaches. With the lateral approach, the surgical field is wide, and the approach to the lateral ventricle is relatively easy. On the other hand, the vertical approach has the advantage of reducing intraoperative bleeding and operating time as the resection line of the radial fiber is short, and understanding the three-dimensional anatomy is relatively easy. The lateral approach is generally used for atrophic lesions, whereas the vertical approach is for hypertrophic lesions. Hemispherotomy is expected to not only suppress epileptic seizures but also improve psychomotor development by protecting the unaffected cerebral hemisphere. However, this method is one of the most invasive surgeries in epilepsy surgery, and it is important to fully consider its indications. Furthermore, understanding the neural fiber pathway is important for actual surgery.

Stereotactic neurosurgery is an established technique, but it has several limitations. In frame-based stereotaxy using a stereotactic frame, frame setting errors may decrease the accuracy of the procedure. Frameless stereotaxy using neuronavigation requires surgeons to shift their view from the surgical field to the navigation display and to advance the needle while assuming a physically uncomfortable position. To overcome these limitations, several researchers have applied augmented reality in stereotactic neurosurgery. Augmented reality enables surgeons to visualize the information regarding the target and preplanned trajectory superimposed over the actual surgical field. In frame-based stereotaxy, a researcher applies tablet computer-based augmented reality to check for the setting errors of the stereotactic frame, thereby improving the safety of the procedure. Several researchers have reported performing frameless stereotaxy guided by head-mounted-display-based augmented reality that enables surgeons to advance the needle at a more natural posture. These studies have shown that augmented reality can address the limitations of stereotactic neurosurgery. Conversely, they have also revealed the limited accuracy of current augmented reality systems for small targets, which indicates that further development of augmented reality systems is needed.

Cerebrospinal fluid (CSF) production and absorption concept significantly changed in the early 2010s from "third circulation theory" and "classical bulk flow theory" to a whole new one as follows: First, CSF is mainly produced from interstitial fluid excreted from the brain parenchyma, and CSF produced from the choroid plexus plays an important role in maintaining brain homeostasis. Second, CSF is not absorbed in the venous sinus via the arachnoid granules, but mainly in the dural lymphatic vessels. Finally, the ventricles and subarachnoid spaces have several compensatory direct CSF pathways at the borders attached to the choroid plexus, e.g., the inferior choroidal point of the choroidal fissure, other than the foramina of Luschka and Magendie. In idiopathic normal pressure hydrocephalus (iNPH), the lateral ventricles and basal cistern are enlarged simultaneously due to the compensatory direct CSF pathways. The average total intracranial CSF volume increased from about 150 mL at 20 years to about 350 mL at 70 years due to the decrease in brain volume with aging and further increased above 400 mL in patients with iNPH. CSF movements are composed of a steady microflow produced by the rhythmic wavy movement of motile cilia on the ventricular surface and dynamic pulsatile flow produced by the brain and cerebral artery pulsation, respiration, and head movement. Pulsatile CSF movements might totally decrease with aging, but it in the ventricles might increase at the foramina of Magendie and Luschka dilation. Aging CSF dynamics are strongly associated with ventricular dilatation in iNPH.

Organized hematoma, which exhibits a net-like appearance on imaging studies, is one of the predisposing factors for the recurrence of chronic subdural hematoma. Patients who are positive for the net-like appearance are often treated with only burr hole surgery. We investigated the relationship between postoperative structural changes in the net-like appearance and the recurrence rate of chronic subdural hematoma. Of the 949 patients with chronic subdural hematoma treated with primary burr hole surgery between January 2010 and April 2021 at our hospital, 268 who were considered positive for the net-like appearance on T2- and T2 star-weighted magnetic resonance images were extracted. We followed the structural changes in the net-like appearance postoperatively and subsequently classified the patients into three groups: decreasing type, shifting type, and no change and deterioration type. The relationship between each structural change and the recurrence rate in the three groups was investigated. Postoperative recurrence requiring surgery occurred in 3.5% of the subjects with decreasing type, 0% with shifting type, and 100% with deterioration type of the net-like appearance (P < 0.05), indicating differences in the recurrence rates according to postoperative structural changes in the magnetic resonance images (MRI) features of chronic subdural hematoma. Our results indicate that the risk of postoperative chronic subdural hematoma recurrence can be predicted by focusing on the structural changes in the postoperative net-like appearance on MRI.

The goal of this study is to perform correlation analysis of Computed tomography (CT) and magnetic resonance imaging (MRI) results in posterior ligament complex (PLC) injury and define the morphological traits of thoracolumbar (TL) burst fractures connected to PLC injury. Forty patients with surgically repaired TL burst fractures between January 2013 and December 2020 were retrospectively analyzed. The patients were split into two groups for comparison based on MRI (Group P: patients with a confirmed or suspected PLC injury; Group N: patients with PLC injury denied). The radiographic morphological examination based on CT scans and clinical evaluation was performed and compared between two groups. The thoracolumbar injury classification and severity score (TLICS), the load sharing classification (LSC) scores, and the number of patients with neurological impairments were considerably greater in Group P. Loss of height of the fracture (loss height), local kyphosis of the fracture (local kyphosis), and supraspinous distance were significantly higher in Group P and significantly associated with PLC injuries indicating severe vertebral body destruction and traumatic kyphosis in multivariate logistic analysis [odds ratio: 1.90, 1.06, and 1.13, respectively]. Cutoff value for local kyphosis obtained from the receiver operating characteristic curve was 18.8. If local kyphosis is greater than 18.8 degrees on CT scans, we should take into account the probability of the highly damaged burst fracture associated with PLC injury. In this situation, we should carefully assess MRI to identify the spinal cord injury or spinal cord compression in addition to PLC injury because these instances likely present with neurological abnormalities.

In idiopathic tarsal tunnel syndrome (TTS), walking seems to make symptoms worse. The findings imply that an ankle movement dynamic component may have an impact on the etiology of idiopathic TTS. We describe how the ankle movement affects the nerve compression caused by the surround tissue, particularly the posterior tibial artery. We enrolled 8 cases (15 sides) that had TTS surgery after tarsal tunnel (TT) MRI preoperatively. Dorsiflexion and plantar flexion were the two separate ankle positions used for the T2* fat suppression 3D and MR Angiography of TT. Based on these findings, we looked at how the two different ankle positions affected the posterior tibial artery's ability to compress the nerve. Additionally, we assessed the posterior tibial artery's distorted angle. We divided the region around the TT into four sections: proximal and distal to the TT and proximal half and distal half to the TT. Major compression cause was posterior tibial artery. Most severe compression point was proximal half in the TT in all cases without one case. In each scenario, the nerve compression worsens by the plantar flexion. The angle of the twisted angle of the posterior tibial artery was significantly worsened by the plantar flexion. In idiopathic TTS, deformation of posterior tibial artery was the primary compression component. Nerve compression was exacerbated by the plantar flexion, and it was attributable with the change of the distorted angle of the posterior tibial artery. This could be a contributing factor of the deteriorating etiology by walking in idiopathic TTS.