Human-relevant near-organ neuromodulation of the immune system via the splenic nerve.

Neuromodulation of immune function by stimulating the autonomic connections to the spleen has been demonstrated in rodent models. Consequently, neuroimmune modulation has been proposed as a new therapeutic strategy for the treatment of inflammatory conditions. However, demonstration of the translation of these immunomodulatory mechanisms in anatomically and physiologically relevant models is still lacking. Additionally, translational models are required to identify stimulation parameters that can be transferred to clinical applications of bioelectronic medicines. Here, we performed neuroanatomical and functional comparison of the mouse, rat, pig, and human splenic nerve using in vivo and ex vivo preparations. The pig was identified as a more suitable model of the human splenic innervation. Using functional electrophysiology, we developed a clinically relevant marker of splenic nerve engagement through stimulation-dependent reversible reduction in local blood flow. Translation of immunomodulatory mechanisms were then assessed using pig splenocytes and two models of acute inflammation in anesthetized pigs. The pig splenic nerve was shown to locally release noradrenaline upon stimulation, which was able to modulate cytokine production by pig splenocytes. Splenic nerve stimulation was found to promote cardiovascular protection as well as cytokine modulation in a high- and a low-dose lipopolysaccharide model, respectively. Importantly, splenic nerve-induced cytokine modulation was reproduced by stimulating the efferent trunk of the cervical vagus nerve. This work demonstrates that immune responses can be modulated by stimulation of spleen-targeted autonomic nerves in translational species and identifies splenic nerve stimulation parameters and biomarkers that are directly applicable to humans due to anatomical and electrophysiological similarities.

A method to identify, dissect and stain equine neuromuscular junctions for morphological analysis.

Morphological study of the neuromuscular junction (NMJ), a specialised peripheral synapse formed between a lower motor neuron and skeletal muscle fibre, has significantly contributed to the understanding of synaptic biology and neuromuscular disease pathogenesis. Rodent NMJs are readily accessible, and research into conditions such as amyotrophic lateral sclerosis (ALS), Charcot-Marie-Tooth disease (CMT), and spinal muscular atrophy (SMA) has relied heavily on experimental work in these small mammals. However, given that nerve length dependency is an important feature of many peripheral neuropathies, these rodent models have clear shortcomings; large animal models might be preferable, but their size presents novel anatomical challenges. Overcoming these constraints to study the NMJ morphology of large mammalian distal limb muscles is of prime importance to increase cross-species translational neuromuscular research potential, particularly in the study of long motor units. In the past, NMJ phenotype analysis of large muscle bodies within the equine distal pelvic limb, such as the tibialis cranialis, or within muscles of high fibrous content, such as the soleus, has posed a distinct experimental hurdle. We optimised a technique for NMJ location and dissection from equine pelvic limb muscles. Using a quantification method validated in smaller species, we demonstrate their morphology and show that equine NMJs can be reliably dissected, stained and analysed. We reveal that the NMJs within the equine soleus have distinctly different morphologies when compared to the extensor digitorum longus and tibialis cranialis muscles. Overall, we demonstrate that equine distal pelvic limb muscles can be regionally dissected, with samples whole-mounted and their innervation patterns visualised. These methods will allow the localisation and analysis of neuromuscular junctions within the muscle bodies of large mammals to identify neuroanatomical and neuropathological features.

Ex vivo biomechanical evaluation of polyester and polyblend suture techniques to perform equine laryngoplasty.

