The tentorial incisura can be defined as the space surrounded by the free edge of the cerebellar tentorium. It provides the only communication between the supratentorial and infratentorial spaces, and contains many vital structures such as the components comprising the circle of Willis, cranial nerves, and deep venous systems. Surgery of the tentorial incisura requires correct knowledge of the normal anatomy, and furthermore, variations of the deep venous system should also be well recognized.

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  We describe basic knowledge necessary for the transsylvian approach. From a surgical point of view, diverse patterns of sylvian veins can be treated as two distinct but connected venous pathways consisting of superficial sylvian veins and deep middle cerebral vein system. In contrast to previous understanding, many technical drawbacks inherent to standard pterional approach can be overcome by working on temporal region rather than just working on the frontal region. For example, dissection of sylvian veins should be carried out between the superior temporal gyrus and frontosylvian vein when frontoorbital veins are to be preserved. Veins and arteries on the mesial temporal lobe (Planum polare) should be skeletonized to retract mesial temporal lobe toward posterolateral direction. This manipulation provides abundant working space with less frontal retraction in aneurysm surgery. Understanding microanatomy in various disease processes is of paramount importance to practice microsurgery, and we must put emphasis on intensive practice-based learning to acquire the necessary skills to implement the transsylvian approach.

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  Objective : The authors present the anatomical and angiographical details that enable surgeons to quickly locate middle cerebral artery (MCA) aneurysms and to gain proximal control without unnecessary delay or premature rupture.
  Materials and Methods : The anatomical dissections were performed in 10 adult cadaveric heads from 1993 to 2011 at the Department of Neurological Surgery, University of Florida. The angiographic and the surgical data were derived from 93 MCA aneurysms operated on by Hung Tzu Wen (HTW) from 1996 to 2012 at the Hospital das Clínicas, University of São Paulo and Hospital Samaritano, Brazil.
  Results : MCA aneurysms arise most frequently from the M1 segment and less frequently from M2. From a practical viewpoint, the M1 extends from the carotid bifurcation to the MCA genu (on the basal surface of the cerebrum) with specific topographical relationships along the way, and the M2 extends from the MCA genu to the sylvian or “M” point (on the lateral surface), also with specific topographical relationships. The key for the angiographical analysis of an MCA aneurysm is to establish its topographical relationship to the genu of the MCA. If it is proximal to the genu, it is important to estimate its distance to the carotid bifurcation and to the MCA genu. If it is distal to the MCA genu, it is important to estimate its distance to the genu and to the sylvian point ( “M” point). Also, it is important to evaluate the direction of the dome of the aneurysm, as it indicates the structures to which the dome is attached. The key for locating an MCA aneurysm intraoperatively is the relationship between the MCA genu and the tip of the pars triangularis. The tip of the pars triangularis is a reliable intraoperative landmark (even when it is obscured by severe subarachnoid hemorrhage) and it is located just distal to the MCA genu and approximately 2 cm distal to the sharp transition between the basal and the lateral surfaces of the cerebrum. Once the pars triangularis is identified, the MCA genu can also be quickly estimated and identified, and thereby so will the aneurysm.
  Conclusion : The carotid bifurcation, genu of the MCA, and the “M” point on the AP view carotid angiography, and the sylvian triangle on the lateral projection constitute the cardinal landmarks for locating MCA aneurysms angiographically. Correlating the angiographic location of the aneurysm to the pars triangularis of the inferior frontal gyrus constitutes the key for then locating the MCA aneurysm intraoperatively.

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  Objective : The authors intend to demonstrate the currently used technique of anterior temporal lobectomy plus amygdalohippocampectomy for treating refractory temporal epilepsy as developed by the lead author (HTW). The anatomy based modifications presented in this paper have been gradually added to the original technique throughout a 13-year span to make these surgeries both safer and faster.
  Material and methods : Three hundred and forty-six anterior temporal lobectomies plus amygdalohippocampectomies were performed by HTW from 1999 to 2011. The intraoperative observation of the difficulties encountered in each case motivated the search for modifications to overcome those difficulties.
  Results : The major modifications are : patient positioning with less rotation of the head and more extension of the neck, interfascial dissection of the temporalis fascia, detachment of the temporalis muscle from the angle formed by the frontal and the temporal processes of the zygomatic bone, craniotomy below the superior temporal line, a 2.5 to 3.0cm neocortical removal with subpial “peeling” technique, locating the temporal horn using the grey matter overlying the occipitotemporal sulcus, and resection of the amygdala based on a modified carotid-choroidal line. The modified sequence for the hippocampectomy is as follows : anterior disconnection, lateral disconnection, opening the choroidal fissure and the medial disconnection, and the posterior disconnection. Whenever possible, all the arachnoid membranes of the cisterns have to be kept intact during the intradural stage of the surgery. The overall seizure-free rate was 86%, and the complications were presented.
  Conclusion : The careful intraoperative observation of the procedural difficulties, the anatomy-based modifications to overcome those challenges, and extensive practice of the microsurgical techniques helped the authors to design the above described technical modifications, making medial temporal resections safer and faster.

