Konstantin V. Slavin

Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: long-term results from a randomized, multicenter, double-blinded, controlled study.

Background Recent studies evaluated short-term efficacy and safety of peripheral nerve stimulation (PNS) of the occipital nerves for managing chronic migraine. We present 52-week safety and efficacy results from an open-label extension of a randomized, sham-controlled trial. Methods In this institutional review board-approved, randomized, multicenter, double-blinded study, patients were implanted with a neurostimulation system, randomized to an active or control group for 12 weeks, and received open-label treatment for an additional 40 weeks. Outcomes collected included number of headache days, pain intensity, migraine disability assessment (MIDAS), Zung Pain and Distress (PAD), direct patient reports of headache pain relief, quality of life, satisfaction and adverse events. Statistical tests assessed change from baseline to 52 weeks using paired t-tests. Intent-to-treat (ITT) analyses of all patients (Nu2009=u2009157) and analyses of only patients who met criteria for intractable chronic migraine (ICM; Nu2009=u2009125) were performed. Results Headache days were significantly reduced by 6.7 (±8.4) days in the ITT population (pu2009<u20090.001) and by 7.7 (±8.7) days in the ICM population (pu2009<u20090.001). The percentages of patients who achieved a 30% and 50% reduction in headache days and/or pain intensity were 59.5% and 47.8%, respectively. MIDAS and Zung PAD scores were significantly reduced for both populations. Excellent or good headache relief was reported by 65.4% of the ITT population and 67.9% of the ICM population. More than half the patients in both cohorts were satisfied with the headache relief provided by the device. A total of 183 device/procedure-related adverse events occurred during the study, of which 18 (8.6%) required hospitalization and 85 (40.7%) required surgical intervention; 70% of patients experienced an adverse event. Conclusion Our results support the 12-month efficacy of PNS of the occipital nerves for headache pain and disability associated with chronic migraine. More emphasis on adverse event mitigation is needed in future research. Trial registration: Clinical trials.gov (NCT00615342).

Effects of stellate-ganglion block on hot flushes and night awakenings in survivors of breast cancer: a pilot study

BACKGROUNDnDebilitating hot flushes and sleep dysfunction often affect survivors of breast cancer, most notably in those taking anti-oestrogen medications. Conventional treatments have been only partially effective in diminishing these issues, and some have serious risks. We did a pilot study to investigate our hypothesis that stellate-ganglion block can be a safe and effective treatment for hot flushes and sleep dysfunction in this patient population.nnnMETHODSn13 survivors of breast cancer (in remission) with severe hot flushes and night awakenings were treated with stellate-ganglion block at the anterolateral aspect of the C6 vertebra on the right side under fluoroscopy. Patients recorded hot flushes in a daily diary by use of the Hot-Flash Score, devised by Sloan and colleagues, and night awakenings by use of the Pittsburgh Sleep Quality Index. Both instruments were used 1 week before the procedure [A40] and then weekly after the procedure for 12 weeks. We used the generalised-estimating-equations method to analyse the longitudinal measurements of the number of hot flushes and night awakenings over time. This method is a popular approach to analysing datasets that have repeated measures from the same person, and is robust because it does not need the complete distribution of the outcomes to be specified. This trial is registered on the International Standard Randomised Controlled Trial Number register (ISRCTN14318565).nnnFINDINGSnThere were no adverse events resulting from the stellate-ganglion block, although patients had temporary Horners syndrome indicating the effectiveness of the block. Five patients had only one stellate-ganglion block and eight had two stellate-ganglion blocks. The total number of hot flushes decreased from a mean of 79.4 (SD 37.4) per week before the procedure to a mean of 49.9 (SD 39.9) per week during the first 2 weeks after the procedure (p=0.0002). The total number of hot flushes continued to decrease over the remaining follow-up period (weeks 3-12), and stabilised at a mean of 8.1 (SD 5.6) per week (p<0.0001). The number of very severe hot flushes was decreased to near zero by the end of the follow-up period (week 12; p<0.0001). Night awakenings decreased from a mean of 19.5 (SD 14.8) per week before the procedure to a mean of 7.3 (SD 7.1) per week during the first 2 weeks after the procedure (p<0.0001). The total number of night awakenings continued to decrease over the remaining follow-up period (weeks 3-12) and stabilised at a mean of 1.4 (SD 1.2) per week (p<0.0001).nnnINTERPRETATIONnThe findings of this study suggest that stellate-ganglion block can provide survivors of breast cancer with relief from hot flushes and sleep dysfunction with few or no side-effects. Long-term relief of symptoms has the potential to improve overall quality of life and increase compliance with anti-oestrogen medications for breast cancer.

