The venous structures in the petroclival region, along with the veins leading to the petroclival lesions, are explained along with their anatomical characteristics. 1) The inferior petrosal sinus forms an ampulla called the petrosal confluens at its proximal end. There venous tributaries gather firstly and then drain secondarily to the jugular bulb. The main channel, which is big enough to let an intravenous catheter through, always exists between the IX and X-XI nerves. The main channel often opens below the jugular bulb. The inferior petroclival vein is a small vessel running in the extracranial groove of the petroclival fissure, pouring into the petrosal confluens. Although it is small, when extraordinarily dilated, it might be a useful route to introduce an intravenous catheter. 2) The basilar venous plexus has networks between the IPS of either side. Even when the IPS is obstructed, a catheter can be delivered to the cavernous sinus from the other side via the basilar venous plexus. 3) The petrosal vein can be categorized into three groups according to its draining point: medial, intermediate, and lateral. A petrosal vein of the medial type is most frequent. The most important tributary is the vein of the cerebellopontine fissure, which usually joins the medial petrosal vein. 4) Veins bridging from the temporal lobe to the lateral end of the transverse sinus, including the vein of Labbe, are threatened with avulsion injury during temporal lobe elevation for the transpetrosal approach. The sphenopetrosal sinus should be spared when the middle fossa dura is sectioned to access the petroclival lesions.

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Recently, Magnetic Resonance Angiography and three-dimensional CT angiography have become important tools for neurosurgeons and neuroradiologists. In the daily clinical diagnosis, the number of diagnostic cerebral angiographies performed has actually been reduced, but its dominant position in the evaluation of detailed information for advanced treatment of skull base diseases, such as dural arteriovenous fistulas, arteriovenous malformations, or skull base tumors, still remains and is much required. Classical venous anatomy and landmarks are not described in this chapter. We illustrate how to obtain much clearer venous images and analyze venous hemodynamic conditions from the aspect of endovascular treatment or direct surgery. Practically important points of venous findings for treatments are also described here mainly from the standpoint of "venous cross roads".

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The authors presented microvascular decompression procedures based on the microsurgical anatomy. Attention is paid in this approach to the trigeminal nerve and the petrosal vein as obstacles. The infratentorial lateral supracerebellar approach is recommended instead of Dandy's cerebellar route. The microsurgical anatomy of the superior petrosal vein and its tributaries is also reviewed. The superior petrosal vein should be preserved during microvascular decompression for trigeminal neuralgia as much as possible. However, neurosurgeons often meet venous complex using this approach and have to make a surgical decision to sacrifice the tributaries for optimal exposure of the trigeminal nerve. Even in this situation, the authors emphasize that the vein of the cerebellopontine fissure should always be preserved in order to avoid congestive venous complications.

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Surgery for petroclival region tumors is one of the most difficult surgeries because the tumors are located in the deep midline area and furthermore, they are often situated in both the supra- and the infratentorial areas. We have used the posterior transpetrosal approach (PTA) or the lateral suboccipital approach (LSA), depending on the location of the main mass in each case. However, we now use the LSA more frequently after experiencing a certain amount of cases. This is because when using this approach the anatomy of the intraoperative view can be easily understood and it requires less time to expose the tumor. The LSA for petroclival tumor surgery means the infratentorial lateral supracerebellar approach, and the transtentorial approach can be added from the inferior side, if necessary. The main obstacles for the approach include the superior petrosal veins. Surgeons should know well the anatomy of the veins. In the case of the PTA, the superior petrosal veins are not a big problem but the vein of Labbe, temporal bridging veins, bridging veins to the tentorial edge and tentorial sinuses are obstacles. Herein, we describe the basic procedures and techniques of the LSA and the PTA and then, we explain the surgical anatomy of the deep venous system near the tentorial edge and the methods for dealing with the veins, especially the superior petrosal vein.

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Solitary fibrous tumor in the central nervous system is rare. We report the case of a 41-year-old man who presented with progressive dementia and a solitary fibrous tumor (SFT) arising from the dura mater of the anterior cranial fossa with intracranial and extracranial extension through the cribriform plate. The tumor was removed totally via combined transcranial and endoscopic transnasal approaches. Immunohistochemical examination of the resected specimen showed it to be strongly positive for CD34 and vimentin and negative for S-100 protein and epithelial membrane antigen (EMA), suggesting SFT. The location of the tumor and the multicystic features characterized the case. We stress the importance of including SFT in the differential diagnosis of tumors originating from the anterior cranial fossa with intracranial and extracranial extension.

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A 32-year-old male presented with 3- to 4-year history of back pain, bilateral leg dysesthesia, gait disturbance, dysuria, and difficulty with erection. On radiological imaging, an extradural arachnoid cyst extending from T_<10> to L_1 was noted. The cyst was totally excised, and a recapping laminoplasty was performed. During surgery, a dural fistula that allowed the extradural cyst to communicate with the subarachnoid space was found. Postoperatively, the patient's neurological deficit improved. On histology, findings characteristics of an extradural arachnoid cyst were noted. This cyst was thought to have occurred due to a valve-like mechanism between the cyst cavity and the subarachnoid space. Such patients have a good prognosis when they are diagnosed early and the cyst is removed after the fistula communicating with the subarachnoid space is closed.

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The ideal surgical treatment of cervical radiculopathy remains controversial. Recent reports from orthopedic surgeons in Japan recommend microscopic posterior foraminotomy. We observed a case of cervical spondylotic radiculopathy treated with microscopic posterior foraminotomy. This technique has several advantages, such as preservation of cervical motion, no need for external bracing, and a lower risk of complications. Careful patient selection and microsurgical technique is essential in obtaining consistent and excellent results. Here we report the details of surgical technique and the procedure for this treatment.

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Intrathecal baclofen therapy (ITB) has become the one of the standard treatments for severe spasticity. A preexisting ventricle peritoneal shunt in those patients is not a contraindication for ITB, but we should be aware of complications related to these two devices. The authors performed ITB in three patients who had ventriculoperitoneal shunts previously inserted. The first case is a 41-year-old man, who developed spasticity and dystonia after whole brain and whole spine radiotherapy for a pineal tumor, illustrated severe paralytic ileus one month after pump implantation. The second case is a 22-year-old man with spastic paraparesis after severe brain injury who did not have any complications. The third case is a 14-year-old boy with a history of a cerebral hemorrhage associated with acute leukemia who developed subcutaneous cerebrospinal fluid collection around the catheter tract and pump two months after implantation, which was due to shunt dysfunction. Both complicated cases were treated successfully by reducing the dose of baclofen or changing the pressure setting of the shunt. Patients with ventriculoperitoneal shunts can be successfully treated by ITB, although there is minor additional risk of complications related to cerebrospinal fluid flow dynamics.

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