To evaluate the surgical risk of brain arteriovenous malformations (AVM), the Spetzler-Martin grade is effective and correlated to the occurrence of postoperative deficits. Therefore, intractable AVMs for surgical treatment were defined as the following two groups : 1) High-grade AVMs (Spetzler-Martin grade IV & V) with need to resect, 2) Low grade AVMs (grade I, II, and III) with high surgical risks evaluated by criteria or grading other than Spetzler-Martin grade.
  The former are mostly high-grade AVMs with hemorrhagic onset presenting with repetitive hemorrhage and progressive symptoms. On the other hand, it is not easy to evaluate the real risks of surgery for low-grade AVMs. There are a variety of risks in treating grade III AVMs.
  We think that using a combination of Spetzler-Martin grade and neuroimaging, especially diffusion-tensor tractography is one of the best ways to determine whether surgical treatment is advised. In our series, postoperative deterioration of motor function in AVM patients was related to the minimal distant between the nidus and corticospinal tract on tractography. We found that AVMs more than 16mm distant from the corticospinal tract could be resected safely.

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  Marginal dose to the nidus is the decisive factor in order to attain complete AVM obliteration in radio-surgery. For large AVM's, the volume of irradiated surrounding normal brain increases and a sufficient dose for complete obliteration cannot be given while still avoiding radiation induced complications. Historically, conventional fractionated radiation has been tried but the results were disappointing, maybe due to the very slight difference, if any, in α/β ratio between the nidus and the brain. Hypo-fractionated radiation has also been tried but results that surpass that of single fraction treatment have not been reported at present. Repeat treatment for residual nidus after low dose treatment and volume-staged treatment for larger nidus have been performed and are reported to have some value. In both strategies, bleeding during the long latent period is a problem. Using the recent state-of-the-art technology including radiation devices and planning computers with ever advancing embolization technique, better results may be accomplished in the future.

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  AVM embolization has long been recognized as one of the most useful endovascular procedures. Although it stands out in preoperative situations, its efficacy as a preradiosurgical treatment is not fully accepted. The cause of this discrepancy may be due to errors on both sides : embolization and radiosurgery. An adequate combination strategy with effective embolization to prevent recanalization combined with accurate planning will yield better results. Thanks to the development of catheter and high image resolution the safety of embolization has increased dramatically. Preoperative risk assessment and technical improvements may reduce intraoperative ischemic and hemorrhagic complications ; however, delayed bleeding due to drainage occlusion remains unresolved. This complication may occur even after the radiosurgery. When faced with the life-threatening possibility of drainer occlusion, rapid radical measures should be employed. High grade AVM is considered an untreatable disease according to the recent guideline. However, the resultant size reduction to grade-up cases of Spetzler-Martin grade IV (particularly the S-2 group) with staged embolization or radical treatment by Onyx, will afford an opportunity for treatment, and targeted embolization of the bleeding source for cases with repeated hemorrhage combined with radiosurgery may be an option to maintain the patient QOL.

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  Cavernous malformations are clusters of dilated sinusoidal channels with thin walls devoid of elastin and smooth muscle. They have no intervening brain tissue. They occur both in sporadic and familial forms. The genes responsible for cavernous malformations have been identified. Recent reports show that mutations of these responsible genes are involved not only in familial but also in sporadic forms. Germline and somatic mutations may occur before cavernous malformations develop (two-hit mechanism). Two patterns, with mulberry-like and hematoma-like appearances, are seen intraoperatively, and from histological findings, mulberry-like appearance may change into hematoma-like one by intralesional hemorrhage. Cavernous malformation treatments include open surgery and radiosurgery. Open surgery is usually chosen for the treatment of symptomatic hemorrhagic cavernous malformations because post-radiosurgical annual bleeding risks at the early phase seem to be higher than those of open surgery. If open surgery has a high risk because of lesion location, radiosurgery becomes an effective alternative treatment. Brainstem cavernous malformations have high annual bleeding and re-bleeding incidence, so if the lesion is accessible with low risk, open surgery is recommended.

