Cranial nerves travel through various structures, including cisterns, venous sinuses, and brain parenchyma. Although cranial nerves within the cistern are relatively easy to detect using standard magnetic resonance (MR) imaging techniques such as three-dimensional constructive interference in steady state (3D-CISS) or fast imaging employing steady state acquisition (FIESTA), cranial nerves within other structures are often found to be quite difficult to depict. Modern MR techniques on high field systems illustrated by T2 reversed (T2R) or three dimensional anisotropy contrast (3DAC) PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) are steadily changing this conventional view. Now, cranial nerves can be visualized under virtually any kind of environment.

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The microsurgical anatomy of the paraclinoid area and the surgical approach to paraclinoid aneurysms were reported. Aneurysms arising from the ICA between the site of its exit from the roof of the cavernous sinus and the origin of the posterior communicating artery have been termed paraclinoid aneurysms. Direct surgery of paraclinoid aneurysms requires an anterior clinoidectomy for adequate exposure of the paraclinoid space. The optic nerve is typically displaced superomedially by the aneurysm which often results in visual deficits. To preserve visual function, intraoperative damage to the optic nerves needs to be minimized and proper attention must be paid to safeguard the ophthalmic artery and superior hypophyseal artery. We examined the causes of optic nerve injuries and described useful methods to preserve the visual function

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In the cavernous sinus or cavernous sinus portion, various tumors arise. However, the most common tumors are trigeminal neurinomas, meningiomas, and pituitary tumors extending into the cavernous sinus. We surgically removed those tumors via a modified Dolenc approach. Under a usual frontotemporal curvelinear skin incision, craniotomy is performed. Thereafter, orbitotomy, the opening of the superior orbital fissure and optic canal, and anterior clinoidectomy are extradullary performed. The space between the superficial and inner layers constituting the lateral wall of the cavernous sinus is dissected, and the 3rd, 4th and 5th nerves are exposed. The dissection is continued until the exposure of the main trunk of the 5th nerve and Meckel's cave. The Dolenc approach is the best approach for the removal of trigeminal neurinomas. Regardless the direction of the tumor extension, the tumor can be removed by the Dolenc approach with minimal cranial nerve injury. Surgery for trigeminal neurinomas is done by basically only an extradural procedure. In meninigioma surgery in and around the cavernous sinus, most meningiomas involve the cranial nerves, intradural major cerebral arteries, and perforators. In the surgery for such meningiomas, we remove the extracavernous part of the tumor, and leave the intracavernous part to avoid injury of cranial nerves. In the follow-up period, stereotactic radiosurgery is adopted for the residual part of the tumor if the size of the residual part increases. For pituitary tumors extending into the cavernous sinus, the tumor can be removed through the pericarotid space and the anterior loop of the carotid artery after anterior clinoidectomy. In the surgery for tumors in and around the cavernous sinus, precise anatomical knowledge is most important, and cadaver dissection study is most helpful to understand the complex anatomy of the cavernous sinus. The characteristic points of each cavernous sinus tumor such as location, anatomical relation between the tumor and cranial nerves, and extension of the tumor have to be understood in order to avoid serious complications like injuries of the cranial nerves, major cerebral arteries, and perforators.

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Among the various brainstem lesions, cavernous angiomas and localized gliomas may be surgically resected. When these lesions are resected, meticulous care is essential not only to achieve the goal of postoperative functional recovery, but also to not cause any postoperative neurological deficits. Two key points for obtaining this purpose are knowing the detailed anatomy of the brainstem, and fully evaluating the optimal surgical approach in order to achieve minimal postoperative funcitonal damage. Intraoperative electrophysiological monitoring and mapping of the brainstem are essential to obtain the best surgical results with minimal funtional damage. In the present report, by showing different cases of brainstem cavernous angiomas, the selection of the optimal surgical approach will be discussed in terms of functional preservation.

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We retrospectively studied 43 patients with pediatric cerebral arteriovenous malformation, 15 boys and 28 girls aged 4 to 15 years (mean 11.7 years), who underwent gamma knife radiosurgery (GKS) at our hospital. The mean nidus volume was 4.5 ml(0.1〜17 ml), and the mean prescription dose at the nidus margin was 19.9 Gy(12〜25 Gy). The actuarial obliteration rate was 50.0% at 3 years and 80.0% at 5 years, based on angiography in 24 patients and magnetic resonance (MR) imaging in 4 patients. The delivered peripheral dose tended to be correlated with obliteration rate (p=0.09). Fourteen of the 43 patients developed radiation-induced change in the brain tissue on follow-up MR imaging, and 4 of these 14 patients were symptomatic. Eight of the 14 patients with edema of the brain tissue required steroid therapy. None suffered permanent neurological complication. Three of the 43 patients suffered postradiosurgical hemorrhage. No patient developed long-term complication such as cyst formation or chronic encapsulated expanding hematoma. These findings suggest that GKS is effective for the treatment of pediatric cerebral arteriovenous malformation, especially if located in deep or eloquent areas. In contrast, we recommend direct surgery for cerebral arteriovenous malformation in surgical accessible regions because of the relatively high rate of radiation-induced change of brain tissue on follow-up MR imaging.

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The treatment goal of acoustic neuromas in the era of radiosurgery is preserving not only facial nerve function but also hearing function. Gamma knife radiosurgery is a useful treatment for small to medium size tumors below 3 cm in diameter. In large tumors above 3 cm in diameter, we attempted intentional partial tumor resection preserving cranial nerve functions and performing boost radiosurgery. We have described the surgical techniques of position, craniotomy, and the pitfalls involved in tumor resection for intentional partial resection of acoustic neuromas by the suboccipital retrosigmoid approach, based on our experience with 43 patients.

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Meningitis frequently causes cerebral infraction but rarely causes aneurysm formation and rupture. Magnetic resonance imaging (MRI) and computer tomography (CT) revealed abnormal density areas of suspected cerebral infarctions in the left frontal and occipital lobes. Although her general condition was improved by medication the sudden onset of subarachnoid hemorrhage with a huge hematoma in the fronto-temporal lobe was observed on the 11th day of treatment. Cerebral angiography showed a fusiform aneurysm at the distal branch of a right middle cerebral artery. Because the extravasation from the aneurysm occurred during the procedure, the aneurysm was trapped and resected through the left pterional approach. The partial dilated frontal branch, not observed in the pre-operative angiography, originated from the aneurysm. The dilated vessel was trapped and resected. Histologically, inflammatory cells markedly infiltrated into the whole wall of the aneurysm. The aneurysm had no elastic lamina, but the elastic lamina was preserved in the dilated abnormal branch. We suggest the aneurysm formation and multiple cerebral infarctions were caused by the strong extravascular inflammation resulting from meningitis.

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We report a rare case of delayed cerebrospinal fluid rhinorrhea after penetrating craniofacial injury caused by chopstick. A 50-year-old male had a transmaxillar penetrating injury with a chopstick when the patient was 2 years old. The patient had suffered from recurrent meningitis 3 times after trauma. Forty-eight years after a penetrating craniofacial injury, the patient experienced rhinorrhea of cerebrospinal fluid (CSF), and surgical repair of the CSF fistula at the anterior skull base was performed. Previous penetrating craniofacial injury should be considered in patients with recurrent CSF rhinorrhea and meningitis.

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