Coordinated movements are achieved by well-timed activation of selected muscles. This process relies on intact cerebellar circuitry, as demonstrated by motor impairments following cerebellar lesions. ...Based on anatomical connectivity and symptoms observed in cerebellar patients, we hypothesized that cerebellar dysfunction should disrupt the temporal patterns of motor cortical activity, but not the selected motor plan. To test this hypothesis, we reversibly blocked cerebellar outflow in primates while monitoring motor behavior and neural activity. This manipulation replicated the impaired motor timing and coordination characteristic of cerebellar ataxia. We found extensive changes in motor cortical activity, including loss of response transients at movement onset and decoupling of task-related activity. Nonetheless, the spatial tuning of cells was unaffected, and their early preparatory activity was mostly intact. These results indicate that the timing of actions, but not the selection of muscles, is regulated through cerebellar control of motor cortical activity.
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•High-frequency stimulation blocked cerebellar outflow and impaired motor behavior•Response patterns and coordinated firing of CTC neurons were disrupted•The spatial tuning and early preparatory activity of neurons were unaffected•Cerebellar control of local and global cortical synchrony supports motor timing
Nashef et al. blocked cerebellar outflow using high-frequency stimulation. This impaired motor timing and coordination, as seen in cerebellar patients. Cortical responses and synchronization were altered, yet spatial tuning was maintained. Motor timing and coordination are regulated by a cerebellar signal that organizes activity of a cortical subnetwork.
Abstract Objective Cervical spine surgery is a common procedure for treatment of wide variety of pathologies. In this paper we report approach-related complication rates experienced by our patients. ...Methods We retrospectively evaluated patients' data treated surgically for cervical pathologies from February 2011 to October 2013. Medical records were collected and evaluated. We compared anterior cervical approach to posterior cervical approach for patients operated due to all cervical pathologies and a sub-analysis was performed for cervical myelopathy patients. Results The study included 251 patients (192 anterior vs. 59 posterior). The anterior approach patients were younger (not significant) but the indications for surgery varied significantly. Mean number of levels treated was 2.2 and 3.5 for anterior and posterior approach respectively (statistically significant). Neurologic status change was favorable for both surgical approaches. Total and deep wound infection rates (5.8% vs. 11.9%; p=0.008; 0.5% vs. 8.5%; p<0.0005) were significantly higher for the posterior approach As well as total complication rate (7.8% vs. 20.3%; p=0.005). Sub-analysis including only cervical myelopathy patients (131 anterior vs. 33 posterior) demonstrated again higher levels of deep wound infections and total infection rates for posterior approach (0% vs. 12%; p<0.0005; 12% vs. 1.5%;p<0.005). Total complication rate in the myelopathy group was higher for posterior approach (6.1% vs. 18.1%;p=0.026). Conclusions Both the posterior and the anterior approaches are highly efficacious in preventing neurologic deterioration and in most cases improve neurological function. This study demonstrates that the anterior approach was associated with significantly lower rates of complication especially infection related complications.
In higher mammals, motor timing is considered to be dictated by cerebellar control of motor cortical activity, relayed through the cerebellar-thalamo-cortical (CTC) system. Nonetheless, the way ...cerebellar information is integrated with motor cortical commands and affects their temporal properties remains unclear. To address this issue, we activated the CTC system in primates and found that it efficiently recruits motor cortical cells; however, the cortical response was dominated by prolonged inhibition that imposed a directional activation across the motor cortex. During task performance, cortical cells that integrated CTC information fired synchronous bursts at movement onset. These cells expressed a stronger correlation with reaction time than non-CTC cells. Thus, the excitation-inhibition interplay triggered by the CTC system facilitates transient recruitment of a cortical subnetwork at movement onset. The CTC system may shape neural firing to produce the required profile to initiate movements and thus plays a pivotal role in timing motor actions.
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•Cerebellar activation recruited cortical neurons across large areas and all layers•Cortical response to cerebellar activation was dominated by late inhibition•At movement onset, responsive cortical neurons were transiently synchronized•Cerebellar shaping of motor cortical activity may time initiation of movements
Nashef et al. identified a motor cortical subnetwork recruited by cerebellar volley that was transiently synchronized at movement onset. Cerebellar control of cortical firing was dominated by inhibition that shaped task-related firing of neurons and may dictate motor timing.
