Topic:Nerves
The study of nerves in horses encompasses the structure, function, and disorders of the equine nervous system. This system is responsible for transmitting signals between different parts of the body and coordinating actions and sensory information. Key components include the central nervous system, consisting of the brain and spinal cord, and the peripheral nervous system, which includes nerves extending throughout the body. Research in this area investigates the role of nerves in equine behavior, movement, and response to stimuli, as well as conditions such as neuropathies and nerve injuries. This topic includes a collection of peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and clinical implications of the nervous system in horses.
Comparison of speed of onset and analgesic effect of 2% mepivacaine hydrochloride deposited within or outside the neurovascular bundle at the level of the proximal sesamoid bones in horses with naturally occurring forefoot-related lameness. To compare the speed of onset and analgesic effect of mepivacaine deposited within or immediately outside the neurovascular bundle at the base of the proximal sesamoid bones in horses. Methods: 6 horses with naturally occurring forefoot-related lameness. Methods: In a crossover study design, horses were randomly assigned to receive 1 of 2 treatments first, with the second treatment administered 3 to 7 days later. Trotting gait was analyzed with an inertial sensor-based motion analysis system immediately before treatment to determine degree of lameness. Afterward, ultrasound guidance was used t...
Efficacy and duration of effect for liposomal bupivacaine when administered perineurally to the palmar digital nerves of horses. To determine the efficacy and duration of effect for liposomal bupivacaine following perineural administration to the medial and lateral palmar digital nerves of horses. Methods: 9 nonlame mares. Methods: For each horse, 2 mL of liposomal bupivacaine (13.3 mg/mL; total dose, 53.2 mg or approx 0.11 mg/kg) or sterile saline (0.9% NaCl) solution was injected adjacent to the medial and lateral palmar digital nerves at the level of the distal aspect of the proximal sesamoid bones of a randomly selected forelimb. Twenty-one days later, the opposite treatment was administered in the contralateral for...
Endoscopic recurrent laryngeal neuropathy grade prevalence in a sample of thoroughbred yearlings at public auction in South Africa (2013-2019). Endoscopy of thoroughbred (TB) yearlings at public auctions is common in South Africa. Laryngeal function (LF) is a common concern of buyers of young TBs. Cancellation of sale because of LF abnormalities is a concern for both the vendor and the buyer, with recurrent laryngeal neuropathy (RLN) being a common cause of sale cancellation. The aim of this descriptive study was to determine the prevalence of RLN at South African premier TB yearling sales. This study was designed as a retrospective descriptive analysis of upper respiratory tract (URT) endoscopic examinations to determine RLN grade, p...
Diffusion of Radiodense Contrast Medium Following Perineural Injection of the Deep Branch of the Lateral Plantar Nerve Using Two Different Techniques in Horses: an In Vivo Study.  This article evaluates and compares the diffusion pattern of radiopaque contrast medium following perineural analgesia of the deep branch of the lateral plantar nerve performed using two different techniques: weight-bearing or flexed. Methods:  This was an experimental study. Methods:  Eight horses were enrolled. Perineural injection of the right and left deep branch lateral plantar nerves was performed with a weight-bearing or flexed technique, using radiopaque contrast medium (iohexol). Radiographic evaluation was performed after 5 (T5), 15 (T15) and 30 (T30) minutes. The diffusion o...
Facial nerve paralysis in 64 equids: Clinical variables, diagnosis, and outcome. Facial nerve paralysis (FNP) in equids is not well described in the veterinary literature. Objective: To investigate the causes of FNP and associations among clinical variables, diagnosis, and outcome. Methods: Sixty-four equids presenting with FNP between July 2000 and April 2019. Cases of postanesthetic FNP were excluded. Methods: Medical records were retrospectively reviewed. Variables were evaluated for associations with outcomes (diagnosis and case outcome) using logistic regression. Results: The most common cause of FNP was trauma (n = 20). Additional diagnoses included central nervous s...
Quantitative motor unit action potential analysis of paraspinal muscles, diagnostic imaging and necropsy findings in 36 horses suspected of cervical impairment. Aims: To determine the relation between quantitative electromyography (QEMG) of the cervical ventral serratus muscle, radiographic findings and post-mortem gross and histopathological examination in order to calculate the ability of QEMG to localize the region of cervical compressive neuropathy and myelopathy in horses. Methods: In this clinical, non-randomised, partially blinded study (QEMG and histology), 36 warmblood horses with clinical suspicion of cervical spine disease were examined with QEMG in different segments of the ventral serratus muscle. Results were compared to normative data. ...