Current algorithm for the surgical treatment of facial pain

BackgroundFacial pain may be divided into several distinct categories, each requiring a specific treatment approach. In some cases, however, such categorization is difficult and treatment is ineffective. We reviewed our extensive clinical experience and designed an algorithmic approach to the treatment of medically intractable facial pain that can be treated through surgical intervention.MethodsOur treatment algorithm is based on taking into account underlying pathological processes, the anatomical distribution of pain, pain characteristics, the patients age and medical condition, associated medical problems, the history of previous surgical interventions, and, in some cases, the results of psychological evaluation. The treatment modalities involved in this algorithm include diagnostic blocks, peripheral denervation procedures, craniotomy for microvascular decompression of cranial nerves, percutaneous rhizotomies using radiofrequency ablation, glycerol injection, balloon compression, peripheral nerve stimulation procedures, stereotactic radiosurgery, percutaneous trigeminal tractotomy, and motor cortex stimulation. We recommend that some patients not receive surgery at all, but rather be referred for other medical or psychological treatment.ResultsOur algorithmic approach was used in more than 100 consecutive patients with medically intractable facial pain. Clinical evaluations and diagnostic workups were followed in each case by the systematic choice of the appropriate intervention. The algorithm has proved easy to follow, and the recommendations include the identification of the optimal surgery for each patient with other options reserved for failures or recurrences. Our overall success rate in eliminating facial pain presently reaches 96%, which is higher than that observed in most clinical series reported to dateConclusionThis treatment algorithm for the intractable facial pain appears to be effective for patients with a wide variety of painful conditions and may be recommended for use in other institutions.

Spinal Cord Stimulation for the Treatment of Vascular Pathology

Multiple studies have shown proved efficacy of spinal cord stimulation (SCS) in peripheral vascular disease (PVD). The exact mechanism by which SCS acts in the treatment of PVD is not completely understood, and may include stimulating the release of nitric oxide, modulation of the sympathetic nervous system, or modulation of prostaglandin production. Patient selection criteria have been well defined and SCS should be reserved for patients with end-stage lower limb PVD unresponsive to medical therapy and not amenable to surgical reconstruction but in whom disease has not caused inevitable limb loss. This article reviews the outcomes, techniques, patient selection criteria, and putative mechanisms of SCS for PVD.

A model for simulating Local Field Potential in the thalamus of Essential Tremor patient during deep brain stimulation

Local Field Potential (LFP) is simulated by adding the neuronal membrane potential of a group of model neurons surrounding a typical intra-operative micro-electrode used to localize the target for deep brain stimulation (DBS) in Essential Tremor (ET). Each neuronal membrane potential is modeled as an Ornstein Uhlenbeck Process (OUP) and the model parameters are extracted from real neuronal recording during DBS surgery following the method in [1]. n n nBefore any test stimulation through the macro ring of the microelectrode, the LFP is simulated according to: n n n n n(1) n n n nWhere, x is the membrane potential of each neuron and r is the distance from the recording tip. The simulated signal, lfp is then low pass filtered (1-40 Hz) to produce the final signal. n n nWith stimulation on, the LFP is simulated similarly but only over time intervals in between two stimulation pulse which is free of the stimulation voltage artifact caused by amplifier saturation. The stimulation artifact time duration is estimated as: n n n n n(2) n n n nWhere, l(r) is the stimulation intensity at distance r from the recording tip and follows a similar inverse square decay as in (1), τ is the membrane time constant (an OUP model parameter) and S is the neuronal firing threshold. Thus the LFP simulated during stimulation depends on the stimulation intensity, pulse width and frequency. n nThe stimulation parameters used are: frequency: 160 Hz (125 samples/period), pulse width: 0.4 ms, intensity:1.5 mA n nIt was found that the power in the (5-12) Hz band decreases by 26.4% during stimulation. There is increased synchronization in neuronal activity of the thalamus in the theta band (4-7 Hz) for patients with ET [2]. The suppression of tremor by DBS is reflected in the reduction of power in the tremor frequency band. n nSuch a model , can potentially be used to find an optimal set of stimulation parameters that will produce the maximum suppression in the tremor power. n n n nFigure 1 n nSpectrum of LFP before stimulation (in red) and during stimulation (in blue).

Relating thalamic neuronal activity and EMG for validating predictive control of deep-brain stimulation in Essential Tremor patients

Neuronal activity at the VIM nucleus of the thalamus was recorded in Essential Tremor (ET) patients during implantation of deep-brain stimulation (DBS) electrodes and compared with surface-EMG (sEMG) taken both during implantation and at later outpatient sessions at University of Illinois Hospital, Chicago. The goal of these studies was to investigate if it is possible to use sEMG signals for predicting onset of tremor and consequently whether predictive EMG-control of DBS in ET patients does or does not contradict predictive features of neuronal activity in the brain. For this purpose, we examined spike-rate and local field potentials (LFP) at and in the vicinity of VIM. Specifically, we compared spike-rate, LFP and sEMG recorded before versus after applying short DBS pulse-trains during implantation surgery, as well as sEMG recorded from limbs or neck of the patients. Out of 4 ET patients involved in the tests, we have implant-session data for 3 patients. Three patients had follow-up EMG testing.