Skull base surgery needs extensive bone resection, long operating time and has many possible complications. Thus it appears to be "very much invasive surgery". However, it can provide excellent or better results than before, if it is applied properly. To make skull base surgery less invasive it is important to consider not only tactics but also strategy. Preoperative evaluation and selection of approach should be well considered. Bone removal is tailored for each case and unnecessary preparation should be avoided. Thorough anatomical knowledge and sophisticated operative technique are of course mandatory to do less invasive skull base surgery. Examples are illustrated about pertosectomy.

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The present status of minimally invasive pediatric neurosurgery is described on the basis of the authors' recent experiences. These include the applications of interactive image-guided neurosurgery, neuroendoscopy, interventional neuroradiology, etc., for pediatric patients. The new technologies of surgical navigation and image analysis makes it possible to resect such intrinsic brain lesions as glioma and cortical dysplasia with minimum invasiveness. Neuroendoscopy also is an important technique among minimally invasive procedures, and hydrocephalus and some intracranial cystic lesions can safely be managed by third ventriculostomy and cyst fenestration, respectively. The rapid expanding applications of endovascular therapy of the brain also is true in pediatric neurosurgery, and vein of Galen aneurysmal malformations now can be safely treated with transarterial embolization. The aforementioned technologies are developing dramatically, and many neurosurgical diseases have come to be treated safely and less invasively. However, it should be stressed that, even with the new technologies, patient selection is a critical component in all neurosurgical operations.

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During the last ten years, patients with cerebral arteriovenous malformations (AVMs) were treated with palliative maneuvers such as partial embolization, radiosurgery, or feeder ligation alone. Forty three patients were followed up from 0.5 to 169 (49.4±39.8) months. Twenty five bleeding attacks from AVMs were observed in 18 patients. The annual risk of bleeding was 14.1%/year. Persistent progressive neurological deficit was noted in 1 patient. Major neurological deficits occurred in 10 patients (23.2%) and the mortality rate was 9.3%. Therefore palliative treatment did not completely prevent bleeding, and may have worsened the bleeding risk.

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It has become increasingly clear that complete surgical excision is the best therapeutic approach for the majority of brain tumors. There is, however, always a risk in cases of radical excision of tumors located within the eloquent cortex. In order to minimize neurological deficits occurring as a result of such damage, we have utilized electrical mapping of the cortex with awake craniotomy. This report summarizes our experience of awake craniotomy in 34 patients who underwent radical excision of tumors located within the proximity of the motor cortex. In 4 patients, craniotomy was performed under conscious sedation (Group A). The remaining 30 patients underwent total intravenous anesthesia (TIVA) with tracheal intubation in 5 patients (Group B) or securement of the air way with a laryngeal mask in 25 patients (Group C). TIVA was discontinued in these patients during cortical mapping and tumor excision, the laryngeal mask was temporarily removed, if necessary, and they were maintained conscious with appropriate sedation. TIVA and conscious sedation were both achieved mainly by intravenous infusion of propofol. In 7 patients, some problems were encountered during the conscious sedation : pain and agitation in 2 (1 in each of Groups B and C), seizure in 2 (1 in each of Groups B and C) and brain swelling in 3 (2 in Group A and 1 in Group C). Following surgery, 50% of Group A, 40% of Group B and 40.9% of Group C patients were able to recall episodes of conscious sedation during tumor excision. The larygeal mask proved useful since it permits TIVA during procedures for exposure and closure, and cortical mapping and tumor excision can be performed under conscious sedation.

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The present study assess the need to order blood and perform blood transfusion during aneurysm surgery. Two hundred and eighty-nine patients who underwent aneurysm surgery (157 ruptured aneurysms and 132 unruptured aneurysms ) between 1995 and 1997 were analyzed retrospectively. For 150 patients, red cell concentrates or autologous blood (400 or 800 ml) were prepared preoperatively for blood loss following aneurysm rupture during surgery. Twenty-eight patients (9.7%) had premature aneurysm rupture. In seven (2.4%) of these patients, the intraoperative blood transfusion was required to maintain a normal arterial pressure. Although preoperative estimation of blood loss during aneurysm surgery is difficult, a large amount of blood preparation is not necessary. The risks associated with homologous blood transfusion are significant. The blood typing and screening method and the autologous blood obtained prior to craniotomy reduced the need for homologous blood transfusion. Furthermore techniques to decrease blood loss and the timing of blood transfusion should be considered on an indisividual basis.

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The etiology of the internal carotid artery (ICA) superior wall aneurysm remains obscure, but recently pathological dissection of the ICA has been reported as a possible mechanism. Obstructing the entry into the dissected cavity is a rational treatment for dissecting aneurysm. Rebleeding after surgery is not uncommon with this risky aneurysm. This 52-year-old woman presented with a sudden onset of severe headache and emesis. Past medical history was unremarkable. Hunt-Hess grade was 2. Initial computerized tomography of the head revealed a SAH of group 3 in Fisher's Classification. A cerebral angiogram was obtained immediately and showed a amall uplift of the right ICA at the cisternal portion. Two weeks later, angiographic study clearly revealed a right ICA superior wall aneurysm that was unrelated to any arterial junction. We treated the ICA superior wall aneurysm with hemostatic agents administrated intravenously. The aneurysm disappeared without surgery 6 months later. This case is the first documentation of the angiographic resolution of a dissecting aneurysm of the anterior circulation. This case may show the natural history of ICA superior wall aneurysm.

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The authors report 2 cases of so-called "kissing aneurysms", that is, 2 adjacent aneurysms which have their own necks and adhere partially to each other. Both cases presented subarachnoid hemorrhage and had kissing aneurysms which originated from the internal carotid-posterior communicating artery and ipsilateral internal carotid-anterior choroidal artery respectively. Kissing aneurysms often pose some problems in diagnosis and treatment. In Case 1, angiography failed to demonstrate 2 aneurysmal necks. In Case 2, oblique views made it possible to obtain the diagnosis of kissing aneurysms. Much attention should be paid in the angiographical diagnosis not to overlook the presence of 2 separate aneurysms, especially when multiloculated aneurysm shadow is revealed on conventional angiography projections. Neck clipping for each aneurysm is best for the treatment of kissing aneurysms. The success of treatment in clipping kissing aneurysms is much dependent on the thorough dissection of the adhesion between the aneurysms. Clipping of kissing aneurysms was performed in both cases, however, in Case 2 premature rupture occurred during the application of a clip because of the perforation of incompletely dissected neck. When tight adhesion between 2 aneurysmal necks is present, careful and meticulous dissection between aneurysms is especially needed.

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A simplified and safer ventriculo-peritoneal shunt method for hydrocephalus was performed in 14 patients. In addition to the common shunt operation kit, the only additional instruments needed were a surgineedle and a split cannula. The peritoneal cavity was punctured at the subumbilical region with a split cannula, using the same procedure as in a laparoscopy. The umbilical portion was pulled after inflating the abdomen with room air. This procedure shortened the surgical time and gave good results in all 14 patients, including 4 cases of shunt revision.

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