OBJECTIVE: To validate the use of a polyblend tape suture in equine laryngoplasty (PL). STUDY DESIGN: Experimental study. ANIMALS: Thirty-two cadaveric larynges. METHODS: Each larynx was randomly assigned to 1 of 4 groups: PL with polyblend tape suture (TigerTape), without (TT) or with a cannula (TTC) in the muscular process of the arytenoid cartilage, and PL with polyester suture (Ethibond), without (EB) or with a cannula (EBC). Construct stiffness, total migration, creep, and drift values were measured after 3000 cycles. The specimens were then loaded to failure to assess their residual properties: load at failure, total energy, displacement, and 2 stiffness coefficients. RESULTS: After cyclic testing, the total migration and creep were lower in TTC (6.36 ± 1.20 mm; 1.35 ± 0.38 mm/s) than in EB (11.12 ± 4.20 mm; 3.39 ± 2.68 mm/s) and in the TT constructs (11.26 ± 1.49 mm; 3.20 ± 0.54 mm/s); however, no difference was found with EBC (9.19 ± 3.18 mm; 2.14 ± 0.99). A correlation was found between total migration and creep (R = .85). The TTC constructs failed at higher loads (129.51 ± 33.84 N) than EB (93.16 ± 18.21 N) and EBC (81.72 ± 13.26 N) whereas the EB and EBC constructs were less stiff than TT and TTC (P < .001). CONCLUSION: Biomechanical properties were generally superior for the TTC constructs tested under cyclical loading. The TT and TTC constructs failed at a higher load than EB and EBC constructs. The cannula in TTC and EBC reduced the failure at the muscular process. CLINICAL SIGNIFICANCE: These results provide evidence to support the in vivo evaluation of the polyblend tape suture with or without a cannula in the muscular process for laryngoplasty in horses.

Imaging of focal seizures with Electrical Impedance Tomography and depth electrodes in real time.

Intracranial EEG is the current gold standard technique for localizing seizures for surgery, but it can be insensitive to tangential dipole or distant sources. Electrical Impedance Tomography (EIT) offers a novel method to improve coverage and seizure onset localization. The feasibility of EIT has been previously assessed in a computer simulation, which revealed an improved accuracy of seizure detection with EIT compared to intracranial EEG. In this study, slow impedance changes, evoked by cell swelling occurring over seconds, were reconstructed in real time by frequency division multiplexing EIT using depth and subdural electrodes in a swine model of epilepsy. EIT allowed to generate repetitive images of ictal events at similar time course to fMRI but without its significant limitations. EIT was recorded with a system consisting of 32 parallel current sources and 64 voltage recorders. Seizures triggered with intracranial injection of benzylpenicillin (BPN) in five pigs caused a repetitive peak impedance increase of 3.4 ± 1.5 mV and 9.5 ± 3% (N =205 seizures); the impedance signal change was seen already after a single, first seizure. EIT enabled reconstruction of the seizure onset 9 ± 1.5 mm from the BPN cannula and 7.5 ± 1.1 mm from the closest SEEG contact (p<0.05, n =37 focal seizures in three pigs) and it could address problems with sampling error in intracranial EEG. The amplitude of the impedance change correlated with the spread of the seizure on the SEEG (p <<0.001, n =37). The results presented here suggest that combining a parallel EIT system with intracranial EEG monitoring has a potential to improve the diagnostic yield in epileptic patients and become a vital tool in improving our understanding of epilepsy.

Thyrohyoideus muscle innervation in the horse.

OBJECTIVE: To describe the innervation of the thyrohyoideus (TH) muscle and to confirm our findings with stimulation of first cervical (C1) nerve branches. STUDY DESIGN: Ex vivo phase 1 and clinical phase 2. ANIMALS: Fourteen head and neck specimens and 17 client-owned horses. METHODS: In phase 1, the cranial nerve (CN) XII and the C1 nerve were dissected with their branches in 20 dissections were performed on 14 specimens (6 left and right side and 8 only left or right) Anatomy was noted. Samples of nerve bifurcations were collected for histological confirmation of anatomical findings. First cervical nerve branches were stimulated in horses undergoing cervical nerve graft to treat laryngeal hemiplegia. RESULTS: The nerve innervating the TH muscle arose directly from the C1 nerve in 17 of 20 dissections, from an anastomotic branch between CN XII and the C1 nerve in two of 20 dissections, and from the C1 nerve and the anastomotic branch in one of 20 dissections. No direct connection between the TH muscle and CN XII was found. Histological examination revealed that the anastomosis was composed of C1 nerve fibers passing over to CN XII. First cervical stimulation resulted in TH muscle contraction in 16 of 17 horses. CONCLUSIONS: The innervation of the TH muscle originated from the C1 nerve according to dissection, histological, and conduction studies, with variation in the branching pattern. CLINICAL SIGNIFICANCE: Care should be taken to preserve the C1 nerve during prosthetic laryngoplasty. The surgical technique for C1 nerve grafts should be reconsidered in light of these findings, along with new options to treat dorsal displacement of the soft palate..