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  Neuroradiological examinations play an important role in diagnosis and surgery for epilepsy patients. Since the introduction of the 3T MR imager, we have had the means to easily perform high-resolution MR imaging, diffusion tensor imaging (DTI), and MR spectroscopy. These MR imaging modalities provide important information on focus diagnosis and surgery for temporal lobe epilepsy. Safe and accurate temporal lobe epilepsy surgery can be accomplished by simulating the surgery preoperatively based on three-dimensional fusion images and then performing the surgery under multi-image guidance with PET and SPECT.

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  Medial sphenoid wing meningioma, at the advanced stage of its growth, creates several compartments partitioned by the internal carotid artery, Willis arterial ring and its perforators, the optic nerve, and the tentorial edge. According to the classification type, which we newly propose takes into consideration the meningioma's main attachment on the skull base, each type has a characteristic compartment formation. For example when infra-Willis portions of the tumor make the main attachment on the skull base, total removal is often difficult because these tumors tend to form more complicated compartments. We discuss the operative techniques and resectability of these tumors and emphasize that the concept of compartment formation is important and that, in order to preserve the perforators, the tumor should be taken out via the route that the tumor came in.

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  Amyotrophic lateral sclerosis (ALS) is a fatal neurologic disease caused by progressive degeneration of the upper and lower motor neurons. An effective treatment for ALS has not been established, the average survival period is from two to three years.
  Early symptoms of ALS are diverse and according to previous reports, 26.6% of patients are initially misdiagnosed, and approximately 10% of patients undergo inappropriate spinal surgery.
  We report a case with progression of symptoms after lumbar spine surgery. The patient was a 68-year-old man. He was admitted complaining of low back pain with difficulty walking. The patient showed abnormal sensation in the lower extremities, and slight weakness of the left biceps femoris muscle, but muscle atrophy was not evident. Magnetic resonance imaging (MRI) showed lumbar spinal canal stenosis and a disc herniation of L4/5, so we performed decompressive surgery for this lesion. Despite complete decompression, the patient's symptoms did not improve. In addition, new problems developed in the early postoperative period including respiratory failure and lower extremity muscle atrophy. Following further examination, the patient was eventually diagnosed with ALS and died in the course of 4 months after surgery.
  In this report, we discuss the symptoms associated with ALS with lower back pain. And we also consider the impact of surgery and anesthesia on the natural course of ALS.

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  Introduction : The purpose of this study was to evaluate the epileptogenic zone in a patient with unilateral hippocampal sclerosis, whose ictal discharges on scalp EEG indicated onset on the contralateral side.
  Case presentation : A 34-year-old man had intractable complex partial seizures since six years of age. His seizures presented with automatism of both arms with mild dystonia on the right side. Scalp ictal EEG revealed rhythmic theta waves over the left anterior temporal region, indicating left temporal lobe origin. On the contrary, neuroimaging findings of right hippocampal sclerosis on MRI, hypo-metabolism in the right temporal lobe on ¹⁸F-FDG-PET, and hypo-accumulation in the right mesial temporal lobe on ¹¹C-FMZ-PET strongly support right mesial temporal lobe origin. Invasive EEG monitoring revealed that ictal discharges originated from the right mesial temporal lobe and immediately propagated to the left temporal lobe. The patient became seizure-free after selective right amygdalo-hippocampectomy.
  Conclusion : Although this case showed a discrepancy between neuroimaging and other findings such as semiology and scalp ictal EEG, consistent findings on both MRI and PET should be a strong indicator in deciding the side of surgery.

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