Large-Scale Network Analysis of Whole-Brain Resting-State Functional Connectivity in Spinal Cord Injury: A Comparative Study.

Network analysis based on graph theory depicts the brain as a complex network that allows inspection of overall brain connectivity pattern and calculation of quantifiable network metrics. To date, large-scale network analysis has not been applied to resting-state functional networks in complete spinal cord injury (SCI) patients. To characterize modular reorganization of whole brain into constituent nodes and compare network metrics between SCI and control subjects, fifteen subjects with chronic complete cervical SCI and 15 neurologically intact controls were scanned. The data were preprocessed followed by parcellation of the brain into 116 regions of interest (ROI). Correlation analysis was performed between every ROI pair to construct connectivity matrices and ROIs were categorized into distinct modules. Subsequently, local efficiency (LE) and global efficiency (GE) network metrics were calculated at incremental cost thresholds. The application of a modularity algorithm organized the whole-brain resting-state functional network of the SCI and the control subjects into nine and seven modules, respectively. The individual modules differed across groups in terms of the number and the composition of constituent nodes. LE demonstrated statistically significant decrease at multiple cost levels in SCI subjects. GE did not differ significantly between the two groups. The demonstration of modular architecture in both groups highlights the applicability of large-scale network analysis in studying complex brain networks. Comparing modules across groups revealed differences in number and membership of constituent nodes, indicating modular reorganization due to neural plasticity.

Evaluation of Whole-Brain Resting-State Functional Connectivity in Spinal Cord Injury: A Large-Scale Network Analysis Using Network-Based Statistic.

Large-scale network analysis characterizes the brain as a complex network of nodes and edges to evaluate functional connectivity patterns. The utility of graph-based techniques has been demonstrated in an increasing number of resting-state functional MRI (rs-fMRI) studies in the normal and diseased brain. However, to our knowledge, graph theory has not been used to study the reorganization pattern of resting-state brain networks in patients with traumatic complete spinal cord injury (SCI). In the present analysis, we applied a graph-theoretical approach to explore changes to global brain network architecture as a result of SCI. Fifteen subjects with chronic (> 2 years) complete (American Spinal Injury Association [ASIA] A) cervical SCI and 15 neurologically intact controls were scanned using rs-fMRI. The data were preprocessed followed by parcellation of the brain into 116 regions of interest (ROI) or nodes. The average time series was extracted at each node, and correlation analysis was performed between every pair of nodes. A functional connectivity matrix for each subject was then generated. Subsequently, the matrices were averaged across groups, and network changes were evaluated between groups using the network-based statistic (NBS) method. Our results showed decreased connectivity in a subnetwork of the whole brain in SCI compared with control subjects. Upon further examination, increased connectivity was observed in a subnetwork of the sensorimotor cortex and cerebellum network in SCI. In conclusion, our findings emphasize the applicability of NBS to study functional connectivity architecture in diseased brain states. Further, we show reorganization of large-scale resting-state brain networks in traumatic SCI, with potential prognostic and therapeutic implications.

Hemorrhagic Complications Associated with Ventriculostomy in Patients Undergoing Endovascular Treatment for Intracranial Aneurysms: A Single-Center Experience.

BACKGROUND: Currently, a complete understanding of post-ventriculostomy hemorrhagic complications in subarachnoid hemorrhage due to ruptured aneurysms remains unknown. The present study evaluates the impact of periprocedural risk factors on rates of external ventricular drain (EVD)-associated hemorrhage in the setting of endovascular treatment of intracranial aneurysms. METHODS: A retrospective chart review of 107 patients who underwent EVD placement within 24 h of endovascular coiling was performed. CT of head without contrast was obtained after drain placement and before endovascular treatment. Post-procedural CT was also obtained within 48 h of embolization and was reviewed for new/worsened track hemorrhages. Chi-squared test was used in evaluation. RESULTS: Ninety-three of the 107 patients reviewed met the inclusion criteria. Four (25%) of the 16 patients on antiplatelet medications at presentation experienced post-EVD hemorrhage compared to 11 (14.3%) of 77 that were not (p = 0.29). Of the 13 patients given intraprocedural antiplatelets, 3 (23.1%) demonstrated hemorrhage compared to 12 (15%) of 80 not administered these medications (p = 0.46). Further, of 36 patients with intraprocedural anticoagulation, 6 (16.7%) exhibited hemorrhage compared to 9 (15.8%) of 57 in those without (p = 0.91). In 17 patients who received DVT prophylaxis, 2 (11.8%) exhibited hemorrhage compared to 13 (17.1%) of 76 who did not (p = 0.59). No post-EVD hemorrhage had attributable neurologic morbidity. CONCLUSION: Our results, demonstrating no significant risk factor related to EVD-associated hemorrhage rates, support the safety of EVD placement in the peri-endovascular treatment period.

Alterations in Cortical Sensorimotor Connectivity following Complete Cervical Spinal Cord Injury: A Prospective Resting-State fMRI Study.

Functional magnetic resonance imaging (fMRI) studies have demonstrated alterations during task-induced brain activation in spinal cord injury (SCI) patients. The interruption to structural integrity of the spinal cord and the resultant disrupted flow of bidirectional communication between the brain and the spinal cord might contribute to the observed dynamic reorganization (neural plasticity). However, the effect of SCI on brain resting-state connectivity patterns remains unclear. We undertook a prospective resting-state fMRI (rs-fMRI) study to explore changes to cortical activation patterns following SCI. With institutional review board approval, rs-fMRI data was obtained in eleven patients with complete cervical SCI (>2 years post injury) and nine age-matched controls. The data was processed using the Analysis of Functional Neuroimages software. Region of interest (ROI) based analysis was performed to study changes in the sensorimotor network using pre- and post-central gyri as seed regions. Two-sampled t-test was carried out to check for significant differences between the two groups. SCI patients showed decreased functional connectivity in motor and sensory cortical regions when compared to controls. The decrease was noted in ipsilateral, contralateral, and interhemispheric regions for left and right precentral ROIs. Additionally, the left postcentral ROI demonstrated increased connectivity with the thalamus bilaterally in SCI patients. Our results suggest that cortical activation patterns in the sensorimotor network undergo dynamic reorganization following SCI. The presence of these changes in chronic spinal cord injury patients is suggestive of the inherent neural plasticity within the central nervous system.

Syringosubarachnoid shunting using a myringotomy tube.

BACKGROUND: Syringomyelia results from obstruction of cerebrospinal fluid (CSF) flow due to a multitude of causes. Often symptoms of pain, weakness, and sensory disturbance are progressive and require surgical treatment. We present here a rare technique for syringosubarachnoid shunting. CASE DESCRIPTION: We present the case of a 38-year-old male who suffered a traumatic cervical spinal cord injury due to a motor vehicle accident. With progressive pain and motor decline, a magnetic resonance imaging was obtained and showed a new syrinx extending cervical multiple segments. A unique surgical procedure using a myringotomy tube to shunt CSF into the subarachnoid space was employed in this case. The patient's examination stabilized postoperatively, and at 2 months and 6 months follow-up visits, his strength and sensation continued to improve. CONCLUSION: We used a myringotomy tube for syringosubarachnoid shunting for the surgical management of a posttraumatic syrinx with good results. This technique minimizes suturing and may minimize shunt-related complications.