Clinical practice based on personal experience, prejudice, and the opinion of autorities may be filled with dogma, misunderstanding, and unverified belief. Clinical studies of inappropriate design, in which biases from various sources result in wrong conclusions, may mislead clinicians. Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. Because he randomized controlled trial is more likely to inform us and less likely to mislead us, it has become the gold standard for judging whether a treatment does more good than harm. When designing a clinical trial, we can, in turn, utilize the knowledge of clinical epidemiology, which provides theoretical background to evidence-based medicine ; for example, techniques that minimize systematic biases have been successfully developed. Discussing the study design of the Japan EC-IC bypass Trial (JET study), we illustrated how to design clinical trials to generate the best evidence in light of clinical epidemiology.

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In general, whenever the term "risk" is used, an associated "benefit" is expected, either consciously or subconsciously. The relationship between "risk" and "benefit" is deemed to be equal, However, "benefit" has an advantage. An undesirable result (=risk) is only recognized as the opposite side of a desirable result and a bigger "risk" will be allowed when the "benefit" is also bigger. The general public may accept that the avoidance of life theatening crisis and the prevention of serious diseases are two such bigger benefits. Medical researchers can calculate to show a prolongation of life expectancy or a major-symptom-free life expectancy. On the contrary, in some cases, risks, especially mental and social risks, are difficult to show objectively because the undesirable results are decided subjectively. In this paper, a concept of and procedures for risk analysis are described under consideration of the physical, mental, and social losses caused by preventive surgery trials.

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Risk/benefit analysis is the most critiacal issue in the decision to use carotid endarterectomy for cerebrovascular ischemia. We analyzed the surgical results of our 135 carotid endarterectomy cases and compared the resultsto previous mass studies. Our operative mortality was 2.2% and morbidity was 1.5%. The complication rate decreased as the surgeon's experience level increased. Rupture of the suture site occurred in 2 cases and cardiac arrhythmia was the resultant cause of mortality. Morbidity was directly related to technical error during surgery. We discussed the technique for high carotid bifurcation cases. We also made a cost/benefit analysis and realized that carotid endarterectomy costs more than medical treatment alone as far as in-patient's costs are concerned. The data are useful for decision making in the carotid endarterectomy.

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Several important points to reduce the risk associated with the surgical treatment of cerebral arteriovenous malformations are described. Sharp dissection of arachnoid tissue covering the superficial draining veins and the nidus render the veins mobile and a part of the nidus free from the neighboring intact gyrus. Huge draining veins are freed from the underlying structure in the early stage of the operation so they can be retracted or displaced. In the parenchyma, a portion of the nidus is devoid of vascular connections to the surrounding brain. Blunt dissection of the nidus from the parenchyma with a minimal coagulation procedure exposes tiny feeding arteries just at the entrance to the nidus. Coagulation and incision of the feeders at this stage allows for a more precise sparing of transit arteries than does the conventional active coagulation method. Using these techniques, the results of a series of 58 cases showed only one major morbidity, which occurred in a case of grade IV AVM. The present results point to the safety and effectiveness of this presented resection technique.

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Removal of the anterior clinoid process is well-recognized for its value as a treatment for lesions of the cavernous sinus as well as the paraclinoid area. The anterior clinoid process is located as a medial extension of the lesser sphenoid wing and lateral to the optic canal. Removal of this anterior clinoid process reveals a tight dural ring medially that fixes the internal carotid artery to the surrounding osseous structures at the point of its transdural passage and the carotico-oculomotor membrane laterally that separates the cavernous sinus. Surgical anatomy of the anterior clinoid process, preoperative examination, surgical techniques, and the prevention of complications following the removal of the anterior clinoid process are reviewed.

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Microsurgical techniques are basic and essential techniques in neurosurgical operations. Therefore, neurosurgeons have to master these techniques. Microvascular anastomosis in rats is the most suitable training method for mastering microsurgical techniques. In this report, methods of microvascular anastomosis (end-to-end anastomosis and end-to-side anastomosis) in rats are described in detail. Usage of instruments and treatment of rats by such methods as anesthetization and fixation are described. Not only microvascular anastomosis but also exposure of the carotid artery and femoral artery/vein and division of the descending aorta and inferior vena cava provide good training for acquiring microsurgical techniques.

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Methods for safe drilling in a craniotomy around the occipital condyle are mentioned and the differences in the operative view between before and after removal of each bony element are discussed. In the field obtained just after craniotomy, the lateral rim of the foramen magnum (posterior part of the jugular tubercle) obstructs the view toward the anterior part of the posterior fossa. Drilling of this area, carried out by following the posterior condylar emissary vein and imaging the sigmoid-magnum triangle, exposes the lower cerebellopontine angle and the region ventral to the brainstem. In order to drill down the high jugular tubercle, drilling of part of the occipital condyle is also required to make room to reach the tuberclr toward its summit, as the dura covering the posterior part of the tubercle is hard to elevate. Additional drilling of the posterior part of the occipital condyle makes a wider space available, especially around the vertebral artery. Therefore, a specifically tailored operation should be scheduled for each case, considering which bony part is to be removed.

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Vascular anastomosis is one of the most fundamental techniques in microsurgery. Therefore, technical training is essential before clinical application. This surgical procedure contains sharp dissection, hemostasis using bipolar coagulation, and anastomosis techniques, which are all basic techniques in neurosurgery. It is important to cautiously confirm the luminal surface of the anastomotic site under the operative microscope. Suturing without sufficient microscopic confirmation should be avoided. It is also important to perform anastomosis under favorable conditions, such as a shallow and bloodless operative field. The surgeon must abandon the attitude of seeking perfection of brilliant skillfulness in performing the anastomosis. Instead, steadiness, coolness and patience are all key to success in microvascular anastomosis.

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Proper set up for microneurosurgery is extremely important to achieve a successful surgery and an excellent result. Although, it is not too much to say that the preparation and set up for a surgery determines the goal, there have been no systematic descriptions of this field in the literature. In this paper, I stressed the importance of an operative design based on the risk/benefit balance as influenced by each disease, the technical level of both the surgeon and the facilities of the institute, and adequate preoperative simulation. Further, I presented and clarified the meaning of the patients' position and the surgeons' position, and also revealed tricks to prepare operative fields and to handle operative tools by example of the my own cases.

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The aim of anesthetic management for craniotomy is to maintain a balance between cerebral oxygen supply and demand, brain volume reduction and brain protection. All inhalational agents dilate cerebral blood vessles, whereas intravenous anesthetics, except for ketamine, are cerebral vasoconstrictors. Therefore, intravenous anesthesia is advantageous for craniotomy. Most anesthetics have a brain protective property, however, nitrous oxide deteriorates the outcome of cerebral ischemia. In conclusion, total intravenous anesthesia with propofol, fentanyl and vecuronium is best for craniotomy in Japan.

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