Lumbar trans-spinal direct current stimulation: A modeling-experimental approach to dorsal root ganglia stimulation.

Introduction: The excitability of spinal motor neurons (MN) can be altered through subthreshold currents, such as transcutaneous spinal direct-current stimulation (tsDCS). Current evidence shows that tsDCS can interfere with ascending somatosensory pathways and lower motor neurons' (LMN) excitability, which points to its therapeutic potential for repairing altered spinal responses. We aim to define the best tsDCS montage for maximizing the electric field (E-field) in the lumbar spinal cord (L-SC) by computer modeling; and to apply this montage to measure the effect on LMN excitability and somatosensory evoked potentials (SSEP). Methods: A human volume conductor model was obtained from an available database. The E-field distribution was calculated considering three different electrode settings aiming at maximizing the field at L-SC and right dorsal root ganglia (DRG). The best electrode setting was then selected and applied in a blind crossover pseudo-randomized study including 14 subjects. tsDCS was delivered for 15 min (cathodal vs. sham) over L2 vertebra level (4 mA, 144 mC/cm2), and its effect on F-waves, H-reflex (including homosynaptic depression, HD) and SSEPs was investigated in the lower limbs. Results: All simulated montages showed higher current density and E-field magnitudes between the electrodes (>0.15 V/m), with a major longitudinal component and with rostral-caudal direction. The induced E-field involved the sensory ganglia and was maximum in the right T8-left L2 montage, which was the one selected for the experimental protocol. We disclosed a statistically significant increase of the H-reflex amplitude at 0.1 Hz, after cathodal tsDCS (c-tsDCS) on both sides. No other significant change was observed. Discussion: Our results can suggest the c-tsDCS applied to the L-SC and DRG can modulate synaptic efficiency increasing lower motor neurons response to Ia fibers excitation. The possible implications of our findings for treating clinical conditions will be addressed in future studies.

The ataxic neuropathies.

Ataxia is a frequent symptom in neurological cases with many causes. Sensory ataxia (due to involvement of the proprioceptive pathways) is observed in conditions affecting the central nervous system (spinal cord disorder) and the peripheral nervous system (peripheral neuropathy). The latter correspond to what we refer to as 'ataxic neuropathies'. Ataxic neuropathies represent a wide and heterogeneous spectrum of disorders that may affect dorsal root nerves, dorsal root ganglia, nerve trunks, distal nerve endings or all of them together. The identification of a predominant sensory ataxia in a case of peripheral neuropathy should raise the possibility of some specific etiologies. We propose here to present the main causes of ataxic neuropathies, which are identified with diagnostic workflows that are dictated by the topography of the likely sites of lesions in the proprioceptive pathway together with the timing of their occurrence (acute, subacute, or chronic).

Assessment of anoxia tolerance and photoperiod dependence of GABAergic polarity in the pond snail Lymnaea stagnalis.

The pond snail Lymnaea stagnalis is reported to be anoxia-tolerant and if the tolerance mechanism is similar to that of the anoxia-tolerant painted turtle, GABA should play an important role. A potentially confounding factor investigating the role of GABA in anoxia tolerance are reports that GABA has both inhibitory and excitatory effects within L. stagnalis central ganglion. We therefore set out to determine if seasonality or photoperiod has an impact on: 1) the anoxia-tolerance of the intact pond snail, and 2) the response of isolated neuroganglia cluster F neurons to exogenous GABA application. L. stagnalis maintained on a natural summer light cycle were unable to survive any period of anoxic exposure, while those maintained on a natural winter light cycle survived a maximum of 4h. Using intracellular sharp electrode recordings from pedal ganglia cluster F neurons we show that there is a photoperiod dependent shift in the response to GABA. Snails exposed to a 16h:8h light:dark cycle in an environmental chamber (induced summer phenotype) exhibited hyperpolarizing inhibitory responses and those exposed to a 8h:16h light:dark cycle (induced winter phenotype) exhibited depolarizing excitatory responses to GABA application. Using gramicidin-perforated patch recordings we also found a photoperiod dependent shift in the reversal potential for GABA. We conclude that the opposing responses of L. stagnalis central neurons to GABA results from a shift in intracellular chloride concentration that is photoperiod dependent and is likely mediated through the relative efficacy of cation chloride co-transporters. Although the physiological ramifications of the photoperiod dependent shift are unknown this work potentially has important implications for the impact of artificial light pollution on animal health.