Ultrasonography-Guided Perineural Injection of the Ramus ventralis of the 7 and 8th Cervical Nerves in Horses: A Cadaveric Descriptive Pilot Study. To describe the feasibility and dye diffusion of selective perineural injection of the 7 and 8th cervical nerve (C7 and C8) under ultrasonographic guidance in horses. Prospective experimental pilot cadaver study. Four equine cadavers of similar body weight (420-480 kg) and neck conformation. Five C7 and five C8 were perineurally injected with a dye solution. Anatomic dissections including vertebral canal opening were conducted to confirm nerve dye staining and describe the extent of color diffusion. The of the spinal cervical nerves was visualized in all cadavers. All the injections we...
Ultrasound-guided continuous block of median and ulnar nerves in horses: development of the technique. To develop a technique for ultrasound-guided continuous median and ulnar peripheral nerve block in horses. Methods: Anatomical and prospective experimental study. Methods: A total of 16 thoracic limbs from horse cadavers and 18 adult horses. Methods: This study was conducted in three phases. Phase 1: Dissection of median and ulnar nerves in the antebrachial region of two cadaver limbs to identify localizing landmarks. Description of sonoanatomy in 14 cadaver limbs using ultrasound-guided perineural infiltration of a combination of cellulose gel (5 mL), contrast medium (4 mL) and methylene blue...
Effect of auriculopalpebral nerve block on equine intraocular pressure measured by rebound tonometry (TonoVet® ). To assess rebound tonometry intraocular pressure (IOP) in unsedated horses without and with auriculopalpebral (AP) nerve blocks. Methods: Twenty-two client- and twenty university-owned horses (84 total eyes) with unremarkable ophthalmic examinations were evaluated. Methods: One eye of each horse was chosen randomly, an AP block performed for that eye, and IOP measured in both eyes with a TonoVet . The process was repeated for the contralateral eye 72Â hours later under the same conditions as the initial measurements. Horses were unsedated for nerve blocks and tonometry. Linear mixed-effects mo...
Persistent Bilateral Mydriasis Associated With a Pituitary Adenoma in a Horse. Severe bilateral mydriasis and bilaterally decreased vision were observed in a 23-year-old crossbred warmblood gelding with a history of pituitary pars intermedia dysfunction. Ten years after the onset of clinical signs, it was killed humanely because of worsening of clinical signs and loss of therapeutic responsiveness. Postmortem examination of the head was performed to confirm the suspected pituitary neoplasm and to investigate secondary oculomotor lesions. Pathomorphologic examination revealed an expansile space-occupying pituitary adenoma and degenerative changes in the preganglionic ocul...
Ganglioglioma of the Right Cerebrothalamus in a 7-Year-Old Quarter Horse Cross Gelding. Intracranial neoplasia in horses is rare compared to other species. Detailed information such as neurological, electroencephalographic, and histopathological examination of horses with intracranial neoplasia associated with seizures is scarce in the literature. Furthermore, ganglioglioma has not been reported in the horse. A 7-year-old Quarter horse cross Paint gelding was examined due to recurrent seizure-like episodes of 1-year duration. The seizures had been increasing in frequency and length, occurring up to 20 times a day at the time of presentation. Neurological examination revealed inte...
Assessing pathological changes within the nucleus ambiguus of horses with recurrent laryngeal neuropathy: An extreme, length-dependent axonopathy. Equine recurrent laryngeal neuropathy (RLN) is a naturally occurring model of length-dependent axonopathy characterized by asymmetrical degeneration of recurrent laryngeal nerve axons (RLn). Distal RLn degeneration is marked, but it is unclear whether degeneration extends to include cell bodies (consistent with a neuronopathy). With examiners blinded to RLN severity, brainstem location, and side, we examined correlations between RLN severity (assessed using left distal RLn myelinated axon count) and histopathological features (including chromatolysis and glial responses) in the nucleus ambiguu...
Equine Stereotaxtic Population Average Brain Atlas With Neuroanatomic Correlation. There is growing interest in the horse for behavioral, neuroanatomic and neuroscientific research due to its large and complex brain, cognitive abilities and long lifespan making it neurologically interesting and a potential large animal model for several neuropsychological diseases. Magnetic resonance imaging (MRI) is a powerful neuroscientific research tool that can be performed , with adapted equine facilities, or in the research setting. The brain atlas is a fundamental resource for neuroimaging research, and have been created for a multitude animal models, however, none currently exist f...
Neuromas at the castration site in geldings. Inguinal pain, unexplained hind limb lameness, back pain or behavioural problems in geldings could be attributable to painful neuromas that develop as a consequence of crushing and severing the testicular nerves during castration. The presence of neuroma in this anatomical location has never been reported, hence the knowledge of possible clinical relevance is limited. The aim of this study was to histologically investigate the testicular nerves at the castration site in geldings for the presence of neuromas. Proximal spermatic cord remnants were collected from 20 geldings admitted to routine p...
