Benefits and Risks of Prophylactic Cerebrospinal Fluid Catheter and Evoked Potential Monitoring in Symptomatic Spinal Cord Ischemia Low-Risk Thoracic Endovascular Aortic Repair.

BACKGROUND: To assess risks and benefits of a standardized strategy to prevent symptomatic spinal cord ischemia (SSCI) after thoracic endovascular repair (TEVAR) using routine cerebrospinal fluid (CSF) catheter placement and evoked potential (EP) monitoring. METHODS: One hundred and ninety-five patients underwent 223 SSCI low-risk TEVAR procedures between 1998 and 2014. CSF catheter was used to measure CSF pressure and drain CSF if necessary throughout the procedure and up to 24 hours thereafter. EPs were used to monitor spinal cord integrity throughout the procedure. RESULTS: Underlying pathologies included descending thoracic aortic aneurysm in 115 (52%), type B aortic dissection in 85 (38%), traumatic aortic rupture in 16 (7%), and others in 7 (3%) patients. CSF catheter was inserted before TEVAR in 116 procedures (52%). Active CSF draining was required in 29 patients (25%). The CSF catheter caused no major and 11 (10%) minor complications. EP were monitored during 88 (40%) procedures. We observed a reduction in the amplitude, prolonged latencies, or complete signal loss in nine procedures. There were no EP monitoring-related complications. SSCI incidence was higher in patients without CSF drainage (0.8% vs 4.7%, p = 0.031). CONCLUSION: Use of CSF drainage is associated with a significant lower incidence of SSCI after SSCI low-risk TEVAR than nonuse, whereas the complication rate associated with CSF drainage insertion or removal is very low. Routine EP monitoring is a useful tool to detect immediate arterial inflow obstruction to the spinal cord. The combination of these two methods serves as a safe and reliable standardized strategy in reducing the incidence of SSCI to a minimum.

Personalized chronic adaptive deep brain stimulation outperforms conventional stimulation in Parkinson's disease.

Deep brain stimulation is a widely used therapy for Parkinson's disease (PD) but currently lacks dynamic responsiveness to changing clinical and neural states. Feedback control has the potential to improve therapeutic effectiveness, but optimal control strategy and additional benefits of "adaptive" neurostimulation are unclear. We implemented adaptive subthalamic nucleus stimulation, controlled by subthalamic or cortical signals, in three PD patients (five hemispheres) during normal daily life. We identified neurophysiological biomarkers of residual motor fluctuations using data-driven analyses of field potentials over a wide frequency range and varying stimulation amplitudes. Narrowband gamma oscillations (65-70 Hz) at either site emerged as the best control signal for sensing during stimulation. A blinded, randomized trial demonstrated improved motor symptoms and quality of life compared to clinically optimized standard stimulation. Our approach highlights the promise of personalized adaptive neurostimulation based on data-driven selection of control signals and may be applied to other neurological disorders.

Sub-harmonic entrainment of cortical gamma oscillations to deep brain stimulation in Parkinson's disease: Model based predictions and validation in three human subjects.

OBJECTIVES: The exact mechanisms of deep brain stimulation (DBS) are still an active area of investigation, in spite of its clinical successes. This is due in part to the lack of understanding of the effects of stimulation on neuronal rhythms. Entrainment of brain oscillations has been hypothesised as a potential mechanism of neuromodulation. A better understanding of entrainment might further inform existing methods of continuous DBS, and help refine algorithms for adaptive methods. The purpose of this study is to develop and test a theoretical framework to predict entrainment of cortical rhythms to DBS across a wide range of stimulation parameters. MATERIALS AND METHODS: We fit a model of interacting neural populations to selected features characterising PD patients' off-stimulation finely-tuned gamma rhythm recorded through electrocorticography. Using the fitted models, we predict basal ganglia DBS parameters that would result in 1:2 entrainment, a special case of sub-harmonic entrainment observed in patients and predicted by theory. RESULTS: We show that the neural circuit models fitted to patient data exhibit 1:2 entrainment when stimulation is provided across a range of stimulation parameters. Furthermore, we verify key features of the region of 1:2 entrainment in the stimulation frequency/amplitude space with follow-up recordings from the same patients, such as the loss of 1:2 entrainment above certain stimulation amplitudes. CONCLUSION: Our results reveal that continuous, constant frequency DBS in patients may lead to nonlinear patterns of neuronal entrainment across stimulation parameters, and that these responses can be predicted by modelling. Should entrainment prove to be an important mechanism of therapeutic stimulation, our modelling framework may reduce the parameter space that clinicians must consider when programming devices for optimal benefit.