Anatomy of the vestibulum esophagi and surgical implications during prosthetic laryngoplasty in horses.

OBJECTIVE: To describe the anatomy of the entry to the equine esophagus (vestibulum esophagi) and to assess the risk of penetrating its adventitia and/or lumen during laryngoplasty. STUDY DESIGN: Ex vivo cadaveric study. SAMPLE POPULATION: Five isolated equine larynges and 39 equine head and neck specimens. METHODS: The anatomy of the vestibulum esophagi was studied by dissection of 5 cadaver specimens. Then, a bilateral laryngoplasty was performed, including 5 suture placements through the muscular processes, caudal, rostral, and sagittal, with straight and curved needles. Two of the 3 surgeons performing the implantations were unaware of the goals of the study. Suture positions and iatrogenic trauma to the lumen and/or adventitia of the vestibulum esophagi were identified during dissection of the specimens. Risk factors for penetrating the adventitia were evaluated with a multivariate regression model. RESULTS: The vestibulum esophagi spans between both wings of the thyroid cartilage over the entire width of the larynx, covering the rostral spine (arcuate crest) of the arytenoid cartilages. It is covered by the thyropharyngeus and cricopharyngeus muscles. Masked surgeons were associated with a significantly higher number of adventitia penetrations (72%) compared to the nonmasked surgeon (9%). The lumen of the vestibulum esophagi was penetrated in 4.6% of suture placements and only by the 2 masked surgeons. CONCLUSION: Penetration of the adventitia was more common when surgeons were unaware of the anatomical extent of the vestibulum esophagi. CLINICAL SIGNIFICANCE: Anatomical knowledge of the extent of the vestibulum esophagi reduces the risk of penetrating its lumen or adventitia during suture placement on the muscular process of the arytenoid cartilage.

Ex vivo biomechanical stability of 5 cricoid-suture constructs for equine laryngoplasty.

OBJECTIVE: To determine the biomechanical properties of 5 suture constructs in the equine cricoid under cyclic loading and load to failure testing. STUDY DESIGN: Ex vivo study. SAMPLES: Seventy-five equine cadaver larynges. METHODS: Each larynx was implanted with 1 of 5 cricoid-suture constructs. The standard laryngoplasty, where a suture is passed once through the cricoid, including its caudal edge, was used in 2 constructs: 1 with 5 USP Ethibond (ES) and 1 with 2 mm Fibertape (FS). In the third construct, the 2 mm Fibertape was passed twice through the cricoid including its caudal edge (Double Loop-DL). Constructs 4 and 5 used 2 mm Fibertape in a U-shaped loop passed through the cricoid but excluding its caudal edge. One construct was supported with a metallic button (MB) on the caudo-ventral aspect of the cricoid while the other included only the U-shaped loop (U). Constructs were subjected to cyclic loading and to single cycle to failure. Reduction of the left-to-right arytenoid angle quotient (LRQ), suture migration, and load at failure were compared. RESULTS: LRQ reduction after cyclic loading was lower in MB and U than ES constructs. During cyclic loading, suture migration was reduced in MB, U, and DL compared to ES constructs. Mean load at failure was lower in FS and U than in ES constructs. CONCLUSION: Loss of abduction after equine laryngoplasty may be reduced and pullout forces increased by applying a MB construct in the cricoid cartilage. In vivo testing is required to verify these results.

