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James T. MacKenzie, Matthew B. Podgorsak, and Douglas Moreland

T he Leksell Gamma Knife (Elekta, Stockholm, Sweden) delivers a highly focused radiation dose that is used to treat both benign and malignant intracranial lesions. The treatment procedure involves the localization of a target lesion by using CT or magnetic resonance imaging and then delivering radiation “shots” to those sites. Each radiation shot involves the combination of 201 highly focused beams of radiation emitted from 60 Co sources that converge on a centrally positioned target. The exact (x, y, and z) coordinates of the target for each treatment are

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Mendel Castle-Kirszbaum, Julian Maingard, Tony Goldschlager, and Ronil V. Chandra

I ntraoperative localization of the pathological level in spinal surgery is crucial, not only to ensure the best chance of surgical cure but also to avoid the significant morbidity of wrong-site surgery, which is considered a sentinel event in many jurisdictions. 10 Correct intraoperative identification of the spinal level may be difficult because of obesity, congenital variation in patients’ anatomy, and the inherent difficulties of visualization using fluoroscopy, particularly in the lower cervical and upper thoracic regions. Methods of preoperative marking

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Sait Naderi, Uğur Türe, and T. Glenn Pait

The first reference to spinal cord injury is recorded in the Edwin Smith papyrus. Little was known of the function of the cord before Galen's experiments conducted in the second century AD. Galen described the protective coverings of the spinal cord: the bone, posterior longitudinal ligament, dura mater, and pia mater. He gave a detailed account of the gross anatomy of the spinal cord. During the medieval period (AD 700–1500) almost nothing of note was added to Galen's account of spinal cord structure. The first significant work on the spinal cord was that of Blasius in 1666. He was the first to differentiate the gray and white matter of the cord and demonstrated for the first time the origin of the anterior and posterior spinal nerve roots. The elucidation of the various tracts in the spinal cord actually began with demonstrations of pyramidal decussation by Mistichelli (1709) and Pourfoir du Petit (1710). Huber (1739) recorded the first detailed account of spinal roots and the denticulate ligaments. In 1809, Rolando described the substantia gelati-nosa. The microtome, invented in 1824 by Stilling, proved to be one of the fundamental tools for the study of spinal cord anatomy. Stilling's technique involved slicing frozen or alcohol-hardened spinal cord into very thin sections and examining them unstained by using the naked eye or a microscope. With improvements in histological and experimental techniques, modern studies of spinal cord anatomy and function were initiated by Brown-Séquard. In 1846, he gave the first demonstration of the decussation of the sensory tracts. The location and direction of fiber tracts were uncovered by the experimental studies of Burdach (1826), Türck (1849), Clarke (1851), Lissauer (1855), Goll (1860), Flechsig (1876), and Gowers (1880). Bastian (1890) demonstrated that in complete transverse lesions of the spinal cord, reflexes below the level of the lesion are lost and muscle tone is abolished. Flatau (1894) observed the laminar nature of spinal pathways.

The 20th century ushered in a new era in the evaluation of spinal cord function and localization; however, the total understanding of this remarkable organ remains elusive. Perhaps the next century will provide the answers to today's questions about spinal cord localization.

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Santhosh Kumar Kannath, Praveen Alampath, Jayadevan Enakshy Rajan, Bejoy Thomas, P. Sankara Sarma, and Kapilamoorthy Tirur Raman

the MR images were blinded to the angiographic findings, which were correlated with the gold-standard spinal angiographic study. The accuracy of localization and interobserver agreements were calculated by Kendall's tau and the side of fistula was assessed by kappa statistics. Results A retrospective review identified 16 patients with SDAVF who met the inclusion criteria during the study period from January 2007 to January 2013. The demographic characteristics of these patients are presented in Table 1 . The level and side of fistula were accurately predicted

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Zach Folzenlogen and D. Ryan Ormond

C ortical localization was pioneered by early inquisitive neurosurgeons. Through meticulous observation and eventually cortical stimulation, they unlocked many functional regions of the brain. The variability among individual patients was also recognized, leading to the era of intraoperative functional mapping. With this understanding, lesion resection became safer and led to improved survival in our surgical patients. Early Theories on Brain Function Understanding the function of the brain and its functional arrangement had crude beginnings. The first theories

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Steven M. Stufflebeam, Hesheng Liu, Jorge Sepulcre, Naoaki Tanaka, Randy L. Buckner, and Joseph R. Madsen

A n important factor for success in the surgical treatment of epilepsy is the accurate localization of the seizure onset zone. 25 Finding a structural lesion on MR imaging, such as mesial temporal sclerosis or a focal cortical dysplasia, improves the likelihood of controlling the illness after the surgery. 12 However, in two-thirds of patients with focal epilepsy there are no identifiable brain lesions on conventional MR imaging, and it is sometimes difficult to identify the source of epileptic discharges with scalp EEG. When the location of the

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Yun-Sik Dho, Young Jae Kim, Kwang Gi Kim, Sung Hwan Hwang, Kyung Hyun Kim, Jin Wook Kim, Yong Hwy Kim, Seung Hong Choi, and Chul-Kee Park

S ince the introduction of intraoperative navigation devices in 1986, use of a neuronavigation system with MRI has become common for brain tumor surgery. 25 Since the introduction of the MRI-based neuronavigation system (MRI-NVS) for brain surgery, accurate localization of brain lesions during surgery has been intuitively possible through imaging, leading to innovation in neurosurgery. 14 , 15 , 18 In general, careful positioning of the patient and registration will result in fine accuracy when using the MRI-NVS. However, because the MRI used for the MRI

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Andrew R. Turnbull

I n patients with brain tumors, false localizing signs can be caused by a local disturbance at a distance from the site of the tumor, and whose interpretation may lead to error in the clinical localization of that tumor. This case is being reported to record a multiplicity of rare signs which influenced both diagnosis and surgical management. Case Report A 40-year-old woman was admitted because of a 9-month history of intermittent headache. In the week prior to admission she had developed progressively severe pain in the back of her neck, vomiting

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Franck-Emmanuel Roux, Leila Boukhatem, Louisa Draper, Oumar Sacko, and Jean-François Démonet

cortical stimulations were used to localize areas of functional cortex after determining the afterdischarge threshold by electrocorticography, that is, by using a strip electrode inserted between the brain and the skull. Care was taken to avoid afterdischarges during the entire stimulation procedure. No stimulation lasted longer than 5–6 seconds. The cortex was directly stimulated using the bipolar electrode of the Nimbus cortical stimulator (1-mm electrodes separated by 6 mm, Newmedic). The current amplitude was progressively increased by 1 mA, beginning at 2 mA. We

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Linton T. Evans, Richard Morse, and David W. Roberts

and molecular underpinnings of epilepsy in tuberous sclerosis are not well defined. Abnormal expression of glutamate and γ-aminobutyric acid receptors in dysplastic neurons and giant cells of cortical tubers has been described, 35 as well as impaired glutamate transport in astrocytes in a mouse model of TSC. 36 Interestingly, not all tubers are associated with electroencephalographic abnormalities. Imaging studies frequently reveal tubers for which there is no epileptiform correlate. Conversely, other studies have demonstrated localized epileptiform activity