Arteriovenous malformations(AVMs)of the brain are potentially curable lesions that otherwise present significant risk of disability or death to the patient. A variety of therapeutic options are available for managing AVMs including microsurgical resection, embolization, stereotactic radiosurgery or a combination of these treatments. The primary advantages of neurosurgical resection include immediate and almost certain cure, immediate elimination of the risk of hemorrhage, and the absence of longterm delayed complications. Surgery, however, is more invasive than other therapeutic options and is associated with the potential for perioperative morbidity or mortality. Preoperative and intraoperative complications in the surgical management of AVMs of the brain are discussed along with techniques for management and avoidance. By carefully assessing surgical complications, neurosurgeons are better able to reduce risk and improve the outcome for their patients.

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The development of neuronavigation has been a history of a stereotactic procedure which was recognized as a basic concept of minimally invasive neurosurgery. The reduction of the operation and elimination of unnecessary procedures by neuronavigation reduces blood loss and complications, and expands the operative indications in more difficult cases. It is a new eye for surgeons, in its ability to recognize and observe accurately the target organ and brain structures during surgery. Surgeons need to have a strategic system which consists of augmented functional reality and an image space(virtual space)in which the images of the navigator are analyzed and integrated. These analyzed navigation images are based on medical images and operative information. According to the conditions, which may change, doctors can discuss via the common image space details about simulation, navigation and a new strategy while in an operating theater.

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A new system for intraoperative monitoring was developed. The system was named the multi-modality monitoring system combining a variety of functional and anatomical monitoring, and coupled to a multi-viewer system. Anatomical monitoring included a neuronavigation system and a neuroendoscope. Functional monitoring included electrophysiological monitoring, such as evoked EMG and evoked potentials(ABR, SEP). The multi-viewer system can integrate and present these multi-modality data from anatomical and functional monitorings in a way that operators can understand easily and effectively.

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Mild hypothermia is now in the limelight again in the field of neurosurgery. At our institute, we have used such mild hypothermia during surgery for several kinds of vascular diseases since 1994. We will attempt here to evaluate the outcome of these cases and to discuss the usefulness and limitations of this method in the neurosurgical field. In 78 cases(aneurysm, 55 ; arteriovenous malformation, 10 ; other vascular lesions, 13), we employed the mild hypothermia method intraoperatively. After the onset of anesthesia, surface cooling was performed with double water-cooling blankets. The core body temperature was maintained at between 32 and 34℃. Once the operating microscope portion of the procedure was completed, the patient was actively rewarmed using a warm air blanket in combination with a warm water blanket. The warm air blanket was employed in the intensive care unit to complete rewarming to 36℃. Although most patients were extubated in the operating room, some patients remained intubated in the neurosurgical intensive care unit, without muscle relaxant reversal, until the core temperature exceeds 35℃. In general, the clinical outcome in our mild hypothermic patients with difficult intracranial and extracranial vascular lesions was excellent. No skin or peripheral nerve injury resulted from the surface cooling. Among the physiological data, the heart rate was significantly lower in the hypothermia group. No thrombocytopenia was observed. No other patients experienced and clinical bleeding problems intraoperatively. While premature ventricular contraction was noted in 1(1.3%)of the 78 hypothermic patients, this did not have any major influence on the clinical course. Mild hypothermia may provide an effective method of brain protection against ischemia during microsurgery. It is considered especially useful in surgery for the clipping of aneurysms and carotid endarterectomy when temporary clips are utilized.

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Neuronavigator is the first commercial surgical navigation system and was reported in 1987. It translates the site of operation into CT/MRI coordinates, and provides a surgeon with correct 3D-orientation during surgery. The use of it and its analogue system enhances the ability to detect the lesion and protect important neural tissue during surgery. We have used the neuronavigator for 206 cases in our clinic since 1989. Here we present several utilities which are relatively peculiar in neurosurgical services. They are utilities in surgery close to the motor cortex, in epilepsy surgery, in stereotactic hematoma aspiration, in combination with a TCD flow meter and in an anterior approach to cervical spondylosis. Several cases are demonstrated to depict their use.

