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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.
Retrospective Evaluation of Hemithyroidectomy in 14 Horses. To describe the presentation, presurgical diagnostic findings, treatment, and outcome of horses with histologically confirmed, unilateral thyroid neoplasia. The complications, particularly laryngeal hemiplegia, were investigated. Retrospective case series. Client-owned horses (n=14). Medical records of horses presenting with a unilateral thyroid mass due to neoplasia from 2003-2015 were reviewed. Horses must have undergone preoperative clinical evaluations that included ultrasound examination of the mass and upper airway endoscopy. Short-term follow-up at 2 weeks after surgery and owner questi...
Effect of auriculopalpebral nerve block on Schirmer tear test I values in normal horses. To compare Schirmer tear test I (STTI) values collected in normal horses with and without an auriculopalpebral nerve block. Methods: Schirmer tear test I values were measured in 20 clinically normal horses (38 eyes) with a median age of 12 years. The order of eyes tested was randomized. Within 24-48 h, at the same time of day, tear measurements were collected again after administration of an auriculopalpebral nerve block. Each block was performed a minimum of 5 min prior to each STT I. A repeated-measures model was used to analyze differences between STT I values in eyes with and without nerve...
Nociceptive and sympathetic innervations in the abaxial part of the cranial horn of the equine medial meniscus: an immunohistochemical approach. In athletic horses, diseases leading to lameness are of great importance due to the loss of performance and the resultant economic concerns. Although stifle lesions are frequent in the hindlimb, due to the large size and complexity of the joint, and although meniscal tears have been identified as the most common soft tissue injuries in this joint, little is known about the mechanism that causes the painful sensation and thus the lameness. The aim of our study was to highlight any peripheral fibres involved in meniscal nociception in five macroscopically sound cranial horns of the equine medial...
Equestrian-Related Traumatic Brain Injury in the Pediatric Population. Equestrian activities can be undertaken for competition or leisure. Accidents can lead to bodily injuries. In particular, traumatic brain injury (TBI) can be devastating. Limited data exist regarding the pediatric population with respect to patterns of injury and related neurosurgical intervention. Methods: We retrospectively reviewed data for all pediatric patients diagnosed with equestrian-related injuries with neurological injuries from 2005 through June 2015. Results: Nine patients (1 male and 8 females) had neurological injuries. Their mean age was 10.4 years (range 2.9-16.8 years). Intra...
Evaluation of a caudolateral approach for arthrocentesis and injection of the equine elbow joint. The objectives of this study were to evaluate the likelihood of successful arthrocentesis of the equine elbow joint using the caudolateral approach and to determine if the deep branch of the radial nerve (DBRN) varies in its proximity to the site of centesis. Methylene blue (MB) was injected into 71 elbow joint specimens immediately caudal to the lateral collateral ligament using a 3.8-cm needle advanced to its hub. The elbow joints were dissected, staining of the synovial structures assessed and the proximity of DBRN to the site of centesis evaluated. The articular cartilage of all 71 joints ...
Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of needle type and size in equine cadavers. The aim of this study was to investigate a new approach for equine maxillary nerve blocks, which can facilitate several orofacial surgeries. Current techniques aim at the maxillary foramen and approach via the zygomatic arch, conferring the risk of injury to several delicate structures in the target area. To investigate the feasibility of a retrograde approach from the infraorbital foramen, an anatomic study of the infraorbital canal and its surrounding structures was performed on 13 cadaveric skulls using computed tomography and anatomical dissection. Measurements included canal length and vo...
Glaucoma with Descemet’s membrane detachment in five horses. To describe the clinical and histopathologic features of glaucoma associated with Descemet's membrane (DM) detachment in five horses without prior history of intraocular surgery. Methods: Three Appaloosa horses and two Thoroughbreds were included in this study. The affected horses ranged in age from 16 to 27 years and presented with severe diffuse corneal edema. Methods: Five eyes were enucleated due to intraocular hypertension and/or chronic corneal ulceration. The enucleated globes were evaluated by the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). Each globe was routinely ...