Effects of Functional Electrical Stimulation on Denervated Laryngeal Muscle in a Large Animal Model.

Bilateral vocal fold paralysis (BVCP) is a life-threatening condition that follows injury to the Recurrent Laryngeal nerve (RLn) and denervation of the intrinsic laryngeal musculature. Functional electrical stimulation (FES) enables restoration and control of a wide variety of motor functions impaired by lower motor neuron lesions. Here we evaluate the effects of FES on the sole arytenoid abductor, the posterior cricoarytenoid (PCA) muscle in a large animal model of RLn injury. Ten horses were instrumented with two quadripolar intramuscular electrodes in the left PCA muscle. Following a 12-week denervation period, the PCA was stimulated using a once-daily training session for 8 weeks in seven animals. Three animals were used as unstimulated controls. Denervation produced a significant increase in rheobase (P < 0.001). Electrical stimulation produced a 30% increase in fiber diameter in comparison with the unstimulated control group (33.9 ± 2.6 µm FES+, 23.6 ± 4.2 µm FES-, P = 0.04). A trend toward a decrease in the proportion of type 1 (slow) fibers and an increase in type 2a (fast) fibers was also observed. Despite these changes, improvement in PCA function at rest was not observed. These data suggest that electrical stimulation using a relatively conservative set of stimulation parameters can reverse the muscle fiber atrophy produced by complete denervation while avoiding a shift to a slow (type 1) fiber type.

Bilateral Functional Electrical Stimulation for the Treatment of Presbyphonia in a Sheep Model.

OBJECTIVES: The aim of the study was to increase muscle volume and improve phonation characteristics of the aged ovine larynx by functional electrical stimulation (FES) using a minimally invasive surgical procedure. METHODS: Stimulation electrodes were placed bilaterally near the terminal adduction branch of the recurrent laryngeal nerves (RLN). The electrodes were connected to battery powered pulse generators implanted subcutaneously at the neck region. Training patterns were programmed by an external programmer using a bidirectional radio frequency link. Training sessions were repeated automatically by the implant every other day for 1 week followed by every day for 8 weeks in the awake animal. Another group of animals were used as sham, with electrodes positioned but not connected to an implant. Outcome parameters included gene expression analysis, histological assessment of muscle fiber size, functional analysis, and volumetric measurements based on three-dimensional reconstructions of the entire thyroarytenoid muscle (TAM). RESULTS: Increase in minimal muscle fiber diameter and an improvement in vocal efficiency were observed following FES, compared with sham animals. CONCLUSION: This is the first study to demonstrate beneficial effects in the TAM of FES at molecular, histological, and functional levels. FES of the terminal branches of the RLN reversed the effects of age-related changes and improved vocal efficiency. LEVEL OF EVIDENCE: NA Laryngoscope, 134:848-854, 2024.

Overcoming temporal dispersion for measurement of activity-related impedance changes in unmyelinated nerves.

Objective.Fast neural electrical impedance tomography is an imaging technique that has been successful in visualising electrically evoked activity of myelinated fibres in peripheral nerves by measurement of the impedance changes (dZ) accompanying excitation. However, imaging of unmyelinated fibres is challenging due to temporal dispersion (TP) which occurs due to variability in conduction velocities of the fibres and leads to a decrease of the signal below the noise with distance from the stimulus. To overcome TP and allow electrical impedance tomography imaging in unmyelinated nerves, a new experimental and signal processing paradigm is required allowing dZ measurement further from the site of stimulation than compound neural activity is visible. The development of such a paradigm was the main objective of this study.Approach.A finite element-based statistical model of TP in porcine subdiaphragmatic nerve was developed and experimentally validatedex-vivo. Two paradigms for nerve stimulation and processing of the resulting data-continuous stimulation and trains of stimuli, were implemented; the optimal paradigm for recording dispersed dZ in unmyelinated nerves was determined.Main results.While continuous stimulation and coherent spikes averaging led to higher signal-to-noise ratios (SNRs) at close distances from the stimulus, stimulation by trains was more consistent across distances and allowed dZ measurement at up to 15 cm from the stimulus (SNR = 1.8 ± 0.8) if averaged for 30 min.Significance.The study develops a method that for the first time allows measurement of dZ in unmyelinated nerves in simulation and experiment, at the distances where compound action potentials are fully dispersed.