Ganglión dorsal de muñeca: resección artroscópica con técnica “en seco”. seguimiento mínimo de dos años / Dorsal wrist ganglion: arthroscopic resection with “dry” technique. minimum follow-up of two years

Introducción: el objetivo de este estudio fue comunicar los resultados a mediano plazo de la resección artroscópica de gangliones dorsales de muñeca utilizando la técnica “en seco”. Materiales y Métodos: Se evaluó retrospectivamente a 22 pacientes (22 muñecas) con un seguimiento mínimo de 2 años. Once mujeres y 11 hombres con una edad promedio de 29 años (rango 18-57). Se realizaron evaluaciones clínicas preoperatoria, al mes de la cirugía y en el último control. Se evaluaron la movilidad y la fuerza de puño comparativas, el dolor y la función según la escala analógica visual, los puntajes funcionales QuickDASH y de Wrightington, el retorno laboral y las complicaciones intraquirúrgicas y posquirúrgicas. Seguimiento promedio: 42 meses (rango 24-60). Se realizó un análisis estadístico mediante la prueba t. Resultados: Hubo 2 recidivas del ganglión. No se registraron otras complicaciones. La movilidad y la fuerza de puño comparativas mejoraron significativamente, 99% y 100%, respectivamente. El dolor y la función también mejoraron significativamente, al igual que el puntaje QuickDASH. Según la escala de Wrightington, 18 casos resultaron excelentes; 3, buenos, y uno fue malo. Veintiuno de los 22 pacientes retornaron a sus tareas laborales sin limitaciones, 20 refirieron estar satisfechos con el resultado. Conclusión: La resección artroscópica utilizando la técnica “en seco” representa una alternativa segura y eficaz para el tratamiento de los gangliones dorsales de muñeca, logra aliviar el dolor, y una mejoría funcional y estética en la mayoría de los pacientes mediante una rehabilitación temprana, con una baja incidencia de recidiva.

Introduction: the purpose of this study is to describe the medium-term results of arthroscopic resection of dorsal wrist ganglia using the “dry technique”. Methods: Twenty-two patients (22 wrists) were retrospectively evaluated with a minimum follow-up of 2 years. Eleven women and 11 men with an average age of 29 years (range 18-57). A clinical evaluation was performed preoperatively, at one month, and at the last control visit. Comparative wrist motion and grip strength, pain and function according to the visual analogue scale, functional QuickDASH and Wrightington scores, return to work, and intra and postoperative complications were evaluated. Mean follow-up was 42 months (range 24-60). Statistical analysis was performed using t test. Results: Two cases of ganglion recurrence were observed. No other complication was reported. Wrist motion and grip strength improved significantly, reaching 99% and 100%, respectively. Pain and function also improved significantly, as the functional QuickDASH score. According to Wrightington score, 18 cases were excellent, 3 were good, and one por result. Twenty-one patients returned to their tasks without limitation, 20 of them refered to be satisfied with the final result. Conclusion: Arthroscopic resection using the “dry technique “ represents a safe and effective alternative for the treatment of dorsal wrist ganglia, achieving pain relief, and functional and aesthetic improvement in most patients with early rehabilitation and a low incidence of recurrence.

The electrophysiology characteristics of dorsal root ganglion neurons in rats with TNBS-induced colitis / 第二军医大学学报

Objective: To investigate the electrophysiology characteristics of dorsal root ganglion (DRG) neurons in rats with 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)-induced colitis, so as to provide reference for a better understanding of inflammatory bowel disease(IBD). Methods: SD rats(male, 160-200 g)were randomly divided into two groups. Experimental colitis was induced in colitis group (n=5) by intracolonic administration of TNBS (40 mg/kg diluted in 70% ethanol), and control rats (n = 5) received normal saline in the same manner. Rats were sacrificed on the eighth day (acute inflammation phase) after administration of TNBS or normal saline, and the DRG neurons were obtained to investigate its electrophysiology characteristics by the whole-cell patch clamping. Results: The body weight of rats in the experimental group was significantly decreased. H-E staining showed severe damage of the intestinal mucosa glands and inflammatory cell infiltration, indiating successful model creation. The action potential threshold of DRG neurons was significantly decreased in rats with TNBS-induced colitis (P<0. 05). Conclusion: The excitability of DRG neurons is increased in rat model of TNBS-induced colitis.

Segmental and Regional Innervation of Acupoint "Taixi" (KI 3) Area in the Rat: A Horseradish Peroxidase Method Study / 针刺研究

L6.A longitudinal column of HRP-labeled motoneurons was found in the dorsolateral and mediolateral portions of the spinal cord,distributing in the lamina Ⅸ from the caudal L4 to the rostral L6.Additionally,the transganglionic HRP-labeled central projection axonal terminals were found to be dense in the central part of laminae Ⅰ-Ⅱ from L4 to the rostral L6,and to scatter in the central part of gracile nucleus.Conclusion HRP-labeled primary afferent and efferent innervating acupoint "Taixi"(KI 3) are DRGs of L4-L6,the dorsolateral and mediolateral motoneuron columns of L4-L6,and the centrally projecting axonal terminals of laminae Ⅰ-Ⅱ of the spinal cord and the gracile nucleus.