Mechanical nociceptive thresholds of dorsal laminae in horses after local anaesthesia of the palmar digital nerves or dorsal branches of the digital nerve. We examined the hypothesis that the palmar digital nerves (PDNs), but not the dorsal branches (DBs) of the digital nerves, innervate the sensitive dorsal laminae of the equine foot by evaluating the effects of perineural anaesthesia of the PDNs and DBs separately on pain sensation evoked via mechanical stimulation of the dorsal laminae and other regions of the equine foot. Six clinically normal mares were used in a crossover design. A portable dynamometer was used to evaluate mechanical nociceptive thresholds at different points on the dorsal laminae, bulbs of the heel, coronary band and sole ...
Fixation of supraglenoid tubercle fractures using distal femoral locking plates in three Warmblood horses. Three horses that were presented with supraglenoid tubercle fractures were treated with open reduction and internal fixation using distal femoral locking plates (DFLP). Placing the DFLP caudal to the scapular spine in order to preserve the suprascapular nerve led to a stable fixation, however, it resulted in infraspinatus muscle atrophy and mild scapulohumeral joint instability (case 1). Placing the DFLP cranial to the scapular spine and under the suprascapular nerve resulted in a stable fixation, however, it resulted in severe atrophy of the supraspinatus and infraspinatus muscles and scapulo...
Perineural Injection of the Ethmoidal Nerve of Horses. To describe the anatomical location of the ethmoidal nerve in the equine periorbital region and to determine the accuracy of a technique used to deposit local anesthetic solution adjacent to the nerve. Methods: Prospective experimental study. Methods: Adult equine cadaver heads (n=6 for preliminary dissection; n=15 [30 nerve sites] for evaluation of injection technique). Methods: Preliminary dissections were performed to identify landmarks for injection of local anesthetic adjacent to the ethmoidal nerve. For evaluation of the injection technique a 20 gauge 6 cm spinal needle was inserted into...
Transoesophageal ultrasound and computer tomographic assessment of the equine cricoarytenoid dorsalis muscle: Relationship between muscle geometry and exercising laryngeal function. Early detection of recurrent laryngeal neuropathy (RLN) is of considerable interest to the equine industry. Objective: To describe two imaging modalities, transoesophageal ultrasound (TEU) and computed tomography (CT) with multiplanar reconstruction to assess laryngeal muscle geometry, and determine the relationship between cricoarytenoid dorsalis (CAD) geometry and function. Methods: Two-phase study evaluating CAD geometry in experimental horses and horses with naturally occurring RLN. Methods: Equine CAD muscle volume was determined from CT scan sets using volumetric reconstruction with Live...
P2Y(1) receptors mediate purinergic relaxation in the equine pelvic flexure. In the equine large intestine, the knowledge of the basic mechanisms underlying motility function is crucial to properly treat motility disorders. P2Y1 receptors are responsible for mediating purinergic colonic relaxation in several species. In vitro experimental studies of the circular muscle from the equine pelvic flexure (n = 6) were performed to characterize inhibitory and excitatory neuromuscular transmission. Electrophysiological studies showed that electrical field stimulation (EFS) evoked biphasic inhibitory junction potentials (IJPs) in smooth muscle cells: a fast IJP (IJPf) follo...
Extrapyramidal system neurotoxicity: animal models. The central nervous system's extrapyramidal system provides involuntary motor control to the muscles of the head, neck, and limbs. Toxicants that affect the extrapyramidal system are generally clinically characterized by impaired motor control, which is usually the result of basal ganglionic dysfunction. A variety of extrapyramidal syndromes are recognized in humans and include Parkinson's disease, secondary parkinsonism, other degenerative diseases of the basal ganglia, and clinical syndromes that result in dystonia, dyskinesia, essential tremor, and other forms of tremor and chorea. This cha...
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-wee...
Comparative Study of the Major White Matter Tracts Anatomy in Equine, Feline and Canine Brains by Use of the Fibre Dissection Technique. The spatial anatomy of the white matter tracts is a subject of growing interest not only for researchers but also for clinicians. Imagistic methods have some limitations so that they should be confronted with dissection studies. The aim of this paper was to provide a three-dimensional view of the major white matter tracts in equine, feline and canine brains by use of the fibre dissection technique. Twenty cerebral hemispheres (six equine, four feline and 10 canine brains) were prepared according to the Klingler method. Stepwise mediolateral and lateromedial blunt dissections were performed usi...
