Embryologically, the neural tube develops in a segmental fashion. It consists of neuromeres along the cranio caudal axis. Segmentation of the spinal cord follows the development of mesodermal somites, of which the number of the somites is unique to the individual species, but the number of the rhombomeres of the brain stem is fixed to either 7 or 8 irrespective of the species. Classic telencephalic topological subdivisions determined by the cytoarchitecture have proven to be similar to histogenetic units defined by regulatory genes expressed in each neuromere. The vascular system of the central nervous system develops respecting these segmentally-arranged histogenetic units.
  Basic arterial angioarchitecture of the spinal cord, brain stem, and brain consist of both centrifugal and centripetal perforating arteries in each histogenetic unit. That is, the central (ventral) perforating arteries supply the ipsilateral parenchyma centrifugally, and the peripheral (dorsal) perforating arteries of the vasa corona of the spinal cord, short/long circumferential arteries of the brain stem, and anterior/middle/posterior cerebral arteries of the brain perfuse the parenchyma centripetally. In this manner, the angioarchitecture of the central nervous system is organized on the basis of the 3-dimensional patterning of the neural structure.

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  The anatomy of perforating arteries is quite important in microneurosurgery, because any blood flow insufficiency in the perforating arteries can cause serious neurological deficits. Especially in aneurysm clipping, surgeons must be aware of the anatomical variation of the perforators related to the aneurysm. For example, the anterior choroidal artery sometimes arises from the aneurysm itself or it may also arise as 2-4 independent vessels. Lenticulostriate arteries usually arise from the posterior aspect of the M1 segment, but also from the M1-M2 bifurcation or the M2 segment. Hypothalamic arteries originate from the posterior aspect of the anterior communicating artery and are ordinarily difficult to confirm by the pterional approach. To preserve perforator blood flows, surgeons must first identify all of the perforators around an aneurysm. Neuroendoscopy helps us in this task by allowing us to observe the blind area of the microscope. Also, clips must be placed in such a way as to spare the blood flow of the perforators. After clipping, the patency of the perforators is confirmed by Doppler ultrasonography, indocyanine green (ICG) videoangiography and motor-evoked potential (MEP) monitoring. As each of these intraoperative monitoring methods may yield a false-negative result on its own, the combination of multiple modalities is mandatory for avoiding neurological complications due to perforator injury.

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  The fiber dissection technique for detecting neuronal fibers and tracts has been used since the beginning of the 17th century. The complexity of brain preparation and the time consuming execution of fiber dissection itself have led to the neglect of this method, particularly since the advent of MR diffusion tensor images, histological tracer techniques and other methods. We focused on difficulty of understanding the tertiary structure that is one of the weak points of the fiber dissection method. We used 3-dimensional models for each dissection step that were generated using freely available software to overcome this weak point. Nevertheless, this technique is still important and reliable, and it is particularly useful for providing neurosurgeons with a clearer understanding of the structure of the brain.

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  We retrospectively analyzed the one-year complication rates and preventable deaths associated with neurosurgical treatment. We analyzed data from inpatients who were admitted to a medium-scale, 376-bed, acute-care hospital in 2013. Of the 413 admitted patients, 215 underwent neurosurgical interventions (including 54 endovascular procedures), and 22 died (5.3%).
  Recently, the average age of admitted patients has increased, and advanced age is more prevalent in fatal cases. In half of the deaths that occurred during hospitalization, the cause of death was not a complication of the primary disease. In 18.2%, infectious complications were the cause of death. Of the 3 cases of acute cardiac failure that were analyzed, 2 had a suspected pulmonary embolism.
  Using D-dimer screening tests, deep venous thrombosis was diagnosed in 3.1% of all patients and was diagnosed in more than 6% of subarachnoid hemorrhage and intracerebral hemorrhage cases. As for surgical site infections, antibiotics other than cefazolin were used in 12.9% of all cases perioperatively. In 20.2% of cerebral angiography and 47.6% of surgical cases, microorganisms were recovered at the end of the procedure from the disinfected area. Patient safety must be secured not only with proper surgical techniques but also with appropriate perioperative management. These findings clearly indicate that establishing an evidence-based acute care system is requisite for patient safety even in the field of neurosurgery.

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  Intracranial electroencephalography (IEEG) is useful as an evaluation component of resective surgery when the results of noninvasive tests are incongruent in patients with refractory neocortical epilepsy. High-frequency oscillations (HFOs>80 Hz) have recently been recognized as having a strong relationship to the epileptogenic zone, and the complete resection of HFOs has been considered a favorable prognostic indicator for surgical outcome. It is sometimes difficult, however, to comprehend dynamic changes in ictal HFOs recorded via subdural electrodes.
  We performed surgical treatment on a medically intractable patient diagnosed with occipital lobe epilepsy after analyzing the patient's HFOs with IEEG using the original program. The patient has achieved seizure-free status one year after surgery. Our method of creating a brain surface topographic map of interictal HFOs and a topographic movie of ictal HFOs was useful for easy understanding of seizure onset zone and epileptic HFOs propagation. It may also be helpful for determining the necessary extent of surgical resection to include the epileptogenic zone, thus promoting better postsurgical seizure outcomes.

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  Young patients with Marfan syndrome are likely to have acute aortic dissection of the thoracic aorta. Cerebral malperfusion caused by aortic dissection involving carotid artery may result in stroke.
  Forty-one-year-old man with Marfan syndrome underwent total aortic arch replacement and presented right hemiparesis. 3D-CT angiography showed that dissection involved bilateral common carotid artery. MRI showed acute infarction in left hemisphere. Meanwhile, SPECT showed decreased cerebral blood flow in right MCA territory. Dissection site extended from immediately after anastomosis of left common carotid artery up to bifurcation and from anastomosis of brachiocephalic artery to right internal carotid artery. First, tandem stenting of left common carotid artery was successfully performed via open retrograde cervical approach. Next day, multiple stents were deployed anterogradely via trans left brachial artery approach. Cerebral perfusion improved without any complications. Access route, device crossing across aortic arch graft, and obtaining and keeping true lumen were considered to be key points of this treatment. Endovascular stenting was safe and effective. Retrograde approach with exposure of carotid artery is a safe and reliable way to keep true lumen.

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  A 61-year-old man presented with repeated transient ischemic attacks (TIAs) associated with weakness of the right extremities and aphasia. MRI and MRA revealed severe stenosis of the left internal carotid artery (ICA) without cerebral ischemic changes. Carotid endarterectomy was chosen for revascularization of the symptomatic left ICA stenosis due to the presence of a bulky fragile plaque. Single photon emission computed tomography (SPECT) showed left total hemispheric hypoperfusion with steal phenomenon, which suggested the possibility of hyperperfusion syndrome (HPS) occurring after CEA.
  To alleviate the severely hemodynamically compromised state and to prevent HPS after CEA, we performed a low flow bypass (left superficial temporal artery-middle cerebral artery anastomosis : STA-MCA anastomosis) in advance. The left CEA was then performed three weeks after confirmation of improved cerebral hemodynamics with postoperative SPECT. The patient did not experience any symptoms of HPS or cerebral ischemia, and resumed his previous activities without recurrence of TIAs.
  Stepwise revascularization may attenuate the risk of HPS in severely hemodynamically compromised patients. However, the indications should be strictly limited because multidisciplinary revascularization may increase the complication rate because of the compounding of risk from each treatment.

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