Is Electrical Nerve Stimulation the Answer for Management of Equine Headshaking?

A Systematic Approach to Dissection of the Equine Brain-Evaluation of a Species-Adapted Protocol for Beginners and Experts

Introduction of new imaging modalities for the equine brain have refocused attention on the horse as a natural model for ethological, neuroanatomical, and neuroscientific investigations. As opposed to imaging studies, strategies for equine neurodissection still lack a structured approach, standardization and reproducibility. In contrast to other species, where adapted protocols for sampling have been published, no comparable guideline is currently available for equids. Hence, we developed a species-specific slice protocol for whole brain vs. hemispheric dissection and tested its applicability and practicability in the field, as well as its neuroanatomical accuracy and reproducibility. Dissection steps are concisely described and depicted by schematic illustrations, photographs and instructional videos. Care was taken to show the brain in relation to the raters' hands, cutting devices and bench surface. Guidance is based on a minimum of external anatomical landmarks followed by geometric instructions that led to procurement of 14 targeted slabs. The protocol was performed on 55 formalin-fixed brains by three groups of investigators with different neuroanatomical skills. Validation of brain dissection outcomes addressed the aptitude of slabs for neuroanatomical studies as opposed to simplified routine diagnostic purposes. Across all raters, as much as 95.2% of slabs were appropriate for neuroanatomical studies, and 100% of slabs qualified for a routine diagnostic setting. Neither autolysis nor subfixation significantly affected neuroanatomical accuracy score, while a significant negative effect was observed with brain extraction artifacts. Procedure times ranged from 14 to 66 min and reached a mean duration of 23.25 ± 7.93 min in the last of five trials in inexperienced raters vs. 16 ± 2.83 min in experts, while acceleration of the dissection did not negatively impact neuroanatomical accuracy. This protocol, derived analogously to the consensus report of the International Veterinary Epilepsy Task Force in dogs and cats, allows for systematic, quick and easy dissection of the equine brain, even for inexperienced investigators. Obtained slabs feature virtually all functional subcompartments at suitable planes for both diagnostic and neuroscientific investigations and complement the data obtained from imaging studies. The instructive protocol and brain dissection videos are available in Supplementary Material.

Movement Caused by Electrical Stimulation of the Lumbosacral Region in Standing Horses

Electrical stimulation is commonly used as a modality for physical therapy in human and veterinary medicine. However, studies measuring the movement generated by electrical stimulation in horses are rare. The present study therefore evaluates the range of movement provoked by a commercially available physical therapy unit (FES310) and contrasts it with the movement generated by manually induced pelvic inclination (back rounding). Ten horses were tested on three measurement days over one week. Electrical stimulation was applied via a back treatment pad (belonging to the FES310 system) containing six electrodes (three on either side of the spine) placed over the lumbosacral region. This system produced a pulsed, biphasic electrical stimulation in a rectangular waveform which was gradually increased to a maximum of 10 volts. Before and after electrical stimulation testing, manual pelvic inclination was achieved by pressure on two points lateral to the root of the tail. Muscle tone and lameness were evaluated before and after treatments. Skinfold thickness, body condition score, and body mass were measured to detect possible confounding factors. Using kinematics, the angle ranges during movement of ten three-dimensional angles of the trunk, the pelvis, and the hind limbs were further analyzed. Movement was produced with manual stimulation in every tested individual on all measurement days and with electrical stimulation on at least one measurement day. The electrical stimulation led to significantly (P < .05) smaller angle ranges which were 15 %-57 % of the median of the manually stimulated movement. Strong positive correlations between angle ranges of the electrically generated movement were found for the hind limbs implicating their involvement in the movement created. Correlations between skinfold thickness, body condition score, and body mass with the angle ranges were weak and not significant. Before and after electrical and manual stimulation, muscle tone and lameness were similar. In the present study, both electrical and manual stimulation were proven to produce significant trunk and hind limb movement. Within this study's electrical stimulation treatment protocol, the movement generated by electrical stimulation was significantly less than the movement caused by manual pelvic inclination. However, electrical stimulation could easily be applied over a longer period and in a higher frequency than it would be possible for manual pelvic inclination. This treatment shows potential for stabilization and or mobilization of the lumbosacral region, although its efficiency as a therapeutic tool and its effect on specific orthopedic problems and is to be evaluated in further research.