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The fundamental aim during neurosurgical procedures is to minimize the extent of surgical invasiveness. The recent development of a computer-assisted neurosurgical navigation system has facilitated less invasive neurosurgery by localizing lesions more precisely. This report assesses the utility of frameless and armless neuronavigation systems. The system we have been using relies on application of magnetic field technology to position measurement. It has the benefit of achieving excellent three-dimensional orientation by real-time anatomical interaction without interfering with basic neurosurgical procedures, although several kinds of metals can interfere with magnetic field. Surgical tracking, indicated as dots on MRI, is useful for confirming the extent of lesion removal. However, intraoperative brain distortion may occur, especially in cases where lesions are located in either hemisphere. Neuronavigation systems must be used with a better understanding of their benefits and pitfalls.

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Our report describes the case of a 26-year-old man with multilevel thoracic disc herniation, osteophytes and ossification of ligaments which occurred at the Th9-10, Th10-11 and Th11-12 levels. The physical findings included : features of a possible underlying muscloskeletal abnormality such as Weill-Marchesani syndrome ; kyphosis of the thoracic spine ; mild brachymorphy ; hard and thick sikn ; and muscular habitus. The herniated discs and osteophytes at the Th9-10 and Th10-11 levels were excised microsurgically, and excellent results were obtained. There are 16 reported cases of multilevel disc herniations in the literature. We discuss the etiology and clinical characteristics of this rare condition.

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A case of calcified and ossified extradural hematoma in a 14-year-old girl is reported. The patient was struck by a golf club on the right frontal area of the head on September 6, 1993. She was admitted to our hospital on September 9, complaining of headaches and nausea. No skull fracture was visible on the plain skull X-ray. Brain CT scans showed a right frontal extradural hematoma, which appeared as a homogeneous high-density area with mild midline shift. Since her condition was good and she showed no neurological deficit or disturbance of consciousness, she was treated conservatively and discharged from the hospital after hospitalization for 10 days. Eight months later, an oval shadow suggesting calcification of the hematoma capsule was seen in the right frontal region on a skull X-ray. CT scans revealed the hematoma as a low density mass, which had increased in volume, and bone density CT scans showed a marked high destiny rim on the inner surface of the hematoma. in view of the fact that the spontaneous disappearance of the hematoma was no longer likely, the calcified hematoma was surgically removed on August 8, 1994. Histologically thick fibrous connective tissue with inflammatory cells was found in the outer mombrane, and ossification with lamellar bone layers was found in the inner membrane of the hematoma. In almost all cases extradural hematomas which cause no neurological deficit are treated conservatively and disappear spontaneously with time. However, a very small percentage of such hematomas do not disappear and become calcified or ossified hematomas over several months, so it is important to follow up all hematomas periodically using CT or MRI after head trauma. It is proposed that ossified extradural hematomas should be removed surgically, because the long-standing mass with thickening lamellar bone layer is likely to irritate the brain tissue, and some symptoms or signs such as chronic increased intracranial pressure syndrome or epilepsy may appear in future.

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The authors report a case of epidural and orbital abscess caused by chronic sinusitis. An 18-year-old male was admitted to our department with symptoms of swelling or the left eyelid, high-grade fever and frontal headache. Computed tomography revealed a ring-like enhanced mass with a scattered, small gaseous shadow. It spread in the epidural space from the left frontal region over the midline, and a spherical mass just above the left lateral canthus was displayed. Prior to the operation broad spectrum antibiotics were injected. Following a combined procedure of removal of the epidural abscess and left frontal sinusotomy, a thorough inspection confirmed that pachyntic mucosa covered all the surface of the frontal sinus and occluded the nasofrontal duct. A micro-abscess and osteomyelitis were also encountered in the lateral end of the frontal sinus. The mucosa was coagulated and resected as deep as possible along the nasofrontal duct, and draining channels were created into the anterior ethmoid sinus. The frontal sinus was then covered by the Galea propria and was isolated from the epidural space. A culture examination of the abscess content identified β-Streptococcus group F, Eubacterium Lentum and Provotella Corporis. Antibiotics proven to be effective for the bacteria were administered intravenously for 20 days. There were no sign of repeated inflammation at check-ups during 22 months.

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