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Cheerag D. Upadhyaya, Jau-Ching Wu, Cynthia T. Chin, Gopalakrishnan Balamurali, and Praveen V. Mummaneni

T he intraoperative localization of thoracic vertebral levels remains a challenging problem. A recent questionnaire study by Mody et al. 12 found a high prevalence of wrong-level surgeries among spine surgeons with nearly 50% of surgeons performing a wrong-level surgery during their career. Correct-level spine surgery is an important patient safety and quality-of-care issue. 5 Several factors make the thoracic spine especially difficult for proper target level localization including osteoporosis, obesity, scapular/humoral shadow, anatomical variations in

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James H. Wood, Mitchell Parver, John L. Doppman, and Ayub K. Ommaya

incomplete debridement, fragment migration, and surgical draping. This lack of precise localization may result in additional dissection and searching into surrounding cerebral tissue, increased cerebral edema, and prolongation of the neurosurgical procedure. The result of such cerebral embarrassment may be incomplete debridement as verified on postoperative radiographs or damage to vital brain structures. This experiment was devised to test the usefulness of ultrasound for the precise intraoperative localization of intracerebral bone fragments. Materials and Methods

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Gene H. Barnett, Donald W. Kormos, Charles P. Steiner, and Joe Weisenberger

) observed with rotation of the operating table. Observed error is less than 1.0 mm as the detector is mechanically coupled to the table. Distance Measurement The phantom device allows 3-D distances of greater than 20 cm to be accurately measured. Comparison of 24 distance measurements as determined by the phantom and the localizer wand demonstrated a mean discrepancy of 1.14 ± 0.96 mm or a percentage discrepancy over a measured distance of 0.97% ± 0.68%. Intraoperative Localization In five patients, the reference coordinate location of a fourth

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Paolo Belardinelli, Ramin Azodi-Avval, Erick Ortiz, Georgios Naros, Florian Grimm, Daniel Weiss, and Alireza Gharabaghi

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for symptomatic Parkinson’s disease (PD); the clinical benefit may not only mirror modulation of local STN activity but also reflect consecutive network effects on cortical oscillatory activity. Moreover, STN-DBS selectively suppresses spatially and spectrally distinct patterns of synchronous oscillatory activity within cortical-subcortical loops. These STN-cortical circuits have been described in PD patients using magnetoencephalography after surgery. This network information, however, is currently not available during surgery to inform the implantation strategy.

The authors recorded spontaneous brain activity in 3 awake patients with PD (mean age 67 ± 14 years; mean disease duration 13 ± 7 years) during implantation of DBS electrodes into the STN after overnight withdrawal of dopaminergic medication. Intraoperative propofol was discontinued at least 30 minutes prior to the electrophysiological recordings. The authors used a novel approach for performing simultaneous recordings of STN local field potentials (LFPs) and multichannel electroencephalography (EEG) at rest. Coherent oscillations between LFP and EEG sensors were computed, and subsequent dynamic imaging of coherent sources was performed.

The authors identified coherent activity in the upper beta range (21–35 Hz) between the STN and the ipsilateral mesial (pre)motor area. Coherence in the theta range (4–6 Hz) was detected in the ipsilateral prefrontal area.

These findings demonstrate the feasibility of detecting frequency-specific and spatially distinct synchronization between the STN and cortex during DBS surgery. Mapping the STN with this technique may disentangle different functional loops relevant for refined targeting during DBS implantation.

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Akifumi Suzuki and Nobuyuki Yasui

✓ Perplexing findings of cortical somatosensory evoked potentials (SEP's) for determining the central sulcus during a craniotomy are reported in a case of brain tumor. On stimulation of the contralateral median nerve in that patient, phase-reversal of SEP waves N1 and P2 was observed not only across the central sulcus but also across the precentral sulcus. In topographic mapping of the N1-P2 amplitude, the sulcus dividing the maximum polarity was the central sulcus; this was confirmed by the cortical stimulation-evoked motor responses. For accurate localization of the central sulcus by cortical SEP's, the distribution of potentials must be analyzed with extensive exposure of the sensorimotor cortex.

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Christopher D. Witiw, Jonathan S. Citow, Howard J. Ginsberg, Julian Spears, Richard G. Perrin, Michael D. Cusimano, and R. Loch Macdonald

the patient's symptoms and lead to additional surgical procedures and medicolegal complications. 1 , 2 Both the North American Spine Society and the Joint Commission recommend an intraoperative radiograph to confirm the correct spinal level in their guidelines for preventing wrong-level surgery ( http://www.spine.org/Documents/SMaXchecklist.pdf ). 3 Several techniques have been described to improve intraoperative localization in the cervical spine. Singh and colleagues proposed a modified oblique cross fluoroscopy technique to eliminate radiographic obstruction

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Michael J. Strong, Julianne Santarosa, Timothy P. Sullivan, Noojan Kazemi, Jacob R. Joseph, Osama N. Kashlan, Mark E. Oppenlander, Nicholas J. Szerlip, Paul Park, and Clay M. Elswick

articles were included in the systematic review ( Fig. 1 ). FIG. 1. PRISMA flow chart depicting the literature search and study selection. Figure is available in color online only. Several different techniques to facilitate intraoperative localization have been reported in the literature. Some of the more well-described approaches include fiducial metallic markers (screw or gold), metallic coils, polymethylmethacrylate (PMMA), methylene blue, marking wire, use of intraoperative neuronavigation, intraoperative localization techniques (including using a needle

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Zvi Ram, Thomas H. Shawker, Mary H. Bradford, John L. Doppman, and Edward H. Oldfield

P ituitary microadenomas often are not visualized on preoperative magnetic resonance (MR) imaging 1, 2, 6, 9 and may be difficult to find during surgical exploration of the pituitary, particularly in a patient with Cushing's disease. Although ultrasound is routinely used during surgery to localize islet-cell and parathyroid tumors, 5, 7 the use of ultrasound to localize and define pituitary tumors has never been evaluated. To enhance intraoperative localization of pituitary adenomas, we assessed the feasibility of using ultrasound to detect and localize

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Cole A. Giller, Hanli Liu, Dwight C. German, Dheerendra Kashyap, and Richard B. Dewey Jr

mm of the sensors that can also distinguish white matter from gray matter. 13 , 15 Although potential advantages of optical coherence tomography include the visualization of tissue morphology and the detection of blood vessels, the modality may be limited in practice because of its complexity and expense. Another technology yielding similar data to NIR recording is impedance monitoring, 22 which distinguishes gray matter from white matter and has been used for intraoperative localization. Impedance monitoring differs from NIR recording in several ways. First

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James S. Walkden, Zsolt Zador, Amit Herwadkar, and Ian D. Kamaly-Asl

ultrasound, we believe that 6 months' delayed angiography is mandatory to exclude any residual AVM and to assess for any de novo AVM formation, which is described in the pediatric population 7 , 11 , 18 and indeed in our series (Cases 8 and 15). Conclusions Intraoperative Doppler ultrasonography in combination with neuronavigation and integrated operative microscopy is a reliable and useful method for intraoperative localization and guidance in AVM resection in the pediatric population. This technique has shown a very high complete resection rate with extremely low