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  Intracranial dural arteriovenous fistulas (dAVFs) are pathologic dural-based shunts and distinguished from parenchymal AVM by the presence of a dural arterial supply and the absence of a parenchymal nidus. Their symptoms and prognosis are strongly related to the pattern of their venous drainage system. The presence of cortical venous reflux (CVR) is an aggressive feature indicating that there is a high risk of cerebral bleeding or progressive neurological deficits. Endovascular treatment has become the mainstream dAVF therapy. In general, trans-venous coil embolization is adapted to sinusal type dAVFs (i.e. cavernous sinus or transverse-sigmoid dAVFs) and trans-arterial glue embolization is applied to non-sinusal type dAVFs (i.e. anterior skull base or tentorial dAVFs). Direct surgery and stereotactic radiosurgery are indicated in cases in which endovascular approaches have failed or are not feasible.

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  The spinal cord is supplied mainly by an anterior spinal artery with small branches named the sulcal arteries and superficially by the posterior spinal arteries. The spinal cord arterial network has a simple structure with these vessels and connecting vessels such as the vasa corona on the surface of the spinal cord and the arterial basket at the conus medullaris. Spinal angiography under general anesthesia helps to understand this vascular anatomy. Spinal dural arteriovenous fistula (AVF) presents with spinal cord symptoms due to venous hypertension, and can be treated by embolization or surgery. Spinal cord arteriovenous malformation (AVM) presents with pain or bleeding. Perimedullary AVF and filum terminale AVM can be treated by embolization or surgery. However, intramedullary AVM is difficult to be cured. AVF at craniocervical junction including perimedullary and dural AVF may present with subarachnoid hemorrhage or spinal cord symptom, and can be treated mainly by surgery.

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  Von Hippel-Lindau (VHL) disease is neoplastic syndrome that affects multiple organ systems. Most patients with this disease (60-80%) harbor hemangioblastomas and neurosurgeons often treat craniospinal hemangioblastomas in these patients. VHL disease is transmitted across generations in an autosomal dominant manner ; its incidence is 1 in 36,000. The VHL tumor suppressor gene is located on chromosome 3 (3p25) and encodes for the VHL protein, which complexes with several proteins involved in the ubiquitin-dependent proteolysis of hypoxia-inducing factor (HIF). The VHL protein appears to have several functionas and its dysregulation leads to angiogenesis and tumorigenesis. As most patients with VHL disease harbor central nervous system (CNS) hemangioblastomas, their management must be optimized to minimize morbidity and mortality. Although patients with VHL disease harbor not only CNS neoplasm but also cysts and/or neoplasms in other organs, in our study we reviewed the features of and the management strategies for only cranio-spinal hemangioblastomas in patients with VHL disease.

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  In Japan, a new training system for junior residents was introduced in 2004. According to this new system, junior residents must take clinical training courses for 2 years at designated hospitals. They have to study five main fields consisting of internal medicine, general surgery, gynecology, pediatrics, and public health. Because our medical center already provided our own clinical training system to junior residents before this new system was introduced, we have a lot of junior residents who not only who want to become neurosurgeons, but who also are interested in neurosurgery, though they belong to another department. It is very important for us to know what they want to learn from neurosurgical training and analyze this information in order to deliver high quality education. Here we report the results of a 3 year survey about their impressions and requests for our department.
  All junior residents who attended the neurosurgical training course from 2008 to 2011 filled out a questionnaire when they finished the course.
  Analysis of the questionnaire results revealed that the areas which interested them most consisted of intensive care, and perioperative neurosurgical activities besides minor procedures such as lumbar puncture and intratracheal intubation. It also pointed out that there is room for some improvement in our clinical conference and journal club activities.
  The analysis of our questionnaire clearly revealed what our aspiring young surgeons want from their neurosurgical training and it shows that such a questionnaire is a useful tool to get feedback concerning many points from junior residents which can then be used to improve the training system.

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