The microsurgical anatomy of the cavernous sinus and paraclinoid area were reported. The cavernous sinus is located near the center of the head on each side of the skull and sphenoid sinus. Its anterior edge is attached to the margins of the superior orbital fissure and anterior clinoid process. The cavernous sinus has venous connections with the cerebrum, cerebellum, brainstem, face, eye, orbit, nasopharynx, mastoid, and middle ear. The oculomotor, trochlear, ophthalmic and maxillary nerve courses are in the lateral wall of the cavernous sinus. The abducens nerve courses are on the medial side of the ophthalmic nerve. Precise anatomy is important in the surgical management of cavernous sinus lesions. We also examined the surgical approaches to the cavernous sinus in cadaveric dissection.

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Surgery for a paraclinoid aneurysm of the internal carotid artery requires precise knowledge of the anatomy of the paraclinoid region. Among them, the important bony structures include the anteior clinoid process, optic canal, optic strut. As for the vessels, the ophthalmic artery, superior hypophyseal artery and cavernous sinus, as well as the internal carotid artery, are the key structures. Membraneous structures include the dural ring, carotid cave, falciform ligament and nervous structures include the optic nerve and oculomotor nerve. Considering surgical procedures, removal of the anterior clinoid process and optic unroofing, circumferential dissection of the dural ring taking care not to injure the ophthalmic artery are key surgical procedures for use in this region. Surgical points are also described based on these anatomical characteristics.

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Skull base meningiomas can occasionally obstruct the basal venous sinuses as the tumor growth. We therefore analyzed the venous draining pattern from sylvian veins in clinoidal meningiomas. Between 1995 and 2007, twenty patients with clinoidal meningioma underwent surgical intervention at our institute. Venous drainage from sylvian veins was categorized into three patterns, including cortical type, sphenobasal type and sphenoparietal type, according to the main draining vein. Preoperative angiographic evaluation showed 14 patients (70%) as cortical type, 5 patients (25%) as sphenobasal type and 1 patient (5%) as sphenoparietal type. Postoperative clinical courses revealed that dominant sphenobasal sinuses were successfully preserved by skull base techniques in all of the sphenobasal type patients. One sphenoparietal type patient developed a brain contusion conceivably, by the obstruction of the dominant sphenoparietal sinus during tumor resection. Drainers from sylvian veins to the skull base should be carefully evaluated preoperatively and must be preserved, if dominant, in the surgery of clinoidal meningioma.

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In treating cavernous sinus dural arteriovenous fistulas (CSdAVFs), a thorough understanding of angioarchitecture, especially identifying the shunt (s), is mandatory to obtain optimal results by endovascular therapy. In this article, the functional angiology of the cavernous sinus and surrounding structure, which is necessary to obtain the pathophysiology of this disease, is described in the first half. In the latter half, a practical endovascular therapy for CSdAVF, focusing on the idea of superselective shunt occlusion (SSSO) is presented. Since 2003, we have chosen this method as our first line therapy for treating CSdAVFs, and successful SSSO was achieved in nine cases out of fourteen (64.3%). SSSO is highly possible in cases where the shunt segment was obviously identified outside the cavernous sinus. This method can achieve the angiographic cure of CSdAVFs while preserving the normal venous drainage, and since there is less chance of unfavorable permanent cranial nerve palsy it should be considered before sinus packing or mere obliteration of the dangerous venous drainages.

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Objective: In treating cerebral arteriovenous malformations (AVM), the efficacy of presurgical or preradiosurgical embolization is still considered suspicious, mainly due to the high incidence of the endovascular procedure. In this article, the efficacy of presurgical as well as preradiosurgical embolizaton is described. Methods: During January 2005 to July 2007, fifty patients with AVMs were treated in our institute and thirtynine patients were treated by means of "multimodality" therapy including preoperative or preradiosurgical embolization. Among them, twelve patients received preoperative endovascular procedures, whereas seven patients underwent preradiosurgical embolization. As to the endovascular procedures, n-butyl cyanoacrylate (NBCA) was used as the embolic material. The interval between edovascular therapy and surgery/radiosurgery was one to seven days except for one case (mean 4.4 days). Results: One session was required for the endovascular procedures in 14 patients, two in three patients and, four in one patient. There was no permanent morbidity or mortality related to either modality. The modified Rankin Scale Score of the patients treated by multimodality therapy was 0 in eleven, 1 in five, and 2 in three. Conclusion: The main role of presurgical embolization is the occlusion of feeders which seem surgically difficult to access; meanwhile the role of preradiosurgical embolization is AVM volume reduction by intranidal embolization. To achieve effective embolization for AVMs, a thorough discussion among the neurovascular surgeon, radiologist and neuroendovascular physician is mandatory to maintain a high success rate in each modality.

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A 58-year-old woman developed a dural arteriovenous fistula about 13 years after the first surgery for a tentorial meningioma. She initially complained of an unsteady gait, and a left tentorial meningioma was removed via the left suboccipital and occipital craniotomy. Thirteen years later, she complained of tinnitus, and angiography revealed a dural arteriovenous fistula in the left transverse-sigmoid sinus, which was not shown in the previous angiogram. Transarterial embolization was performed, resulting in complete cure. We review the literature on the etiology of postoperative development of dural arteriovenous fistulas. We suspect that the recurrence of meningioma invading and occlusion of the transverse sinus were probably the major contributing factors to the formation of the dural arteriovenous fistula in our patient.

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Lumbosacral nerve root anomalies are occasionally encountered during treatment for degenerative lumbar diseases. In the literature, anatomical studies showed a higher incidence (8.5-30%) of anomalous nerve root than that found in clinical investigations (2.2-4.0%). A 69-year-old female was admitted complaining of low back pain and left sciatica. While her neurological symptoms suggested radiculopathy at the L5 nerve root area, L5/S1 mediolateral disc herniation was noted by radiological examinations. Myelography and the coronal section of her magnetic resonance imaging (MRI) demonstrated an anomalous L5 nerve root (caudal origin) compressed by the L5/S1 herniated disc. With the preoperative knowledge of this nerve root anomaly, microscopic discectomy with adequate exposure achieved effective decompression and satisfactory resolution of clinical symptoms. Attention must be paid to nerve root anomalies, especially when neurological findings are atypical. Preoperative diagnosis of nerve root anomalies is essential for both safe and effective procedures for lumbar spine surgery.

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