Abstract Spine surgery relies heavily on imaging, with X-ray-based devices being the major operating room imaging modality. Radiation exposure is an occupational risk historically recognized shortly ...after the discovery of radiation itself. Exposure of both patients and operating room staff is of rising concern as the knowledge regarding the hazards of radiation is steadily accumulating. In this review, we present the history of radiation exposure limits and updates on current studies demonstrating the risks of low dose exposures. We discuss the methods to reduce operating room staff exposure to the minimal amount and by thus reducing occupational risks. We also recognize that increasing awareness to radiation exposure hazards and promoting the knowledge of methods to reduce exposure of surgeons, nurses, and technicians could result in a reduction of exposure to radiation.
Minimization of the surgical approaches to spinal extradural metastases resection and stabilization was advocated by the 2012 Oncological Guidelines for Spinal Metastases Management. Minimally ...invasive approaches to spine oncology surgery (MISS) are continually advancing. This paper will describe the evolution of minimally invasive surgical techniques for the resection of metastatic spinal lesions and stabilization in a single institute. A retrospective analysis of patients who underwent minimally invasive extradural spinal metastases resection during the years 2013-2019 by a single surgeon was performed. Medical records, imaging studies, operative reports, rates of screw misplacement, operative time and estimated blood loss were reviewed. Detailed description of the surgical technique is provided. Of 138 patients operated for extradural spinal tumors during the study years, 19 patients were treated in a minimally invasive approach and met the inclusion criteria for this study. The mortality rate was significantly improved over the years with accordance of improve selection criteria to better prognosis patients. The surgical technique has evolved over the study years from fluoroscopy to intraoperative 3D imaging and navigation guidance and from k-wire screw insertion technique to one-step screws. Minimally invasive spinal tumor surgery is an evolving technique. The adoption of assistive devices such as intraoperative 3D imaging and one-step screw insertion systems was safe and efficient. Oncologic patients may particularly benefit from the minimization of surgical decompression and fusion in light of the frailty of this population and the mitigated postoperative outcomes associated with MIS oncological procedures.
Study Design:
Retrospective cohort study.
Objectives:
The learning curve associated with the implementation of minimally invasive spinal surgery (MIS) has been the center of attention in numerous ...publications. So far, these studies referred to a single MIS procedure. In our view, minimally invasive surgical skills are acquired simultaneously through a variety of procedures that share common features. The aim of this study was to analyze the skills progression of a single surgeon implementing diverse minimally invasive techniques.
Methods:
We retrospectively collected all patients who underwent spinal surgery for thoracic or lumbar pathology by a single surgeon between 2012 and 2015 at a single institute. Both minimally invasive as well as open surgical techniques were analyzed; these groups were compared on the basis of surgical indications and outcomes. Skills progression analysis in reference to minimally invasive technique was performed.
Results:
A total of 230 patients met the inclusion criteria for this study. MIS group included higher percentage of lumbar discectomy and the open-surgery group included higher percentage of tumor resection surgery. Learning curve evaluation demonstrated increased surgical complexity, evaluated by number of levels treated, over the 4-year period, which corresponded with decreased complication rates.
Discussion:
A gradual increase in surgical complexity over 4 years, together with careful patient selection, enables the surgeon to maintain the rate of complication within acceptable limits. The main challenge facing the MIS community is constructing an education program for MIS surgeons in order to reduce the learning curve–induced complications.
Conclusion:
Advancement of educational aids for MIS surgical skill improvement, including spine models, virtual and augmented reality aids and surgical simulators may reduce the learning curve of spine surgeons.
Cerebellar control of voluntary movements is achieved by the integration of external and internal feedback information to adjust and correct properly ongoing actions. In the forelimb of primates, ...rostral-spinocerebellar tract (RSCT) neurons are thought to integrate segmental, descending, and afferent sources and relay upstream a compound signal that contains both an efference copy of the spinal-level motor command and the state of the periphery. We tested this hypothesis by implanting stimulating electrodes in the superior cerebellar peduncle and recording the activity of cervical spinal neurons in primates. To dissociate motor commands and proprioceptive signals, we used a voluntary wrist task and applied external perturbations to the movement. We identified a large group of antidromically activated RSCT neurons located in deep dorsal sites and a smaller fraction of postsynaptically activated (PSA) cells located in intermediate and ventral laminae. RSCT cells received sensory input from broad, proximally biased receptive fields (RFs) and were not affected by applied wrist perturbations. PSA cells received sensory information from distal RFs and were more strongly related to active and passive movements. The anatomical and functional properties of RSCT and PSA cells suggest that descending signals converging on PSA cells contribute to both motor preparation and motor control. In parallel, RSCT neurons relay upstream an integrated signal that encodes the state of working muscles and can contribute to distal-to-proximal coordination of action. Thus the rostral spinocerebellar system sends upstream an efference copy of the motor command but does not signal abrupt errors in the performed movement.