In vitro effect of ventriculocordectomy before laryngoplasty on abduction of the equine arytenoid cartilage.

OBJECTIVE: To determine whether ventriculocordectomy (VCE) performed before prosthetic laryngoplasty (PL) results in increased rima glottidis size compared with PL alone. STUDY DESIGN: Experimental study. ANIMALS: Equine cadaver larynges (n=13). METHODS: Right arytenoid cartilages were maximally abducted using a standard PL technique. Standard PLs were then performed on the left side and the force required to maximally abduct the left arytenoid cartilage recorded (F(max) ). Photographs were taken of the rima glottidis at zero force and at five equal levels of force up to F(max) . The force applied was released, left VCE performed, and photographs repeated. Arytenoid left:right angle quotients (LRQ) and glottic cross-sectional area ratios (CSAR) were calculated at each force level in each condition (PL and VCE-PL). RESULTS: Mean LRQ and CSAR for both PL and VCE-PL increased with increasing force, initially rapidly before plateauing at ~50% of F(max) . LRQ and CSAR were significantly greater for VCE-PL than for PL (P<.001). When VCE was performed before PL, 12% less force was required to achieve an LRQ of 0.8, and 45% less for a CSAR of 0.8. CONCLUSIONS: In vitro, VCE performed before PL enables the arytenoid cartilage to be abducted to a greater degree for a given PL suture force.

Splenic Nerve Neuromodulation Reduces Inflammation and Promotes Resolution in Chronically Implanted Pigs.

Neuromodulation of the immune system has been proposed as a novel therapeutic strategy for the treatment of inflammatory conditions. We recently demonstrated that stimulation of near-organ autonomic nerves to the spleen can be harnessed to modulate the inflammatory response in an anesthetized pig model. The development of neuromodulation therapy for the clinic requires chronic efficacy and safety testing in a large animal model. This manuscript describes the effects of longitudinal conscious splenic nerve neuromodulation in chronically-implanted pigs. Firstly, clinically-relevant stimulation parameters were refined to efficiently activate the splenic nerve while reducing changes in cardiovascular parameters. Subsequently, pigs were implanted with a circumferential cuff electrode around the splenic neurovascular bundle connected to an implantable pulse generator, using a minimally-invasive laparoscopic procedure. Tolerability of stimulation was demonstrated in freely-behaving pigs using the refined stimulation parameters. Longitudinal stimulation significantly reduced circulating tumor necrosis factor alpha levels induced by systemic endotoxemia. This effect was accompanied by reduced peripheral monocytopenia as well as a lower systemic accumulation of CD16+CD14high pro-inflammatory monocytes. Further, lipid mediator profiling analysis demonstrated an increased concentration of specialized pro-resolving mediators in peripheral plasma of stimulated animals, with a concomitant reduction of pro-inflammatory eicosanoids including prostaglandins. Terminal electrophysiological and physiological measurements and histopathological assessment demonstrated integrity of the splenic nerves up to 70 days post implantation. These chronic translational experiments demonstrate that daily splenic nerve neuromodulation, via implanted electronics and clinically-relevant stimulation parameters, is well tolerated and is able to prime the immune system toward a less inflammatory, pro-resolving phenotype.

Three-dimensional biomechanics of simulated laryngeal abduction in horses.

