Monday, July 23, 2012

Mapping Sensorimotor Cortex With Slow Cortical Potential Resting-State Networks While Awake and Unde

imageBACKGROUND: The emerging insight into resting-state cortical networks has been important in our understanding of the fundamental architecture of brain organization. These networks, which were originally identified with functional magnetic resonance imaging, are also seen in the correlation topography of the infraslow rhythms of local field potentials. Because of the fundamental nature of these networks and their independence from task-related activations, we posit that, in addition to their neuroscientific relevance, these slow cortical potential networks could play an important role in clinical brain mapping. OBJECTIVE: To assess whether these networks would be useful in identifying eloquent cortex such as sensorimotor cortex in patients both awake and under anesthesia. METHODS: This study included 9 subjects undergoing surgical treatment for intractable epilepsy. Slow cortical potentials were recorded from the cortical surface in patients while awake and under propofol anesthesia. To test brain-mapping utility, slow cortical potential networks were identified with data-driven (seed-independent) and anatomy-driven (seed-based) approaches. With electrocortical stimulation used as the gold standard for comparison, the sensitivity and specificity of these networks for identifying sensorimotor cortex were calculated. RESULTS: Networks identified with a data-driven approach in patients under anesthesia and awake were 90% and 93% sensitive and 58% and 55% specific for sensorimotor cortex, respectively. Networks identified with systematic seed selection in patients under anesthesia and awake were 78% and 83% sensitive and 67% and 60% specific, respectively. CONCLUSION: Resting-state networks may be useful for tailoring stimulation mapping and could provide a means of identifying eloquent regions in patients while under anesthesia. ABBREVIATIONS: BOLD, blood oxygenation level dependent ECoG, electrocorticography ECS, electrocortical stimulation PCA, principal component analysis ROC, receiver-operating characteristic SCP, slow cortical potential SM, sensorimotor SSEP, somatosensory evoked potentials SSS, systematic seed selection





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Rate of Return to Military Active Duty After Single Level Lumbar Interbody Fusion: A 5-Year Retrosp

imageBACKGROUND: Lumbar interbody fusion has been extensively studied in the civilian population; however, data regarding its efficacy in the military are lacking. OBJECTIVE: To identify the rate of return to unrestricted active military duty after single-level lumbar interbody fusion surgery. METHODS: The surgical database at a single tertiary care military treatment facility was queried for active-duty patients who underwent a single-level lumbar interbody fusion over a 5-year period. A retrospective chart review was performed with backward stepwise logistic regression analysis, and Fisher exact and Wilcoxon rank sum tests were used for statistical analysis. RESULTS: A total of 102 patients met the inclusion criteria. Mean age at surgery was 34.0 years (range, 19-51 years). Most surgeries (59%) were performed for discogenic pain secondary to degenerative disc disease; the remaining patients underwent surgery for spondylolisthesis (39%) or spinal stenosis (2%). Thirty-nine patients (38%) were treated via an anterior approach (anterior lumbar interbody fusion), whereas 63 patients (62%) underwent fusion via a posterior approach (transforaminal or posterior lumbar interbody fusion). Fifty-six patients (55%) were able to return to unrestricted full active duty, and the remaining 46 patients (45%) were separated from the military. The return to active duty rate was significantly higher in older patients and those ranking E7 (Chief Petty Officer) and above (84.8%). CONCLUSION: Fifty-five percent of the service members who underwent a single-level lumbar interbody fusion returned to unrestricted full duty. Older age and higher rank were statistically significant positive predictors of a successful return to active duty. ABBREVIATIONS: ALIF, anterior lumbar interbody fusion EBL, estimated blood loss PEEK, polyetheretherketone PLIF, posterior lumbar interbody fusion PRT, physical readiness test rh-BMP-2, recombinant bone morphogenetic protein type 2 TLIF, transforaminal lumbar interbody fusion





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Surgical Treatment of Spinal Extradural Arachnoid Cysts in the Thoracolumbar Spine