Cerebellar coordination of voluntary movements relies on integrating feedback information to update motor output. With the use of a novel protocol, we identified spinal neurons constituting the ascending and descending components of the forelimb spinocerebellar system in behaving primates. The data suggest that descending information contributes to both motor preparation and execution, whereas ascending information conveys the spinal level motor command, such that internal and external feedback is relayed through parallel pathways.
Abstract Spinal metastases are the most frequently encountered spinal tumour and can affect up to 50% of cancer patients. Both the incidence and prevalence of metastases are thought to be rising due ...to better detection and treatment options of the systemic malignancy resulting in increased patient survival. Further, the development and access to newer imaging modalities have resulted in easier screening and diagnosis of spine metastases. Current evidence suggests that pain, neurological symptoms and quality of life are all improved if patients with spine metastases are treated early and aggressively. However, selection of the appropriate therapy depends on several factors including primary histology, extent of the systemic disease, existing co-morbidities, prior treatment modalities, patient age and performance status, predicted life expectancy and available resources. This article reviews the currently available therapeutic options for spinal metastases including conventional external beam radiation therapy, open surgical decompression and stabilisation, vertebral augmentation and other minimally invasive surgery (MIS) options, stereotactic spine radiosurgery, bisphosphonates, systemic radioisotopes and chemotherapy. An algorithm for the management of spine metastases is also proposed. It outlines a multidisciplinary and integrated approach to these patients and it is hoped that this along with future advances and research will result in improved patient care and outcomes.
Anterior cervical corpectomy and fusion (ACCF) is an effective technique to address multi-level degenerative cervical myelopathy. However, as the number of surgical levels increases, the outcomes ...worsen with respect to complication rates, range of motion and length of surgery. This study aimed to determine the clinical outcome of ACCF procedures performed using a new distally curved and shielded drilling device.
A retrospective study was conducted on 43 ACCF procedures in which the device was used for osteophyte removal. Patient files were reviewed to assess the early clinical results and complications following ACCF. Clinical outcomes were evaluated using patient neck and arm pain scores and SF-36 questionnaires. Hospitalization characteristics were compared with historical controls.
All procedures were uneventful and without major complications or neurological deterioration. Single-level ACCF procedures required an average of 71 min and followed by an average hospitalization of 3.3 days. Osteophyte removal, verified by intraoperative imaging, was satisfactory. Average neck pain score was improved by 0.9 points (p = 0.24). Average arm pain score was improved by 1.8 points (p = 0.06). SF-36 scores were improved in all domains.
The new curved device enabled safe and efficient removal of osteophytes sparing adjacent vertebral removal in ACCF procedures, thus improving the clinical outcome.
Abstract
Objective
Nontraumatic acute cervical disk herniation resulting in acute severe neurologic deficit is a rare entity described in a limited number of case reports. We describe the management ...and outcome in patients presenting with severe neurologic deterioration caused by acutely herniated cervical disks.
Methods
Four patients (mean age 39.5 years) presented to our tertiary care academic medical center from September 2012 to September 2013 with severe progressive neurologic deficits due to cervical disk herniation and were included in the series. Patients' surgical, medical, and imaging records were retrospectively reviewed under an Institutional Review Board waiver of informed consent.
Results
Patients in the series presented with acute neurologic deterioration, including paraparesis, Brown-Séquard syndrome, or quadriparesis deteriorating to quadriplegia. Emergent magnetic resonance imaging (MRI) scans and emergent decompression and fusion for acute soft disk herniation were performed in all cases. All patients recovered to excellent functional status with Frankel score improvement from B (one patient)/C (three patients) to E (three patients)/D (one patient).
Conclusions
Acute cervical disk herniation with acute neurologic deterioration is a medical emergency necessitating emergent MRI and surgical decompression. Clinical presentation varies. In patients with rapid-onset neurologic deterioration, a high level of suspicion for this rare entity is indicated.
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