OBJECTIVE: To investigate the influence of simulated contraction of the cricoarytenoideus dorsalis (CAD) muscle on the 3-D motion of the arytenoid cartilage. SAMPLE POPULATION: 5 larynges from equine cadavers. PROCEDURES: Serial computed tomographic scans of each larynx were conducted at 7 incremental forces simulating contraction of medial, lateral, and combined bellies of the left CAD muscle. Three-dimensional reconstruction of radiopaque markers placed at anatomic landmarks on the left arytenoid and cricoid cartilages enabled quantification of marker displacement according to a Cartesian coordinate system. Rotation (roll, pitch, and yaw) of dorsal and ventral arytenoid planes was calculated relative to a plane formed by the coordinates of 3 markers on the cricoid cartilage by use of Euler angles. RESULTS: Displacement and rotational data showed that rocking motion occurs throughout arytenoid abduction and most of the rotational component is attributable to pitch; greater pitch was associated with action of the lateral belly. Roll of the ventral arytenoid plane was principally associated with action of the medial belly, which counteracted the tendency of the arytenoid cartilage to rotate medially into the rima glottidis lumen. The distance between markers on the arytenoid cartilage was not constant during contraction because of slight deformation of the corniculate process of the arytenoid cartilage, therefore indicating that the arytenoid cartilage is not a rigid body during abduction. CONCLUSIONS AND CLINICAL RELEVANCE: Arytenoid cartilage abduction was dependent on the rocking motion elicited by the lateral belly of the CAD muscle; therefore, laryngoplasty suture placement should mimic the action of the lateral, rather than the medial, muscle belly.

Ex vivo modeling of the airflow dynamics and two-and three-dimensional biomechanical effects of suture placements for prosthetic laryngoplasty in horses.

OBJECTIVE: To identify the degree of left arytenoid cartilage (LAC) abduction that allows laryngeal airflow similar to that in galloping horses, assess 2-D and 3-D biomechanical effects of prosthetic laryngoplasty on LAC movement and airflow, and determine the influence of suture position through the muscular process of the arytenoid cartilage (MPA) on these variables. SAMPLE: 7 equine cadaver larynges. PROCEDURES: With the right arytenoid cartilage maximally abducted and inspiratory airflow simulated by vacuum, laryngeal airflow and translaryngeal pressure and impedance were measured at 12 incremental LAC abduction forces (0% to 100% [maximum abduction]) applied through laryngoplasty sutures passed caudocranially or mediolaterally through the left MPA. Cross-sectional area of the rima glottis and left-to-right angle quotient were determined from photographs at each abduction force; CT images were obtained at alternate forces. Arytenoid and cricoid cartilage markers allowed calculation of LAC roll, pitch, and yaw through use of Euler angles on 3-D reconstructed CT images. RESULTS: Translaryngeal pressure and impedance decreased, and airflow increased rapidly at low abduction forces, then slowed until a plateau was reached at approximately 50% of maximum abduction force. The greatest LAC motion was rocking (pitch). Suture position through the left MPA did not significantly affect airflow data. Approximately 50% of maximum abduction force, corresponding to a left arytenoid angle of approximately 30° and left-to-right angle quotient of 0.79 to 0.84, allowed airflow of approximately 61 ± 6.5 L/s. CONCLUSIONS AND CLINICAL RELEVANCE: Ex vivo modeling results suggested little benefit to LAC abduction forces > 50%, which allowed airflow similar to that reported elsewhere for galloping horses.

Comparison of sinoscopic techniques for examining the rostral maxillary and ventral conchal sinuses of horses.