A study of residual lesions in horses that recovered from clinical signs of chronic equine dysautonomia. Equine dysautonomia (ED) causes degeneration and loss of autonomic neurons. Approximately 50% of chronic cases recover, but it is unclear how they survive neuronal loss. Objective: To assess lesions, autonomic neuron numbers, interstitial cells of Cajal (ICC), and neurodegeneration in recovered cases. Methods: Thirteen cases (group ED), euthanized 10.3 ± 5.2 (1-16) years from diagnosis and 6 age-matched controls (group C). Methods: Prospective, case control; routine post mortem examination, neuron counts in peripheral and enteric ganglia and immunohistochemical assessment of neural networ...
Ex Vivo Assessment of an Ultrasound-Guided Injection Technique of the Lumbosacral Disc in the Horse.  The aim of this study was to describe an ultrasound-guided injection technique of the lumbosacral disc in horses through the cranial vertebral notch of the sacrum and to evaluate both accuracy and potential complications of the technique on equine cadavers. Methods:  Twenty-four injections of the lumbosacral area were performed on 12 equine cadavers shortly after euthanasia under ultrasound guidance with the horse in recumbency using two different dyes (one colour for each side). The lumbosacral area was dissected in each horse and the accuracy of the technique, as well as its potential c...
Morphological variations of the infraorbital canal during CT has limited association with headshaking in horses. Headshaking is a common problem in horses. The etiology is unknown but thought to involve sensory input from branches of the trigeminal nerve, some of which are within the infraorbital canal. The objective of this retrospective cross-sectional study was to describe the CT anatomy and variations of the infraorbital canal in horses with local disease processes and normal horses, and to examine associations between those findings and headshaking. Computed tomography scans were reviewed and morphological changes of the infraorbital canal were described. Presence of changes was then tested for asso...
Ultrasound-Guided Inferior Alveolar Nerve Block in the Horse: Assessment of the Extraoral Approach in Cadavers. Blinded techniques to desensitize the inferior alveolar nerve (IAN) include intraoral, angled, and vertical extraoral approaches with reported success rates of 100%, 73%, and 59%, respectively. It has not been determined whether an ultrasound-guided extraoral approach is feasible. Further, the fascicular nature of the inferior alveolar and lingual nerves of the horse has not been described. The objectives of this study were to describe a low-volume ultrasound-guided vertical extraoral inferior alveolar nerve block technique and to describe the fascicular nature of these nerves. An ultrasound-g...
Surgical correction of a meningoencephalocele in a thoroughbred filly. To describe the surgical correction of a closed meningoencephalocele in a thoroughbred filly. Methods: Case report. Methods: One thoroughbred filly, 1.5 months old at the time of surgery. Methods: A meningoencephalocele was identified at birth and diagnosed with radiography and MRI. The abnormal tissue was excised and submitted for histopathology, the dura was closed, and the defect in the skull was corrected with a titanium mesh. Results: Histopathology confirmed the presence of neural parenchyma consisting of neurons and glial cells. The filly remained without neurologic deficits 7 month...
Is Electrical Nerve Stimulation the Answer for Management of Equine Headshaking? Horses with trigeminal mediated headshaking (TMHS) have a decreased activation threshold of the trigeminal nerve and clinical signs are suspected to be a manifestation of trigeminal neuralgia. Electrical nerve stimulation (ENS) is used for management of neuralgia in humans and appears to work via gate control theory. Use of an equine specific percutaneous ENS program in over 130 TMHS horses has resulted in approximately 50% success return to previous work. Electroacupuncture may also be useful in the management TMHS. Optimization of ENS procedures for TMHS is likely to require a greater unders...
Neuroanatomy of the equine brain as revealed by high-field (3Tesla) magnetic-resonance-imaging. In this study, the morphology of the horse brain (Equus caballus) is decribed in detail using high field MRI. The study includes sagittal, dorsal, and transverse T2-weighted images at 0.25 mm resolution at 3 Tesla and 3D models of the brain presenting the external morphology of the brain. Representative gallocyanin stained histological slides of the same brain are presented. The images represent a useful tool for MR image interpretation in horses and may serve as a starting point for further research aiming at in vivo analysis in this species.
Polyradiculoneuropathy in dourine-affected horses. Dourine is an equine protozoan disease caused by Trypanosoma equiperdum. Dourine-afflicted animals die after developing neurological clinical signs, such as unilateral paresis. The disease has been a problem for many years; however, the pathogenesis regarding the neurological clinical signs of dourine has been unclear. In the present study, we conducted a histopathological examination in order to investigate the mechanisms by which dourine-afflicted horses develop the accompanying neurological clinical signs. Four dourine-afflicted horses in Mongolia were evaluated. An apparently healthy horse...
