“Triceps Brachii Muscle Response to Neurostimulation of the Radial Nerve during Axillary Plexus Blockade: Clinical,Anatomical and Histological Correlation”

Axillary plexus blockade is a common technique in clinical practice with a well-known pattern of structures around the brachial artery. Historically, the only proper response to radial nerve stimulation was considered to be extension of the hand and wrist. Twenty-five axillary blockades were assessed by ultrasound and neurostimulation; the principal objective was to correlate the needle position over the radial nerve with the anatomical and histological structure of that nerve. During the procedure, the needle was directed in two ways to reach the medial or lateral margin of the nerve: above the brachial artery or beneath it. Once the needle reached the nerve, the current was augmented gradually until a response was elicited. For the cadaveric anatomical study, eight axillae were dissected and histological samples were examined. The response of the triceps brachii muscle differed significantly between the two approaches to the radial nerve (P < 0.001), and the mean intensity of stimulation was significantly lower when the nerve was accessed above the artery (0.44 ± 0.15 mA) than below it (0.57 ± 0.17 mA) (P = 0.015). A triceps brachii motor response occurs at lower current intensity and lower needle-nerve distance when the radial nerve is accessed above the artery and over the latissimus dorsi tendon. These findings were correlated with the topography of the radial nerve in the axillary fossa. Clin. Anat. 33:578–584, 2020. © 2019 Wiley Periodicals, Inc.     

Functionally navigated transcranial magnetic stimulation to evoke lingual pressure in stroke survivors with dysphagia and healthy adults: a proof of concept trial

ABSTRACT

Background

Post-stroke dysphagia is characterized by reduced corticolingual excitability and lingual pressure; however, it remains unknown if transcranial magnetic stimulation (TMS) directly facilitates lingual pressure generation.     

Paresthesia‐Free Spinal Nerve Root Stimulation for the Treatment of Chronic Neuropathic Pain

ObjectiveStimulation of the dorsal spinal roots, or spinal nerve root stimulation (SNRS), is a neuromodulation modality that can target pain within specific dermatomal distributions. The use of paresthesia-free stimulation has been described with conventional dorsal column spinal cord stimulation, although has yet to be described for SNRS. This objective of this study was to investigate the efficacy of paresthesia-free high-frequency (1000–1200 Hz) SNRS in the treatment of intractable, dermatomal neuropathic pain.Materials and MethodsA retrospective chart review was performed on 14 patients implanted with SNRS in varying distributions: Ten patients initially received tonic stimulation and crossed over to a paresthesia-free paradigm and four patients received only paresthesia-free stimulation. The primary outcome was reduction in pain severity (visual analog scale [VAS]), measured at baseline and follow-up to 24 months with paresthesia-free stimulation.ResultsAll 14 patients who received paresthesia-free stimulation had significant improvement in pain severity at a mean follow-up of 1.39 ± 0.15 years (VAS 7.46 at baseline vs. 3.25 at most recent follow-up, p < 0.001). Ten patients were initially treated with tonic stimulation and crossed over to paresthesia-free stimulation after a mean of 61.7 months. Baseline pain in these crossover patients was significantly improved at last follow-up with tonic stimulation (VAS 7.65 at baseline vs. 2.83 at 48 months, p < 0.001), although all patients developed uncomfortable paresthesias. There was no significant difference in pain severity between patients receiving tonic and paresthesia-free stimulation.ConclusionsWe present real-world outcomes of patients with intractable dermatomal neuropathic pain treated with paresthesia-free, high-frequency SNRS. We demonstrate its effectiveness in providing pain reduction at a level comparable to tonic SNRS up to 24 months follow-up, without producing uncomfortable paresthesias.     

Frequency of Automatic Stimulations in Responsive Vagal Nerve Stimulation in Patients With Refractory Epilepsy

BackgroundIn vagal nerve stimulation (VNS) therapy, the release of VNS model 106 (AspireSR) allowed for responsive VNS (rVNS). rVNS utilizes a cardiac-based seizure detection algorithm to detect seizure-induced tachycardia to trigger additional stimulation. There are some studies suggesting clinical benefits of rVNS over traditional VNS, but the performance and significance of autostimulation mode in clinical practice are poorly understood.ObjectivesTo assess the effect of initiation of rVNS therapy and altered stimulation settings on the number of daily stimulations and energy consumption in VNS therapy and to compare autostimulation performance in different epilepsy types.Materials and MethodsRetrospective follow-up of 30 patients with drug-resistant epilepsy treated with rVNS including 17 new implantations and 13 battery replaces at a single center in Finland. Our data consist of 208 different stimulation periods, that is, episodes with defined stimulation settings and both autostimulation and total stimulation performance-related data along with clinical follow-up.ResultsThe variation in autostimulation frequency was highly dependent on the duration of the OFF-time and autostimulation threshold (p < 0.05). There was a large additional effect of autostimulation mode on therapy time and energy consumption with longer OFF-times, but a minor effect with shorter OFF-times. Significantly more autostimulations were triggered in the temporal lobe and multifocal epilepsies than in extratemporal lobe epilepsies.ConclusionsThe initiation of autostimulation mode in VNS therapy increased the total number of stimulations. Shortening the OFF-time leads to a decreased number and share of automatic activations. Epilepsy type may affect autostimulation activity.     

Meta-analysis of the effects of transcranial direct current stimulation on inhibitory control

BackgroundInhibitory control refers to a central cognitive capacity involved in the interruption and correction of actions. Dysfunctions in these cognitive control processes have been identified as major maintaining mechanisms in a range of mental disorders such as ADHD, binge eating disorder, obesity, and addiction. Improving inhibitory control by transcranial direct current stimulation (tDCS) could ameliorate symptoms in a broad range of mental disorders.ObjectiveThe primary aim of this pre-registered meta-analysis was to investigate whether inhibitory control can be improved by tDCS in healthy and clinical samples. Additionally, several moderator variables were investigated.MethodsA comprehensive literature search was performed on PubMed/MEDLINE database, Web of Science, and Scopus. To achieve a homogenous sample, only studies that assessed inhibitory control in the go-/no-go (GNG) or stop-signal task (SST) were included, yielding a total of 75 effect sizes from 45 studies.ResultsResults of the meta-analysis indicate a small but significant overall effect of tDCS on inhibitory control (g = 0.21) which was moderated by target and return electrode placement as well as by the task. The small effect size was further reduced after correction for publication bias.ConclusionBased on the studies included, our meta-analytic approach substantiates previously observed differences between brain regions, i.e., involvement of the right inferior frontal gyrus (rIFG) vs. the right dorsolateral prefrontal cortex (rDLPFC) in inhibitory control. Results indicate a small moderating effect of tDCS on inhibitory control in single-session studies and highlight the relevance of technical and behavioral parameters.