OBJECTIVE: To develop a reliable technique for sinoscopic examination of the ventral conchal (VCS) and rostral maxillary sinuses (RMS) of horses STUDY DESIGN: Descriptive study ANIMALS: Cadaveric equine heads (n=40) METHODS: The VCS and RMS were examined endoscopically using: (1) rostral trephination of the RMS (rostral RMS approach); (2) caudal trephination of the RMS (caudal RMS approach); (3) conchofrontal sinus (CFS) trephination followed by RMS trephination at a site identified by endoscopic transillumination of the maxillary bone at the most rostral aspect of the caudal maxillary sinus (CMS) (light-indicated RMS approach); (4) CFS trephination with fenestration of the ventral conchal bulla (VCB; frontal VCB approach); (5) CMS trephination with VCB fenestration (caudal VCB approach); and (6) CFS and CMS trephination with VCB fenestration (combined VCB approach). RESULTS: Success in observing the rostral and caudal aspects of the VCS and RMS with each approach were: (1) rostral RMS approach (0 horses; 16 horses [40%]); (2) caudal RMS approach (0 horses; 11 horses [28%]); (3) light-indicated RMS approach (3 horses [8%]; 24 horses [60%]); (4) frontal VCB approach (24 horses [60%]; 29 horses [73%] respectively); (5) caudal VCB approach (16 horses [40%] both structures); and (6) combined VCB approach (27 horses [68%]; 35 horses [88%]). CONCLUSIONS: Trephination into the CFS coupled with fenestration of the VCB provided consistent access to both the rostral and caudal aspects of the RMS and VCS. A trephine hole into the RMS provided poor access to the VCS, and placed the reserve crowns of the maxillary cheek teeth at risk of damage. CLINICAL RELEVANCE: The RMS and VCS can be best examined endoscopically using approaches with fenestration of the VCB.

Sinoscopic treatment of rostral maxillary and ventral conchal sinusitis in 60 horses.

OBJECTIVE: To evaluate the use of sinoscopy for detection and treatment of ventral conchal sinus (VCS) and/or rostral maxillary sinus (RMS) disease in horses. STUDY DESIGN: Case series ANIMALS: Horses (n=60) with suspected paranasal sinus disease. METHODS: Horses were evaluated by sinoscopy through a conchofrontal sinus (CFS) portal with ventral conchal bulla (VCB) fenestration. Other endoscopic sinus approaches and adjunctive diagnostic tests; oral examination, computed tomography, radiography, scintigraphy and endoscopic examination of the upper portion of the respiratory tract were used in some horses. RESULTS: The CFS approach permitted adequate observation of the RMS and VCS in 53 horses (88%). Hemorrhage caused by VCB fenestration prevented examination of the RMS and/or VCS in 12 horses (21%). Observation of lesions was possible in all horses diagnosed with neoplasia, sinus cysts, and progressive ethmoidal hematomas. Endoscopy of the paranasal sinuses was useful diagnostically in 82% of horses with primary sinusitis. Other diagnostic modalities were usually required to confirm a diagnosis of dental sinusitis. CONCLUSIONS: Trephination into the CFS with VCB fenestration is a minimally invasive technique that provides consistent access to the RMS and VCS. It facilitates diagnosis of many sinus disorders and endoscopically guided treatment of many horses with sinus cysts and primary sinusitis, in combination with sinus lavage. CLINICAL RELEVANCE: Many diseases affecting the RMS and VCS can be diagnosed and resolved endoscopically using a CFS approach with VCB fenestration, thus avoiding the need for osteoplastic sinus surgery and its associated risks and complications.

Investigation into pathophysiology of naturally occurring palatal instability and intermittent dorsal displacement of the soft palate (DDSP) in racehorses: Thyro-hyoid muscles fatigue during exercise.

Exercise induced intermittent dorsal displacement of the soft palate (DDSP) is a common cause of airway obstruction and poor performance in racehorses. The definite etiology is still unclear, but through an experimental model, a role in the development of this condition was identified in the dysfunction of the thyro-hyoid muscles. The present study aimed to elucidate the nature of this dysfunction by investigating the spontaneous response to exercise of the thyro-hyoid muscles in racehorses with naturally occurring DDSP. Intramuscular electrodes were implanted in the thyro-hyoid muscles of nine racehorses, and connected to a telemetric unit for electromyographic monitoring implanted subcutaneously. The horses were recruited based on upper airway function evaluated through wireless endoscopy during exercise. Five horses, with normal function, were used as control; four horses were diagnosed as DDSP-affected horses based on repeated episodes of intermittent dorsal displacement of the soft palate. The electromyographic activity of the thyro-hyoid muscles recorded during incremental exercise tests on a high-speed treadmill was analyzed to measure the mean electrical activity and the median frequency of the power spectrum, thereafter subjected to wavelet decomposition. The affected horses had palatal instability with displacement on repeated exams prior to surgical implantation. Although palatal instability persisted after surgery, only two of these horses displaced the palate after instrumentation. The electromyographic traces from this group of four horses showed, at highest exercise intensity, a decrease in mean electrical activity and median power frequency, with progressive decrease in the contribution of the high frequency wavelets, consistent with development of thyro-hyoid muscle fatigue. The results of this study identified fatigue as the main factor leading to exercise induced palatal instability and DDSP in a group of racehorses. Further studies are required to evaluate the fiber type composition and metabolic characteristics of the thyro-hyoid muscles that could predispose to fatigue.