An atypical presentation of multi-systemic B-cell lymphoma in a horse. This report describes an unusual presentation of multicentric B-cell lymphoma with central and peripheral nerve involvement in a horse that was presented with acute onset, severe, multiple limb lameness, and muscle atrophy. This case highlights the importance of including neoplasia in the differential list in horses presenting for severe limb lameness associated with muscle atrophy, muscle fasciculations, and weakness. Présentation atypique d’un lymphome à cellules B multisystémique chez un cheval. Ce rapport décrit la présentation inhabituelle d’un lymphome à cellules B multicentriq...
Asymmetric recurrent laryngeal nerve conduction velocities and dorsal cricoarytenoid muscle electromyographic characteristics in clinically normal horses. The dorsal cricoarytenoid (DCA)Â muscles, are a fundamental component of the athletic horse's respiratory system: as the sole abductors of the airways, they maintain the size of the rima glottis which is essential for enabling maximal air intake during intense exercise. Dysfunction of the DCA muscle leads to arytenoid collapse during exercise, resulting in poor performance. An electrodiagnostic study including electromyography of the dorsal cricoarytenoid muscles and conduction velocity testing of the innervating recurrent laryngeal nerves (RLn) was conducted in horses with normal laryngeal fu...
Luteinizing hormone concentrations in healthy horses and horses with trigeminal-mediated headshaking over an 8-hour period. Trigeminal-mediated headshaking results from a low threshold for firing of the trigeminal nerve. A seasonal component has been implicated in onset of clinical signs, which occur during the spring and summer months. Geldings are overrepresented in the affected population and hormonal differences as compared to a healthy control population of geldings might contribute to headshaking. Objective: To assess concentrations of luteinizing hormone (LH) over an 8-hour period in gelded healthy controls and horses affected with headshaking. Our hypothesis was that geldings with seasonal headshaking would...
An Objective Assessment of the Effect of Anesthetizing the Median Nerve on Lameness Caused by Pain in the Cubital Joint. The median nerve, along with the ulnar nerve, is often anesthetized when performing a lameness examination in horses. Because of the close proximity of the median nerve to the cubital joint, proximal migration of local anesthetic might ameliorate pain originating from the cubital joint. The objective of this study was to determine if a median nerve block will ameliorate lameness caused by pain in the cubital joint. A forelimb lameness was induced in six healthy horses by injecting 100 ng of recombinant equine interleukin 1 beta (IL-1β) into the cubital joint. The median nerve of the lame leg...
The effect of a compression bandage on the distribution of radiodense contrast medium after palmar digital nerve blocks. Studies have shown proximal diffusion of injected drugs in perineural blocks; such diffusion may affect specificity of the nerve block. Objective: To investigate the effect of a compression bandage applied to the pastern region on proximal diffusion of contrast medium injected over the palmar digital nerves. Methods: Experimental study, randomised cross-over design. Methods: Radiodense contrast medium was injected over the lateral and medial palmar digital nerves of the left front limb of nine mature horses. Each horse was injected on two separate occasions, once with a 5 cm wide compression b...
Internal neurolysis of the maxillary branch of the trigeminal nerve for the treatment of equine trigeminal mediated headshaking syndrome. A 5-year-old Hannovarian warmblood gelding was presented for recurrent headshaking exacerbated with exercise. The horse displayed clinical signs of repetitive vertical head movements, face rubbing on the forelimbs and on the ground, repetitive sneezing, and striking the muzzle with his forelimbs. The clinical signs resulted in a horse that could not be ridden and was dangerous. Clinical signs were most persistent in direct sunlight, but occurred with excitement, exercise, or bridling indoors. A diagnosis of equine trigeminal mediated headshaking syndrome was made. Surgical treatment was perfor...
Attentional state and brain processes: state-dependent lateralization of EEG profiles in horses. Lateralization of brain functions has been suggested to provide individuals with advantages, such as an increase of neural efficiency. The right hemisphere is likely to be specialized for processing attention for details and the left hemisphere for categorization of stimuli. Thus attentional processes actually may underlie lateralization. In the present study, we hypothesized that the attentional state of horses could be reflected in the lateralization of brain responses. We used i) a recently developed attention test to measure horses' visual attentional responses towards a standardized stimu...
Causal and functional interpretation of mu- and delta-opioid receptor profiles in mesoaccumbens and nigrostriatal pathways of an oral stereotypy phenotype. Spontaneous stereotypic behaviours are repetitive, compulsive, topographically invariant response patterns commonly observed in captive or domestic animals, which have been linked to dysfunction of basal ganglia input/output pathways. There is evidence that endogenous opioids play a key regulatory role in basal ganglia direct and indirect pathways, but their precise role, both causally and functionally, in spontaneous stereotypic behaviour is unclear. Here we examined the profile of mu- and delta-opioid receptors (density [Bmax] and affinity [Kd]) of basal ganglia structures in stereotypy (nâ€...