imageBACKGROUND: Because an idiopathic spinal extradural arachnoid cyst (SEAC) is rare, its optimal surgical treatment remains controversial. OBJECTIVE: To evaluate the results of surgical treatments for SEACs and to clarify features of the disease associated with poor outcomes. METHODS: Twelve patients with SEACs who underwent surgery at our hospital between 1988 and 2008 were examined retrospectively. The mean follow-up period was 4.7 years. Total resection of the cyst was performed in 7 patients and closure of the dural defect without cyst resection in 5 patients. Surgical outcomes were evaluated with regard to the duration of symptoms, the size of the cyst, and the surgical procedure used. RESULTS: Neurological recovery was observed in all patients, and there was no recurrence. Poor outcomes were observed in patients with a long duration of symptoms (>1 year, P < .01) and large cyst size (>5 vertebrae, P < .05). The surgical procedure had no significant association with the postoperative neurological recovery. However, there was a significant difference in the degree of the mean postoperative kyphotic angle between the patients treated by total resection of the cyst (9.7 degrees) and those treated by closure of the dural defect without cyst resection through selective laminectomy (2.2 degrees) (P < .01). CONCLUSION: There was no significant difference in postoperative neurological recovery between the 2 surgical procedures. However, closure of the dural defect without cyst resection was less invasive, preventing postoperative kyphotic deformity of the thoracolumbar spine. ABBREVIATIONS: CTM, computed tomography myelography JOA, Japanese Orthopaedic Association RR, recovery rate SEAC, spinal extradural arachnoid cyst





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Grafting the C5 Root to the Musculocutaneous Nerve Partially Restores Hand Sensation in Complete Pal

imageBACKGROUND: In complete brachial plexus palsy, we have hypothesized that grafting to the musculocutaneous nerve should restore some hand sensation because the musculocutaneous nerve can drive hand sensation directly or via communication with the radial and median nerves. OBJECTIVE: To investigate sensory recovery in the hand and forearm after C5 root grafting to the musculocutaneous nerve in patients with a total brachial plexus injury. METHODS: Eleven patients who had recovered elbow flexion after musculocutaneous nerve grafting from a preserved C5 root and who had been followed for a minimum of 3 years were screened for sensory recovery in the hand and forearm. Six matched patients who had not undergone surgery served as controls. Methods of assessment included testing for pain sensation using Adson forceps, cutaneous pressure threshold measurements using Semmes-Weinstein monofilaments, and the static 2-point discrimination test. Deep sensation was evaluated by squeezing the first web space, and thermal sensation was assessed using warm and cold water. RESULTS: All grafted patients recovered sensation in a variable territory extending from just over the thenar eminence to the entire lateral forearm and hand. Seven patients were capable of perceiving 2-0 monofilament pressure on the thenar eminence, palm, and dorsoradial aspect of the hand. All could differentiate warm and cold water. None recovered 2-point discrimination. None of the patients in the control group recovered any kind of sensation in the affected limb. CONCLUSION: Grafting the musculocutaneous nerve can restore nociceptive sensation on the radial side of the hand.





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Advanced Technical Skills Are Required for Microsurgical Clipping of Posterior Communicating Artery

imageBACKGROUND: Many neurosurgeons feel competent clipping posterior communicating artery (PCoA) aneurysms and include this lesion in their practice. However, endovascular therapy removes simple aneurysms that would have been easiest to clip with the best results. What remains are aneurysms with complex anatomy and technical challenges that are not well described. OBJECTIVE: A contemporary surgical series with PCoA aneurysms is reviewed to define the patients, microsurgical techniques, and outcomes in current practice. METHODS: A total of 218 patients had 218 PCoA aneurysms that were treated microsurgically during an 11-year period. Complexities influencing aneurysm management included (1) large/giant size; (2) fetal posterior cerebral artery; (3) previous coiling; (4) anterior clinoidectomy; (5) adherence of the anterior choroidal artery (AChA); (6) intraoperative aneurysm rupture; (7) complex clipping; and (8) atherosclerotic calcification. RESULTS: Simple PCoA aneurysms were encountered in 113 patients (51.8%) and complex aneurysms in 105 (48.2%). Adherent AChA (13.8%) and intraoperative rupture (11.5%) were the most common complexities. Simple aneurysms had favorable outcomes in 86.6% of patients, whereas aneurysms with 1 or multiple complexities had favorable outcomes in 78.2% and 75.0%, respectively. Intraoperative rupture (P < .01), large/giant size (P = .04), and complex clipping (P = .05) were associated with increased neurological worsening. CONCLUSION: Because endovascular therapy alters the surgical population, neurosurgeons should recalibrate their expectations with this once straightforward aneurysm. The current mix of PCoA aneurysms requires advanced techniques including clinoidectomy, AChA microdissection, complex clipping, and facility with intraoperative rupture. Microsurgery is recommended for recurrent aneurysms after coiling, complex branches, aneurysms causing oculomotor nerve palsy, multiple aneurysms, and patients with hematomas. ABBREVIATIONS: AChA, anterior choroidal artery GOS, Glasgow Outcome Scale ICA, internal carotid artery ONP, oculomotor nerve palsy PCA, posterior cerebral artery PCoA, posterior communicating artery





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