Duran, M. A. | Search bioRxiv

bioRxiv2026

Selectivity of Lateral Epidural Spinal Cord Stimulation with Varying Electrode Diameters and Stimulation Configurations

Objective. Our prior studies have demonstrated that lateral spinal cord stimulation can evoke somatosensory percepts in the missing foot in individuals with a lower-limb amputation. However, subjects reported concurrent sensations in their residual limb. In this study, we evaluate the hypothesis that using high-density paddle electrodes with smaller contact sizes, and multipolar stimulation configurations could evoke more focal sensations in the foot over a wide range of stimulation amplitudes. Approach. We used a combination of electrophysiology and computational modelling methods to investigate the selective activation of distal nerve branches in response to lateral spinal cord stimulation in cats. In six acute feline experiments, we performed an L3-S1 laminectomy and placed custom 32-electrode paddles laterally over the dura of the spinal cord. We recorded antidromic action potentials in the distal branches of the sciatic and femoral nerve trunks in response to stimulation using three contact diameters (150, 500 and 1000 {micro}m) and two stimulation configurations - monopolar and bipolar stimulation. We replicated the neural recruitment patterns from those experiments in a computational model of the feline lumbar spinal cord. We then used the model to examine neural recruitment with 1.8 mm and 2.5 mm contacts, as well as a tripolar guarded-cathode configuration. Main results. In the electrophysiology experiments, the 500 {micro}m-diameter electrodes achieved the most selective nerve activation (68%) compared to 62% for both 150 and 1000 {micro}m-diameter electrodes. The minimum amplitudes for recruiting nerve branches (i.e., threshold) as well as the dynamic ranges were largely similar for the different contact diameters (median: 35 {micro}A) and stimulation configurations (30 {micro}A for bipolar stimulation; 35 {micro}A for monopolar stimulation). The computational model reproduced the finding that selectivity did not differ significantly among the three contact sizes tested in cat experiments, though it revealed that increasing contact diameter above 1000 {micro}m raised the minimum amplitude required for selective activation and reduced spinal root selectivity. Across both approaches, we consistently recruited large-diameter afferents that are critical for somatosensory applications of spinal cord stimulation. Significance. Our results indicate that, relative to clinical electrodes, reducing the contact diameter of stimulation electrodes can evoke focal sensations, but further reductions below 1000 {micro}m may fail to improve selectivity. This study highlights potential constraints with achieving focal selectivity that are not dependent on the design of the electrodes.

bioengineering↗

bioRxiv2021

Electrical Potentials of Protoscoleces of the Cestode Echinococcus granulosus from Bovine Origin

Larval stages of the tenia Echinococcus granulosus are the infective forms of cystic echinococcosis or hydatidosis, a worldwide zoonosis. The protoscolex that develops into the adult form in the definitive host is enveloped by a complex cellular syncytial tegument, where all metabolic interchange takes place. Little information is available as to the electrical activity of the parasite in this developmental stage. To gain insight into the electrical activity of the parasite at the larval stage, here we conducted microelectrode impalements of bovine lung protoscoleces (PSCs) of Echinococcus granulosus in normal saline solution. We observed two distinct intra-parasitic potentials, a transient peak potential and a stable second potential, most likely representing tegumental and intra-parasitic extracellular space electrical potential differences, respectively. These values changed upon the developmental status of the parasite, its anatomical regions, or time course after harvesting. Changes in electrical potential differences of the parasite provide an accessible and useful parameter for the study of transport mechanisms and potential targets for the development of novel antiparasitic therapeutics. Author summaryHydatid disease is a parasite-caused zoonosis that causes high morbidity and mortality and has a great impact on public health. The disease has no known cure, and the main lines of treatment include surgery and medical treatments which are not satisfactory, so new drug compounds are urgently needed. Genome sequencing of the parasite has identified different genes encoding ion channels in Echinococcus granulosus, making ion channel inhibitors a promising target for treating hydatidosis. However, no easy technical approaches are available to test the electrical contribution of ion channels to parasite physiology. In the present study, we used the microelectrode impalement technique to determine the electrical properties of the larval stages of the parasite harvested from infected cow lungs. We observed transient electrical potentials not previously reported for the parasite, and changes in these parameters associated with its developmental stage and aging. Our findings indicate that microelectrode impalement of protoscoleces of Echinococcus granulosus may be a strategy of choice to explore and test possible drugs suggested for their therapeutic potential against hydatid disease. Further evaluation of parasites coming from other animals and humans may help address important issues in the treatment and prevention of the hydatid disease.

zoology↗