Feasibility of kilohertz frequency alternating current neuromodulation of carotid sinus nerve activity in the pig.

Recent research supports that over-activation of the carotid body plays a key role in metabolic diseases like type 2 diabetes. Supressing carotid body signalling through carotid sinus nerve (CSN) modulation may offer a therapeutic approach for treating such diseases. Here we anatomically and histologically characterised the CSN in the farm pig as a recommended path to translational medicine. We developed an acute in vivo porcine model to assess the application of kilohertz frequency alternating current (KHFAC) to the CSN of evoked chemo-afferent CSN responses. Our results demonstrate the feasibility of this approach in an acute setting, as KHFAC modulation was able to successfully, yet variably, block evoked chemo-afferent responses. The observed variability in blocking response is believed to reflect the complex and diverse anatomy of the porcine CSN, which closely resembles human anatomy, as well as the need for optimisation of electrodes and parameters for a human-sized nerve. Overall, these results demonstrate the feasibility of neuromodulation of the CSN in an anesthetised large animal model, and represent the first steps in driving KHFAC modulation towards clinical translation. Chronic recovery disease models will be required to assess safety and efficacy of this potential therapeutic modality for application in diabetes treatment.

Electrode fabrication and interface optimization for imaging of evoked peripheral nervous system activity with electrical impedance tomography (EIT).

OBJECTIVE: Non-invasive imaging techniques are undoubtedly the ideal methods for continuous monitoring of neural activity. One such method, fast neural electrical impedance tomography (EIT) has been developed over the past decade in order to image neural action potentials with non-penetrating electrode arrays. APPROACH: The goal of this study is two-fold. First, we present a detailed fabrication method for silicone-based multiple electrode arrays which can be used for epicortical or neural cuff applications. Secondly, we optimize electrode material coatings in order to achieve the best accuracy in EIT reconstructions. MAIN RESULTS: The testing of nanostructured electrode interface materials consisting of platinum, iridium oxide, and PEDOT:pTS in saline tank experiments demonstrated that the PEDOT:pTS coating used in this study leads to more accurate reconstruction dimensions along with reduced phase separation between recording channels. The PEDOT:pTS electrodes were then used in vivo to successfully image and localize the evoked activity of the recurrent laryngeal fascicle from within the cervical vagus nerve. SIGNIFICANCE: These results alongside the simple fabrication method presented here position EIT as an effective method to image neural activity.

Transpalpebral eye enucleation in 40 standing horses.

OBJECTIVE: To report a technique for eye enucleation in standing sedated horses and to report outcome in 40 horses. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n=40) requiring eye enucleation. METHODS: The eye was enucleated using a transpalpebral technique in 40 horses restrained in stocks and sedated. Anesthesia of orbital structures was provided by local nerve blocks and infiltration of the surgical site with local anesthetic solution. RESULTS: Affected eyes were successfully enucleated with the horse standing. Short-term complications included moderate swelling (5 horses) and wound discharge (1). Long-term complications were not observed. CONCLUSIONS: A diseased eye can be safely enucleated with a horse standing. CLINICAL RELEVANCE: Enucleating an equine eye in the standing position eliminates the risks and costs of general anesthesia.