Correlations Among Ultrasonographic Measurements of Optic Nerve Sheath Diameter, Age, and Body Weight in Clinically Normal Horses. Early diagnosis of high intracranial pressure (ICP) is critical for minimizing progressive brain injury due to reduced cerebral perfusion. In people, detecting enlargement of the optic nerve sheath diameter (ONSD) by transpalpebral ultrasonography has been found to be an accurate test for high ICP. Aims of this prospective, observational, cross-sectional study were to test hypotheses that (1) ultrasonographic measurement of ONSD would be repeatable in horses, (2) have acceptable interobserver agreement, and (3) would be correlated with age and body weight. The sample population included 48 hor...
Evidence of the Primary Afferent Tracts Undergoing Neurodegeneration in Horses With Equine Degenerative Myeloencephalopathy Based on Calretinin Immunohistochemical Localization. Equine degenerative myeloencephalopathy (EDM) is characterized by a symmetric general proprioceptive ataxia in young horses, and is likely underdiagnosed for 2 reasons: first, clinical signs overlap those of cervical vertebral compressive myelopathy; second, histologic lesions--including axonal spheroids in specific tracts of the somatosensory and motor systems--may be subtle. The purpose of this study was (1) to utilize immunohistochemical (IHC) markers to trace axons in the spinocuneocerebellar, dorsal column-medial lemniscal, and dorsospinocerebellar tracts in healthy horses and (2) to dete...
Neurologic Diseases in Horses. This article focuses on the gross examination of the brain and spinal cord and outlines the main lesions and neuroanatomic location related to neurologic diseases in horses.
Pathophysiology of free-bullet slaughter of horses and ponies. Forty-six equines were observed during routine commercial slaughter in an abattoir. The animals were shot once with a .22 calibre long rifle with hollow point rounds. Indicators of sensibility/insensibility were evaluated immediately after the shot (prior to exsanguination) and the resulting pathophysiology of free-bullet injury was assessed. All animals were rendered immediately insensible, with only one pony showing signs of a shallow depth of concussion, with an intermittently positive palpebral reflex but no other signs of brainstem function. All animals (100%) had some degree of damage to...
IMAGING DIAGNOSIS – UNILATERAL TRIGEMINAL NEURITIS MIMICKING PERIPHERAL NERVE SHEATH TUMOR IN A HORSE. A 16-year old Warmblood gelding presented with a nonhealing corneal ulcer and absent corneal sensation in the left eye. A lesion affecting the maxillary and ophthalmic branches of the left trigeminal nerve was suspected. Magnetic resonance (MR) imaging identified marked thickening of the ophthalmic and maxillary branches of the left trigeminal nerve. The nerve was iso- to hypointense on T1-weighted and T2-weighted images with heterogeneous enhancement. A peripheral nerve sheath tumor was suspected, however granulomatous neuritis was histopathologically confirmed. These inflammatory changes can...
Laryngeal advancement surgery improves swallowing function in a reversible equine dysphagia model. Pharyngeal dysphagia is a debilitating, sometimes fatal condition in horses, with multiple aetiologies. The pathophysiology is complex and not fully understood. Treatment is largely supportive. Laryngeal advancement surgery may diminish symptoms of dysphagia and improve swallowing in affected horses. Objective: 1) to induce reversible moderate and marked pharyngeal dysphagia by regional anaesthesia of branches of the glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves; 2) to characterise the dysphagia produced by each model; and 3) to determine whether laryngeal advancement surgery i...
Ultrasonographic detection of early atrophy of the intrinsic laryngeal muscles of horses. To describe the ultrasonographic changes in the cricoarytenoideus dorsalis (CAD) and cricoarytenoideus lateralis (CAL) muscles of horses before and at various times during the 32 weeks after unilateral neurectomy of the right recurrent laryngeal nerve. Methods: 28 healthy Standardbreds. Methods: For each horse, the appearance of the CAD and CAL muscles on the right (neurectomized) and left (control) sides was serially monitored ultrasonographically by percutaneous (CAD and CAL) and transesophageal (CAD) approaches. The ultrasonographic images were assessed to determine the mean pixel intensity...
ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY. For accurate interpretation of magnetic resonance (MR) images of the equine brain, knowledge of the normal cross-sectional anatomy of the brain and associated structures (such as the cranial nerves) is essential. The purpose of this prospective cadaver study was to describe and compare MRI and computed tomography (CT) anatomy of cranial nerves' origins and associated skull foramina in a sample of five horses. All horses were presented for euthanasia for reasons unrelated to the head. Heads were collected posteuthanasia and T2-weighted MR images were obtained in the transverse, sagittal, and do...
Cerebral and brainstem electrophysiologic activity during euthanasia with pentobarbital sodium in horses. An overdose of pentobarbital sodium administered i.v. is the most commonly used method of euthanasia in veterinary medicine. Determining death after the infusion relies on the observation of physical variables. However, it is unknown when cortical electrical activity and brainstem function are lost in a sequence of events before death. Objective: To examine changes in the electrical activity of the cerebral cortex and brainstem during an overdose of pentobarbital sodium solution for euthanasia. Our testing hypothesis is that isoelectric pattern of the brain in support of brain death occurs bef...
Validation of the accuracy of needle placement as used in diagnostic local analgesia of the maxillary nerve for investigation of trigeminally mediated headshaking in horses. Diagnostic local anaesthesia of the maxillary nerve is a valuable aid in the diagnosis of trigeminally mediated headshaking in horses. Our objective is to validate the accuracy of needle placement in this procedure and to identify any correlation between accuracy of the technique and operator experience. Using a small volume of contrast medium, the procedure was performed bilaterally on 30 horse cadaver heads by three groups with different levels of experience with the technique. The location of deposition was then identified using computed tomography (CT). Contrast medium was deposited around...
Vascular hamartoma in the central nervous system of a foal. Vascular hamartomas are non-neoplastic developmental anomalies of vessels. Cases of cerebral vascular hamartomas have been previously reported in dogs and cats. A 4-week-old Freiberger foal had shown persistent problems with breathing and swallowing since birth, and bilateral laryngeal paralysis was diagnosed. The foal subsequently developed left sided facial nerve paralysis and a secondary corneal ulcer in the left eye. Necropsy revealed a pinkish mass in the obex region of the brain. The mass was further investigated by histology and immunohistochemistry. Histologically, the mass consisted o...
Encephalitozoon cuniculi-Associated Equine Encephalitis: A Case Report. A case of encephalitis of unknown origin in the horse was investigated. Postmortem examination findings revealed a nonsuppurative granulomatous meningoencephalitis in the right hemisphere of the cerebral cortex. Testing for West Nile virus, equine herpes virus, equine infectious anemia, , , and were negative. The horse had a titer for , and sections from the affected area of the brain tested positive for the organism using both polymerase chain reaction (PCR) and immunohistochemistry. Amplicons generated using PCR were sequenced, and genotype II was identified. This is the first case of gen...
Tracheal resection and anastomosis after traumatic tracheal stenosis in a horse. To report a resection and anastomosis technique to treat trauma-induced tracheal stenosis. Methods: Case report. Methods: A 9-year-old Warmblood gelding. Methods: Endoscopy, radiography, and ultrasonography were used to diagnose a single ring tracheal stenosis; the stenotic region was resected and adjacent tracheal rings anastomosed with an end-to-end technique. Results: The anastomosis healed completely despite formation of a unilateral partial mucosal stenosis "web," which was subsequently removed by transendoscopic laser surgery. During tracheal anastomosis, the left recurrent laryngeal ner...
The Inferior Alveolar Nerve of the Horse: Course and Anatomical Relationship with Mandibular Cheek Teeth. The precise location of neurovascular structures within the relatively long mandibular canal of the horse is of paramount importance in surgical procedures of the area. The inferior alveolar nerve (IAN) enters the mandibular canal on the medial (lingual) surface of the mandible and innervates all the mandibular teeth. During its course, the nerve moves laterally, crossing the roots of the inferior cheek teeth. However, the exact anatomical relationships occurring between the IAN and the roots of the equine mandibular cheek teeth have not been described in detail. In this study, the mandibles o...
